R. Scott Anderson

Northern Arizona University, Flagstaff, Arizona, United States

Are you R. Scott Anderson?

Claim your profile

Publications (90)264.21 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Reconstructing climates of the past relies on a variety of evidence from a large number of sites to capture the varied features of climate and the spatial heterogeneity of climate change. This review summarizes available information from diverse Holocene paleoenvironmental records across eastern Beringia (Alaska, westernmost Canada and adjacent seas), and it quantifies the primary trends of temperature- and moisture-sensitive records based in part on midges, pollen, and biogeochemical indicators (compiled in the recently published Arctic Holocene database, and updated here to v2.1). The composite time series from these proxy records are compared with new summaries of mountain-glacier and lake-level fluctuations, terrestrial water-isotope records, sea-ice and sea-surface-temperature analyses, and peatland and thaw-lake initiation frequencies to clarify multi-centennial- to millennial-scale trends in Holocene climate change. To focus the synthesis, the paleo data are used to frame specific questions that can be addressed with simulations by Earth system models to investigate the causes and dynamics of past and future climate change. This systematic review shows that, during the early Holocene (11.7–8.2 ka; 1 ka = 1000 cal yr BP), rather than a prominent thermal maximum as suggested previously, temperatures were highly variable, at times both higher and lower than present (approximate mid-20th-century average), with no clear spatial pattern. Composited pollen, midge and other proxy records average out the variability and show the overall lowest summer and mean-annual temperatures across the study region during the earliest Holocene, followed by warming over the early Holocene. The sparse data available on early Holocene glaciation show that glaciers in southern Alaska were as extensive then as they were during the late Holocene. Early Holocene lake levels were low in interior Alaska, but moisture indicators show pronounced differences across the region. The highest frequency of both peatland and thaw-lake initiation ages also occurred during the early Holocene. During the middle Holocene (8.2–4.2 ka), glaciers retreated as the regional average temperature increased to a maximum between 7 and 5 ka, as reflected in most proxy types. Following the middle Holocene thermal maximum, temperatures decreased starting between 4 and 3 ka, signaling the onset of Neoglacial cooling. Glaciers in the Brooks and Alaska Ranges advanced to their maximum Holocene extent as lakes generally rose to modern levels. Temperature differences for averaged 500-year time steps typically ranged by 1–2 °C for individual records in the Arctic Holocene database, with a transition to a cooler late Holocene that was neither abrupt nor spatially coherent. The longest and highest-resolution terrestrial water isotope records previously interpreted to represent changes in the Aleutian low-pressure system around this time are here shown to be largely contradictory. Furthermore, there are too few records with sufficient resolution to identify sub-centennial-scale climate anomalies, such as the 8.2 ka event. The review concludes by suggesting some priorities for future paleoclimate research in the region.
    Full-text · Article · Jan 2016 · Quaternary Science Reviews
  • Martina T. Tingley · R. Scott Anderson · Darrell Kaufman · Megan Arnold

    No preview · Article · Nov 2015 · Quaternary International

  • No preview · Article · Nov 2015 · Quaternary International
  • R. Scott Anderson · Ana Ejarque · Johnathan Rice · Clayton Lebow

    No preview · Article · Nov 2015 · Quaternary International
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Paleoenvironmental records from two sites in and near a northern Norway coastal mountain range detail changes in vegetation and climate since the melting of Late Pleistocene ice. Our record from Hollabåttjønnen Bog spans the last ca. 9.5 cal yr. We use pollen, molecular biomarkers and tephra stratigraphy from multiple cores, as well as GPR profiles of the bog, to detail changes within the bog as well as to reflect regional climate change. Peat growth was initiated in the early Holocene (ca. 9.5-7.8 cal ka BP) when pollen and biomarker data suggest relatively wet conditions. Drier conditions followed this ca. 7.8-3.5 cal ka BP. An abrupt transition to wetter conditions occurred by 3.5 cal ka BP, which continued to the present, as reflected in leaf wax isotope and pollen data. An increase in bog disturbance is found beginning ca. 1.1 cal yr BP, evidenced by indications of grazing animals or human use. The Kulivatn Lake data extend our temporal reconstructions back to the Younger Dryas interval. Sedimentary charcoal is rare in these sediments, suggesting that fire has been relatively unimportant during the post-glacial. The comparison of the bog with a lake sediment profile provides complementary evidence of paleoenvironmental change.
    Full-text · Conference Paper · Oct 2015
  • [Show abstract] [Hide abstract]
    ABSTRACT: Paleoenvironmental records from two sites in and near a northern Norway coastal mountain range detail changes in vegetation and climate since the melting of Late Pleistocene ice. Our record from Hollabåttjønnen Bog spans the last ca. 9.5 cal yr. We use pollen, molecular biomarkers and tephra stratigraphy from multiple cores, as well as GPR profiles of the bog, to detail changes within the bog as well as to reflect regional climate change. Peat growth was initiated in the early Holocene (ca. 9.5-7.8 cal ka BP) when pollen and biomarker data suggest relatively wet conditions. Drier conditions followed this ca. 7.8-3.5 cal ka BP. An abrupt transition to wetter conditions occurred by 3.5 cal ka BP, which continued to the present, as reflected in leaf wax isotope and pollen data. An increase in bog disturbance is found beginning ca. 1.1 cal yr BP, evidenced by indications of grazing animals or human use. The Kulivatn Lake data extend our temporal reconstructions back to the Younger Dryas interval. Sedimentary charcoal is rare in these sediments, suggesting that fire has been relatively unimportant during the post-glacial. The comparison of the bog with a lake sediment profile provides complementary evidence of paleoenvironmental change.
    No preview · Conference Paper · Oct 2015
  • [Show abstract] [Hide abstract]
    ABSTRACT: Sediment cores from Upper and Lower Whitshed Lakes located near Cordova, Alaska were used to create a tephrochronology and to reconstruct environmental and climatic change during the past 15,000 years. Independent age models were developed for both lakes using radiocarbon dates, and profiles of short-lived radioisotopes for the surface of the cores. The geochemistry of seven unique tephras was analyzed for major oxides and used along with the stratigraphy of magnetic susceptibility (MS) to correlate four visible and disseminated tephra layers between the two lakes. The correlated tephra were used to synchronize the age model s, which reduced the uncertainty in both the age models and the age estimates of the tephras. Several proxies for productivity were analyzed in the cores: organic matter, biogenic silica (BSi), and spectrally inferred chlorophyll-a . Following deglaciation by 14.6 ka, these proxies indicate a return to colder, unproductive conditions during the Younger Dryas (12.5 – 11.6 ka). From 10. 9 to 2 .7 ka, BSi in both lakes is generally high and stable. From 2.7 to 1.7 ka Upper Whitshed Lake BSi declined from 30 to 10%, coupled with a decrease in the relative concentration of chlorophyll - a (650 – 700 nm trough area), most likely due to a reduction in nitrogen input as alder (Alnus) was replaced by conifers (Picea and Tsuga) (Tingley and others , 2013). In Lower Whitshed Lake a much smaller shift in BSi occurs at the same time (from 30 to 22%). Upper Whitshed BSi is negatively correlated with summer precipitable water as represented by the local grid point in NCEP climate reanalysis product, suggesting that the reduction in BSi after 2.7 ka could also be driven by increased summer cloudiness (reduced photosynthesis), or increased summer precipitation (increased sedimentation, diluting BSi) From 1663 ± 52 until 1964 CE, Lower Whitshed Lake was connected with the Gulf of Alaska due to a rise in RSL (Garret and others , 2015). The sill rose above sea level during the 1964 Great Alaska Earthquake. The paired-lake comparison allows for an investigation of the replicability and uncertainty of proxies analyzed in both lakes. Spikes in MS associated with visible and disseminated tephra are found in both lakes. Millennial - scale patterns within BSi and OM are similar between the two lakes, and these proxies correlate significantly between the two lakes (R2 = 0.18, p = 0.020; R2 = 0.4 4, p = 0.001, respectively). However, the BSi records contain substantially more variability between the records compared to the signal that is common to the records and the signal-to-noise ratio is less than 1, suggesting that a large portion of the variability in these records is not climatically driven. Discrepancies in the BSi record are likely driven by different environmental conditions within the lakes, potentially caused by a marine influence on Lower Whitshed Lake.
    No preview · Conference Paper · Jun 2015
  • Source
    Ana Ejarque · R.Scott Anderson · Alexander R. Simms · Beau J. Gentry
    [Show abstract] [Hide abstract]
    ABSTRACT: Download at: http://authors.elsevier.com/a/1QZyA-4PRdY9U Using a novel combination of paleoecologic proxies including pollen, non-pollen palynomorphs (NPPs), macroscopic charcoal, and Spheroidal Carbonaceous Particles (SCPs), 5000 years of landscape change, fire history and land-use have been reconstructed from Dune Pond, Santa Barbara County, California. The pond was sensitive to Holocene regional climatic variability, showing different phases of lower (4600–3700 cal yr BP, 2100–700 cal yr BP, historical period) and higher (3700–2100 cal yr BP, 700–150 cal yr BP) local moisture availability. During this period the landscape was dominated by a coastal mosaic vegetation including dune mats, coastal scrub and salt marshes on the dunes and backdunes, with chaparral and oak woodland growing in the valley plains and foothills. Fire was intimately linked with such dominating mosaic vegetation, and the combination of wet conditions and the presence of nearby human settlement were a trigger favoring coastal fires for at least two periods: from 3100 to 1500 cal yr BP and from 650 cal yr BP until the 18th century. In both cases fire was an important tool to keep an open coastal landscape attractive to hunting wildlife. Finally, matching this varied range of high-resolution paleoecological proxies with historical records we could characterize the development of colonial transported landscapes following the Euro-American settlement of Santa Barbara. The introduction of livestock grazing by Spanish colonists favored erosive processes and the introduction of fecal-borne parasites in freshwater bodies, negatively impacted salt and brackish coastal marshes, and promoted the invasion of alien grasses and ruderals. This agro-pastoral landscape was consolidated during the American period, with a greater role for cultivation, the development of industrial activities and increased population. Despite negative environmental consequences such as the loss of native habitats, exotic land-uses and plants introduced during the historical period significantly contributed to the configuration of a cultural landscape which forms part of the cultural heritage of California.
    Full-text · Article · Mar 2015 · Quaternary Science Reviews
  • Source

    Full-text · Dataset · Feb 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Download at: http://www.sciencedirect.com/science/article/pii/S0033589414001343 Using a combination of pollen, non-pollen palynomorphs (NPPs) and charcoal particle stratigraphies from sediment cores from two sites, along with historical records, we reconstructed paleoenvironmental change in midcoastal California. The San Antonio Creek section contains a discontinuous, Holocene-length record, while Mod Pond includes a continuous late Holocene record. Together the records allow for interpretation of most of the present interglacial. The longer record documents coastal sage scrub and chaparral dominated by woodland elements early in the Holocene to about 9000 yr ago, a potential decline in woodland communities with drying conditions during the middle Holocene to about 4800 yr ago, and an expansion of coastal sage scrub with grassland during the late Holocene. Evidence for climatic fluctuations during the last 1000 yr at Mod Pond is equivocal, suggesting that the Medieval Climate Anomaly–Little Ice Age had modest impact on the Mod Pond environment. However, evidence of significant environmental change associated with cultural transitions in the 18th–19th centuries is stark. Introduction of non-native plants, establishment of cattle and sheep grazing, missionization of the native population, changes in burning practices during the Spanish period and enhanced cropping activities during North American settlement worked together to substantially modify the mid-California coastal landscape in about a century's time.
    Full-text · Article · Feb 2015 · Quaternary Research
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In North America, terrestrial records of biodiversity and climate change that span Marine Oxygen Isotope Stage (MIS) 5 are rare. Where found, they provide insight into how the coupling of the ocean-atmosphere system is manifested in biotic and environmental records and how the biosphere responds to climate change. In 2010-2011, construction at Ziegler Reservoir near Snowmass Village, Colorado (USA) revealed a nearly continuous, lacustrine/wetland sedimentary sequence that preserved evidence of past plant communities between ~ 140 and 55 ka, including all of MIS 5. At an elevation of 2705 m, the Ziegler Reservoir fossil site also contained thousands of well-preserved bones of late Pleistocene megafauna, including mastodons, mammoths, ground sloths, horses, camel, deer, bison, black bear, coyotes, and bighorn sheep. In addition, the site contained more than 26,000 bones from at least 30 species of small animals including salamanders, otters, muskrats, minks, rabbits, beavers, frogs, lizards, snakes, fish, and birds. The combination of macro- and micro-vertebrates, invertebrates, terrestrial and aquatic plant microfossils, a detailed pollen record, and a robust, directly dated stratigraphic framework shows that high-elevation ecosystems in the Rocky Mountains of Colorado are climatically sensitive and varied dramatically throughout MIS 5.
    Full-text · Article · Nov 2014 · Quaternary Research
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Improved predictions of drought require an understanding of natural and human-induced climate variability. Long-term records across glacial–interglacial cycles provide the natural component of variability, however few such records exist for the southwestern United States (US) and quantitative or semi-quantitative records of precipitation are absent. Here we use the hydrogen isotope (δD) value of C28n-alkanoic acid in lacustrine sediments of Pleistocene age to reconstruct δD values of precipitation in northern New Mexico over two glacial–interglacial cycles (∼550,000–360,000 years before present) and obtain a record of monsoon strength. Overall, reconstructed δD values range from −53.8‰ to −94.4‰, with a mean value of −77.5 ± 8‰. Remarkably, this variation falls within the measured present-day summer monsoonal and winter weighted means (−50.3 ± 3‰ and −106.4 ± 20‰ respectively), suggesting that processes similar to those of present time also controlled precipitation during Marine Isotope Stage (MIS) 13 to 10. Using the δD summer monsoonal and winter mean values as end-members, we interpret our reconstructed δD record of precipitation as a direct, and semi-quantitative, indicator of monsoon strength during MIS 13 to 10. Interglacial periods were characterized by greater monsoon strength but also greater variability compared to glacial periods. Pronounced cycles in the strength of the monsoon occurred during interglacial periods and in general were positively correlated with maximum mean annual temperatures. Our estimates of monsoon strength are supported by independent proxies of ecosystem productivity, namely, TOC, δ13C of TOC and Si/Ti ratio and warm pollen taxa Juniperus and Quercus. Interglacial variability in the strength of the monsoon resembles a response to the land-sea surface temperature contrast (LSTC) except for the early part of MIS 11. During this period, LSTC would have remained relatively strong while monsoonal strength decreased to a minimum. This minimum occurred following the warmest interval of MIS 11, suggesting a more complex driving of monsoon strength during warm periods. In addition, this period of monsoon minimum coincided with a core section of mud-cracked sediments that suggest low monsoonal precipitation was an important factor in the onset of drought. Our estimates of monsoon strength represent a record of natural variability in the region that is relevant to present time, in particular the variability during interglacial MIS 11, which is considered an analog for the current interglacial. Our results suggest that natural variability can cause significant reductions in monsoonal precipitation with the implication of a potentially adverse effect from sustained warming. http://authors.elsevier.com/a/1Pnhg-4PRZkml
    Full-text · Article · Sep 2014 · Quaternary Science Reviews
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Historical ecology is becoming an important focus in conservation biology and offers a promising tool to help guide ecosystem management. Here, we integrate data from multiple disciplines to illuminate the past, present, and future of biodiversity on California's Channel Islands, an archipelago that has undergone a wide range of land-use and ecological changes. Our analysis spans approximately 20,000 years, from before human occupation and through Native American hunter–gatherers, commercial ranchers and fishers, the US military, and other land managers. We demonstrate how long-term, interdisciplinary research provides insight into conservation decisions, such as setting ecosystem restoration goals, preserving rare and endemic taxa, and reducing the impacts of climate change on natural and cultural resources. We illustrate the importance of historical perspectives for understanding modern patterns and ecological change and present an approach that can be applied generally in conservation management planning.
    Full-text · Article · Aug 2014 · BioScience
  • Erin M. Herring · R. Scott Anderson · George L. San Miguel
    [Show abstract] [Hide abstract]
    ABSTRACT: Continuous sediment, charcoal, and pollen records were developed from a ~7-m sediment core from Prater Canyon in Mesa Verde National Park (MEVE), Colorado, USA. Sediment input into the canyon is episodic and is linked to precipitation runoff and vegetation cover. Pollen recovered from the Prater Canyon sediment core reflect the vegetation changes within the MEVE region. During the period recorded, the vegetation of the region surrounding Prater Canyon transitioned from xeric adapted species in an open environment to a more mesic, Pinus edulis–Juniperus osteosperma (piñon–juniper) woodland over the last 1500 years. Two distinct changes in fire frequency occurred. Before 4080 cal. yr BP, fires occurred at a much more frequent rate (2.5–12 fires/200 years) than from 4060 cal. yr BP to present (0–2 fires/200 years). Most importantly, the variations occurring in the charcoal record for the past 2500 years coincide with both shifts in human occupation and climate fluctuations within the region, with burning increasing during Ancestral Puebloan occupation and moist but increasingly dry conditions, and declines in both at the end of the ‘Medieval Climate Anomaly’ (MCA). The record from Prater Canyon demonstrates the importance of the Ancestral Puebloans in landscape modification during their occupation from ad1 to 1300. Charcoal deposition also increased during the 20th- to 21st-century transition with the highest deposition rates of the core recorded then.
    No preview · Article · Jul 2014 · The Holocene
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Paleoecological studies from Rocky Mountain high elevations encompassing the previous interglacial (MIS 5e) are rare. The ~ 10-m composite profile from the Ziegler Reservoir site (2705 m asl) of central Colorado allows us to determine paleoenvironments from MIS 6–MIS 4 using pollen assemblages that are approximately equivalent to marine oxygen isotope stages. During Pollen Zone (PZ) 6 time, pollen assemblages dominated by Artemisia (sagebrush) suggest that alpine tundra or steppe occurred nearby. The transition to PZ 5e was characterized by a rapid increase in tree pollen, initially Picea (spruce) and Pinus (pine) but also Quercus (oak) and Pseudotsuga menziesii (Douglas-fir). Non-arboreal pollen (NAP) types increased during PZ 5d, while Abies (fir) and Juniperus (juniper) increased during PZ 5c. Pollen evidence suggests that temperatures during PZ 5b were as cold as during PZ 6, with the site again surrounded by alpine tundra. Picea dominated during PZ 5a before the onset of cooler conditions during PZ 4. The MIS 6–MIS 5e transition here was similar to the MIS 2–MIS 1 transition at other Rocky Mountain sites. However, the Ziegler Reservoir pollen record contains evidence suggesting unexpected climatic trends at this site, including a warmer-than-expected MIS 5d and cooler-than-expected MIS 5b.
    Full-text · Article · Jun 2014 · Quaternary Research
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The recent continental-scale outbreak of native bark beetles in western North America is unprecedented at least since Euro-American settlement. Observational and modeling evidence suggest that warm temperatures observed during the late 20th century altered beetle population dynamics by accelerating beetle reproductive cycles leading to exponential population growth. The linkage between beetle outbreaks and climate warming has motivated efforts to reconstruct these disturbances using long-term environmental records using lake sediments. Here, we present data from across western North America in an effort to understand how beetle remains retrieved from lake sediments may be used as a proxy for reconstructing severe outbreaks and ecosystem response over centennial to millennial timescales. We (1) review existing literature related to beetle taphonomy; (2) present previously unpublished data of beetle remains in lake sediments; (3) comment on the development of a methodology to retrieve terrestrial beetle remains from lake sediments; (4) discuss potential controls on beetle carcass taphonomy into the sediment matrix; and lastly (5) speculate on the use of primary and secondary attack beetle remains as indicators of past outbreak episodes. Our synthesis suggests that the remains of primary attack beetles are rarely preserved in lake sediments, at least using small-diameter piston devices common in multi-proxy studies. Alternatively, remains of secondary attach beetles may be common but further work is required to understand how these insects can be used to aid in interpreting past forest disturbances, including bark beetle outbreaks and wildfire. A number of factors may influence whether or not bark beetle remains become entrained in the area of sediment focusing including lake water chemistry, fish predation and scavenging, and weather conditions during peak beetle emergence.
    Full-text · Article · Apr 2014 · Quaternary International
  • [Show abstract] [Hide abstract]
    ABSTRACT: Marked changes in sediment types deposited in Cabin Lake, near Cordova, Alaska, represent environmental shifts during the early and late Holocene, including fluctuations in the terminal position of Sheridan Glacier. Cabin Lake is situated to receive meltwater during periods when the outwash plain of the advancing Sheridan Glacier had aggraded. A brief early Holocene advance from 11.2 to 11.0 cal ka is represented by glacial rock flour near the base of the sediment core. Non-glacial lake conditions were restored for about 1000 years before the water level in Cabin Lake lowered and the core site became a fen. The fen indicates drier-than-present conditions leading up to the Holocene thermal maximum. An unconformity spanning 5400 years during the mid-Holocene is overlain by peat until 1110 CE when meltwater from Sheridan Glacier returned to the basin. Three intervals of an advanced Sheridan Glacier are recorded in the Cabin Lake sediments during the late Holocene: 1110–1180, 1260–1540 and 1610–1780 CE. The sedimentary sequence also contains the first five reported tephra deposits from the Copper River delta region, and their geochemical signatures suggest that the sources are the Cook Inlet volcanoes Redoubt, Augustine and Crater Peak, and possibly Mt Churchill in the Wrangell Volcanic field.
    No preview · Article · Nov 2013 · Journal of Quaternary Science
  • Source
    R Scott Anderson · Ana Ejarque · Peter M Brown · Douglas J Hallet
    [Show abstract] [Hide abstract]
    ABSTRACT: Pollen, non-pollen palynomorphs (NPPs), and charcoal particle stratigraphies are used to determine environmental change at Glenmire, Point Reyes Peninsula, northcentral coastal California, over the last c. 6200 years. Pollen was not preserved in early Holocene sediments when climate was drier than present. However, groundwater tables rose after c. 6200 cal. BP, allowing for greater subsequent preservation of organic matter. Middle and late Holocene environments were a mosaic of vegetation types, including mixed conifer forest with coastal scrub grassland prior to c. 4000 cal. BP. Subsequently, hardwoods such as alder (Alnus) and coastal scrub (e.g. Artemisia, Baccharis) expanded until c. 2200 cal. BP, followed by tanoak (Lithocarpus densiflorus), Douglas fir (Pseudotsuga menziesii), and coast redwood (Sequoia sempervirens). With increasing amounts of oak (Quercus), this mosaic of vegetation types continued to dominate until the arrival of Euro-Americans in the early to mid-1800s. The fire history is probably tied closely to human settlement, since natural ignitions are rare. Elevated charcoal amounts coincide with increased sedentism of the native populations by about 3500 cal. BP. Increased sedentism may have caused a more intense and constant use of the coastal environment around Glenmire. For the most recent centuries, we compared historical records of explorations, Spanish Mission establishment, consolidation of the native Coast Miwok population, ranching by Mexican nationals, and dairying by Americans at the height of California’s gold rush with the paleoecological record. The Glenmire record thus documents changing fire use following the AD 1793 fire suppression proclamation; declines in native forest species; introductions of non-native species, including those associated with livestock grazing and land disturbance; and an increase in coprophilous fungi (NPPs) associated with the presence of large numbers of sheep and cattle, among other changes. During the historical period, the sedimentary record of historical fires closely matches the nearby fire-scar tree-ring record.
    Full-text · Article · Oct 2013 · The Holocene
  • Shira Tracy · Mitchell Power · R. Scott Anderson

    No preview · Article · Oct 2013 · Quaternary International
  • R. Scott Anderson · Darrell S. Kaufman · Caleb Schiff · Tom Daigle · Edward Berg

    No preview · Article · Oct 2013 · Quaternary International

Publication Stats

2k Citations
264.21 Total Impact Points

Institutions

  • 1987-2016
    • Northern Arizona University
      • • School of Earth Sciences and Environmental Sustainability
      • • Department of Biological Sciences
      Flagstaff, Arizona, United States
  • 1985-2015
    • The University of Arizona
      • Department of Geosciences
      Tucson, Arizona, United States