EVIDENCE FOR MILLENNIAL-SCALE CLIMATE VARIABILITY IN THE SURFACE WATERS ABOVE ODP SITE 984, NE ATLANTIC OCEAN DURING THE LAST GLACIAL INTERVAL (MIS 4-2)

Abstract. The last glacial period (LGP; ca. 110–10 kyr BP) was marked by the existence of two types of abrupt climatic changes, Dansgaard–Oeschger (DO) and Heinrich (H) events. Although the mechanisms behind these are not fully understood, it is generally accepted that the presence of ice sheets played an important role in their occurrence. While an important effort has been made to investigate the dynamics and evolution of the Laurentide ice sheet (LIS) during this period, the Eurasian ice sheet (EIS) has not received much attention, in particular from a modeling perspective. However, meltwater discharge from this and other ice sheets surrounding the Nordic seas is often implied as a potential cause of ocean instabilities that lead to glacial abrupt climate changes. Thus, a better comprehension of the evolution of the EIS during the LGP is important to understand its role in glacial abrupt climate changes. Here we investigate the response of the EIS to millennial-scale climate variability during the LGP. We use a hybrid, three-dimensional, thermomechanical ice-sheet model that includes ice shelves and ice streams. The model is forced off-line via a novel perturbative approach that, as opposed to conventional methods, clearly differentiates between the spatial patterns of millennial-scale and orbital-scale climate variability. Thus, it provides a more realistic treatment of the forcing at millennial timescales. The effect of both atmospheric and oceanic variations are included. Our results show that the EIS responds with enhanced ice discharge in phase with interstadial warming in the North Atlantic when forced with surface ocean temperatures. Conversely, when subsurface ocean temperatures are used, enhanced ice discharge occurs both during stadials and at the beginning of the interstadials. Separating the atmospheric and oceanic effects demonstrates the major role of the ocean in controlling the dynamics of the EIS on millennial timescales. While the atmospheric forcing alone is only able to produce modest iceberg discharges, warming of the ocean leads to higher rates of iceberg discharges as a result of relatively strong basal melting at the margins of the ice sheet. Our results clearly show the capability of the EIS to react to glacial abrupt climate changes, and highlight the need for stronger constraints on the ice sheet's glacial dynamics and climate–ocean interactions.

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Ecological thresholds and patterns of millennial-scale climate variability: The response of vegetation in Greece during the last glacial period

Geology ◽

10.1130/g20118.1 ◽

2004 ◽

Vol 32 (2) ◽

pp. 109 ◽

Cited By ~ 106

Author(s):

P.C. Tzedakis ◽

M.R. Frogley ◽

I.T. Lawson ◽

R.C. Preece ◽

I. Cacho ◽

...

Keyword(s):

Climate Variability ◽

Glacial Period ◽

Last Glacial Period ◽

Ecological Thresholds ◽

Last Glacial ◽

The Last Glacial ◽

Millennial Scale

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Multi-Proxy Approach for Identifying Heinrich Events in Sediment Cores from Hatton Bank (NE Atlantic Ocean)

Geosciences ◽

10.3390/geosciences10010014 ◽

2019 ◽

Vol 10 (1) ◽

pp. 14 ◽

Cited By ~ 1

Author(s):

Miriam Sayago-Gil ◽

Nieves López-González ◽

David Long ◽

Luis Miguel Fernández-Salas ◽

Pablo Durán-Muñoz

Keyword(s):

Atlantic Ocean ◽

Sediment Cores ◽

Interglacial Period ◽

Ne Atlantic ◽

Depositional History ◽

Geochemical Composition ◽

Heinrich Events ◽

Ne Atlantic Ocean ◽

History Of ◽

The Last Glacial

A series of six gravity cores has been used to reconstruct the depositional history of Hatton Bank (Rockall Plateau, NE Atlantic Ocean). The cores have been studied for magnetic susceptibility (MS), geochemical composition, grain size distribution, and a semi-quantitative foraminiferal association. Two main interbedded facies have been described: (i) calcareous ooze; and (ii) lithogenous silt. The study reveals prominent peaks from the MS signal, silt, Mg/Ca, Fe/Ca, Al/Ca, and Rare Earth Elements normalised by Continental Crust (REE/CC), which are sensitive indicators for Heinrich events (H1, H2, H3, H4, and H5) and ash layers. These peaks may relate to alternations in dominance of the calcareous and lithogenic facies. The sediment displays a high percentage of carbonate in interglacial layers but is lithogenic-dominated in glacial stages. The layers with prominent lithic-rich and foraminifera-poor sediments (established as Heinrich layers) may be related to a possible palaeoclimatic effect, where freshwater discharged during iceberg melting may have reduced the formation of North Atlantic Deep Water (NADW). In the study area, the mean sedimentation rates for the last glacial as ~4.2 cm ka−1 and ~1.4 cm ka−1 for the last ~18 ka (interglacial period) have been estimated. Besides this evidence, Fe/Ca and MS peaks may reflect the presence of basalt, either introduced through ice-rafting or transported and redistributed by bottom currents in the study area. Certain indices, including MS and Fe/Ca, are proposed as good proxies for detecting Heinrich events and ash layers in the Hatton Bank sediments and, in consequence, are parameters that can be used to infer strengthened/weakened NADW formation, according to stadials/interstadials. Moreover, we suggest that the northernmost boundary of the area with evidence of Heinrich events may be situated around 57°38′ N in the Hatton–Rockall area, at least for H4, based on the variation of the Mg/Ca and Fe/Ca curves.

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Mollusk record of millennial climate variability in the Loess Plateau during the Last Glacial Maximum

Boreas ◽

10.1080/03009480210648 ◽

2002 ◽

Vol 31 (1) ◽

pp. 20-27 ◽

Cited By ~ 31

Author(s):

Naiqin Wu ◽

Tungsheng Liu ◽

Xiuping Liu ◽

Zhaoyan Gu

Keyword(s):

Climate Variability ◽

Last Glacial Maximum ◽

Loess Plateau ◽

Glacial Maximum ◽

The Loess Plateau ◽

Last Glacial ◽

The Last Glacial Maximum ◽

The Last Glacial

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Suspended particulate matter in a submarine canyon (Whittard Canyon, Bay of Biscay, NE Atlantic Ocean): Assessment of commonly used instruments to record turbidity

Marine Geology ◽

10.1016/j.margeo.2021.106439 ◽

2021 ◽

Vol 434 ◽

pp. 106439

Author(s):

Sabine Haalboom ◽

Henko de Stigter ◽

Gerard Duineveld ◽

Hans van Haren ◽

Gert-Jan Reichart ◽

...

Keyword(s):

Particulate Matter ◽

Atlantic Ocean ◽

Suspended Particulate Matter ◽

Submarine Canyon ◽

Bay Of Biscay ◽

Ne Atlantic ◽

Suspended Particulate ◽

Ne Atlantic Ocean

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<i>δ</i><sup>13</sup>C decreases in the upper western South Atlantic during Heinrich Stadials 3 and 2

Climate of the Past ◽

10.5194/cp-13-345-2017 ◽

2017 ◽

Vol 13 (4) ◽

pp. 345-358 ◽

Cited By ~ 4

Author(s):

Marília C. Campos ◽

Cristiano M. Chiessi ◽

Ines Voigt ◽

Alberto R. Piola ◽

Henning Kuhnert ◽

...

Keyword(s):

Climate Change ◽

South Atlantic ◽

Meridional Overturning Circulation ◽

Glacial Period ◽

Last Deglaciation ◽

Last Glacial Period ◽

Last Glacial ◽

Change Events ◽

The Last Glacial ◽

Millennial Scale

Abstract. Abrupt millennial-scale climate change events of the last deglaciation (i.e. Heinrich Stadial 1 and the Younger Dryas) were accompanied by marked increases in atmospheric CO2 (CO2atm) and decreases in its stable carbon isotopic ratios (δ13C), i.e. δ13CO2atm, presumably due to outgassing from the ocean. However, information on the preceding Heinrich Stadials during the last glacial period is scarce. Here we present δ13C records from two species of planktonic foraminifera from the western South Atlantic that reveal major decreases (up to 1 ‰) during Heinrich Stadials 3 and 2. These δ13C decreases are most likely related to millennial-scale periods of weakening of the Atlantic meridional overturning circulation and the consequent increase (decrease) in CO2atm (δ13CO2atm). We hypothesise two mechanisms that could account for the decreases observed in our records, namely strengthening of Southern Ocean deep-water ventilation and weakening of the biological pump. Additionally, we suggest that air–sea gas exchange could have contributed to the observed δ13C decreases. Together with other lines of evidence, our data are consistent with the hypothesis that the CO2 added to the atmosphere during abrupt millennial-scale climate change events of the last glacial period also originated in the ocean and reached the atmosphere by outgassing. The temporal evolution of δ13C during Heinrich Stadials 3 and 2 in our records is characterized by two relative minima separated by a relative maximum. This w structure is also found in North Atlantic and South American records, further suggesting that such a structure is a pervasive feature of Heinrich Stadial 2 and, possibly, also Heinrich Stadial 3.

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