Hydrological changes in eastern europe during the last 40,000 yr inferred from biomarkers in Black Sea Sediments

2013 ◽  
Vol 80 (3) ◽  
pp. 502-509 ◽  
Author(s):  
Frauke Rostek ◽  
Edouard Bard
Keyword(s):  
Black Sea ◽  
Ice Cores ◽  
Russian Plain ◽  
The Black Sea ◽  
Permafrost Degradation ◽  
Glacial Period ◽  
Last Glacial Period ◽  
Last Glacial ◽  
Hydrological Changes ◽  
The Last Glacial

The Black Sea is connected to a large drainage area including the European Russian Plain, part of the Alps and southeastern Europe. To study the hydrological changes in this basin over the last 40,000 years, we measured specific terrigenous biomarkers for wetland vegetation in well-dated sediments from the northwestern Black Sea, spanning the last glacial period (lacustrine phase) and the Holocene (marine phase). Low abundances of these biomarkers are observed during the North Atlantic ice melting and cooling events known as Heinrich Events 4 to 2, the Last Glacial Maximum and the Younger Dryas Event. Increased biomarker inputs characterize the mild climate phases known as Dansgaard–Oeschger Interstadials, the Bølling/Allerød and Preboreal Warmings indicating increased erosion due to permafrost degradation, higher primary productivity and/or wetland extension in the drainage basin. The final retreat of the Fennoscandian Ice Sheet from the Russian Plain occurs during the early part of Heinrich Event 1 and is characterized by increased biomarker concentrations in a typical series of four deglacial clay layers. For the last glacial period, the correspondence in timing between the biomarker records and the atmospheric CH4 record from ice cores, suggests an important CH4 contribution due to boreal permafrost thawing and wetland emission.

scholarly journals Millennial and sub-millennial scale climatic variations recorded in polar ice cores over the last glacial period

2010 ◽  
Vol 6 (1) ◽  
pp. 135-183 ◽  
Author(s):  
E. Capron ◽  
A. Landais ◽  
J. Chappellaz ◽  
A. Schilt ◽  
D. Buiron ◽  
...  
Keyword(s):  
Climatic Variability ◽  
Ice Sheets ◽  
Ice Cores ◽  
Glacial Period ◽  
Last Glacial Period ◽  
Last Glacial ◽  
Dronning Maud Land ◽  
Mis 5 ◽  
The Last Glacial ◽  
Millennial Scale

Abstract. Since its discovery in Greenland ice cores, the millennial scale climatic variability of the last glacial period has been increasingly documented at all latitudes with studies focusing mainly on Marine Isotopic Stage 3 (MIS 3; 28–60 thousand of years before present, hereafter ka) and characterized by short Dansgaard-Oeschger (DO) events. Recent and new results obtained on the EPICA and NorthGRIP ice cores now precisely describe the rapid variations of Antarctic and Greenland temperature during MIS 5 (73.5–123 ka), a time period corresponding to relatively high sea level. The results display a succession of long DO events enabling us to highlight a sub-millennial scale climatic variability depicted by i) short-lived and abrupt warming events preceding some Greenland InterStadial (GIS) (precursor-type events) and ii) abrupt warming events at the end of some GIS (rebound-type events). The occurrence of these secondary events is suggested to be driven by the Northern Hemisphere summertime insolation at 65° N together with the internal forcing of ice sheets. Thanks to a recent NorthGRIP-EPICA Dronning Maud Land (EDML) common timescale over MIS 5, the bipolar sequence of climatic events can be established at millennial to sub-millennial timescale. This provides evidence that a linear relationship is not satisfactory in explaining the link between Antarctic warming amplitudes and the duration of their concurrent Greenland Stadial (GS) for the entire glacial period. The conceptual model for a thermal bipolar seesaw permits a reconstruction of the Antarctic response to the northern millennial and sub-millennial scale variability over MIS 5. However, we show that when ice sheets are extensive, Antarctica does not necessarily warm during the whole GS as the thermal bipolar seesaw model would predict.

scholarly journals NALPS19: Sub-orbital scale climate variability recorded in Northern Alpine speleothems during the last glacial period

2019 ◽  
Author(s):  
Gina E. Moseley ◽  
Christoph Spötl ◽  
Susanne Brandstätter ◽  
Tobias Erhardt ◽  
Marc Luetscher ◽  
...  
Keyword(s):  
Climate Variability ◽  
Asian Monsoon ◽  
Ice Core ◽  
Ice Cores ◽  
High Elevation ◽  
Glacial Period ◽  
Last Glacial Period ◽  
Last Glacial ◽  
Change State ◽  
The Last Glacial

Abstract. Sub-orbital-scale climate variability of the last glacial period provides important insights into the rates that the climate can change state, the mechanisms that drive that change, and the leads, lags and synchronicity occurring across different climate zones. Such short-term climate variability has previously been investigated using speleothems from the northern rim of the Alps (NALPS), enabling direct chronological comparisons with highly similar shifts in Greenland ice cores. In this study, we present NALPS19, which includes a revision of the last glacial NALPS δ18O chronology over the interval 118.3 to 63.7 ka using eleven,newly-available, clean, precisely-dated stalagmites from five caves. Using only the most reliable and precisely dated records, this period is now 90 % complete and is comprised of 15 stalagmites from seven caves. Where speleothems grew synchronously, major transitional events between stadials and interstadials (and vice versa) are all in agreement within uncertainty. Ramp-fitting analysis further reveals good agreement between the NALPS19 speleothem δ18O record, the GICC05modelext NGRIP ice-core δ18O record, and the Asian Monsoon composite speleothem δ18O record. In contrast, NGRIP ice-core δ18O on AICC2012 appears to be considerably too young. We also propose a longer duration for the interval covering Greenland Stadial (GS) 22 to GS-21.2 in line with the Asian monsoon and NGRIP-EDML. Given the near-complete record of δ18O variability during the last glacial period in the northern Alps, we offer preliminary considerations regarding the controls on mean δ18O. We find that as expected, δ18O values became increasingly more depleted with distance from the oceanic source regions, and increasingly depleted with increasing altitude. Exceptions were found for some high-elevation sites that locally display δ18O values that are too high in comparison to lower-elevation sites, thus indicating a summer bias in the recorded signal. Finally, we propose a new mechanism for the centennial-scale stadial-level depletions in δ18O such as "pre-cursor" events GS-16.2, GS-17.2, GS-21.2, and GS-23.2, as well as the "within-interstadial" GS-24.2 event. Our new high-precision chronology shows that each of these δ18O depletions occurred shortly following rapid rises in sea level associated with increased ice-rafted debris and southward shifts in the Intertropical Convergence Zone, suggesting that influxes of meltwater from moderately-sized ice sheets may have been responsible for the cold reversals causing the AMOC to slow down similar to the Preboreal Oscillation and Older Dryas deglacial events.

scholarly journals Ostracods as ecological and isotopic indicators of lake water salinity changes: the Lake Van example

2019 ◽  
Vol 16 (10) ◽  
pp. 2095-2114 ◽  
Author(s):  
Jeremy McCormack ◽  
Finn Viehberg ◽  
Derya Akdemir ◽  
Adrian Immenhauser ◽  
Ola Kwiecien
Keyword(s):  
Lake Water ◽  
Lake Level ◽  
Water Salinity ◽  
Glacial Period ◽  
Lake Van ◽  
Faunal Assemblage ◽  
Last Glacial Period ◽  
Last Glacial ◽  
Hydrological Changes ◽  
The Last Glacial

Abstract. Ostracods are common lacustrine calcitic microfossils. Their faunal assemblage and morphological characteristics are important ecological proxies, and their valves are archives of geochemical information related to palaeoclimatic and palaeohydrological changes. In an attempt to assess ostracod ecology (taxonomic diversity and valve morphology) combined with valve geochemistry (δ18O and δ13C) as palaeosalinity indicators, we analysed sedimentary material from the International Continental Scientific Drilling Program (ICDP) Ahlat Ridge site from a terminal and alkaline lake, Lake Van (Turkey), covering the last 150 kyr. Despite a low species diversity, the ostracod faunal assemblage reacted sensitively to changes in the concentration of total dissolved salts in their aquatic environment. Limnocythere inopinata is present throughout the studied interval, while Limnocythere sp. A is restricted to the Last Glacial period and related to increased lake water salinity and alkalinity. The presence of species belonging to the genus Candona is limited to periods of lower salinity. Valves of Limnocytherinae species (incl. L. inopinata) display nodes (hollow protrusions) during intervals of increased salinity. Both the number of noded valves and the number of nodes per valve appear to increase with rising salinity, suggesting that node formation is related to hydrological changes (salinity and/or alkalinity). In contrast to Lake Van's bulk δ18O record, the δ18O values of ostracod valves do record relative changes of the lake volume, with lower values during high lake level periods. The δ13C values of different species reflect ostracod habitat preferences (i.e. infaunal vs. epifaunal) but are less sensitive to hydrological changes. However, combined with other proxies, decreasing Holocene δ13C values may indicate a freshening of the lake water compared to the low lake level during the Last Glacial period. The Lake Van example underscores the significance and value of coupling ostracod ecology and valve geochemistry in palaeoenvironmental studies of endorheic lake basins.

scholarly journals Millennial and sub-millennial scale climatic variations recorded in polar ice cores over the last glacial period

2010 ◽  
Vol 6 (3) ◽  
pp. 345-365 ◽  
Author(s):  
E. Capron ◽  
A. Landais ◽  
J. Chappellaz ◽  
A. Schilt ◽  
D. Buiron ◽  
...  
Keyword(s):  
Climatic Variability ◽  
Ice Core ◽  
Ice Sheets ◽  
Ice Cores ◽  
Glacial Period ◽  
Last Glacial Period ◽  
Last Glacial ◽  
Mis 5 ◽  
The Last Glacial ◽  
Millennial Scale

Abstract. Since its discovery in Greenland ice cores, the millennial scale climatic variability of the last glacial period has been increasingly documented at all latitudes with studies focusing mainly on Marine Isotopic Stage 3 (MIS 3; 28–60 thousand of years before present, hereafter ka) and characterized by short Dansgaard-Oeschger (DO) events. Recent and new results obtained on the EPICA and NorthGRIP ice cores now precisely describe the rapid variations of Antarctic and Greenland temperature during MIS 5 (73.5–123 ka), a time period corresponding to relatively high sea level. The results display a succession of abrupt events associated with long Greenland InterStadial phases (GIS) enabling us to highlight a sub-millennial scale climatic variability depicted by (i) short-lived and abrupt warming events preceding some GIS (precursor-type events) and (ii) abrupt warming events at the end of some GIS (rebound-type events). The occurrence of these sub-millennial scale events is suggested to be driven by the insolation at high northern latitudes together with the internal forcing of ice sheets. Thanks to a recent NorthGRIP-EPICA Dronning Maud Land (EDML) common timescale over MIS 5, the bipolar sequence of climatic events can be established at millennial to sub-millennial timescale. This shows that for extraordinary long stadial durations the accompanying Antarctic warming amplitude cannot be described by a simple linear relationship between the two as expected from the bipolar seesaw concept. We also show that when ice sheets are extensive, Antarctica does not necessarily warm during the whole GS as the thermal bipolar seesaw model would predict, questioning the Greenland ice core temperature records as a proxy for AMOC changes throughout the glacial period.

scholarly journals Bipolar volcanic synchronization of abrupt climate change in Greenland and Antarctic ice cores during the last glacial period

2020 ◽  
Vol 16 (4) ◽  
pp. 1565-1580
Author(s):  
Anders Svensson ◽  
Dorthe Dahl-Jensen ◽  
Jørgen Peder Steffensen ◽  
Thomas Blunier ◽  
Sune O. Rasmussen ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Volcanic Eruptions ◽  
Abrupt Climate Change ◽  
Glacial Period ◽  
Deuterium Excess ◽  
Last Glacial Period ◽  
Last Glacial ◽  
The Antarctic ◽  
The Last Glacial

Abstract. The last glacial period is characterized by a number of millennial climate events that have been identified in both Greenland and Antarctic ice cores and that are abrupt in Greenland climate records. The mechanisms governing this climate variability remain a puzzle that requires a precise synchronization of ice cores from the two hemispheres to be resolved. Previously, Greenland and Antarctic ice cores have been synchronized primarily via their common records of gas concentrations or isotopes from the trapped air and via cosmogenic isotopes measured on the ice. In this work, we apply ice core volcanic proxies and annual layer counting to identify large volcanic eruptions that have left a signature in both Greenland and Antarctica. Generally, no tephra is associated with those eruptions in the ice cores, so the source of the eruptions cannot be identified. Instead, we identify and match sequences of volcanic eruptions with bipolar distribution of sulfate, i.e. unique patterns of volcanic events separated by the same number of years at the two poles. Using this approach, we pinpoint 82 large bipolar volcanic eruptions throughout the second half of the last glacial period (12–60 ka). This improved ice core synchronization is applied to determine the bipolar phasing of abrupt climate change events at decadal-scale precision. In response to Greenland abrupt climatic transitions, we find a response in the Antarctic water isotope signals (δ18O and deuterium excess) that is both more immediate and more abrupt than that found with previous gas-based interpolar synchronizations, providing additional support for our volcanic framework. On average, the Antarctic bipolar seesaw climate response lags the midpoint of Greenland abrupt δ18O transitions by 122±24 years. The time difference between Antarctic signals in deuterium excess and δ18O, which likewise informs the time needed to propagate the signal as described by the theory of the bipolar seesaw but is less sensitive to synchronization errors, suggests an Antarctic δ18O lag behind Greenland of 152±37 years. These estimates are shorter than the 200 years suggested by earlier gas-based synchronizations. As before, we find variations in the timing and duration between the response at different sites and for different events suggesting an interaction of oceanic and atmospheric teleconnection patterns as well as internal climate variability.

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