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Centennial-scale Holocene climate variability revealed by a high-resolution speleothem \delta^18$O record from S.W.~Ireland

Authors:
Copyright © 2001 by the American Association for the Advancement of Science
Volume 294(5545) 9 November 2001 pp 1328-1331
Centennial-Scale Holocene Climate Variability Revealed by a High-Resolution
Speleothem [delta]
18
O Record from SW Ireland
[Research: Reports]
McDermott, Frank
1
; Mattey, David P.
2
; Hawkesworth, Chris
3
1
Department of Geology, University College Dublin, Dublin 4, Ireland.
2
Geology Department, Royal Holloway College, University of London, Egham,
Surrey, TW20 OEX, UK.
3
Department of Earth Sciences, Bristol University, Bristol BS8 1RJ, UK.
21 June 2001; accepted 17 September 2001
Outline
? Abstract
? References and Notes
Graphics
?
Fig. 1
? Fig. 2
? Fig. 3
Abstract
Evaluating the significance of Holocene submillennial [delta]
18
O variability in the Greenland ice cores is crucial for
understanding how natural climate oscillations may modulate future anthropogenic warming. A high-resolution oxygen
isotope record from a speleothem in southwestern Ireland provides evidence for centennial-scale [delta]
18
O variations that
correlate with subtle [delta]
18
O changes in the Greenland ice cores, indicating regionally coherent variability in the early
Holocene. Evidence for previously undetected early Holocene cooling events is presented, but mid- to late-Holocene ice
rafting in the North Atlantic appears to have had little impact on [delta]
18
O at this ocean margin site.
It is widely accepted that climate variability on time scales of 10
3
to 10
5
years is driven primarily by orbital, or so-called
Milankovitch, forcing. Less well understood is the cause of the centennial- to millennial-scale variability that characterizes the
[delta]
18
O records of both the glacial and interglacial intervals of the GRIP and GISP2 ice cores (1, 2), yet this higher frequency
variability may be important for predicting future climate change. Unlike the last interglacial (isotope stage 5), the Holocene
[the last 11,700 years or 11.7 thousand years before the present (ky B.P.)] appeared to be anomalously stable because [delta]
18
O in the GRIP and GISP2 ice cores seemed to be relatively constant
(1, 2)
. More recently, millennial-scale climate variability
has been detected in several Holocene climate proxy records, but there is little consensus about the precise timing, amplitude,
or cause of these fluctuations (3-10). An emerging paradigm is that sub-Milankovitch climate variability is driven by a weak
internal quasi-periodic (1500 ± 500 year) forcing of unknown origin that operates irrespective of whether the system is in a
glacial or an interglacial mode (5, 9, 10). In the context of concerns about the impact of anthropogenic greenhouse gases, it is
important to establish whether these relatively low-frequency (~1500 year) events or higher frequency oscillations might
determine the natural trends in global mean temperatures over the next few centuries. Therefore, a key question is the extent to
which subtle higher frequency (century-scale) [delta]
18
O variations in the Holocene sections of the Greenland ice cores reflect
regional climatic signals rather than local effects or noise. Until now, that has been difficult to test, due to a paucity of
sufficiently high resolution palaeoclimatic records. But here we present a newly found high-resolution O isotope time series
for a well-dated stalagmite (CC3) from Crag cave in southwestern Ireland
(Fig. 1)
, which shows that these subtle features are
regional and not local signals.
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Fig. 1. Map of the North Atlantic region showing the locations of GRIP and GISP2 ice cores, cores VM28-14, VM29-191, 28-03 and Crag Cave in southwestern Ireland.
Approximately 1640 laser ablation [delta]
18
O measurements (11) were carried out along the growth axis of the 465-mm-long
stalagmite, resulting in a high-resolution Holocene [delta]
18
O record
(12-14)
. Chronological control is provided by 13 TIMS U-
series dates [Web table 1 (13)]. Before 5 ky B.P., the resolution is 2 to 20 times better than that of the published (2-m segment)
[delta]
18
O data for the GRIP and GISP2 ice cores and is about a factor of two worse than that of the ice cores since 5.3 ky B.P.
The average resolution is approximately an order of magnitude better than in the North Atlantic cores that record evidence for
quasi-periodic (1475 ± 500 year) ice rafting during the Holocene (5, 9, 10). Such events should, therefore, be discernible in the
new data set if they had a large impact on the [delta]
18
O of precipitation and/or mean annual air temperatures at this ocean
margin site.
The new data are plotted against time (calendar years B.P.) in Fig. 2. [delta]
18
O varies from -11.65 to -0.82 per mil ()
[Vienna Pee Dee Belemnite (VPDB)], but typically varies by ±1.75 around a mean value of -3.26 (VPDB). The
approximate timing of historic climate variability (8) is also shown (e.g., the Little Ice Age, Medieval Warm Period, Dark Ages
Cold Period, Roman Warm Period). Colder periods (e.g., Little Ice Age and Dark Ages Cold Period) appear to be associated
with lower [delta]
18
O (Fig. 2A). Because [delta]
18
O may be modified by temporal changes in the oceanic moisture source and/or
storm track trajectories, it is not possible to calculate temperature changes precisely (15). On the basis of present-day spatial
[delta]
18
O-temperature relations, the magnitude of [delta]
18
O variability around the mean is probably too large to ascribe to
changes in air temperature alone. Thus, temperature-driven changes in speleothem [delta]
18
O appear to have been accentuated
by synchronous changes in the [delta]
18
O of water vapor supplied to the site, resulting in a strong overall apparent relation
between temperature and speleothem [delta]
18
O.
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Fig. 2. (
A
) CC3 [delta]
18
O record for the period since 10 ky B.P. (upper curve) compared with the GISP2 record (lower curve). Individual U-Th dates and their ± 1
[sigma] error bars are shown in the upper part of the diagram. Open circles represent the published low-resolution conventionally sampled and analyzed [delta]
18
O data
(15), demonstrating the accuracy of the new laser-ablation data. The 8200 year event was not detected in the conventional [delta]
18
O data because of coarse sampling
resolution. The GISP2 curve is the 2-m data set with a resolution of approximately 24 years per [delta]
18
O analysis at 10 ky B.P., increasing to about 7 years per analysis
at 0.2 ky B.P. Also shown is the timing of the Bond et al. (5) ice-rafting events (1 through 6). RWP, Roman Warm Period; DACP, Dark Ages Cold Period; MWP,
Medieval Warm Period; LIA, Little Ice Age. Textural and mineralogical descriptions of stalagmite CC3 are given in given in (15). (
B
) Timing of events a through h and
the 8200 year event in the GISP2 record (y axis) compared with that in CC3 (x axis). Event timing is defined as [delta]
18
O minima or maxima. Error bars shown at
±2.5% for the CC3 chronology and 2.0% for the GISP2 chronology are estimates of dating uncertainties at the 2[sigma] level. The timing of events in both records is
identical within the dating uncertainties. Age differences for events range from essentially zero (event a) to 2.6% (event h).
Also shown in Fig. 2A (arrows labeled 1 through 6) is the approximate timing of abrupt cooling associated with North
Atlantic ice-rafting events (5, 9, 10). Only event 5 has a clear expression in either the CC3 record (upper curve, Fig. 2A) or in the
GISP2 ice core data (lower curve, Fig. 2A). Event 5, the so-called "8200 year cooling event," is defined in CC3 by eight data
points centered on 8.32 ± 0.12 ky B.P., and it exhibits a large (~8) decrease in [delta]
18
O. Event 6 (~9.45 ky B.P.) (5) does
not have a clear expression in the CC3 record, although it occurs just before several high-amplitude (>4) O isotope shifts in
the CC3 speleothem record
(Fig. 2A)
. Thus, several shifts to lower [delta]
18
O occur between approximately 9.4 and 8.8 ky B.P.,
some of which may be recorded in the lower resolution GISP2 record (arrows, Fig. 3). Detection of these events in sediments
from the North Atlantic (5, 10) is precluded by the relatively low resolution of the latter records.
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Fig. 3. Close up of period between 9500 and 8000 years showing the new laser ablation CC3 record (upper curve) and the GISP2 curve. The vertical shaded line at 8470
years B.P. labeled LLB denotes the approximate timing of the Laurentide Lakes Burst event
(24)
. U-series ages and their 1[sigma] error bars are shown in the upper part
of the diagram. Arrows denote timing of [delta]
18
O fluctuations in the new high-resolution record, interpreted as meltwater release events.
The 8200 year event, recognized as the only major Holocene [delta]
18
O event in the GRIP and GISP2 ice cores (1, 2) has
been interpreted to reflect a cooling of 7° ± 3°C (16). Cooling events dated between 8.4 to 8.0 ky B.P. have also been
documented in Europe (17-21), North America (6, 22), Northern Canada (23, 24), the Asian and North African moonsonal
domains
(25, 26)
, and the equatorial Cariaco Basin
(27)
. The timing of the 8200 year event in speleothem CC3 is within the
dating uncertainties of the GISP2 core, estimated at ±1 to 2% for this part of the Holocene (28). Thus, the maximum amplitude
occurs at 8.32 ± 0.12 ky B.P. compared with 8.215 ky B.P. in GISP2 and is coeval with faunal evidence for cooling at 8.30 ±
0.06 ky B.P. in core 28-03 from the Norwegian Channel (17). Shifts to lower [delta]
18
O between 9.4 and 8.8 ky B.P., detected
because of the very high resolution of this part of the record (1 to 3 years per analysis), are interpreted as precursor meltwater
release events (29) to the catastrophic 8200 year event. The extent to which these centennialscale changes in [delta]
18
O may be
linked to ice-rafting events in the North Atlantic is impossible to assess at present because of the relatively coarse resolution of
the latter records
(5, 10)
.
The amplitude of the shift to lower [delta]
18
O at 8.32 ky B.P. (~8) is too large to ascribe solely to a reduction in mean
annual air temperature (29). Instead, we attribute it predominantly to freshening of the surface of the adjacent North Atlantic
ocean by isotopically depleted meltwater. Evidence from planktonic foraminifera for a coeval shift in [delta]
18
O in North
Atlantic surface waters is equivocal (5, 9, 10, 30), possibly because enrichments in [delta]
18
O were offset by the lower [delta]
18
O
values of waters derived from melting drift-ice or because of a change in depth habitat in response to surface cooling (5, 10).
The chronology of our new record is consistent with suggestions (19, 24) that the 8200 year event was triggered by a
catastrophic release of meltwaters by sudden draining of large ice-dammed lakes on the margins of the Laurentide ice sheet in
northeastern Canada
(31)
, dated to 8.47 ± 0.30 ky B.P.
(24)
. The absence of a clear shift in [delta]
18
O in the speleothem data
during the other North Atlantic ice-rafting events at about 5.9, 4.3, 2.8, and 1.4 ky B.P. (5), despite the high resolution of the
new data (7 to 18 years per analysis), is important. It suggests that unlike the 8200 year event, the later Holocene ice rafting
events (5, 10) failed to trigger large changes in [delta]
18
O and, by implication, may not have established a detectable meltwater
cap on the mid-latitude North Atlantic (29).
Although precise comparisons between the GISP2 and CC3 records are hampered by dating uncertainties, the low amplitude
of the variations, and differences in sampling resolution, the subtle pattern of [delta]
18
O variability between approximately 8.4
and 4.5 ky B.P. is strikingly similar in both records (Fig. 2A). Excluding the 8200 year event, which is clearly common to both
records, approximately eight peaks and troughs may be correlated within the combined dating uncertainties in this time
interval (labeled a through h, Fig. 2A). Figure 2B illustrates that the timing of each event coincides in both records within the
dating uncertainties. Cooling events b, d, f, and h (Fig. 2A) may reflect weaker North Atlantic thermohaline overturning at 7.73,
7.01, 5.21, and 4.2 ky B.P., respectively (8). We interpret these covariations to mean that the subtle [delta]
18
O variability in the
early and mid-Holocene sections of the Greenland ice cores reflects coherent climate-driven in-phase changes in the [delta]
18
O
of precipitation over a large region around the eastern North Atlantic margin. Differences in the shape of individual peaks and
troughs are attributed to second
-
order effects such as temporal changes in the vapor source, trajectory, and rainout efficiency
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of clouds supplying moisture to these sites. The GISP2 and CC3 data appear to be decoupled in the latter part of the
Holocene, but the CC3 data exhibit variations that are broadly consistent with a Medieval Warm Period (MWP) at ~1000 ±
200 years ago and a two-stage Little Ice Age (LIA), as reconstructed by inverse modeling of temperature profiles in the
Greenland Ice Sheet (32).
The coherent [delta]
18
O variations in CC3 and GISP2 (events a through h, Fig. 2A) indicate that many of the subtle
multicentury [delta]
18
O variations in the Greenland ice cores reflect regional North Atlantic margin climate signals rather than
local effects. Spectral analysis of the data confirms the importance of multicentury variability with peaks centerd on 625, 169,
and 78 years. Taken together with historically documented variability (e.g., LIA and MWP in Fig. 2A) we argue that high-
frequency (centennial-scale) oscillations, perhaps reflecting North Atlantic thermohaline circulation changes (8, 33) may have a
more detectable impact on the climates of North Atlantic ocean-margin sites than the lower frequency events exquisitely
recorded by ice-rafting proxies.
References and Notes
1. W. Dansgaard et al., Nature
364,
218 (1993).
[Context Link]
2. P. M. Grootes, M. Stuiver, J. W. C. White, S. J. Johnsen, J. Jouzel, Nature
366,
552 (1993).
[Context Link]
3. P. A. Mayewski et al., J. Geophys. Res.
102,
26345 (1997). [Context Link]
4. R. B. Alley et al. Geology
25,
483 (1997).
[Context Link]
5. G. Bond et al. Science
278,
1257 (1997).
[Fulltext Link]
[Context Link]
6. I. D. Campbell, C. Campbell, M. J. Apps, N. W. Rutter, A. B. G. Bush, Geology
26,
471 (1998).
[Context Link]
7. F. S. Hu, H. E. Wright, E. Ito, K. Lease, Nature
400,
437 (1999).
[Context Link]
8. G. G. Bianchi, I. N. McCave, Nature
397,
515 (1999).
[Fulltext Link]
[BIOSIS Previews Link] [Context Link]
9. P. DeMenocal, J. Ortiz, T. Guilderson, M. Sarnthein, Science
288,
2198 (2000).
[Fulltext Link]
[Context Link]
10. G. Bond et al., in Mechanisms of Global Climate Change at Millennial Scales. P. U. Clark, R. S. Webb, L. D. Keogwin, Eds. (Geophysical Monograph
Series, American Geophysical Union, Washington, DC, 1999), vol. 12, pp. 35-58. [Context Link]
11. D. P. Mattey, M. Brownless, isotopes in Palaeoclimate Research, Abs. Vol. Conf. Leicester University (April 1999).
[Context Link]
12. The laser ablation-gas chromatography-isotope ratio mass spectrometry (LA-GC-IRMS) system uses a 25-W CO
2
laser heat source with a continuous
helium flow sample chamber to a gas chromatograph (GC) and mass spectrometer (MS). CO
2
is thermally released by 400-ms laser bursts (beam diameter,
approximately 150 µm) and is swept through a 80-cm packed GC column into the MS for isotope analysis, relative to a pulse of reference gas injected at the
start of the run. Analysis of Cararra marble and other standards gives similar [delta]
13
C values to those obtained by conventional acid digestion, but [delta]
18
O
values that are systematically lowered by 2. Replicate analyses of standards indicate that the isotope data are reproducible to better than 0.1 for [delta]
13
C
and 0.2 for [delta]
18
O. Using a system of forward and reverse profiling along the central growth axis of the stalagmite, a spatial resolution of 250 µm was
achieved. After the 2 correction, the new data accurately reproduce the first-order features of the coarse resolution O isotope record for this speleothem
(open circles,
Fig. 2A
) constructed previously by dental-drill sampling and conventional gas-source MS. Previous work has shown that O isotopes were
incorporated in isotopic equilibrium with the cave drip-waters
(15)
.
[Context Link]
13. Web table 1 is available at Science Online at www.sciencemag.org/cgi/content/full/294/5545/1328/DC1 . Ages were assigned by linear interpolation
between the dated intervals.
[Context Link]
14. For the latter part of the Holocene (since 5500 calendar years ago), each O isotope analysis represents 10 to 22 years, but the resolution is subdecadal for
all of the period before 5300 years ago, reflecting higher speleothem growth rates.
[Context Link]
15. F. McDermott et al. Quat. Sci. Rev.
18,
1021 (1999).
[Context Link]
16. K. M. Cuffey, R. B. Alley, P. M. Grootes, J. M. Bolzan, S. Anandakrishnan, J. Glaciol.
40,
341 (1994).
[Context Link]
17. D. Klitgaard-Kristensen, H. P. Sejrup, H. Haflidason, S. Johnsen, M. Spurk, J. Quat. Sci.
13,
165 (1998). [Context Link]
18. D. R. Rousseau, R. Precce, N. Limondin-Lozouet, Geology
26,
651 (1998).
[Context Link]
19. U. von Grafenstein, H. Erienkeuser, J. Muller, J. Jouzel, S. Johnsen, Clim. Dyn.
14,
73 (1998).
[Context Link]
20. A. Korhola, J. Weckstrom,
Quat. Res.
54,
284 (2000).
[Context Link]
Page
5
de
6
Ovid: McDermott: Science, Volume 294(5545).November 9, 2001.1328
-
1331
18/12/2001
21. A. Nesje, S. O. Dahl, J. Quat. Sci.
16,
155 (2001).
[Context Link]
22. W. E. Dean, Geol. Soc. Am. Spec. Pap.
276,
135 (1993).
[Context Link]
23. D. A. Fisher, R. M. Koerner, N. Reeth, Holocene
5,
19 (1995).
[Context Link]
24. D. C. Barber et al. Nature
400,
344 (1999).
[Fulltext Link]
[BIOSIS Previews Link]
[Context Link]
25. F. A. Street-Perrott, R. A. Perrott, Nature
358,
607 (1990).
[Context Link]
26. F. Sirocko et al., Nature
364,
322 (1993).
[BIOSIS Previews Link]
[Context Link]
27. K. Hugen, J. T. Overpeck, L. C. Peterson, S. Trumbore, Nature
380,
51 (1996).
[Context Link]
28. R. B. Alley et al. J. Geophys. Res.
102,
26367 (1997).
[Context Link]
29. The temperature dependence of [delta]
18
O in precipitation varies in space and time, but if air temperature was the only variable responsible, a decrease of
approximately 20°C would be required to explain the 8 decrease. This is based on the average d[delta]
18
O/dT relation in modern precipitation (~0.6 °C
-1
),
and the water-calcite fractionation that accompanies speleothem deposition (~-0.24 °C
-1
). Because the mean annual air temperature of the region is 10.4°C
and speleothem deposition continued through the event, changes in air temperature alone cannot account for a [delta]
18
O shift of this magnitude. Similar
arguments apply to the lower amplitude events between 9.4 and 8.8 ky B.P.
(Fig. 3)
.
[Context Link]
30. J. C. Duplessy, E. Bard, L. Labeyrie, J. Duprat, J. Moyes, Paleoceanography
8,
341 (1993).
[Context Link]
31. P. U. Clark, W. W. Fitzhugh, Quat. Res.
34,
296 (1990).
[Context Link]
32. D. Dahl-Jensen et al., Science
282,
268 (1998).
[Fulltext Link]
[Context Link]
33. H. W. Arz, S. Gerhardt, J. Pätzold, U. Röhl, Geology
29,
239 (2001).
[Context Link]
34. We gratefully acknowledge the assistance of M. Brownless during the course of this study. M. Gilmour (Open University) is thanked for providing the
four new TIMS U-Th dates. We thank the cave owners at Crag for their enthusiastic cooperation. We thank G. Bond and an anonymous reviewer for
constructive reviews.
Accession Number: 00007529-200111090-00017
Copyright (c) 2000-2001 Ovid Technologies, Inc.
Version: Version rel4.5.0, SourceID 1.5686.1.11
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... 4000-3300 cal a BP) sees lower than present DOI: 10.1002DOI: 10. /jqs.2983 precipitation in the Norwegian glacier record (Bakke et al., 2005); by contrast temperatures in south-west Ireland inferred from speleothems show a broad thermal minimum c. 3800 to 3400 cal a BP (McDermott et al., 2001). It is notable that this period is also characterized by a marked negative departure in chlorine in the GISP2 record, inferred as a weakening of the Icelandic low-pressure system between c. 4500 and 3600 cal a BP (O'Brien et al., 1995;Mayewski et al., 2004). ...
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Past warm intervals lasting from decades to centuries can be observed throughout the late Holocene geologic record using various proxy physical, chemical and fossil indices, in conjunction with seasonal information such as the timing of the first flowers of the spring season, or by the dates of first freezing and thaws of fresh water bodies, that have been recorded in various journals. Three important warm intervals that have been identified over the past 3500 years include the Late Bronze Age Optimum (BAO)(~1350 to ~1200 BC), the Iron/Roman Age Optimum (I/RAO)(~250 BC to ~400 AD) and the Medieval Warm Period (MWP)(~950 to ~1250 AD). The early phase of the BAO featured maximum development of the Hittite Empire and the evolution of the palace economy. The timing and duration of the later I/RAO show considerable variation from place to place in the Northern Hemisphere. MWP proxy records from several regions indicate that, like the I/RAO pattern, peak warmth occurred at different times in different places included in the Period’s overall footprint. Paleo-temperatures, both slightly cooler and warmer than present, have been reported. The WMP occurred during the Middle Ages at a time of the expansion of major commercial routes along the Mediterranean Sea coast and during an interval when Vikings explored and settled in some areas of the North Atlantic region.Sea level rise is among the suite of important ocean-related negative impacts that are often associated with contemporary global warming scenarios. Both early and modern societies have developed effective adaptation strategies and mitigation techniques to resist rising sea levels and flooding. Many of these have utility for Canada in both inland and especially in coastal areas of the Maritime Provinces. Early sea level rise and tidal flow mitigation measures include the construction of dykes around low-lying areas, sand dune stabilization and shoreline armoring using large boulders in concert with breakwaters and groynes. Today, there is also opportunity for the application of beach nourishment and artificial dune construction to resist erosion by storm waves and alongshore currents but these typically require annual maintenance to remain effective. Last resort mechanisms range from stilt home construction to abandonment (managed retreat) of previously impacted coastal areas. It is very likely that, when needed, Canadians will be able to apply a broad range of modern and ancient effective technologies and to engage engineering expertise to develop new (e.g., hybrid) approaches for combating specific negative coastal impacts than were available to BAO, I/RAO and MWP societies.
... Stalagmite d 18 O data from the Irish Crag Cave show a dominant sharp peak anomaly at 8.32 AE 0.12 ka BP. This anomaly is partly explained in terms of enhanced isotopic fractionation in precipitation during the 8.2-ka BP event (McDermott et al., 2001). The stalagmite (K3) from Katerloch Cave (Austria; Boch et al., 2009) exhibits a similar timing and structure of the anomaly found in the PN stalagmite at 8.13 AE 0.04 ka BP, where the minimum d 18 O values occur at 8.12 AE 0.04 ka BP and are characterized by a rapid decrease and a more gradual recovery. ...
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A distinct shift in δ18O, δ13C and trace element contents of the Père Noël (PN) stalagmite from southern Belgium revealed an abrupt climatic anomaly at 8.13 ± 0.03 ka BP (before present = before 1950 AD). This anomaly is characterized by a maximum drop in the δ18O (−1.4‰ compared the mean) between 8.13 and 8.10 ka BP (±0.03). This drop of δ18O coincides with a decrease in δ13C and trace element (Sr, Ba and Mg) concentrations suggesting drier conditions. Our precise chronology provides the timing of the outburst of proglacial lakes Agassiz and Ojibway that caused the δ18O, δ13C and trace elemental anomalies at 8.13–8.10 ± 0.03 ka BP, which corresponds to the 8.2‐ka BP event. The PN stalagmite bears δ18O values in fluid inclusions that covary with the δ18O values in calcite, suggesting that the speleothem calcite δ18O primarily reflects variations in the rainfall δ18O. Comparison of the PN record with different marine and terrestrial archives during the 8.2‐ka BP event shows a good agreement in timing and duration, suggesting that the PN speleothem can be regarded as a valuable proxy to better understand the 8.2‐ka BP event.
... In the last decades, increasing attention has been given to better understanding spatiotemporal variability of the ocean-atmosphere system, and to reconstructing past climate fluctuations using proxy data (Schöne et al., 2005a;Cunningham et al., 2013;Reynolds et al., 2016;Beil et al., 2015). Most of the well-calibrated proxy archives at interannual scales derive from tree rings, ice cores, corals and speleothems (McDermott et al., 2001;Reynolds et al., 2016). However recently, several publications highlighted the potentiality of annually long-term records of bivalve mollusks for climate reconstruction such as sea surface temperature (SST) (Schöne et al., 2004;Black et al., 2009;Cunningham et al., 2013;Reynolds et al., 2016), North Atlantic Oscillation (NAO) (Schöne et al., 2003) and Atlantic Multidecadal Oscillation (AMO) (Wanamaker et al., 2011). ...
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Seasonally formed, perennial growth increments of various organisms may possibly contain information about past environmental changes, well before instrumental measurements occurred. Such annually resolved proxy records have been mainly obtained from terrestrial archives, with a paucity of similar data originating from marine habitats. Iceland represents ideal conditions to develop both, tree ring (dendro) and bivalve shell (sclero) chronologies from adjacent sites. Here we introduce the first network of Icelandic birch (Betula pubescens Ehrh.) and rowan (Sorbus aucuparia) dendrochronologies, as well as ocean quahog (Arctica islandica L.) sclerochronologies. In order to identify the dominant external drivers of tree and shell growth, we assess the common growth trends and growth extremes within and between the terrestrial and marine records, as well as relationships of both archives with instrumental-based meteorological indices. Capturing a strong signal of June–August mean air temperature, the dendrochronologies are significantly positively correlated to each other. The sclerochronologies, however, reveal much lower growth coherency, which likely results from different sampling strategies and growth habitats. Disagreement between the dendro- and sclerochronologies possibly originates from unequal sample size, offset in the seasonal timing and rate of the growth, as well as varying sensitivities to different environmental factors. Our results emphasize the importance of considering a wide range of species and taxa to reconstruct a more complete picture of terrestrial and marine ecosystem functioning and productivity across various spatiotemporal scales.
Thesis
Küstenprozesse zu verstehen ist wichtig, um sich an mögliche Küstenveränderungen anpassen zu können. Eine Projektion von zukünftigen Küstenveränderungen kann nur auf der Grundlage eines gegenwärtigen und vergangen Küstenverständnisses durchgeführt werden. Das Verstehen der vergangenen Küstenbedingungen, welches auf den in den Küstensedimenten erhaltenen Hinweisen beruht, erfordert den Faktor Zeit. Küstensedimente bestehen aus organischem Material und/oder Mineralien, abhängig von ihren geologischen Ablagerungsbedingungen. Optisch stimulierte Lumineszenz (OSL) ist ein leistungsfähiges Werkzeug zur Datierung verschiedener geologischer Materialien. In dieser Studie wurden in drei Untersuchungsgebieten OSL Datierungen mittels des Einzelproben-Protokolls mit regenerierter Dosis (SAR) an mineralreichen Küstensedimenten durchgeführt. Erstens wurde OSL in Songkhla in Südthailand auf Quarz-Feinkorn Sand aus Wellen-, Wind-, Lagunen- und Fluvialumgebungen angewendet, um die geologische Entwicklung aufzuzeigen. Zweitens wurden in Trassenheide an der Ostseeküste Deutschlands anhand von Quarzen in der Sand-Fraktion Küstendünen datiert, die bisher anhand der Bodenfarbe klassifiziert worden sind. Drittens wurden in Ephesos in der Türkei vor- und nach-antike Hafensedimente mit Quarzen und Feldspäten der Silt-Fraktion (Polymineral) datiert. Die Alter wurden dann mit Studien und Radiokohlenstoff-Alter aus der Umgebung verglichen. Nach der Messung des Lumineszenzsignals und der Anwendung statistischer Methoden zeigte die Äquivalentdosis Werte zwischen 0,56 und 153 Gy. Die Dosisrate sand-reicher Sedimente (durchschnittlich 0,91 Gy / ka) war niedriger als die der schluffreichen Sedimente (durchschnittlich 2,74 Gy/ka). OSL Alter zwischen ca. 160-0,6 ka zeigten Fehler von weniger als 10%. Es wurden zwei Probleme gefunden: zum einen die unvollständige Bleichung und zum anderen der Einfluss der Verwitterung. In Songkhla wurde der Verwitterungeffekt aufgrund eines sehr niedrigen Kaliumgehalts (Effekt auf die Dosisrate) beobachtet, was zu einem überschätzten Alter führte (nachgewiesen durch den Meeresspiegeltrend). Dieses Problem wurde durch Verwendung eines zeitabhängigen Dosisratenmodells gelöst. In Ephesos wurden Hafensedimente wahrscheinlich in trübem Wasser gebildet und dort gab es dann auch nicht genügend Sonnenlicht zum Zurücksetzen des OSL-Signals. Das unvollständige Bleichen führte zu überschätzten Altern (nicht konsistent in der Alters-Tiefen-Kurve). Gut gebleichte Proben konnten jedoch beobachtet werden, wenn Quarz- und Feldspatalter (in den polymineralischen Fraktionen) übereinstimmten. In Songkhla hat OSL anhand sandiger Sedimentproben die Hypothese eines Meeresspiegelhochstandes sowohl im letzten Interglazial (ca. 127 ka) als auch im mittleren Holozän (ca. 6 ka) bewiesen. Nach dem Meeresspiegelstand bei ca. 127 ka sank der Meeresspiegel und Songkhla war mehrere hundert Kilometer von der Küste entfernt. Vor 50 bis 17 ka gab es Wind-, Fluss-, und Seeablagerungen, die mittels OSL datiert werden konnten. In dieser Studie wurde OSL auch verwendet, um gemischte, feine und grobe Sedimente zu datieren, die als Lagune (ca. 7 ka) klassifiziert wurden. OSL-Alter von Holozänproben stimmten mit den in früheren Studien vorhergesagten Meeresspiegelkurven überein. In Trassenheide waren OSL-Alter das bessere Datierungswerkzeug, um die Dünenentwicklung zu klassifizieren. Dünenbildungen wurden durch OSL-Alter auf ca. 2,5-1,6 ka (Römische Warmzeit) und auf ca. 0,6 ka (nach der Mittelalterlichen Warmzeit) datiert. Während 1,6-0,6 ka gab es keine Dünenbildung, was mit einer starken Küstenerosion in der Ostsee zu dieser Zeit zusammenhängen könnte. In Ephesus beschrieben konsistente OSL- und 14C-Alter die geologische Entwicklung seit ca. 3 ka, als Ephesus einen marinen Ablagerungsraum darstellte. Um etwas 2,5 ka entwickelte sich das Delta schnell; OSL-Alter zeigen eine sehr hohe Ablagerungsrate von bis zu 65 mm/Jahr. Eine intensive Hafennutzung fand um ca. 2 ka statt. OSL-Alter aus dieser Studie stimmen mit früheren 14C-Altern an Seesedimenten überein, die aus nahe gelegene Kernproben im selben Untersuchungsgebiet stammten. Zusammenfassend kann gesagt werden, dass OSL ein sehr nützliches Werkzeug ist, um den geochronologischen Rahmen für Küstensedimente zu liefern und mit ihr können die geologische Entwicklung, der Meeresspiegelwechsel und archäologische Ereignisse seit dem späten Pleistozän gut beschrieben werden. Durch Kombination mit anderen Methoden und Daten, wie z.B. Paläontologie, Paläoklimatologie, tragen OSL Datierungen dazu bei das Verständnis der Paläogeographie von Küstengebieten zu fördern.
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This bibliometric analysis deals with research on the decline and fall of the Western Roman Empire in connection with climate change. Based on the Web of Science (WoS) database, we applied a combination of three different search queries for retrieving the relevant literature: (1) on the decline and fall of the Roman Empire in general, (2) more specifically on the downfall in connection with a changing climate, and (3) on paleoclimatic research in combination with the time period of the Roman Empire and Late Antiquity. Additionally, we considered all references cited by an ensemble of selected key papers and all citing papers of these key papers, whereby we retrieved additional publications (in particular, books and book chapters). We merged the literature retrieved, receiving a final publication set of 85 publications. We analyzed this publication set by applying a toolset of bibliometric methods and visualization programs. A co-authorship map of all authors, a keyword map for a rough content analysis, and a citation network based on the publication set of 85 papers are presented. We also considered news mentions in this study to identify papers with impacts beyond science. According to the literature retrieved, a multitude of paleoclimatic data from various geographical sites for the time of late antiquity indicate a climatic shift away from the stability of previous centuries. Recently, some scholars have argued that drought in Central Asia and the onset of a cooler climate in North-West Eurasia may have put Germanic tribes, Goths, and Huns on the move into the Roman Empire, provoking the Migration Period and eventually leading to the downfall of the Western Roman Empire. However, climate is only one variable at play; a combination of many factors interacting with each other is a possible explanation for the pattern of long-lasting decline and final collapse. Currently, the number of records from different locations, the toolbox of suitable analytic methods, and the precision of dating are evolving rapidly, contributing to an answer for one of the most classic of all historical questions. However, these studies still lack the inevitable collaboration of the major disciplines involved: archeology, history, and climatology. The articles of the publication set analyzed mainly result from research in the geosciences.
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Heinrich events, the massive episodic disgorgement of sediment-laden ice from the Laurentide Ice Sheet to the North Atlantic Ocean, are a puzzling instability of the Ice-Age climate system. Although there is broad agreement on the defining characteristics of Heinrich events, the glaciological mechanisms remain controversial. Paleoceanographic records show that Heinrich events tend to occur at the culmination of a cooling cycle, termed the Bond cycle, and this has invited the interpretation that the events are a fast response of the Laurentide Ice Sheet to external atmospheric changes. A vexing issue for glaciologists is how a fast and timely response to an external forcing can possibly be reconciled with the known physics of glaciers and ice sheets. Fast changes in glacier behavior can only occur if some flow instability is excited. Thus glaciologists tend to favor the idea that the climate change occurring at the culmination of a Bond cycle is an atmospheric response to ice sheet instability. However, a free-running cyclic flow instability, such as that exhibited by surging glaciers, could not satisfy the timing requirements. Using computer modeling we explore ways to resolve these conflicts.
[Fulltext Link] [Context Link]
  • G Bond
G. Bond et al. Science 278, 1257 (1997). [Fulltext Link] [Context Link]
  • U Von Grafenstein
  • H Erienkeuser
  • J Muller
  • J Jouzel
  • S Johnsen
U. von Grafenstein, H. Erienkeuser, J. Muller, J. Jouzel, S. Johnsen, Clim. Dyn. 14, 73 (1998). [Context Link]
  • W Dansgaard
W. Dansgaard et al., Nature 364, 218 (1993). [Context Link]
  • P A Mayewski
P. A. Mayewski et al., J. Geophys. Res. 102, 26345 (1997). [Context Link]
  • I D Campbell
  • C Campbell
  • M J Apps
  • N W Rutter
  • A B G Bush
I. D. Campbell, C. Campbell, M. J. Apps, N. W. Rutter, A. B. G. Bush, Geology 26, 471 (1998). [Context Link]
  • D C Barber
D. C. Barber et al. Nature 400, 344 (1999). [Fulltext Link] [BIOSIS Previews Link] [Context Link]
  • J C Duplessy
  • E Bard
  • L Labeyrie
  • J Duprat
  • J Moyes
J. C. Duplessy, E. Bard, L. Labeyrie, J. Duprat, J. Moyes, Paleoceanography 8, 341 (1993). [Context Link]
  • D Klitgaard-Kristensen
  • H P Sejrup
  • H Haflidason
  • S Johnsen
  • M Spurk
D. Klitgaard-Kristensen, H. P. Sejrup, H. Haflidason, S. Johnsen, M. Spurk, J. Quat. Sci. 13, 165 (1998). [Context Link]
  • W E Dean
W. E. Dean, Geol. Soc. Am. Spec. Pap. 276, 135 (1993). [Context Link]