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Storm frequency and magnitude in response to Holocene climate variability, Lake Tutira, North-Eastern New Zealand
Abstract
A mid to late Holocene record of storm events is preserved in the sediments of Lake Tutira, located on the eastern North Island of New Zealand. Previous studies of a 6 m sediment core established a storm chronology for the last 2250 years (Eden, D.N., Page, M.J., 1998. Palaeoclimatic implications of a storm erosion record from late Holocene lake sediments, North Island, New Zealand. Palaeogeogr. Palaeoclimatol. Palaeoecol. 139, 37–58). Here we extend the record, using a 27 m sediment core, to lake formation ∼ 7200 cal. yr ago. Outside the last ∼ 500 yr of human influence, the core records landscape response to natural climate variability and to tectonism/volcanism associated with the active collisional plate boundary setting.
... To explore this in the Whanganui we compare the record of flooding in the catchment over the last 2000 years with a range of regional and sub-hemispheric hydroclimate proxies ( Figure 9). As a measure of flooding, we use the average occurrence of events that have recurrence time of more than 30 years, which is the phases, as was also found in the Lake Tutira record (Page et al., 2010). Subtropical storms and extropical cyclones, and / or more slow-moving low pressure systems associated with blocking synoptic conditions (cf. ...
... Figure 9. Comparison of (hydro)climatic records: (A) Total Solar Irradiance curve ( Bard et al., 2000); (B) Southern Annular Mode (SAM) index (70-yr filtered; Abram et al., 2014); (C) Frequency of El-Niño events from the Galapagos Islands (Conroy et al., 2008); (D) Patagonian drought indices -charcoal densities (curve) and Cipreses dry phases (horizontal grey bars; Moreno et al., 2014); (E) Lake Tutira storminess (NE of North Island in New Zealand) index curve (Eden and Page, 1998) and phases (horizontal grey bars) of increased storm occurrence (Page et al., 2010); (F) Antarctica EPICA Dome C ice core temperature anomalies (Masson-Delmotte et al., 2004), averaged per century as an indicator for SAM strength (after Gomez et al., 2012); (G) Probability distribution based on 'activity' dates for fluvial environments on Northland, New Zealand (Richardson et al., 2014); (H) Flood activity of the Whanganui River, based on the frequency of large events (>30-yr recurrence time), averaged over a moving 150-yr window (this study). Periods of prolonged above-average Whanganui flood occurrence are shaded in grey in the background. ...
... 2000 yr, and periods of increased flooding in the Whanganui match episodes of enhanced storminess at Tutira(Figure 9e). In updated work, extending the Tutira record to cover the last 7200 yr,Page et al. (2010) report major periods of enhanced storminess between 500-700 and 1100-1250 cal. yr BP (cf.Figure 9e), which match closely with two periods of increased flooding in the Whanganui catchment. ...
Palaeofloods in the Whanganui River, North Island, New Zealand are investigated using floodplain sedimentary archives at two locations in the lower Whanganui catchment. The ca. AD 232 Taupo volcanic eruption transformed the lower valley of the Whanganui River, emplacing a substantial volume of volcanogenic mass flow material and providing a new starting point for subsequent alluvial sedimentation. At Atene a high–resolution archive of flood sediments is preserved in a valley meander cutoff in the lower reaches of the Whanganui Gorge, where a ~9 m core was extracted. At Crowley House further down valley, two ~5 m cores were also extracted from a terrace-confined floodplain. Organic material from these cores allows the timing of floods at these sites to be constrained using 11 radiocarbon dates (ten from Atene, one from Crowley House). Flood magnitudes are reconstructed using XRF core-scanned geochemistry as a proxy for flood unit grain size. An age-depth model at Atene identifies three distinct phases of sedimentation with above average flood activity recorded at 1450–1125, 950, 650–500, and 400–325 cal. yr BP, which can be linked to the El Niño Southern Oscillation (ENSO) and strengthening of the Southern Hemisphere Westerly Wind circulation. Large floods also cluster in the late 1800s, reflecting a combination of enhanced storminess and land cover change, which also resulted in deeper erosion of regolith in the catchment, revealed by cosmogenic analysis at Crowley House. Climatic and non-climatic drivers are responsible for floods in the Whanganui catchment over the past ~2000 years, with the largest floods occurring during La Niña and positive Southern Annular Mode conditions. The timing of the largest single flood in the Whanganui in this period is consistent with the volcanic-resetting event itself of AD 232. This study demonstrates the close relationship between regional climate variability in the south-western Pacific Ocean and the occurrence of extreme floods in New Zealand, and the importance of using multi-centennial length hydrological series for effective flood risk assessment.
... Bartholy et al., 2009), but to assess the centennial to millennial cycles, it is necessary to use information from sedimentary sequences which have recorded the paleostorm events. This field of research, the palaeotempestology, was successfully applied to evidence the millennial frequency of cyclones during the mid-to late-Holocene in the western North Atlantic (Donnelly and Woodruff, 2007), Northwest Florida (Liu and Fearn, 2000; Lane et al., 2011; Das et al., 2013), the Northeastern United States (Parris et al., 2010), the Central Pacific (Toomey et al., 2013), Southern Japan (Woodruff et al., 2009), Western Australia (Nott, 2011), Northeastern New Zealand (Page et al., 2010), Northern Europe (Sorrel et al., 2009Sorrel et al., , 2012 ), or the Northwestern Mediterranean (Dezileau et al., 2011; Sabatier et al., 2012). The new storminess proxies established in these works were tentatively correlated with ice-rafted debris (IRD) indices and records of sea-surface temperature (SST) or solar irradiance in order to study the relationship with climate dynamics (Donnelly and Woodruff, 2007; Sabatier et al., 2012; Sorrel et al., 2012; Van Vliet-Lano€ e et al., 2014 ). ...
... Consequently, the coastal lakes and wetlands such as lagoons or maritime marshes at the back of coastal barriers provide a relevant geomorphic setting to track the paleostorm activity (Sabatier et al., 2008Sabatier et al., , 2010a Woodruff et al., 2009; Dezileau et al., 2011; Lane et al., 2011; Otvos, 2011). Different methods have been used to detect these tempestites in a sedimentary sequence: biological indicators such as foraminifera (Collins et al., 1999; Hippensteel and Martin, 1999; Hawkes and Horton, 2012; Pilarczyk et al., 2014), diatom (Parsons, 1998; Page et al., 2010), molluscs (Jelgersma et al., 1995; Sabatier et al., 2008 Sabatier et al., , 2012), or pollen (Liu et al., 2008 ); sedimentological characteristics such as grain-size (Liu and Fearn, 2000; Sabatier et al., 2008 Sabatier et al., , 2012 Horton et al., 2009; Parris et al., 2010; Dezileau et al., 2011; Toomey et al., 2013), mineralogy (Sabatier et al., 2010aSabatier et al., , 2012), or microtextural features of quartz grains (Costa et al., 2012); and elemental or isotopic geochemistry (Lambert et al., 2008; Woodruff et al., 2009; Page et al., 2010; Sabatier et al., 2010a Sabatier et al., , 2012 Dezileau et al., 2011; Das et al., 2013). This paper focuses on the study of paleostorms from highresolution geochemical and sedimentogical analyses of a lagoonal sequence in the Northwestern Mediterranean. ...
... Consequently, the coastal lakes and wetlands such as lagoons or maritime marshes at the back of coastal barriers provide a relevant geomorphic setting to track the paleostorm activity (Sabatier et al., 2008Sabatier et al., , 2010a Woodruff et al., 2009; Dezileau et al., 2011; Lane et al., 2011; Otvos, 2011). Different methods have been used to detect these tempestites in a sedimentary sequence: biological indicators such as foraminifera (Collins et al., 1999; Hippensteel and Martin, 1999; Hawkes and Horton, 2012; Pilarczyk et al., 2014), diatom (Parsons, 1998; Page et al., 2010), molluscs (Jelgersma et al., 1995; Sabatier et al., 2008 Sabatier et al., , 2012), or pollen (Liu et al., 2008 ); sedimentological characteristics such as grain-size (Liu and Fearn, 2000; Sabatier et al., 2008 Sabatier et al., , 2012 Horton et al., 2009; Parris et al., 2010; Dezileau et al., 2011; Toomey et al., 2013), mineralogy (Sabatier et al., 2010aSabatier et al., , 2012), or microtextural features of quartz grains (Costa et al., 2012); and elemental or isotopic geochemistry (Lambert et al., 2008; Woodruff et al., 2009; Page et al., 2010; Sabatier et al., 2010a Sabatier et al., , 2012 Dezileau et al., 2011; Das et al., 2013). This paper focuses on the study of paleostorms from highresolution geochemical and sedimentogical analyses of a lagoonal sequence in the Northwestern Mediterranean. ...
... 3.1.1. Environmental setting Lake Tutira was formed by hillslope collapse~7.2 ka, possibly triggered by a large earthquake, which dammed the southern valley outlet (Adams, 1981;Trustrum and Page, 1992;Cochran et al., 2006;Page et al., 2010). This small (1.8 km 2 ) and shallow lake, with a mean depth of 21 m and maximum depth of 42 m (Irwin, 1978), is a sediment and nutrient trap and repository of storm-induced erosion (e.g., Guthrie-Smith, 1999-first printed in 1921Adams, 1981;Page et al., 1994a;Eden and Page, 1998;Gomez et al., 2002). ...
... Hence, the preserved event record has formed in response to a number of drivers of varying frequency and magnitude. Lake Tutira is~100 km downwind of the active TVZ and this close proximity led to the preservation of twelve discrete air-fall tephras in the lake sediments Page et al., 2010), and some form important chronostratigraphic markers in the adjacent marine sequence (e.g., Gomez et al., 2007;Gerber et al., 2010;Pouderoux et al., 2012b). Lake tephra deposits have been used previously, along with other age markers (e.g., pollen, diatoms, radiocarbon and 137 Cs activity), to establish the late-Holocene sedimentation history (e.g., Page and Trustrum, 1997;Eden and Page, 1998). ...
... Redeposited tephras contain non-volcanic material and occur in both graded and massive beds and laminae . The twelve tephras, together with three radiocarbon dates from wood fragments provide the chronology to interpolate linearly the ages of storm events (e.g., Page et al., 2010). This tight temporal control affords Lake Tutira the best chronostratigraphic record spanning the late to mid-Holocene in the WSS. ...
A fundamental goal of the Earth Science community is to understand how perturbations on Earth's surface are preserved in the stratigraphic record. Recent Source to Sink (S2S) studies of the Waipaoa Sedimentary System (WSS), New Zealand, are synthesized herein to provide a holistic perspective of the processes that generate, transport and preserve sedimentary strata and organic carbon on the Waipaoa margin in the late Quaternary. Rapid uplift associated with subduction processes and weak sedimentary units have conspired to generate rapid rates of incision and erosion in the Waipaoa catchment since the Last Glacial Maximum (LGM). We show that although much of the sediment exported offshore during this time interval originated from valley excavation, a substantial portion emanated from hillslopes, mostly through deep-seated landslide and earthflow processes that were vigorous during periods of rapid fluvial incision just prior to the Pleistocene–Holocene transition. Lacustrine sediments deposited in naturally-dammed 7-ky-old Lake Tutira provide a record of Holocene environmental controls on upper catchment sedimentation in the WSS, with 1400 storms identified. Storm frequency is modulated by the waxing and waning of atmospheric teleconnections between the tropics and Antarctica. Furthermore, clear long-term changes in sediment yield are evident from the Lake Tutira record following human settlement as conversion to pasture is accompanied by a 3-fold increase in the long-term lake sediment accumulation rate.
... In this paper we extend the hypothesis that ENSO and SAM interact to influence storm activity over northeastern New Zealand, by examining published, high-resolution paleoclimate records from the west-central region of the North Island and southern South America. First, we use the signature of large rainfall events preserved in Lake Tutira core LT24 Page et al., 2010; Figure 1), in conjunction with the sediment record from Poverty Shelf core MD972122 (Gomez et al., 2004a Figure 1), to contextualize the regional response erosion processes had to variations in eastern North Island rainfall that were a product of interactions between ENSO and the SAM in middle and late Holocene. Then we consider variations in Holocene rainfall across the North Island, by comparing the Lake Tutira record with the master speleothem carbon isotope (δ 13 C) record from caves in the Waitomo district of the west-central North Island (Williams et al., 2004; Figure 1). ...
... The ~7000 yr long Lake Tutira record is derived from terrigenous (silt and sand) deposits generated by mass-wasting processes operating during extreme rainstorms Page et al., 2010). Contemporaneously, the marine core from Poverty Shelf not only records changes in the mode and intensity of sediment production, but also the erosional response to rainfall events of diverse magnitude and frequency (Gomez et al., 2004a. ...
... Conversely, the teleconnection weakens when the climate modes are out of phase. Terrigenous sediment layers in core LT24 from Lake Tutira (39.22°S, 176.89°E; Figure 1) provide an uncensored and sensitive record of upland storm-driven erosional activity that initiated surface and channel erosion and shallow landslides on hillslopes in the surrounding 32 km 2 catchment Page et al., 2010). Layer thickness and lithotype are positively correlated with storm rainfall, and an assemblage of 397 clay layers and sand-silt-clay graded beds records variations in the South Pacific atmospheric circulation linked to ENSO and the SAM, that combined to influence the frequency of the largest magnitude rainstorms (event rainfall ≥300 mm) during the middle and late Holocene . ...
Intercorrelated terrestrial and marine records from New Zealand, Chile and Argentina provide the first evidence of a coherent pan-Pacific response to the growing influence that El Niño-Southern Oscillation (ENSO) and multicentury variations in the interaction between ENSO and the Southern Annular Mode (SAM) exerted on rainfall in the Southern Hemisphere mid-latitudes during the middle and late Holocene. Rainfall is also strongly influenced by moisture originating from the prevailing southern westerly winds (SWW), and we find that the variations in rainfall forced by the interaction of ENSO and the SAM are superimposed on an underlying long-term trend induced by a temporal strengthening of the westerly circulation. We conclude that the evolution of rainfall across the South Pacific reflects the influence seasonal insolation exerts on: (1) ENSO/SAM interactions; and (2) the strength of the SWW.
... The flooding risk of coastal areas may significantly be enhanced by the meaningful sea level rise expected by the IPCC (Pachauri et al., 2014), crossed with the evolution of meteorological hazards activity (e.g. Paciorek et al., 2002;Page et al., 2010;Ulbrich and Christoph, 1999) and the expected increase of worldwide coastal population (Lutz and Samir, 2010;Neumann et al., 2015). Marine flooding is induced by intense meteorological and oceanological parameters producing a significant morphogenic activity over coastal environments (Fig. 1). ...
... It remains, however, the most used and accurate dating method found in bibliography for Holocene sedimentological stratigraphy (e.g. Engel et al., 2012;May et al., 2016;Page et al., 2010). This higher uncertainty does not allow the detection of a precise past storm impact estimated to a day or a month. ...
This paper presents the benefits of multiplying environmental indicators to better understand the impacts of past storm events on the environment. It aims to describe the methodological approaches
used to reconstruct past extreme events from washover deposits, at the three main temporal scales used in scientific bibliography: i) the long timescale (Holocene, since 12 000 years BP), ii) the meso timescale (for the last millenary) and iii) the short timescale (Anthropocene, for the last centuries). This methodology is based on a “multiproxy” analysis using sedimentology, geochemistry and various methods of isotope dating. Linking these methods with other disciplines such as history, archaeology and meteorology leads us to confirm with great certainty the existence of these extreme events, and to expose their impacts on the environment and on past coastal
societies. These different approaches enable us to enhance and refine our knowledge of coastal hazards, but also to apprehend possible storm influences in the context of climate change.
... Lu and Liu 2006) and geochemical indices (e.g. Lambert et al. 2008;Woodruff et al. 2009;Page et al. 2010;Sabatier et al. 2010Sabatier et al. , 2012Das et al. 2013). Over the past few decades, application of overwash deposits have successfully facilitated the reconstruction of storm activities during mid to late Holocene in the Gulf coast (e.g. ...
... Nott 2011), Northeastern New Zealand (e.g. Page et al. 2010), Northern Europe (e.g. Sabatier et al. 2012) and the Northwestern Mediterranean (e.g. ...
Numerous studies have been carried out to identify storm deposits and decipher storm-induced sedimentary processes in coastal and shallow-marine areas. This study aims to provide an in-depth review on the study of coastal storm deposits from the following five aspects. 1) The formation of storm deposits is a function of hydrodynamic and sedimentary processes under the constraints of local geological and ecological factors. Many questions remain to demonstrate the genetic links between storm-related processes and a variety of resulting deposits such as overwash deposits, underwater deposits and hummocky cross-stratification (HCS). Future research into the formation of storm deposits should combine flume experiments, field observations and numerical simulations, and make full use of sediment source tracing methods. 2) Recently there has been rapid growth in the number of studies utilizing sediment provenance analysis to investigate the source of storm deposits. The development of source tracing techniques, such as mineral composition, magnetic susceptibility, microfossil and geochemical property, has allowed for better understanding of the depositional processes and environmental changes associated with coastal storms. 3) The role of extreme storms in the sedimentation of low-lying coastal wetlands with diverse ecosystem services has also drawn a great deal of attention. Many investigations have attempted to quantify widespread land loss, vertical marsh sediment accumulation and wetland elevation change induced by major hurricanes. 4) Paleostorm reconstructions based on storm sedimentary proxies have shown many advantages over the instrumental records and historic documents as they allow for the reconstruction of storm activities on millennial or longer time scales. Storm deposits having been used to establish proxies mainly include beach ridges and shelly cheniers, coral reefs, estuary-deltaic storm sequences and overwash deposits. Particularly over the past few decades, the proxies developed from overwash deposits have successfully retrieved many records of storm activities during the mid to late Holocene worldwide. 5) Distinguishing sediments deposited by storms and tsunamis is one of the most difficult issues among the many aspects of storm deposit studies. Comparative studies have investigated numerous diagnostic evidences including hydrodynamic condition, landward extent, grain property, texture and grading, thickness, microfossil assemblage and landscape conformity. Perhaps integrating physical, biological and geochemical evidences will, in the future, allow unambiguous identification of tsunami deposits and storm deposits.
... As an inland sink, lakes have accommodation space to trap a high proportion of inflowing particulates from the catchment (Owens and Slaymaker, 1993) and it is hydrodynamically unfavorable to remobilize material out of most lakes (Dearing, 1991;Wetzel, 2001). Additionally, anoxic bottom waters that are often present preclude bioturbation, thereby facilitating preservation of stratigraphy (Edmondson, 1991;Page et al., 1994Page et al., , 2010. The relatively small source-to-sink area ratio of a lake allows for a rapid response to environmental changes and forcing variables (Cohen, 2003). ...
... By removing the event-bed layers, an event-bed-free stratigraphic column of accumulating mass with depth -'eventfree depth' or 'EFD' (Bronk Ramsey et al., 2012) is established, and reflects the background sediment accumulation rate (Brown et al., 2002;Page and Trustrum, 2010;Howarth et al., 2013). In this way, an age-mass model is constructed in the contemporary period that allows interpretation of age with mass unbiased by thick event beds ( Figure 9). ...
Sediment cores retrieved from landslide-dammed Loon Lake recorded events back to the 5th century AD in a forested, mountainous catchment, thereby providing an opportunity to compare the impacts of known recent perturbations, including floods and timber harvesting with those of an early period in the cores, floods, fires, and earthquakes. High-resolution multi-parameter (grain size, %TC, %TN, and magnetic susceptibility) data allowed the core stratigraphy to be classified as background sedimentation and events. 137Cs and radiocarbon dating, as well as a varved record in the last 75 years provided age control. Mean mass accumulation rate from 1939 to 1978 AD, the time of peak timber harvest and a cool wet phase of the Pacific Decadal Oscillation, was 0.79 (0.74-0.92, 95% C.L.) g cm-2 y-1, significantly higher than mean rates of both the more recent contemporary period (coincident with the passing of the legislation that regulated harvesting practices in the region), 1979-2012 AD, at 0.58 (0.48-0.70) and the entire early period, 0.44 (0.41-0.46). Several event deposits are coeval with independently estimated ages of eight Cascadia subduction zone earthquakes in the early period, including the 1700 AD Mw 9.0 event. These deposits are predominantly formed by hyperpycnal flows, as are the known event deposits in the contemporary period. The high mass accumulation rate and greater frequency of thick event deposits during the early contemporary period point to the extraordinary role of timber harvesting in priming the landscape for subsequent sedimentary delivery during floods.
... The speed of this clearance was dramatic in drier areas, such as the eastern South Island, where it occurred in decades (McWethy et al., 2010; 2014; Woodward et al., 2014a; 2014b) and forest recovery following fires was rare (McGlone and Basher, 1995). Polynesian deforestation in less accessible (and generally wetter) parts of the North Island occurred later at around c. 400 years BP (Wilmshurst et al., 2004), although in the drier eastern North Island, a human impact on the environment is recorded in the last 500 years of the Lake Tutira record (Page et al., 2010). The extent of Ma ¯ori forest clearance is depicted inFigure 1. Polynesian occupation was followed in the early 1800s by European settlement. ...
... database of 14 C dated Holocene fluvial units, which focuses on centennial-scale periods of activity derived from multiple catchments (cf.,Figure 2), there is little evidence to suggest that Ma ¯ori settlement and deforestation had a major impact on flooding and river dynamics in New Zealand. This is in contrast with wetland and lake records (cf., Page et al., 2010; Woodward et al., 2014a; 2014b), where a much clearer impact is discernible. River activity deduced from meta-analysis represents catchment behaviour at a large spatial scale (national/regional), as well as a longer temporal scale (centennial). Polynesian impacts discerned from lake records were over within a matter of decades (McWethy e ...
New Zealand provides a useful environment to test the notion that the Anthropocene is a new geological epoch. There are two well-dated anthropogenic impact 'events': Polynesian settlement c. AD 1280, and European colonisation c. AD 1800. Little attention, however, has been given to regional catchment response to these, although it has been assumed that both Polynesian and European farming and land use management practices significantly increased erosion rates across most of New Zealand. This paper addresses the nature and timing of human impacts on river systems using meta-analysis of a recently compiled nationwide database of radiocarbon-dated fluvial deposits. This shows highly variable human impacts on erosion and sedimentation in river systems, which are often difficult to separate from naturally driven river activity. Catchment-scale data with high resolution dating control record clearer evidence of human disturbance. In Northland, anthropogenic alluviation is recorded from c. AD 1300 linked to early Polynesian settlement, enhanced further in the late 19th and 20th centuries by European land clearance, when sedimentation rates exceeded 25mmyear-1. This study demonstrates significant geographical variability in the timing of human impact on river dynamics in New Zealand, despite two synchronous phases of human settlement, and highlights the difficulty of formally designating a simple and single 'Anthropocene Epoch/Age'.
... These include records from the Auckland maars (Newnham et al., 2007a;Augustinus et al., 2008Augustinus et al., , 2011, Lake Poukawa, drilled as part of the PEP II project (Pole-Equator-Pole; Shulmeister and Dodson, 2002), Kaipo bog (Newnham and Lowe, 2000;Hajdas et al., 2006), Okarito bog (Vandergoes et al., 2005;Newnham et al., 2007b), the Subantarctic islands (McGlone et al., 2002;, and Lake Maratoto (Green and Lowe, 1985), which has recently been selected as the Australasian auxiliary record for the "Global Stratotype Section" for the base of the Holocene, defined by the Konini tephra (unit b), and palynology (Walker et al., 2009). Lake Tutira was also drilled as part of the MARGINS program, and has recorded evidence of large storms and earthquakes over the mid-late Holocene (Page et al., 2010) as well as ENSO/SAM interactions (Gomez et al., 2012). We would like to suggest that several of these lakes and bogs are suitable candidates for "iconic" status (see Kathryn Fitzsimmons' article -this issue), especially Lake Maratoto. ...
... Novel environment and temperature proxies have also been applied over the last decade, including using chironomid (midges) remains from lakes (e.g., Vandergoes et al., 2008), phytoliths (e.g. , diatoms (e.g. Page et al., 2010), and coleopteran (beetle) remains from lake and soil profiles (e.g. Marra et al., 2006Marra et al., , 2009. ...
Extract
With the AQUA milestone of 30 years it seems an appropriate time to review the progress and achievements of Quaternary research in New Zealand. This article highlights some of the major achievements since the formal review of New Zealand’s Quaternary record by Newnham et al. (1999) ["Quaternary environmental change in New Zealand: a review." Progress in Physical Geography 23, 567-610]. The focus here is on paleoclimate and geochronology and is by no means a comprehensive review. We encourage members to write future articles for Quaternary Australasia (QA) about their exciting projects to keep the wider Australasian community informed.
... These include records from the Auckland maars (Newnham et al., 2007a;Augustinus et al., 2008Augustinus et al., , 2011, Lake Poukawa, drilled as part of the PEP II project (Pole-Equator-Pole; Shulmeister and Dodson, 2002), Kaipo bog (Newnham and Lowe, 2000;Hajdas et al., 2006), Okarito bog (Vandergoes et al., 2005;Newnham et al., 2007b), the Subantarctic islands (McGlone et al., 2002;, and Lake Maratoto (Green and Lowe, 1985), which has recently been selected as the Australasian auxiliary record for the "Global Stratotype Section" for the base of the Holocene, defined by the Konini tephra (unit b), and palynology (Walker et al., 2009). Lake Tutira was also drilled as part of the MARGINS program, and has recorded evidence of large storms and earthquakes over the mid-late Holocene (Page et al., 2010) as well as ENSO/SAM interactions (Gomez et al., 2012). We would like to suggest that several of these lakes and bogs are suitable candidates for "iconic" status (see Kathryn Fitzsimmons' article -this issue), especially Lake Maratoto. ...
... Novel environment and temperature proxies have also been applied over the last decade, including using chironomid (midges) remains from lakes (e.g., Vandergoes et al., 2008), phytoliths (e.g. , diatoms (e.g. Page et al., 2010), and coleopteran (beetle) remains from lake and soil profiles (e.g. Marra et al., 2006Marra et al., , 2009. ...
... These include records from the Auckland maars (Newnham et al., 2007a;Augustinus et al., 2008Augustinus et al., , 2011, Lake Poukawa, drilled as part of the PEP II project (Pole-Equator-Pole; Shulmeister and Dodson, 2002), Kaipo bog (Newnham and Lowe, 2000;Hajdas et al., 2006), Okarito bog (Vandergoes et al., 2005;Newnham et al., 2007b), the Subantarctic islands (McGlone et al., 2002;, and Lake Maratoto (Green and Lowe, 1985), which has recently been selected as the Australasian auxiliary record for the "Global Stratotype Section" for the base of the Holocene, defined by the Konini tephra (unit b), and palynology (Walker et al., 2009). Lake Tutira was also drilled as part of the MARGINS program, and has recorded evidence of large storms and earthquakes over the mid-late Holocene (Page et al., 2010) as well as ENSO/SAM interactions (Gomez et al., 2012). We would like to suggest that several of these lakes and bogs are suitable candidates for "iconic" status (see Kathryn Fitzsimmons' article -this issue), especially Lake Maratoto. ...
... Novel environment and temperature proxies have also been applied over the last decade, including using chironomid (midges) remains from lakes (e.g., Vandergoes et al., 2008), phytoliths (e.g. , diatoms (e.g. Page et al., 2010), and coleopteran (beetle) remains from lake and soil profiles (e.g. Marra et al., 2006Marra et al., , 2009. ...
... Evidence is growing that climate during the Holocene has been highly variable (e.g. Mayewski et al., 2004), with broad hemispheric changes upon which is superimposed regional variability (Page et al., 2010). Understanding glaciers as key indicators of global climate change has increased during recent years (e.g. ...
... New Zealand, in particular the Southern Alps, has been identified as one of the key areas for testing whether changes in North Atlantic thermohaline circulation during the Holocene force climate change in the Southern Hemisphere (Denton and Broecker, 2008). This is because, with a mid-latitude Southern Ocean setting, New Zealand climate responds to atmospheric and oceanic forcing from polar and sub-tropical regions (Cater et al., 2008;Page et al., 2010). Indeed, Neoglacial advances in New Zealand have been identified by Davis et al. (2009) as being important in assessing potential bipolarity of millennial-scale climate change in the northern and southern polar regions. ...
Evidence for the timings of inter-hemispheric climate fluctuations during the Holocene is important, with mountain glacier moraine systems routinely used as a proxy for climate. In New Zealand such evidence for glacier expansion during the late Holocene is fragmentary and is limited to glaciers in a narrow zone within the Southern Alps. Here, we present the first evidence for late-Holocene glacier expansion on the North Island of New Zealand in the form of two unconsolidated debris ridges on the south side of the stratovolcano, Mt Taranaki/Mt Egmont, at ~1920 m a.s.l. The two ridges are aligned north–south along the western and eastern sides of a small basin (Rangitoto Flat), which is formed between the main Taranaki cone (to the north), and the parasitic cone of Fanthams Peak (to the south). The approximate age of the ridges is constrained by dated eruptive events and the relationship between ridge locations and the spatial positioning of adjacent volcanic landforms. We propose the ridges formed as two lateral moraines on the margins of a cirque glacier during the final construction phase of Fanthams Peak between 3.3 and 0.5 ka BP, during late-Holocene time. This time interval accords with published cosmogenic 10Be dating of moraine-building episodes in the Southern Alps, indicating the Mt Taranaki moraines are a response to the same regional climatic forcings.
... 16 and S3). Catastrophic drainages along these valleys might have been anticipated by a lake level rising above the breccia rim during periods of extreme rainfall, which frequently occurred during the mid-late Holocene (Page et al., 2010;Brook et al., 2017). Alternatively, seismic perturbations while crater lakes are filled to near capacity can be sufficient to cause water to spill over (Gazetas, 1987;Cook et al., 2018;Schaefer et al., 2018). ...
Hydrothermal eruptions are the most violent and hazardous phenomena within geothermal fields. The largest of these may produce kilometer-sized craters and breccia deposits that are tens of meters thick. The geological and hydrothermal priming that leads to these types of eruptions is poorly understood. To understand large hydrothermal eruptions, we investigated a series of prehistoric events at the Rotokawa geothermal field in New Zealand. By revising the stratigraphy and distribution of hydrothermal breccia deposits and correlating these with componentry, crater morphology, and subsurface geological structure, we estimated the frequency, priming processes, triggers, and dynamics of multiple eruptions.
Seventeen large hydrothermal eruptions occurred centuries to millennia apart in the period from ca. 22 cal ka B.P. to ca. 3.4 cal ka B.P. Of six hydrothermal eruptions since ca. 7 ka, four produced oval-shaped craters up to 2 km in diameter, creating a broad, shallow depression within the geothermal field. The two youngest eruptions occurred northeast of earlier eruption centers and have narrower and elongated vents. We infer that in the central depression, newly formed craters rimmed by breccia deposits and high-relief country rock hosted temporary lakes tens of meters deep. Crater-lake breakout(s) and/or seismic events caused sudden pressure reduction above the hydrothermal aquifer, triggering hydrothermal eruptions. Northeast of the basin, hydrothermal alteration produced caprocks above intensively fractured areas. In this case, earthquakes are the most likely trigger for cap-rupture and eruption. All eruptions excavated shallow and large craters mostly within partially altered Oruanui Formation and pre-fragmented breccias. The size and localization of the eruptions was likely due to a combination of (1) availability of undisturbed porous ignimbrite hosting large thermal aquifers, (2) efficient crater excavation within or alongside pre-fragmented breccia, and (3) the location of fracture and fault zones that channeled deep fluid upflow, favoring priming processes.
This study highlights how an interplay of tectonic, magmatic, and hydrologic processes is responsible for the timing, dynamics, and ultimate size of hydrothermal eruptions in geothermal fields. Some events may be very large and destructive depending on the right priming and geological conditions.
... Polynesian deforestation in less accessible (and generally wetter) parts of the North Island occurred later at c. 400 years BP (Wilmshurst et al., 2004). In the drier eastern North Island, a human impact on geomorphic rates has been recorded by periods of accelerated lake sedimentation in the last 500 years of the Lake Tutira record (Page and Trustrum, 1997;Page et al., 2010). ...
Land-cover change attributed to human activity in Australia and New Zealand has had a transformational effect on landscapes over the past ~ 200 years. Initial effects attributed to indigenous populations were insignificant (Australia) or modest (New Zealand). European colonization represented a far more significant disturbance of land cover in both countries and has resulted in complete regime change in some geomorphic systems. This article reviews a selection of geomorphic responses to anthropogenic land-cover change and contrasts system behavior and response between Australia and New Zealand.
... There is growing evidence that the Holocene climate has been much more variable than previously thought (Page et al., 2010). A general trend towards increasing hurricane activity and intensity in the Atlantic basin has been observed since 1923 (Goldenberg et al., 2001;Grinsted et al., 2012), with the potential destructiveness of hurricanes increasing markedly since the mid-1970s (Emanuel, 2005). ...
Organic geochemical proxies (OGPs) preserved in coastal lake sediments have recently been used to reconstruct millennia-long hurricane records. Although OGPs (d 13 C, d 15 N and C/N) appear to be a more sensitive indicator of past storm events than traditional proxies used in paleotempestology, the method has not been tested in many lakes with modern data. In this study, we measured the d 13 C, d 15 N and C/N values of particulate organic matter (POM), along with the salinities and stable isotopic compositions of water (d 18 O and dD), in two coastal lakes on seasonal or much shorter time scales throughout a 3-year period. This work was intended to develop a better understanding of the dynamics of OGPs in these lakes. The time-series data not only show that geochemical properties of these lakes varied seasonally, reflecting variations in lake biological and environmental conditions, but displayed unique variation patterns in response to storms that caused either seawater flooding or freshwater flooding of the lakes. The data show that seawater flooding led to higher d 13 C and d 15 N values, with either lower or no change in the C/N ratios of the POM, generally consistent with a previously proposed conceptual model for detecting seawater flooding events. The data also show that freshwater flooding reduces d 15 N and increases the C/N values of POM, in addition to lowering the salinity, d 18 O and dD of lake water. These time-series modern data demonstrate the feasibility of detecting past storm events that were large enough to cause either seawater or freshwater flooding by examining variation patterns of multiple OGPs in coastal lake sediments. Applying this understanding to a sediment core from one of the study lakes (Mullet Pond, Florida), we reconstructed a centuries-long record of storms based on the variation patterns in OGPs together with 210 Pb ages. The OGP-based storm record suggests that 30 flooding events, including 15 seawater flooding and 15 freshwater flooding incidents, occurred over the last 165 years. Almost all of these flooding events can be matched (within the dating uncertainty) to the historic hurricanes that are known to have passed within 150 km of the study site. This further confirms that OGPs preserved in sediments in coastal lakes of Florida or similar regions may be used as reliable recorders of past storm activity.
... Occasionally, it is not obvious where one deposit begins and ends, or how to delineate between event and non-event sedimentation. For paleotsunami and storm investigations, it is often necessary to use a variety of dating techniques including tephra (Page et al., 2010), 14 C (Libby et al., 1949;Libby, 1955), 210 Pb (Faure, 1986), 137 Cs (DeLaune et al., 1978), pollen (Rich, 1970;Brugam, 1978), and industrial heavy metals (McCaffrey and Thomson, 1980;Bricker-Urso et al., 1989) to obtain a sediment core chronology to better link event deposits to the timing of flood events of interest. One should also carefully observe for evidence of normal grading (i.e., fining upward), which is often indicative of sediment settling out of suspension ( Fig. 23.3). ...
Tsunamis and storms can be incredibly destructive events. The direct observational record of important characteristics of these events, such as flooding height, inundation, and flow speed, is often lacking. Coupled with field data acquisition, a tremendous amount of additional information can be gained through experimental laboratory studies and by applying numerical inverse models to mud and sand deposits often associated with these events. This chapter outlines typical field and sampling approaches to study tsunami-derived deposits, common data modeling techniques for constraining/reconstructing flood conditions from resultant deposits, experimental investigations, and future directions in the field.
... Such layers are preserved in undisturbed areas of the lake and stacked in sediment sequences, providing a great potential to reconstruct long and continuous flood series which may be missed in a fluvial sequence . Across the globe, highresolution lake sediment palaeoflood records have been generated in the last two decades based on multi proxy analysis of sediment layers in upper river catchments (Bøe et al., 2006;Page et al., 2010;Wilhelm et al., 2012;Wirth et al., 2013;Schlolaut et al., 2014;Bird et al., 2016) as well as lower river reaches (Li et al., 2013;Reinwarth et al., 2013;Toonen et al., 2015;Munoz et al., 2018) but none from the Indian subcontinent. ...
... In this context, however, it should be noted that storms are generally highly episodic in time and therefore caution is required when storm activities are invoked as a mechanism for pulsed sedimentation events in geological studies. For example, in the sediments of Lake Tutira (Late Holocene), the average frequency of storms is suggested to be 53 years for the storm layers that are ≥1.0 cm thick (Page et al., 2010). ...
Trace fossils are sensitive indicators for environmental parameters (e.g., hydrodynamics, oxygen content, water depth, depositional rates, salinity), providing invaluable information to understand past depositional regimes not attainable from other sources of approaches. Here we report a new trace fossil assemblage dominated by a potential bivalve trace Parahaentzschelinia from the Lower Permian Snapper Point Formation, which records
deposition in a storm-influenced delta front environment. Dense populations of Parahaentzschelinia occurred in two sections, forming stacked Parahaentzschelinia ichnofabrics and representing multiple burrow adjustments of a single trace maker (tellinid bivalve) subsequent to rapid sedimentation events caused by possible seasonal/annual runoffs. Statistical analysis of burrow lengths and numbers of adjustments suggests up to seven sequences
of sediment accumulation events, supplying 3–13 cm thick clastic deposits at each time. A conservative sedimentation rate of 0.24 cm/year was estimated on the basis of two stacked Parahaentzschelinia ichnofabrics and the probable maximum lifespan of the modern tellinid genus. This rate is generally comparable to those derived from modern deltaic environments, lending further support to the interpretation that the ichnofabrics were
formed in and characteristic of a deltaic setting. Our research highlights the utility of stacked equilibrium structures as a sensitive indicator of certain depositional regimes, and its applicability for assessing sedimentation rates as well as depositional conditions in the geological past.
... Such settings afford the opportunity to uncover valuable data on general patterns of flooding and the frequency of singular extreme flood events (e.g. Bøe et al., 2006;Gilli et al., 2013;Jones et al., 2012;Moreno et al., 2008;Page et al., 2010;Parris et al., 2010;Schillereff et al., 2014;Schlolaut et al., 2014). This paper focuses upon the sedimentary record of Lake Quinault, a 14.6-km 2 moraine-dammed lake that sets base level for the upper Quinault River and serves as a potential trap for incoming fluvial sediment. ...
Sedimentological and geochemical analyses of gravity and piston cores retrieved from Lake Quinault, Washington, reveal an ~4000-year flood-dominated depositional record. Individual flood event layers are identified by combining core stratigraphy, sedimentology, and the ratio of incoherent to coherently scattered x-ray radiation (inc/coh) from µXRF (x-ray fluorescence) core scans. The inc/coh time series is used as a proxy for sediment grain size and, in combination with radiocarbon-anchored core age–depth models, enables the reconstruction of late-Holocene hydrologic variability for the Quinault River catchment. Decadal to centennial variability in inc/coh is interpreted to reflect trends in ocean-atmosphere teleconnections favorable for the formation of land-falling atmospheric rivers along the Pacific Ocean flank of the Olympic Mountains. Such processes likely modulate the rate of flooding and may explain notable increases in the frequency of flood event layers observed during the periods 2350–2450 cal. yr BP and the most recent century (AD 1910–2010). Understanding past hydrologic variability has important implications for the landscape and ecosystem response of Olympic Mountain catchments to future climate warming.
... Kelling and Mullin 1975;Allen 1982;Johnson 1989;Donnelly et al. 2001;Ito et al. 2001;Pochat et al. 2005;Woodruff et al. 2008;Dezileau et al. 2011;Otvos 2011;Phantuwongraj et al. 2013;Li et al. 2014). Impact of storms is relatively less observed on sedimentary succession of non-marine basins such as lacustrine basins and is much less mentioned in geologic records (Greenwood and Sherman 1986;Hamblin 1992;Basilici 1997;Weidong et al. 1997;Eden and Page 1998;Houser and Greenwood 2005;Li et al. 2007;Orpin et al. 2010;Page et al. 2010;Liu et al. 2012;Li et al. 2014;Wang et al. 2015;Nutz et al. 2017Nutz et al. , 2018. ...
Coastal environments are exposed to frequent and intense storm events which are one of the most important elements of sedimentation dynamics in nearshore environments. However, lacustrine storm deposits are rare Late Quaternary sediments of the Lake Van Basin, Turkey, which allow to analyse that kind of storm deposits in a closed lacustrine basin. The storm-induced sedimentary structures evaluated in these deposits reflect erosional and depositional storm processes and encompass erosional surfaces, graded bedding, wave-ripple crossbeds, parallel bedding, shell beds and biogenetic escape structures. They are present in both marginal and relatively deeper lacustrine facies. Evaluations of sedimentological and palaeontological features of storm deposits together with modern storm records of the Lake Van indicate intense storm effect on sedimentation.
... Lagoon records shows that such costal environments are good study areas to record past climatic and environmental changes, as well as extreme sea events. These fields of research were successfully applied in the western North Atlantic (Donnelly and Woodruff, 2007), northwestern Florida (Liu and Fearn, 2000;Lane et al., 2011;Das et al., 2013), the northeastern United States (Parris et al., 2010), the central Pacific (Toomey et al., 2013), southern Japan (Woodruff et al., 2009), western Australia (Nott, 2011), northeastern New Zealand (Page et al., 2010), northern Europe (Sorrel et al., 2012), or the western Mediterranean (Dezileau et al., 2011(Dezileau et al., , 2016Sabatier et al., 2012;Raji et al., 2015;Degeai et al., 2015). Such studies are still scarce in southern Tunisia, despite the importance of these topics in Mediterranean coastal areas. ...
Climate models project that rising atmospheric carbon dioxide
concentrations will increase the frequency and the severity of some extreme
weather events. The flood events represent a major risk for populations and
infrastructures settled on coastal lowlands. Recent studies of lagoon
sediments have enhanced our knowledge on extreme hydrological events such as
palaeo-storms and on their relation with climate change over the last
millennium. However, few studies have been undertaken to reconstruct past
flood events from lagoon sediments. Here, the past flood activity was
investigated using a multi-proxy approach combining sedimentological and
geochemical analysis of surfaces sediments from a southeastern Tunisian
catchment in order to trace the origin of sediment deposits in the El Bibane
Lagoon. Three sediment sources were identified: marine, fluvial and aeolian.
When applying this multi-proxy approach on core BL12-10, recovered from
the El Bibane Lagoon, we can see that finer material, a high content of the
clay and silt, and a high content of the elemental ratios (Fe ∕ Ca and Ti ∕ Ca)
characterise the sedimentological signature of the palaeo-flood levels
identified in the lagoonal sequence. For the last century, which is the period
covered by the BL12-10 short core, three palaeo-flood events were identified.
The age of these flood events have been determined by 210Pb and
137Cs chronology and give ages of AD 1995 ± 6, 1970 ± 9
and 1945 ± 9. These results show a good temporal correlation with
historical flood events recorded in southern Tunisia in the last
century (AD 1932, 1969, 1979 and 1995). Our finding suggests
that reconstruction of the history of the hydrological extreme events during
the upper Holocene is possible in this location through the use of the
sedimentary archives.
... • Area eroded by landslides for the period 1963-2001 was c. 27% greater than for previous periods • The average sediment delivery ratio (1887-2001) was 0.43 • Landslides mobilised 1.17 Mg C ha -1 year -1 • C recovery on landslide scars was c. 0.61 Mg C ha -1 year -1 A record of storm magnitude and frequency has also been established for the last c. 7000 years Page et al. 2010). Major findings included: ...
... The new calendar ages derived are generally consistent with ages obtained in several recent studies including those of Briggs et al. (2006), Gehrels et al. (2006), and Page et al. (2010). The preferred age for Whakaipo tephra in Lowe et al. (2008a) Table 3, were calibrated using the IntCal09 data set (Reimer et al., 2009) after correcting for the Southern Hemisphere offset (Table 3). ...
... The reported ages for these latter two uplifted terraces are slightly younger, so correlation with these is less likely. Earthquake 1 also correlates with the well-dated timing of a major landslide that formed Lake Tutira and several other lakes 30 km north of Ahuriri (Page et al., 2010). Elastic dislocation modeling by Cochran et al. (2006) suggested that the observed subsidence at this time at Wairoa and possible contemporaneous uplift at Mahia could be achieved in a Mw 7.9 earthquake on either the subduction zone or the offshore Lachlan fault (Fig. 2). ...
Sudden changes in microfossils and lithologies in Holocene sediments of a former tidal inlet on the Hikurangi subduction margin provide evidence of 10 large earthquakes. Studies were focused in three former embayments
where intertidal shelly sediment interfingers with freshwater and salt-marsh peat. Paleoelevation histories were reconstructed using the modern analogue technique with foraminiferal assemblages. Land elevation record analysis indicates 8–9 m of mid- to late Holocene tectonic subsidence occurred prior to 1.5 m of uplift during the A.D. 1931 Hawkes Bay earthquake. Chronologies of displacement events were constrained using 50 radiocarbon dates and three widespread air-fall tephras. We infer the following earthquakes: earthquake 1: 7.3–7.0 ka (-1.1 ± 0.3 m), earthquake 2: 5.6–5.1 ka (+0.4 ± 0.4 m), earthquake 3: 5.2–4.9 ka (-0.5 ± 0.5 m), earthquake 4: 4.4–3.8 ka (-0.6 ± 0.5 m), earthquake 5: 2.8–2.4 ka (-0.9 ± 0.5 m), earthquake 6: 1.73–1.70 ka (-1.0 ± 0.3 m), earthquake 7:
1.5–1.3 ka (-0.7 ± 0.5 m), earthquake 8: 1.04–0.89 ka (-1.2 ± 0.4 m), earthquake 9: 0.60–0.44 ka (-0.8 ± 0.6 m), and earthquake 10: A.D. 1931 (+1.5 ± 0.3 m). A further 1.6–2.6 m of subsidence could have occurred by gradual aseismic slip or in smaller earthquakes. The age ranges of four of the recognized earthquakes (earthquakes 1, 6, 8, and 9) overlap with other documented displacement events onshore along 250–600 km of the Hikurangi subduction margin, and with turbidites offshore 100–300 km to the north. These four are considered strong candidates
for large subduction-interface earthquakes. The other five inferred earthquakes are less strongly correlated with along-margin displacement events and offshore turbidites. These could have been caused by upper-plate
fault ruptures (like historic earthquake 10), but subduction-interface sources cannot be ruled out. This evidence for repeated coseismic vertical deformation suggests large coseismic slip on a part of the subduction interface
beneath Hawkes Bay that is currently dominated by aseismic creep processes, such as transient slow-slip events. This clearly indicates multiple slip processes are possible in a single location on a subduction interface.
... Storm genesis of ancient lake deposits below the contemporary wavebase has been seldom reported. However, stormy weather is common on land, which probably affects sedimentation in non-marine basins (Greenwood and Sherman, 1986;Milroy and Wright, 2000;Li et al., 2007;Horppila and Niemisto, 2008;Page et al., 2010;Liu et al., 2012;Li et al., 2014). Unlike marine environments, not only do large waves form in a lake environment during stormy weather conditions, but the storm may also induce seiche activity, i.e. whole lake sloshing movement (Ichinose et al., 2000;Horppila and Niemisto, 2008). ...
Recent progress in facies analysis helps to discriminate storm-induced deposits based on interpretation of sedimentary records of combination of oscillatory and unidirectional flows. Located in the southeastern corner of the Bohai Bay Basin in East China, the Lijin Sag is a NE-SW trending Cenozoic half-graben basin. Part of its Eocene deposits (Bindong deposits), which are deposited far away from a contemporary shoreline, consists of thin bedded fine-sandstones and siltstones, interlayed with dark-gray mudstones. New data from drilling wells permit an interpretation of the sedimentary facies. Based on seismic data, well log data, core data and thin-section analyses, storm-dominated deposits were recognized. Petrologic analysis shows that these deposits mainly consist of fine sand- to silt-sized lithic arkose. Detailed sedimentological analyses on lithofacies were conducted to address flowtypes dominant during their geneses. The beds are normal graded and contain Bouma-like sequences. The typical and complete sedimentary sequence consists of fining-upwards successions from an erosive base, followed by gravity flow-induced massive or faint laminated bed or soft sediment deformation structures and unidirectional-combined-oscillatory flow induced beddings, which are attributed to storm wave and seiche processes. From proximal to distal in plane, the Bindong storm deposits exhibit different lithofacies associations and sedimentary processes, i.e., the proximal facies is coarser and dominated by gravity flows, unidirectional flows and combined flows, and formed under strong hydrodynamic conditions; the transitional facies is formed under full range of flow regimes exhibiting a complete Bouma-like sequence; while the distal facies is dominated by gravity flows and pure unidirectional flows without influence of waves. During the deposition period of the Bindong deposits, the paleo-environmental characteristics, such as paleogeographic position, paleoclimate, provenance, paleo-water depth and paleotopography, provided an advantageous source and site for the formation of storm deposits.
... However, there are data on the frequency and magnitude of landslides, which is often linked to the frequency and magnitude of high intensity rainfall 45 . These data indicate that that there has been considerable variability at different time scales within the instrumental record 44 , and the longer proxy record 46 , with no long-term trends evident 47 . ...
Considering the sea level projections adopted by the DCCS, the key points are: a) Due to vertical land movements, the magnitude of relative sea level changes around the coast of the Wellington region varies significantly, and at centennial scales the effects of a major earthquake and the cumulative effect of slow-slip events are likely to dominate over the effects of global absolute sea level changes. b) It is evident that historic absolute sea level changes observed at Wellington do not agree with estimated historic global absolute sea level changes, or with CMIP5 projections for the available period of overlap this Century. Therefore, it is unlikely that projections of future global absolute sea levels provide a useful estimate of future sea levels in Wellington. c) Relative sea level changes at Wellington are not tracking either the CMIP5 projections for absolute sea level rise, or the MfE guidelines for planning purposes. 1. This is predominantly due to the lack of any statistically significant acceleration, which is an underlying assumption in both the projections and the guidelines. 2. Further, the CMIP5 models do not account for regional-scale variability in the processes driving sea level changes. It is clear that major ocean sub-basins experience different sea level changes at different times, which do not accord with the global average modelled by the sea level projections. Within the sub-basins there are also significant variations. This variability indicates that an anthropic sea level signal is unlike to be detectable at Wellington this Century. 3. Finally, it is clear that the relative contributions of the different components of sea level rise have been changing over the last few decades, which means the processes driving sea level changes are different to those assumed by the projections. d) As identified by the NIWA report on sea level trends and variability for the Wellington, it is unlikely that sea level rise will abruptly accelerate to the rates required to achieve the MfE guidelines. Therefore, the MfE guidelines are an over-estimate of potential sea level rise over the next century, and the values specified should be considered very unlikely. Considering the climate extreme projections adopted by the DCCS, the key points are: a) The projected changes in the frequency and magnitude of extreme wind and precipitation events are smaller than the natural variability of these events at any specific location or between locations within the Wellington region. This is due to the effects of local topography and the scale of the systems associated with extreme events. The projected changes are very unlikely to be detectable during this Century. b) The climate for the Wellington Region is strongly influenced by sea surface temperatures, the local topography, and a range of climate oscillations including ENSO, SAM and PDO. None of these is adequately incorporated into CMIP5 projections (and even less so in earlier projections). It is very unlikely that projections of global mean surface air temperature will provide any useful estimates of future climate for specific locations in the Wellington Region. c) The MfE guidelines utilise downscaled climate projections produced for the IPCC TAR. Apart from being more than a decade out of date, the methodology used was identified by the IPCC TAR as being flawed. The downscaled projections are also provided as a regional “average”, which is very unlikely to provide any useful estimate of future climate for any specific location. d) There appears to be fundamental disagreement over the relative influence of key climate oscillations on the climate of the Wellington Region, particularly the relative affects of ENSO, SAM and PDO on extreme events. Without a better understanding of the influence of these on the present climate of the Wellington Region, it is difficult to accept any projections based on assumed changes to their behaviour in the future. e) There is strong evidence that the CMIP5 models have over-projected future temperature changes, although there is on-going disagreement as to why this has occurred. The same problems are also evident to the earlier models used to produce the MfE guidelines. Until the discrepancies between the out-of-sample observations and model projections are resolved it would be imprudent to rely on model projections for planning purposes.
... These cyclic swings in storminess are not uncommon (e.g. Grant, 1977;Page et al., 2010) and may be why there has been more focus on post-harvesting issues around the country in recent years. ...
In 2012 an opinion piece in this journal on plantation forest harvesting and landscape response advocated a need to better manage the risk of high intensity, low frequency storms during the most vulnerable post-harvest period. With the expectation that there will be more storm damaging events associated with exotic forests we question:
• Whether sufficient resources are being directed towards identifying on-site and off-site values at risk, with a view to better management of adverse environmental effects of forest practices
• Whether more detailed mapping of terrain stability or erosion susceptibility, together with a risk analysis approach, would enable better preventative management at operational level rather than relying on corrective action as at present
• And, if so, could the Erosion Susceptibility Classification (ESC) developed for the National Environmental Standard (NES) for plantation forestry be used to decide if a reconnaissance-level or detailed-level of terrain stability mapping is required.
In posing these questions we provide a brief review of the international experience in assessing storm damage, re-introduce the concept of terrain stability mapping, promote the potential role of new technology in identifying site-specific areas susceptible to storm damage, and conclude with some recommendations.
... For example, previous high-resolution sediment cores recovered from lakes on the North Island (e.g. Page et al., 1994Page et al., , 2010Pepper et al., 2004;Augustinus et al., 2011) highlight the potential for terrestrial palaeoclimate archives from this key Southern Hemisphere location. Importantly, New Zealand is influenced by climatological patterns originating in both the tropics [El-Niño-Southern Oscillation (ENSO) and Interdecadal Pacific Oscillation (IPO)] and the Antarctic [Southern Annular Mode (SAM)]. ...
Laminated sediments in Lake Ohau, Mackenzie Basin, New Zealand, offer a potential high-resolution climate record for the past 17,000 years. Such records are particularly important due to the relative paucity of detailed palaeoclimate data from the Southern Hemisphere mid-latitudes. This paper presents outcomes of a study of the sedimentation processes of this temperate lake setting. Hydrometeorological, limnological and sedimentological data were collected over a fourteen-month period between 2011 and 2013. These data indicate that seasonality in the hydrometeorological system in combination with internal lake dynamics drives a distinct seasonal pattern of sediment dispersal and deposition on a basin-wide scale. Sedimentary layers that accumulate proximal to the lake inflow at the northern end of the lake form in response to discrete inflow events throughout the year and display an event stratigraphy. In contrast, seasonal change in the lake system controls accumulation of light (winter) and dark (summer) laminations at the distal end of the lake, resulting in the preservation of varves. Overall, this study documents the key processes influencing sedimentation in the lake, resulting in a sound climate-proxy model for the generation of a new clastic varve palaeoclimate record from the Southern Hemisphere mid-latitudes.This article is protected by copyright. All rights reserved.
... The resultant current speed is of the order of 10 − 1 m/s, which may not be significant for coarse-grained sediments, but can lead to long distance transport for fine-grained sediments. Superimposed upon these normal hydrodynamic conditions, extreme events (hurricanes, typhoons, winter cold-air outbreaks and earthquakeinduced tsunami, etc.) add further complicated interactions to the coastal-shelf environment (Buynevich et al., 2004;Page et al., 2010;Warner et al., 2012). ...
... gravity flows and slope failures (Mulder et al., 2001;Puig et al., 2004). Repeated storms have occurred along the northern Hikurangi Margin over the Late Holocene (Page et al., 2010), and are likely to have affected the seafloor by remobilising surficial sediments of the shelf or to have triggered sediment liquefaction (Lee and Edwards, 1986;Ma et al., 2010;Goldfinger et al., 2012). Puig et al. (2004) characterized sediment gravity flows directed downcanyon during storms on the California margin, and Mulder et al. ...
... Deposition of particularly old material on the shelf during the middle Holocene (Fig. 11) is consistent with independent evidence for climatic conditions conducive to increased erosion around this time. Study of Holocene deposits from nearby Lake Tutira indicates that the interval between about 4–5 kyr BP was characterized by a higher-than-average storm frequency in northeastern New Zealand (Page et al., 2010; Gomez et al., 2011; Upton et al., 2013). Variations in southern Pacific atmospheric circulation linked to the El Niño-Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) may have led to a period of intensified storm activity (Gomez et al., 2011Gomez et al., , 2013), and to increased riverine sediment flux to the ocean (Upton et al., 2013). ...
... New Zealand's climatically sensitive location, combined with an environmentally responsive landscape comprising short, steep, and well-connected catchments (cf. Fryirs et al., 2007;Macklin et al., 2010), is ideally placed for detecting changes in hydrological and geomorphic systems due to oscillation and interaction of these major climate drivers (e.g., Page et al., 2010). ...
... About 10 years after the initiation of research into modern marine storm facies, the terrigenous aspect of such deposits was also investigated (e.g., Kelling and Mullin, 1975;Kreisa, 1981). More recently, Page et al. (2010) and Orpin et al. (2010) identified several vast Holocene storms in New Zealand and their response in local lacustrine strata records. Modern lacustrine turbidite deposits in mountain areas of the Alps were studied by Fanetti et al. (2008), but he apparently omitted vast storms as trigger mechanisms for these deposits. ...
A Late Cretaceous tempestite in the northern Songliao Basin, China, was studied based on thin-section and granularity analyses of borehole samples. The results indicated that the local tempestite can be categorized into several clastic constituent types, which include bottom erosion structures, graded beds, hummocky cross stratification (HCS), parallel beds, wave marks, and bioturbation structures. Based on these sedimentary characteristics and vertical sequence combinations, four tempestite sedimentary models were developed: (I) an autochthonous tempestite facies, (II) an allochthonous tempestite fades (the proximal subfacies), (III) a second allochthonous tempestite facies (the distal subfacies), and (IV) a turbidite facies. (C) 2012 Published by Elsevier Ltd.
... This may have had also consequences for storm frequencies and direction of moisture-bringing air masses. The storm event record of Lake Tutira, situated close to Hawke's Bay (*330 km SSW of Lake Pupuke,Fig. 1) provides evidences for changes in storm frequencies and magnitudes (Eden and Page 1998; Page et al. 2010). Periods of major storm activity occurred at 500–700, 1,100–1,250, 1,850–2,100, 2,850–3,200, 3,600–4,000, 4,300–4,500, 4,700–4,900, 5,700–5,900, and 6,850–6,900 cal. ...
Maar lakes in the Auckland Volcanic Field are important high-resolution archives of Holocene environmental change in the Southern Hemisphere mid-latitudes. Stable carbon and nitrogen isotope analyses were applied on bulk organic matter and the green alga Botryococcus from a sediment core from Lake Pupuke (Auckland, North Island, New Zealand) spanning the period since 7,165 cal. year BP. The origin of organic matter was established using total-organic–carbon-to-nitrogen ratios (TOC/TN) as well as organic carbon (δ13COM) and nitrogen (δ15N) isotope composition of potential modern sources. This approach demonstrated that the contribution of allochthonous organic matter to the lake sediment was negligible for most of the record. The sedimentary TOC/TN ratios that are higher than Redfield ratio (i.e. >7) are attributed to N-limiting conditions throughout the record. Variations of nitrogen and carbon isotopes during the last 7,165 years are interpreted as changes in the dominant processes in the lake. While epilimnetic primary productivity controlled isotope composition before 6,600 cal. year BP, microbial processes, especially denitrification and methane oxidation, caused overall shifts of the δ15N and δ13C values since the Mid-Holocene. Comparisons with climate reconstructions from the Northern Island suggest that changes in the wind-induced lake overturn and a shift to more pronounced seasonality were the most likely causes for lake-internal changes since 6,600 cal. year BP.
The ~25.5‐ka Ōruanui supereruption (Taupō volcano, New Zealand) erupted >1100 km3 of pyroclastic material during the Last Glacial Maximum. The impacts of this event on climate and the New Zealand environment remain unresolved, particularly on ecological timescales. Using sediment cores from Onepoto maar palaeolake, Auckland (~240 km upwind from source), we have analysed pollen assemblages at contiguous 1‐mm intervals, around an intact 3‐cm layer of the Kawakawa‐Ōruanui Tephra to resolve and assess post‐eruption vegetation impacts and landscape recovery. Sediments immediately above the tephra record a decline in the relative abundance of the dominant canopy species of Fuscospora, and concurrent increase in the abundances of grasses, herbs, ferns and shrubs. These changes reflect a brief (<10 years) part‐defoliation of canopy trees, permitting more light to penetrate and to encourage sub‐canopy vegetation growth. A short‐lived volcanogenic cooling inferred from Antarctic ice core records may have contributed to the changes but cannot be separated from the immediate and direct ecological impacts of ashfall on vegetation following the eruption. Our results, here applied to the world's most recent supereruption, more generally demonstrate the value of millimetre‐scale stratigraphic pollen analysis from non‐varved lacustrine sediments as a tool for assessing past eruptive impacts on sub‐decadal timescales.
Landscapes are dynamic and respond to a range of internal and external processes that influence the balance between erosion and sedimentary preservation. Documenting past depositional and erosional events is fundamental to understanding processes of landscape formation and unpacking the interplay between stream power and sediment supply. Here, we focus on a paleo-landscape reconstruction of the Hautapu River valley in New Zealand, with the aim of investigating the influence of volcanic activity, uplift, and climate on fluvial and landscape dynamics. The study area is characterized by Pliocene marine sediments superimposed by a suite of Late Pleistocene river terraces and associated cover beds. Volcaniclastic deposits of the Mataroa Formation, derived from partial collapse of the Mt. Ruapehu stratovolcano, overlie the oldest terrace level and are used to reconstruct the paleo-landscape. Depth of incision is obtained by comparing remnant terrace surfaces to present day topography. An early channel switching event after c. 125–150 ka is correlated to increased sediment supply and resultant fluvial aggradation following emplacement of the Mataroa Formation. Remobilization of volcaniclastic material resulting in blockage and channel avulsion is considered to have redirected the flow of the Hautapu River into the Mangoiwa Stream valley, evidenced by the gentle gradient, wide and more deeply incised valley geomorphology. A more recent channel abandonment event at c. 15 ka is correlated to subsidence of the Ruapehu Graben and piracy by the Whangaehu River, effectively isolating the Hautapu catchment from Mt. Ruapehu and its active source of volcaniclastic sediment. Simultaneous abandonment of the Mangoiwa Stream valley and re-establishment of the Hautapu River into its former channel is attributed to uplift, pre-existing valley morphology and strength contrasts between the valley fill and its underlying marine succession. Accelerated erosion during cold climate phases is considered to have effectively stripped regolith from deforested highlands leading to a reset of the landscape, greatly increased sediment yields and fluvial aggradation. Subsequent landscape stabilization and ongoing regional uplift during climate amelioration is associated with a reduction in sediment supply and excess stream power, leading to incision and knickpoint retreat.
A recently discovered upland paleolake (Redpath Lake) provides evidence of the expansion of lowland podocarp temperate forest to higher elevations within the tectonically active Waipaoa Sedimentary System (WSS), eastern North Island, New Zealand, during the Last Glacial-Holocene Transition. Interpreted as a localised landslide-dammed lake, lithofacies analyses indicate deposition and preservation in a low energy, sub-aqueous, lacustrine environment. Robust Bayesian-derived age-depth models constrained by key tephra fall beds and independent ¹⁴C dating (n = 7) indicate storm-bed frequency of c. 226 yrs on average. The absence of extensive soft-sediment deformation or lake-bed tilting implies that seismic shaking was insignificant during the Lake’s c. 12 ka yr (17.3–5.5 cal ka BP) existence. Pollen spectra extracted from lacustrine deposits include a mix of montane shrubland and lowland podocarp species spanning a well-dated c. 2200-year (c. 16.3–14.1 cal ka BP) period coeval with a phase of significant climate amelioration (late NZCe–5/NZce-4 mild episode), based on biotic proxies during the latter part of the climatically variable Last Glacial-Interglacial Transition (LGIT) (c. 18.2–11.8 cal ka BP). These pollen spectra represent the first New Zealand record of replacement of montane shrublands in terrestrial uplands of the WSS were replaced by lowland podocarp forest.
Variability of the Southern Hemisphere westerly winds (SWW) are the dominant feature of the climatology of the Southern Hemisphere and they are reflected in the Southern Annular Mode (SAM) which is defined as the difference in the zonal mean sea level pressure at 40°S and 65°S and is expressed as a latitudinal movement in the westerly circulation system. Meteorological data suggests that the SAM plays an important role in modern weather and climate of the Southern Hemisphere. Palaeostudies show that the westerly circulation system established its northern limits of present day airflow by the mid Holocene but the records from South America remain out of phase with those from the SW Pacific. In this study we report on the development of a flood frequency hydrological proxy that is based on the recognition of rapidly deposited layers preserved in lake sediments in southern South Island, New Zealand. Four distinct climate states can be identified: low storm frequency between 10 and 8 cal ka BP; moderate storm frequency between 8 and 5.5 cal ka BP, high storm frequency between 5.5 and 4 cal ka BP and low storm frequency between 4 cal ka BP and 750 cal a BP. A post-750 cal a BP increase storm frequency is likely to be a result of Polynesian vegetation disturbance. These four distinct climate states are driven by variations in the strength or persistence of westerly airflow. Comparison with similar records from east coast of the North Island, New Zealand and Ecuador suggest that all three sites experienced an increase in storm frequency in the middle Holocene. Divergence in the records in the late Holocene can be attributed to variability in the strength of ENSO and SAM in different locations.
L’objectif de cette recherche est de développer des approches méthodologiques afin de reconstituer les évènements extrêmes du passé aux échelles temporelles holocène, millénaire et anthropocène. La méthodologie repose sur une approche pluridisciplinaire employant la sédimentologie, la dendrochronologie, la climatologie et l’histoire du climat. Ces approches ont été appliquées dans trois terrains d’étude : l’Île d’Yeu, les Traicts du Croisic et la Petite mer de Gâvres. Plusieurs évènements extrêmes anciens ont été identifiés et corrélés entre eux par les différentes approches. À l’échelle holocène, les périodes de forts impacts tempétueux semblent être liées aux phases de refroidissement climatique de l’atlantique nord : 600-300, 1700-1100, 2900-2500, 3500-3300, 5500-5100 et 7700-7100 cal y BP. Cependant, à l’échelle millénaire, les liens avec le changement climatique du Petit Âge Glaciaire et l’Oscillation Nord Atlantique sont plus complexes à appréhender. Le couplage des données sédimentologiques avec les archives historiques caractérise seize évènements extrêmes à forts impacts environnementaux et sociétaux. L’un d’entre eux, survenu durant l’hiver 1351 – 1352 (n.st) AD, est qualifié d’« évènement millénaire ». À l’échelle de l’anthropocène, quatre dates principales ressortent de l’analyse sédimentologique : 1990, 1972, 1940 et 1896 AD. La dendrochronologie permet de détecter dix-neuf hivers tempétueux depuis 1955 AD, ce qui a été confirmé par les archives météorologiques et les données de réanalyse. Ces différentes approches permettent d’accroître avec plus de précision la connaissance des aléas côtiers.
The dramatic changes that occurred to the post-glacial landscape in the headwaters of the Waipaoa River basin are a consequence of perturbations about the equilibrium that exists between the rate of tectonic uplift and fluvial incision. At times when the amount of coarse sediment delivered to channels exceeds the capacity of streams to remove it, the channel bed rises at the rate of tectonic uplift. Once bedload overcapacity is replaced by undercapacity and the alluvial cover is depleted, streams reestablish contact with bedrock and recuperate the time lost to fluvial incision. The first major perturbation occurred during the final phase of the last glaciation (ca. 33-17.5. cal.ka), when aggradation was driven by a climate-forced variation in the relative supplies of sediment and water. We suggest that the subsequent transformation of channels in the headwaters of the Waipaoa River basin, from alluvial to bedrock, occurred as the atmospheric and oceanic circulation converged on their contemporary patterns ca. 12. cal.ka. A second major perturbation that continues to the present began ca. 1910-1912. CE, when a massive increase in sediment load was accompanied by a modest increase in water discharge after the native vegetation cover in the headwaters was replaced by pasture. The processes of terrace creation and incision are inherently unsteady, and in five interim cases incision was arrested by a transient increase in the thickness of the alluvial cover that was a response to climatic forcing. Events that disrupted the native vegetation cover in the headwaters also modulated patterns of sediment dispersal and accumulation in other parts of the fluvial system and caused rapid, storm-driven infilling of the Poverty Bay Flats. Tectonic subsidence dictates the course of the Waipaoa River across Poverty Bay Flats which, because the modern rate of floodplain construction by vertical accretion is rapid relative to the amount of destruction by lateral channel migration, has remained virtually unchanged for the past 100 years. During this time the channel assumed a narrower, deeper form that is in equilibrium with the contemporary supply of sediment and hydraulic regime.
Ancient lacustrine storm-deposits that act as petroleum reservoirs are seldom reported. The Lijin Sag, which is located in the southeastern corner of the Bohai Bay Basin in East China, is a NE–SW trending Cenozoic half-graben basin. Some of its Eocene deposits (Bindong deposits) were interpreted as lacustrine tempestites. The Bindong tempestites, which developed in the lower part of the upper fourth member of the Shahejie Formation (Es41), constitute a new kind of petroleum reservoir and are novel petroleum exploration targets in the Bindong Area. However, the characteristics of the Es41 Bindong tempestite reservoirs and their controlling factors are poorly understood. Point-count analyses of thin sections, scanning electron microscope image analyses, X-ray diffractometry data, and the petrophysical parameters of the Bindong tempestite reservoirs were utilized to estimate the reservoir quality. The reservoirs have undergone significant diagenetic alteration, which can be divided into negative and positive aspects. The negative alteration includes compaction, authigenic minerals, and cementation such as carbonates, clay minerals and overgrowths of quartz and feldspar. The uneven distribution of carbonate cement increased the reservoir's heterogeneity, with carbonate cement commonly precipitating along the sandstone-mudstone contacts. The primary porosity was severely reduced because of compaction and extensive carbonate cementation. Positive alteration includes dissolution, carbonate cementation, undercompaction and fractures. Carbonate cementation exhibited both positive and negative effects on the reservoir quality. Overall, the objective reservoir quality is quite poor. A quantitative evaluation of the reservoirs' potential was conducted. The cutoff values of several of the reservoir's parameters were calculated. The lower limits of the porosity and permeability are 8.35–5.85% and 1.2587–0.2753 mD, respectively, depending on the depth. The upper limits of the carbonate and mud content are approximately 18.5% and 9–10%, respectively. A fundamental understanding of these characteristics will provide necessary information for extracting hydrocarbons from analogous subsurface reservoirs.
Based on core observation and grain analysis, the lacustrine storm deposits in Huangshanjie Formation in northern Tarim Basin were studied. The results show that they are mainly composed of middle-fine sandstone and siltstone, being short of coarse sandy conglomerate with bounder clay locally developed. Several typical storm sedimentary structures are recognized, including surface of scour, hommocky cross stratification, graded bedding, wave-ripple bedding, wavy bedding, deformation structures, as well as life-escaping structures. Grain-size probability curves show obvious two-section pattern, with saltation population mainly developed. The ideal storm sequence of this area is a Bouma-like sequence, and from bottom to top consists five segments, namely graded bedding (Sa), parallel bedding (Sb), hummocky cross stratification (Sc), wave-ripple or wavy bedding (Sd), mudstone segment (Se), with Sabde, Sace, Scde and Sde sequences commonly developed. There are two provenances for storm deposits in this area, of which one comes from northwestern Kalpin Uplift, and the other comes from northeastern Kuruketage Uplift. Judging from the sedimentary features and its relationship with provenances, the tempestites of this area are transtional or distal tempestite.
Annually laminated sediments collected from Lake Ohau, New Zealand offer an opportunity to generate a high-resolution paleoclimate record for the Southern Hemisphere mid-latitudes. Correlation between regional precipitation and synoptic climate indices like the Southern Annular Mode, paired with a correlation between Ohau catchment precipitation, lake inflow and suspended sediment yield suggest that the Lake Ohau varves are a potentially powerful tool for estimating the amplitude, timing and interdependence of different climate modes operating in the Southern Hemisphere mid-latitudes over time. A robust chronology and sound climate-proxy model are fundamental requirements for all high-resolution paleoenvironmental records. Here we present a chronology derived from layer counts, and 137Cs and 210Pb ages for the top 60 cm of sediments from the distal basin of Lake Ohau that confirm the varved natured of the sedimentary sequence. Sedimentary facies of different varve motifs are used to develop a hydroclimate-proxy model which links stratigraphy to seasonal hydrology. To establish this relationship we use a model accuracy statistic, which shows a quantitative difference between the annual hydrographs associated with each of three primary varve motifs. Distribution of above average inflow events points to summer and autumn hydrologic regimes as the primary control on the deposition of different motifs. This relationship between varve characteristics and hydrology will serve as a tool to reconstruct lake inflow, and by extension precipitation, on an annual basis throughout the late-Holocene for the South Island of New Zealand.
Mémoire de Géosciences-Rennes n°142. ISBN : 2-914375-83-2
Quantifying how hillslopes respond to river incision and climate change is fundamental to understanding the evolution of uplifting landscapes during glacial-interglacial cycles. We investigated the interplay among uplift, river incision, and hillslope response in the nonglacial Waipaoa River catchment located in the exhumed inner forearc of an active subduction margin on the East Coast of the North Island of New Zealand. New high-resolution topographic data sets (light detection and ranging [lidar] and photogrammetry) combined with field mapping and tephrochronology indicate that hillslopes adjusted to rapid latest Pleistocene and Holocene river incision through the initiation and reactivation of deep-seated landslides. In the erodible marine sedimentary rocks of the Waipaoa sedimentary system, postincision deep-seated landslides can occupy over 30% of the surface area. The ages of tephra cover beds identified by electron microprobe analysis on 80 tephra samples from 173 soil test pits and 64 soil auger sites show that 4000-5000 yr after the initiation of river incision, widespread hillslope adjustment started between the deposition of the ca. 14,000 cal. yr B.P. Waiohau Tephra and the ca. 9420 cal. yr B.P. Rotoma Tephra. Tephrochronology and geomorphic mapping analysis indicate that river incision and deep-seated landslide slope adjustment were synchronous between main-stem rivers and headwater tributaries. Hillslope response in the catchment can include the entire slope, measured from river to ridgeline, and, in some cases, the interfluves between incising subcatchments have been dramatically modified through ridgeline retreat and/or lowering. Using the results of our landform tephrochronology and geomorphic mapping, we derive a conceptual time series of hillslope response to uplift and climate change-induced river incision over the last glacial-interglacial cycle.
Robust regional seismic-hazard assessments require millennialscale paleoseismic histories that extend far beyond the range of historical nd instrumental data. However, it is difficult to resolve the probability density functions for earthquake recurrence from the limited number of major to great earthquakes most paleoseismic records contain. Lake sediment records are repositories of information about paleoearthquake recurrence, with a sensitivity and fidelity over millennial time scales that suggest that they have the potential to yield reliable estimates of the recurrence distribution. We present a 7000 yr paleoseismic record from Lake Tutira (North Island, New Zealand) that ranks among the most detailed Holocene paleoearthquake chronologies available worldwide, and use it to empirically constrain the recurrence distribution of earthquakes with a minimum groundshaking intensity of MMI 7 in one of New Zealand's most seismically active areas. Our analysis confirms that a Poisson process describes the waiting times of single moderate to major and/or great paleoearthquakes in the Hawke's Bay region.
Increased catchment erosion and nutrient loading are commonly recognized impacts of deforestation on global wetlands. In contrast,
an increase in water availability in deforested catchments is well known in modern studies but is rarely considered when evaluating
past human impacts. We used a Budyko water balance approach, a meta-analysis of global wetland response to deforestation,
and paleoecological studies from Australasia to explore this issue. After complete deforestation, we demonstrated that water
available to wetlands increases by up to 15% of annual precipitation. This can convert ephemeral swamps to permanent lakes
or even create new wetlands. This effect is globally significant, with 9 to 12% of wetlands affected, including 20 to 40%
of Ramsar wetlands, but is widely unrecognized because human impact studies rarely test for it.
Records of the frequency and magnitude of floods are needed on centennial or millennial timescales to place increases in their occurrence and intensity into a longer-term context than is available from gauged river-flow and historical records. Recent research has highlighted the potential for lake sediment sequences to act as a relatively untapped archive of high-magnitude floods over these longer timescales. Abyssal lake sediments can record past floods in the form of coarser-grained laminations that reflect the capacity for river flows with greater hydrodynamic energy to transport larger particles into the lake. This paper presents a framework for investigating flood stratigraphies in lakes by reviewing the conditioning mechanisms in the lake and catchment, outlining the key analytical techniques used to recover flood records and highlighting the importance of appropriate field site and methodology selection. The processes of sediment movement from watershed to lake bed are complex, meaning relationships between measureable sedimentary characteristics and associated river discharge are not always clear. Stratigraphical palaeoflood records are all affected to some degree by catchment conditioning, fluvial connectivity, sequencing of high flows, delta dynamics as well as within-lake processes including river plume dispersal, sediment focussing, re-suspension and trapping efficiency. With regard to analytical techniques, the potential for direct (e.g., laser granulometry) and indirect (e.g., geochemical elemental ratios) measurements of particle size to reflect variations in river discharge is confirmed. We recommend care when interpreting fine-resolution geochemical data acquired via micro-scale X-ray fluorescence (μXRF) core scanning due to variable down-core water and organic matter content altering X-ray attenuation. We also recommend accounting for changes in sediment supply through time as new or differing sources of sediment release may affect the hydrodynamic relationship between particle size and/or geochemistry with stream power. Where these processes are considered and suitable dating control is obtained, discrete historical floods can be identified and characterised using palaeolimnological evidence. We outline a protocol for selecting suitable lakes and coring sites that integrates environmental setting, sediment transfer processes and depositional mechanisms to act as a rapid reference for future research into lacustrine palaeoflood records. We also present an interpretational protocol illustrating the analytical techniques available to palaeoflood researchers. To demonstrate their utility, we review five case studies of palaeoflood reconstructions from lakes in geographically varied regions; these show how lakes of different sizes and geomorphological contexts can produce comprehensive palaeoflood records. These were achieved by consistently applying site-validated direct and proxy grain-size measurements; well-established chronologies; validation of the proxy-process interpretation; and calibration of the palaeoflood record against instrumental or historical records.
The Kapiti Coast consists of a coastal plain that merges with cuspate foreland that has been accreting in the lee of Kapiti Island since sea level reached a maximum between 7,000 and 8,000 BP. The current average rate of accre-tion varies between 0.4-0.6 m.y-1, which is consistent with the long-term rate over the Holocene. Despite the overall trend for accretion, some areas have experienced coastal erosion that has affected coastal properties since 1900. The areas consistently affected by erosion are located south of the Tikotu Creek (Raumati and Paekakariki).
The sediments of the Kapiti coastal plain are primarily derived from the major rivers to the north (170 kt.y-1) and local rivers (28 kt.y-1). The supply of sediment appears to be affected by climatic oscillations influencing pre-cipitation and windiness, potentially resulting in a cycle of longshore sediment transport of 50-60 years dur-ation. This cycle appears to significantly affect the migration of inlet systems along the coast.
There is no compelling evidence of any relationship between prehistoric and historic shoreline movement and sea level and climatic changes for the Kapiti Coast. There is evidence that local earthquakes producing abrupt changes in relative sea level, and tsunamis have affected the shoreline stability.
The methodology adopted by Coastal Systems Ltd (CSL) was analysed, and this report discusses the various as-pects that influence the Coastal Erosion Prediction Distance (CEPD) lines produced. The major concerns with the methodology are:
1. The methodology systematically maximises the CEPD at almost every step in the process in order to produce a conservative result. Consequently, the predicted CEPD lines greatly overestimate the risk of coastal erosion for the Kapiti Coast. Hence, it is unreasonable to assume that all of the properties seaward of the CEPD will experience erosion during the prediction periods of 50 or 100 years. The available data indicate that there is in fact a low risk that the majority of properties seaward of the CEPD will be affected by coastal erosion within this time period.
2. Components of the methodology used have been recognised as inappropriate for the purpose. The methodology also did not consider the morphodynamic differences along the coast associated with changing sediment type and foredune vegetation, which influence erosion processes and hence ero-sion hazard.
3. A risk assessment of coastal erosion hazard should include a probabilistic analysis of the drivers and impacts related to coastal erosion. This was not done, so there are no data to quantify risk, or permit a cost-benefit analysis of any proposed management responses.
Applying the CSL methodology as a hindcast for the interval 1950-2007 demonstrated that the methodology is a very poor predictor of past coastal erosion (4% success compared to 87% assuming past trends). This does not provide confidence in the reliability of the methodology for predicting future coastal erosion. Given the identified problems, the CSL methodology cannot be used to make an assessment of the risks of coastal erosion at any point on the Kapiti Coast, and an alternative probabilistic approach should be utilised.
One alternative approach is to evaluate the sediment budget the Kapiti Coast, in order to identify areas unlikely to stop accreting, those that may start eroding in the future, and those that are in sediment deficit. At present the average accretion rate for the Kapiti Coast is of the order 1.2 kt.y-1, which is 2 orders of magnitude smaller than the available sediment supply (~200 kt.y-1). Therefore, it is unlikely that most of the shoreline will change to a long-term sediment deficit.
The determination of the CEPD lines should differ to account for the availability of sediment. Areas with a sedi-ment surplus, and hence accreting, should require a CEPD primarily based on the short-term storm event ero-sion. This is best determined from shore profile data, which would provide the probability distribution for shore-line recession caused by storms.
Areas with an existing or potential sediment deficit should be subject to a process-based probabilistic analysis of the CEPD. An example for the Kapiti Coast based on the methodology of Ranasinghe et al (2012) is given in the report.
Tephras of late Quaternary age are found interbedded with local laharic and fluvial deposits, and with distal rhyolitic tephras from Taupo and Okataina Volcanic Centres. Tephras are identified from their field characteristics and stratigraphic positions relative to dated rhyolitic tephra marker beds. The radiocarbon ages of these rhyolitic tephras proivde a chronology for the andesitic tephras, dating back to 22 500 yr BP. All tephras erupted from Tongariro Volcanic Centre are grouped into two subgroups: the Tongariro Subgroup (redefined) and the newly defined Tukino Subgroup. Tephras identified on the southeastern Mt Ruapehu ring plain are grouped into seven formations on the basis of lithology. -from Authors
This paper is the result of a study of the shallow Mw = 7.8 Hawke's Bay earthquake which occurred in the North Island of New Zealand, 2 February 1931(UT), and which was the final spur to the production of the first earthquake loadings code in New Zealand issued in 1935. This earthquake was a direct hit on two provincial towns (Napier and Hastings) and was the most damaging in New Zealand's history, causing the most casualties, major fires, and much damage to the built and natural environments. It gives the first overall description of the damage (to the buildings and lifelines) in this major event in modern earthquake engineering terms, and presents the first intensity map for the event determined directly in the Modified Mercalli (MM) scale. The zone which experienced the highest intensity (MMlO) was confined to a modest area of onshore land (about 300 km2) above the centre of the rupture surface.
Dating initial colonisation and environmental impacts by Polynesians in New Zealand is controversial. A key horizon is provided by the Kaharoa Tephra, deposited from an eruption of Mt Tarawera, because just underneath this layer are the first signs of forest clearance which imply human settlement. The authors used a log of celery pine from within Kaharoa deposits to derive a new precise date for the eruption via "wiggle-matching" - matching the radiocarbon dates of a sequence of samples from the log with the Southern Hemisphere calibration curve. The date obtained was 1314 ± 12 AD (2σ error), and the first environmental impacts and human occupation are argued to have occurred in the previous 50 years, i.e. in the late 13th - early 14th centuries AD. This date is contemporary with earliest settlement dates determined from archaeological sites in the New Zealand archipelago.
(1) The South Pacific Convergence Zone (SPCZ), one of the most extensive features of the global atmospheric circulation, is shown to vary its location according to both the polarity of the El Nino/Southern Oscillation (ENSO), and of the Interdecadal Pacific Oscillation (IPO). We first demonstrate that the IPO can be regarded as the quasi-symmetric Pacific-wide manifestation of the Pacific Decadal Oscillation that has been described for the North Pacific. Shifts in the position of the SPCZ related to ENSO on interannual time scales and to the IPO on decadal time scales appear to be of similar magnitude and are largely linearly independent. A station pressure-based index of variations in SPCZ latitude is shown to be significantly related to the polarity of the IPO when ENSO influences are accounted for. Movements of this sensitive section of the SPCZ have occurred in phase with those of the IPO since the 1890s. INDEX TERMS: 1620 Global Change: Climate dynamic (3309); 3319 Meteorology and Atmospheric Dynamics: General circulation; 3339 Meteorology and Atmospheric Dynamics: Ocean/atmosphere interactions (0312, 4504); 3309 Meteorology and Atmospheric Dynamics: Climatology (1620)
Hawke's Bay is a region of New Zealand where earliest settlement of indigenous people may have occurred. A sedimentological and palynological study of lake sediments from a small catchment was undertaken to reconstruct erosion, vegetation, and fire histories to determine human environmental impact, and thus add to knowledge of the timing of initial settlement of New Zealand. Precise dating was an essential facet of the research because of the short time span of human occupation in New Zealand. A chronology is proposed based on accelerator mass spectrometry (AMS) radiocarbon dating of palynomorph concentrates. Known-age tephras were used as a check on the validity of the 14C ages obtained using this technique, which is being developed at Rafter Radiocarbon Laboratory. Two episodes of sustained erosion occurred between about 1500 and 1050 BC with a period of ~50 yr at about 1300 BC when no erosion occurred. Five episodes of erosion of very short duration occurred at about 625 BC, 450 BC, 100 BC, AD 950, and AD 1400. Erosion probably resulted from landslides induced by earthquakes or severe storms, with the exception of the last event which coincides with local burning and is probably a consequence of this. A conifer/broadleaved forest surrounded the lake until soon after AD 1075-1300, when a dramatic decline in pollen of forest plants and an increase in charcoal occurred. Forest was replaced by fire-induced scrub, interpreted as a result of anthropogenic burning by prehistoric Polynesians. A further decline in woody vegetation occurred when European-introduced plants appear in the pollen record and extensive pasture was established.
Widespread destruction of lowland podocarp/hardwood forests in Hawke's Bay followed permanent Maori settlement of the region. Forests cleared by fires were rapidly replaced with a bracken fern-scrubland which remained the predominant vegetation until European settlers cleared it away for pasture production in the late 1870s. Deforestation began about 500 calendar years B.P., but proceeded faster in the drier lowlands than in the wetter hill country. When the catchments were covered with either forest or fern-scrubland, soil erosion was minimal because the soil structure was maintained by the network of roots and protected from raindrop impact by a dense canopy. The main effect of storms before European settlement was to transport pulses of mostly riverbank sediment into the lakes. However, after European settlement, soil erosion increased markedly. Removal of soil stabilising vegetation and its replacement with pasture has left soft-rock hill country soils vulnerable to erosion and landslides.
Long tree-ring chronologies have been constructed in the Northern Hemisphere for dendroclimatology and palaeoenvironmental studies, radiocarbon calibration and archaeological dating. Numerous tree-ring chronologies have also been built in the Southern Hemisphere, primarily for dendroclimatology, but multimillennial chronologies are rare. Development of long chronologies from the Southern Hemisphere is therefore important to provide a long-term perspective on environmental change at local, regional and global scales. This paper describes the extension of the New Zealand Agathis australis (kauri) chronology from AD 911 to 1724 BC. Subfossil (swamp) kauri was collected from 17 swamp sites in the upper North Island. Kauri timbers were also obtained from an early twentieth century house on the University of Auckland campus. Twelve site chronologies and 11 independent tree-sequences were constructed and crossmatched to produce a 3631-yr record, which was calendar dated to 1724 BC-AD 1907 against the modern kauri master chronology. A new long chronology, AGAUc04a, was built by combining the modern kauri data with house timbers and subfossil kauri. This new chronology spans 1724 BC-AD 1998. It is of similar length to chronologies from Tasmania and South America and is the longest tree-ring chronology yet built in New Zealand. The greatest significance of the long kauri chronology lies in its potential as a high-quality palaeoclimate proxy, especially with regard to investigation of the El Ninio-Southern Oscillation phenomenon. The chronology also has application to investigation of extreme environmental events, dendroecology, archaeology and radiocarbon calibration.
The stable isotope records of four stalagmites dated by 19 TIMS uranium series ages are combined to produce master chronologies for &dgr; 18O and &dgr; 13C. The &dgr; 18O records display good overall coherence, but considerable variation in detail. Variability in the &dgr; 13C records is greater, but general trends can still be dis cerned. This implies that too fine an interpretation of the structure of individual isotopic records can be unreliable. Speleothem &dgr; 18O values are demonstrated to show a positive relationship with temperature by comparing trends with other proxy records, but also to respond negatively to rainfall amount. Speleothem &dgr; 13C is con sidered to be most influenced by rainfall. The postglacial thermal optimum occurred around 10.8 ka BP, which is similar in timing to Antarctica but up to 2000 years earlier than most Northern Hemisphere sites. Increasingly negative &dgr; 18O values after 7.5 ka BP indicate that temperatures declined to a late mid-Holocene minimum centred around 3 ka BP, but more positive values followed to mark a warm peak about 750 years ago which coincided with the ‘Mediaeval Warm Period’ of Europe. Low &dgr; 18O values at 325 years BP suggest cooling coincident with the ‘Little Ice Age’. A marked feature of the &dgr;13C record is an asymmetric periodicity averaging c. 2250 years and amplitude of c. 1.9‰. It is concluded that this is mainly driven by waterbalance variations with negative swings representing particularly wet intervals. The &dgr;18O record shows a higher-frequency cyclicity with a period of c. 500 years and an amplitude of c. 0.25‰. This is most likely to be temperature-driven, but some swings may have been amplified by precipitation.
Changes in Lake Maratoto and catchment are inferred from variations in sediment character; the correlation and timing were determined from distinctive tephra layers in the sediments and by radiocarbon dating. Nineteen new 14C dates, on gyttja or peat are reported. The Lake originated approx 17 000 yr ago when a small valley was dammed by volcanogenic alluvium (Hinuera formation).-K.R.
Marine core P69 (115 km off the southeastern North Island) has already yielded a 26 000 yr record of carbonate and silica influx, δO18 stratigraphy, foraminifera, and sea‐surface temperatures. A pollen analysis of the core is presented here. The full‐glacial (25 000–15 000 yr BP) pollen assemblages reflect a southern North Island landscape largely covered with scrub and grassland, but only limited areas of cool‐temperate forest. Abundant reworked Tertiary pollen types indicate increased erosion at this time. Rapid spread of podocarp‐dominant forest occurred between 15 000 and 11 500 yr BP, an event that relates only in a general way to increasing sea‐surface temperatures, but coincides exactly with a sharp reduction of wind‐induced upwelling and terrestrially sourced quartz. The abrupt movement southwards of the glacially expanded zone of strong westerlies at c. 15 000 yr BP, rather than warming, appears to be the main factor controlling postglacial reafforestation.
This paper highlights some of the main developments to the radiocarbon calibration program, OxCal. In addition to many cosmetic changes, the latest version of OxCal uses some different algorithms for the treatment of multiple phases. The theoretical framework behind these is discussed and some model calculations demonstrated. Significant changes have also been made to the sampling algorithms used which improve the convergence of the Bayesian analysis. The convergence itself is also reported in a more comprehensive way so that problems can be traced to specific parts of the model. The use of convergence data, and other techniques for testing the implications of particular models, are described.
Ice core derived proxy climate records from Antarctica suggest that decadal, century and possibly even millennial-scale temperature variations in East and West Antarctica may be temporally asynchronous. For example, records from the Antarctic Peninsula indicate a strong 20th century warming in which the high plateau of East Antarctica has not participated. Similarly, a recent Neoglacial cooling, the “Little Ice Age”, was prominent in East Antarctica, but absent in the Peninsula region. A new history of oxygen isotopic ratios (δ18O) and atmospheric dust concentrations from central East Antarctica suggests that the high inland plateau has been dominated by a cooling trend for the last 4000 years. Superimposed upon this isotopically-inferred cooling were a number of warmer events, the largest and most persistent of which occurred ≈ 3600 yr. BP and lasted several centuries. The most prominent event is a prolonged cold phase around 2200 yr. BP which is correlative with a mid-Neoglacial advance on South Georgia Island (Clapperton et al, 1989). Most intriguing are several shorter-term (multi-centennial scale) δ18O oscillations which are similar in magnitude to the glacial-interglacial transition in Antarctic ice cores. Although it is impossible to discount the effect of wind scouring and re-deposition in this low snow accumulation region, this 4000-year history raises important questions about the climate history on the high inland plateau during the last half of the Holocene. Certainly, a better spatial distribution of high resolution δ18O records from East Antarctica are necessary to determine the extent to which the Plateau Remote record is spatially representative.
This paper highlights some of the main developments to the radiocarbon calibration program, OxCal. In addition to many cosmetic changes, the latest version of OxCal uses some different algorithms for the treatment of multiple phases. The theoretical framework behind these is discussed and some model calculations demonstrated. Significant changes have also been made to the sampling algorithms used which improve the convergence of the Bayesian analysis. The convergence itself is also reported in a more comprehensive way so that problems can be traced to specific parts of the model. The use of convergence data, and other techniques for testing the implications of particular models, are described. © 2001 by the Arizona Board of Regents on behalf of the University of Arizona.
Late Holocene lake sediments were used to determine the erosion response of a steepland catchment to land use change. Sediment cores were obtained from Lakes Tutira and Waikopiro, located in a landslide-prone area on the east coast of the North Island, New Zealand. Land use changes were identified in the cores by pollen and diatom analysis, and dated using a sedimentation chronology constructed from tephra layers and historical evidence. During the last 2000 years the catchment has undergone fire-induced changes from indigenous forest to fern/scrub following Polynesian settlement (c. 560 yr B.P.), and then to pasture following European settlement (A.D. 1878). Sedimentation rates under pastoral land use (A.D. 1878-1985) are between 5-6 times the rate under fern/scrub (c.560 yr B.P.-A.D. 1878) and 8-17 times the rate under indigenous forest (1850-c. 560 yr B.P.). Comparison is made with sedimentation rates from other lakes in the region. Well defined storm sediment pulses are present throughout the lake sediments and are responsible for the rapid increase in sedimentation rate under pastoral land use. The presence of these storm sediment pulses, together with a sediment budget for a large cyclonic storm, have identified the role that storms play in erosion and sedimentation processes, and also the influence that land use/vegetation change has had on this role.
Magnitude-frequency analysis provides an approach to assess the effectiveness of rare events for generating and transporting sediment in the 32 km2 Tutira catchment and the 2205 km2 Waipaoa River basin, located in the erodible softrock hill country of the eastern portion of New Zealand's North Island. Shallow landsliding, triggered by high-intensity storms, is an important erosion process throughout out the region. The depositional record of Lake Tutira reveals the relationship between event magnitude and sediment yield of the Tutira catchment during the last 100 years, and illustrates the extent to which climate and land use change have affected the amount of sediment generated by landsliding over the past 2250 years. Magnitude-frequency relationships for hillslope erosion and for sediment deposition are closely related in the Tutira catchment, and large-magnitude, low-frequency landsliding events have been responsible for much of the deposition in Lake Tutira since European settlement. In the Waipaoa River basin, processes that affect sediment output are examined using a sediment budget approach. There, large storms appear to play a lesser role compared with the cumulative influence of more frequent, lower magnitude events. The difference in the effectiveness of large magnitude storms is probably attributable to the lower relative contribution of landsliding to catchment sediment yields, compared with other erosion processes such as gully and stream bank erosion where sediment can be generated by more frequent, lower-magnitude storms. Furthermore, the depositional response of large-magnitude storms may be buffered by transport lags, temporary storage, and a general diffusion of the magnitudes and frequencies of sediment contributions from the spatially variable distribution of erosion processes within the various tributaries. Certainly, the long-term record of sedimentation in Lake Tutira suggests that the magnitude and frequency of the erosional response varies with land use, vegetation type and climatic regime.
It is widely recognised that the acquisition of high-resolution palaeoclimate records from southern mid-latitude sites is essential for establishing a coherent picture of inter-hemispheric climate change and for better understanding of the role of Antarctic climate dynamics in the global climate system. New Zealand is considered to be a sensitive monitor of climate change because it is one of a few sizeable landmasses in the Southern Hemisphere westerly circulation zone, a critical transition zone between subtropical and Antarctic influences. New Zealand has mountainous axial ranges that amplify the climate signals and, consequently, the environmental gradients are highly sensitive to subtle changes in atmospheric and oceanic conditions. Since 1995, INTIMATE has, through a series of international workshops, sought ways to improve procedures for establishing the precise ages of climate events, and to correlate them with high precision, for the last 30 000 calendar years. The NZ-INTIMATE project commenced in late 2003, and has involved virtually the entire New Zealand palaeoclimate community. Its aim is to develop an event stratigraphy for the New Zealand region over the past 30 000 years, and to reconcile these events against the established climatostratigraphy of the last glacial cycle which has largely been developed from Northern Hemisphere records (e.g. Last Glacial Maximum (LGM), Termination I, Younger Dryas). An initial outcome of NZ-INTIMATE has been the identification of a series of well-dated, high-resolution onshore and offshore proxy records from a variety of latitudes and elevations on a common calendar timescale from 30 000 cal. yr BP to the present day. High-resolution records for the last glacial coldest period (LGCP) (including the LGM sensu stricto) and last glacial-interglacial transition (LGIT) from Auckland maars, Kaipo and Otamangakau wetlands on eastern and central North Island, marine core MD97-2121 east of southern North Island, speleothems on northwest South Island, Okarito wetland on southwestern South Island, are presented. Discontinuous (fragmentary) records comprising compilations of glacial sequences, fluvial sequences, loess accumulation, and aeolian quartz accumulation in an andesitic terrain are described. Comparisons with ice-core records from Antarctica (EPICA Dome C) and Greenland (GISP2) are discussed. A major advantage immediately evident from these records apart from the speleothem record, is that they are linked precisely by one or more tephra layers. Based on these New Zealand terrestrial and marine records, a reasonably coherent, regionally applicable, sequence of climatically linked stratigraphic events over the past 30 000 cal. yr is emerging. Three major climate events are recognised: (1) LGCP beginning at ca. 28 000 cal. yr BP, ending at Termination I, ca. 18 000 cal. yr BP, and including a warmer and more variable phase between ca. 27 000 and 21 000 cal. yr BP, (2) LGIT between ca. 18 000 and 11 600 cal. yr BP, including a Lateglacial warm period from ca. 14 800 to 13 500 cal. yr BP and a Lateglacial climate reversal between ca. 13 500 and 11 600 cal. yr BP, and (3) Holocene interglacial conditions, with two phases of greatest warmth between ca. 11 600 and 10 800 cal. yr BP and from ca. 6 800 to 6 500 cal. yr BP. Some key boundaries coincide with tephras.
Zonally symmetric fluctuations of the midlatitude westerly winds
characterize the primary mode of atmospheric variability in the Southern
Hemisphere during all seasons. This is true not only in observations but
also in an unforced 15 000-yr integration of a coarse-resolution (R15)
coupled ocean-atmosphere model. Here it is documented how this mode of
atmospheric variability, known as the Southern Annular Mode (SAM),
generates ocean circulation and sea ice variations in the model
integration on interannual to centennial timescales that are tightly in
phase with the SAM. The positive phase of the SAM is associated with an
intensification of the surface westerlies over the circumpolar ocean
(around 60°S), and a weakening of the surface westerlies farther
north. This induces Ekman drift to the north at all longitudes of the
circumpolar ocean, and Ekman drift to the south at around 30°S.
Through mass continuity, the Ekman drift generates anomalous upwelling
along the margins of the Antarctic continent, and downwelling around
45°S. The anomalous flow diverging from the Antarctic continent also
increases the vertical tilt of the isopycnals in the Southern Ocean, so
that a more intense circumpolar current is also closely associated with
positive SAM. In addition, the anomalous divergent flow advects sea ice
farther north, resulting in an increase in sea ice coverage. Finally,
positive SAM drives increases in poleward heat transport at about
30°S, while decreases occur in the circumpolar region. Ocean and sea
ice anomalies of the opposite sign occur when the SAM is negative. The
ocean and sea ice fluctuations associated with the SAM constitute a
significant fraction of simulated ocean variability poleward of 30°S
year-round. The robustness of the mechanisms relating the SAM to oceanic
variability suggests that the SAM is likely an important source of
large-scale variability in the real Southern Hemisphere ocean.
The precipitation characteristics of three basic circulation types for New Zealand weather [Kidson, J.W. 2000. An analysis of New Zealand synoptic types and their use in defining weather regimes. International Journal of Climatology. 20, 299–316] are explored here as a palaeoclimate reconstruction tool, and are utilised as a way to interpret spatial patterns exhibited by diverse multi-proxy data assemblages. The technique is founded on a modern climate shift analogue for New Zealand where regional precipitation spatial changes accompanied the 1976/77 Inter-decadal Pacific Oscillation (IPO) phase change. The analysis here indicates multi-decadal-scale circulation changes (both in frequency and strength) resulted from the 1976/77 IPO phase change primarily during mid–late summer, late autumn and late winter, and a significant change (a zonal regime frequency and strength increase) occurred for August. From the climatological results, the eastern North Island along with the western and eastern South Island are crucial regions to include in a spatial pattern-based palaeoclimate reconstruction because of sensitivities to zonal circulation changes. Ascribing a climate regime classification to multi-proxy data was subsequently attempted for three discrete timeslices in the Late Holocene, and illustrates that many different types of multi-proxy terrestrial data can successfully be assimilated with some evident advantages and shortcomings. Climate regime classification has good potential for highlighting spatial and temporal gaps in regional palaeoclimate proxy networks, and in the case of New Zealand, potential for connecting local and regional palaeoclimate data to conditions associated with westerly circulation changes, the IPO, and for exploration of Australasian and extra-tropical palaeoclimate archive connections.
Lake Tutira is a small lake formed as a result of a landslide about 6500 radiocarbon years BP. It is situated 100 km east, and downwind, of the central North Island volcanoes and has provided a trap for tephras which have erupted since the mid-Holocene. Detailed studies of cores from the lake and adjacent swamps have revealed 23 tephra layers, which represent tephra deposition into Lake Tutira every 300 years on average. Sixteen of these layers are macroscopic and seven are microscopic, occurring as concentrations of volcanic glass. The tephra layers mark rhyolitic and andesitic tephra eruptions from Taupo, Okataina, Egmont, and Tongariro volcanic centres. They were identified using their ferromagnesian mineralogy, major element compositions of glass shards, and their stratigraphic position, particularly with respect to radiocarbon dates. The Lake Tutira tephra record is the most detailed record yet found in eastern North Island, and the detection of microscopic tephra layers indicates the value of lake sediments and swamps as traps for distal tephras.
From 26 sites in the central and eastern parts of North Island, New Zealand, 37 specimens of wood have been identified botanically and their stratigraphic position established in relation to tephra layers of known age.Driftwood derived mainly from podocarp trees (Dacrydium, Podocarpus) was sampled from five sites associated with old shorelines and river terraces in the Waipaoa River Catchment, and from two sites in the Whakatane River Catchment. The results indicate times at which the corresponding vegetation was growing in the upper parts of these catchments. Stumps between tephra layers sampled from coastal lowlands were mostly from podocarp trees growing in situ during the interval 2,100 to 1,800 yr B.P.The paper also discusses the relationship of earth movements at Gisborne to other events including the Taupo Pumice eruptions, the significance of layers of preserved manuka (Leptospermum) in swamps, and changes in the coastline near Whakatane.
Significant precipitation along the north-central coast of Peru (lat 5°-10°S) occurs exclusively during El Niño incursions of warm water into the Peruvian littoral. Flood deposits from this region therefore provide a proxy record of extreme El Niño events. I present a 3500 yr chronology of the extreme events based on radiocarbon dating of overbank flood sediments from the Rio Casma (lat 9.2°S).The flood-plain stratigraphy suggests that the El Niño phenomenon has occurred throughout the Holocene and that flood events much larger than that which occurred during 1982-1983 occur here at least once every 1000 yr.
Decadal variability of the El Niño–Southern Oscillation (ENSO) teleconnection to the high-latitude South Pacific is examined by correlating the European Centre for Medium-Range Weather Forecasts (ECMWF) 40-yr Re-Analysis (ERA-40) and observations with the Southern Oscillation index (SOI) over the last two decades. There is a distinct annual contrast between the 1980s and the 1990s, with the strong teleconnection in the 1990s being explained by an enhanced response during austral spring. Geopotential height anomaly composites constructed during the peak ENSO seasons also demonstrate the decadal variability.
Empirical orthogonal function (EOF) analysis reveals that the 1980s September–November (SON) teleconnection is weak due to the interference between the Pacific–South American (PSA) pattern associated with ENSO and the Southern Annular Mode (SAM). An in-phase relationship between these two modes during SON in the 1990s amplifies the height and pressure anomalies in the South Pacific, producing the strong teleconnections seen in the correlation and composite analyses. The in-phase relationship between the tropical and high-latitude forcing also exists in December–February (DJF) during the 1980s and 1990s.
These results suggest that natural climate variability plays an important role in the variability of SAM, in agreement with a growing body of literature. Additionally, the significantly positive correlation between ENSO and SAM only during times of strong teleconnection suggests that both the Tropics and the high latitudes need to work together in order for ENSO to strongly influence Antarctic climate.
Late twentieth-century trends in New Zealand precipitation are examined using observations and re- analysis data for the period 1979-2006. One of the aims of this study is to investigate the link between these trends and recent changes in the large-scale atmospheric circulation in the Southern Hemisphere. The contributions from changes in Southern Hemisphere climate modes, particularly the El Niño-Southern Oscillation (ENSO) and the southern annular mode (SAM), are quantified for the austral summer season, December-February (DJF). Increasingly drier conditions over much of New Zealand can be partially explained by the SAM and ENSO. Especially over wide parts of the North Island and western regions of the South Island, the SAM potentially contributes up to 80% and 20%-50% to the overall decline in DJF precipitation, respectively. Over the North Island, the contribution of the SAM and ENSO to precipitation trends is of the same sign. In contrast, over the southwest of the South Island the two climate modes act in the opposite sense, though the effect of the SAM seems to dominate there during austral summer. The leading modes of variability in summertime precipitation over New Zealand are linked to the large-scale atmospheric circulation. The two dominant modes, explaining 64% and 9% of the overall DJF precipitation variability respectively, can be understood as local manifestations of the large-scale climate variability associated with the SAM and ENSO.
Interannual extremes in New Zealand rainfall and their modulation by modes of Southern Hemisphere climate variability are examined in observations and a coupled climate model. North Island extreme dry (wet) years are characterized by locally increased (reduced) sea level pressure (SLP), cold (warm) sea surface temperature (SST) anomalies in the southern Tasman Sea and to the north of the island, and coinciding reduced (enhanced) evaporation upstream of the mean southwesterly airflow. During extreme dry (wet) years in South Island precipitation, an enhanced (reduced) meridional SLP gradient occurs, with circumpolar strengthened (weakened) subpolar westerlies and an easterly (westerly) anomaly in zonal wind in the subtropics. As a result, via Ekman transport, anomalously cold (warm) SST appears under the subpolar westerlies, while anomalies of the opposite sign occur farther north. The phase and magnitude of the resulting SST and evaporation anomalies cannot account for the rainfall extremes over the South Island, suggesting a purely atmospheric mode of variability as the driving factor, in this case the Southern Annular Mode (SAM). New Zealand rainfall variability is predominantly modulated by two Southern Hemisphere climate modes, namely, the El Niño-Southern Oscillation (ENSO) and the SAM, with a latitudinal grada- tion in influence of the respective phenomena, and a notable interaction with orographic features. While this heterogeneity is apparent both latitudinally and as a result of orographic effects, climate modes can force local rainfall anomalies with considerable variations across both islands. North Island precipitation is for the most part regulated by both local air-sea heat fluxes and circulation changes associated with the tropical ENSO mode. In contrast, for the South Island the influence of the large-scale general atmospheric circulation dominates, especially via the strength and position of the subpolar westerlies, which are modu- lated by the extratropical SAM.
The Waipaoa sedimentary system spans ∼100 km from terrestrial upland to continental rise. Alluvial buffering has little effect on sediment flux at the outlet of this mesoscale dispersal system, and hinterland-to-margin transport is accomplished rapidly. Because of this synergy, the floodplain and shelf depocenters are sensitive to changes in sediment production in the hinterland, and natural and anthropogenically forced changes in sediment source dynamics that occur at several temporal and spatial scales leave distinctive signals in the stratigraphic record. Manifested as variations in sediment properties, these signals appear in intercorrelated sediment cores from a headwater riparian storage area and the major terrestrial and marine repositories for sediment discharged during the past 2.4 k.y. The signals represent the landscape response to vegetation and land-use change, short-term fluctuations in climate that affect surface properties and processes, and extreme storms and subduction-thrust earthquakes. Extreme storms are the minimum geomorphologically effective event preserved in the sediment records. Lower-magnitude storms that are integral components of the prevailing hydrometeorological regime create high-frequency fluctuations in sediment properties and collectively contribute to event sequences of >100 yr duration. Events and event sequences comprise a hierarchy of temporally sensitive phenomena, the impacts of which are conditioned by frequency and magnitude. By contrast, vegetation disturbance is a spatially sensitive phenomenon that directly impacts sediment source areas and lowers the threshold of landscape sensitivity to erosion. For this reason, the Taupo eruption of 1.718 ka and the piecemeal vegetation changes that occurred after the arrival of Polynesian settlers also generated strong depositional signals. After European colonization, deforestation of the hinterland altered landscape sensitivity and precipitated the transition to an erosional regime that impacted sediment production and dispersal across the entire magnitude-frequency spectrum of events, regulating sediment delivery to and transport in stream channels. No other perturbation had such a profound impact on the Late Holocene depositional record.