Millennial‐scale environmental changes in the northwestern Japan Sea during the last glacial cycle

Boreas ◽  
2020 ◽  
Author(s):  
Tatiana A. Evstigneeva ◽  
Marina V. Cherepanova ◽  
Sergey A. Gorbarenko ◽  
Xuefa Shi ◽  
Alexander A. Bosin ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Japan Sea ◽  
Glacial Cycle ◽  
Last Glacial ◽  
The Last Glacial ◽  
Millennial Scale

Millennial-scale variability in Antarctic Circumpolar Current and its impacts during the last glacial cycle

2020 ◽  
Author(s):  
Shuzhuang Wu ◽  
Frank Lamy ◽  
Gerhard Kuhn ◽  
Lester Lembke-Jene ◽  
Xu Zhang ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Antarctic Circumpolar Current ◽  
Drake Passage ◽  
Global Ocean ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Circumpolar Current ◽  
Global Ocean Circulation ◽  
The Last Glacial ◽  
Millennial Scale

<p>The Antarctic Circumpolar Current (ACC) is the largest current system in the world, linking the Pacific, Atlantic and Indian Ocean basins. However, the variability of the ACC, which plays a fundamental role on global ocean circulation and climate variability, is still poorly constrained. This information is crucial for understanding the role of the ACC on global ocean circulation in response to global warming. Here, we reconstruct changes in the ACC over the past 155,000 years based on sediment grain size variations recorded in a highly-resolved marine sedimentary record from the central Drake Passage near the Polar Front. Our results show significant changes in the ACC during the last glacial cycle and a remarkable boundary between the glacial and interglacial periods. Substantial decreases (~33% to ~47%) in the ACC flow speed from interglacial to glacial period, which corroborates and extends results of previous studies along the subantarctic northern limit of the ACC into the central Drake Passage. This strong variation of ACC likely plays a significant role in regulating Pacific-Atlantic water mass exchange via the “cold water route” and could significantly affect the Atlantic Meridional Overturning Circulation. Superimposed on these glacial-interglacial changes, we found strong millennial-scale variations in ACC current speed, increasing in amplitude close to full glacial conditions. We hypothesise that the central ACC increases its sensitivity to Southern Hemisphere millennial-scale climates oscillations, likely associated with westerlies’ wind stress and Antarctic sea ice extent once glacial conditions fully formed.</p>

scholarly journals Dansgaard–Oeschger-like events of the penultimate climate cycle: the loess point of view

2020 ◽  
Vol 16 (2) ◽  
pp. 713-727 ◽  
Author(s):  
Denis-Didier Rousseau ◽  
Pierre Antoine ◽  
Niklas Boers ◽  
France Lagroix ◽  
Michael Ghil ◽  
...  
Keyword(s):  
Ice Core ◽  
Spatial Coherence ◽  
Point Of View ◽  
Optically Stimulated Luminescence ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Climate Cycle ◽  
Statistical Similarity ◽  
The Last Glacial ◽  
Millennial Scale

Abstract. The global character of the millennial-scale climate variability associated with the Dansgaard–Oeschger (DO) events in Greenland has been well-established for the last glacial cycle. Mainly due to the sparsity of reliable data, however, the spatial coherence of corresponding variability during the penultimate cycle is less clear. New investigations of European loess records from Marine Isotope Stage (MIS) 6 reveal the occurrence of alternating loess intervals and paleosols (incipient soil horizons), similar to those from the last climatic cycle. These paleosols are correlated, based on their stratigraphical position and numbers as well as available optically stimulated luminescence (OSL) dates, with interstadials described in various Northern Hemisphere records and in GLt_syn, the synthetic 800 kyr record of Greenland ice core δ18O. Therefore, referring to the interstadials described in the record of the last climate cycle in European loess sequences, the four MIS 6 interstadials can confidently be interpreted as DO-like events of the penultimate climate cycle. Six more interstadials are identified from proxy measurements performed on the same interval, leading to a total of 10 interstadials with a DO-like event status. The statistical similarity between the millennial-scale loess–paleosol oscillations during the last and penultimate climate cycle provides direct empirical evidence that the cycles of the penultimate cycle are indeed of the same nature as the DO cycles originally discovered for the last glacial cycle. Our results thus imply that their underlying cause and global imprint were characteristic of at least the last two climate cycles.

scholarly journals DO-like events of the penultimate climate cycle: the loess point of view

2019 ◽  
Author(s):  
Denis-Didier Rousseau ◽  
Pierre Antoine ◽  
Niklas Boers ◽  
France Lagroix ◽  
Michael Ghil ◽  
...  
Keyword(s):  
Ice Core ◽  
Spatial Coherence ◽  
Point Of View ◽  
Optically Stimulated Luminescence ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Climate Cycle ◽  
Statistical Similarity ◽  
The Last Glacial ◽  
Millennial Scale

Abstract. The global character of the millennial-scale climate variability associated with the Dansgaard-Oeschger (DO) events in Greenland has been well-established for the last glacial cycle. Mainly due to the sparsity of reliable data, however, the spatial coherence of corresponding variability during the penultimate cycle is less clear. New investigations of European loess records from MIS 6 reveal the occurrence of alternating loess intervals and paleosols (incipient soil horizons), similar to those from the last climatic cycle. These paleosols are correlated based on their stratigraphical position and numbers, and available optically stimulated luminescence (OSL) dates with interstadials described in various Northern Hemisphere records as well as in GLt_syn, the synthetic 800-kyr record of Greenland ice core δ18O. Therefore, referring to the interstadials described in the record of the last climate cycle in European loess sequences, the MIS 6 interstadials can confidently be interpreted as DO-like events of the penultimate climate cycle. The statistical similarity between the millennial-scale loess-paleosol oscillations during the last and penultimate climate cycle provides direct empirical evidence that the cycles of the penultimate cycle are indeed of the same nature as the DO cycles originally discovered for the last glacial cycle. Our results thus imply that their underlying cause and global imprint was characteristic of at least the last two climate cycles.

scholarly journals Abrupt climate and vegetation variability of eastern Anatolia during the last glacial

2015 ◽  
Vol 11 (11) ◽  
pp. 1491-1505 ◽  
Author(s):  
N. Pickarski ◽  
O. Kwiecien ◽  
D. Langgut ◽  
T. Litt
Keyword(s):  
Environmental Changes ◽  
Environmental Variability ◽  
Ice Cores ◽  
Eastern Anatolia ◽  
Lake Van ◽  
Last Glacial ◽  
Moisture Availability ◽  
Marine Realm ◽  
The Last Glacial ◽  
Millennial Scale

Abstract. Detailed analyses of the Lake Van pollen, Ca / K ratio, and stable oxygen isotope record allow the identification of millennial-scale vegetation and environmental changes in eastern Anatolia throughout the last glacial (~ 111.5–11.7 ka BP). The climate of the last glacial was cold and dry, indicated by low arboreal pollen (AP) levels. The driest and coldest period corresponds to Marine Isotope Stage (MIS) 2 (~ 28–14.5 ka BP), which was dominated by highest values of xerophytic steppe vegetation. Our high-resolution multi-proxy record shows rapid expansions and contractions of tree populations that reflect variability in temperature and moisture availability. These rapid vegetation and environmental changes can be related to the stadial-interstadial pattern of Dansgaard–Oeschger (DO) events as recorded in the Greenland ice cores. Periods of reduced moisture availability were characterized by enhanced occurrence of xerophytic species and high terrigenous input from the Lake Van catchment area. Furthermore, the comparison with the marine realm reveals that the complex atmosphere–ocean interaction can be explained by the strength and position of the westerlies, which are responsible for the supply of humidity in eastern Anatolia. Influenced by the diverse topography of the Lake Van catchment, more pronounced DO interstadials (e.g., DO 19, 17–16, 14, 12 and 8) show the strongest expansion of temperate species within the last glacial. However, Heinrich events (HE), characterized by highest concentrations of ice-rafted debris (IRD) in marine sediments, cannot be separated from other DO stadials based on the vegetation composition in eastern Anatolia. In addition, this work is a first attempt to establish a continuous microscopic charcoal record for the last glacial in the Near East. It documents an immediate response to millennial-scale climate and environmental variability and enables us to shed light on the history of fire activity during the last glacial.

scholarly journals Speleothem Records of the Hydroclimate Variability throughout the Last Glacial Cycle from Manita peć Cave (Velebit Mountain, Croatia)

Geosciences ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 347
Author(s):  
Maša Surić ◽  
Petra Bajo ◽  
Robert Lončarić ◽  
Nina Lončar ◽  
Russell N. Drysdale ◽  
...  
Keyword(s):  
Sea Level ◽  
Environmental Changes ◽  
Carbonic Acid ◽  
Precipitation Amount ◽  
Specific Effect ◽  
Ice Cores ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Mis 3 ◽  
The Last Glacial

We present stable carbon (δ13C) and oxygen (δ18O) isotope records from two partially coeval speleothems from Manita peć Cave, Croatia. The cave is located close to the Adriatic coast (3.7 km) at an elevation of 570 m a.s.l. The site experienced competing Mediterranean and continental climate influences throughout the last glacial cycle and was situated close to the ice limit during the glacial phases. U-Th dating constrains the growth history from Marine Isotope Stage (MIS) 5 to MIS 3 and the transition from MIS 2 to MIS 1. 14C dating was used to estimate the age of the youngest part of one stalagmite found to be rich in detrital thorium and thus undatable by U-Th. On a millennial scale, δ18O variations partly mimic the Dansgaard–Oeschger interstadials recorded in Greenland ice cores (Greenland Interstadials, GI) from GI 22 to GI 13. We interpret our δ18O record as a proxy for variations in precipitation amount and/or moisture sources, and the δ13C record is interpreted as a proxy for changes in soil bioproductivity. The latter indicates a generally reduced vegetation cover towards MIS 3–MIS 4, with shifts of ~8‰ and approaching values close to those of the host rock. However, even during the coldest phases, when a periglacial setting and enhanced aridity sustained long-residence-time groundwater, carbonic-acid dissolution remains the driving force of the karstification processes. Speleothem morphology follows changes in environmental conditions and complements regional results of submerged speleothems findings. Specifically, narrow sections of light porous spelaean calcite precipitated during the glacial/stadial sea-level lowstands, while the warmer and wetter conditions were marked with compact calcite and hiatuses in submerged speleothems due to sea-level highstands. Presumably, the transformation of this littoral site to a continental one with somewhat higher amounts of orographic precipitation was a site-specific effect that masked regional environmental changes.

scholarly journals Abrupt climate variability of eastern Anatolia vegetation during the last glacial

2015 ◽  
Vol 11 (4) ◽  
pp. 3341-3373 ◽  
Author(s):  
N. Pickarski ◽  
O. Kwiecien ◽  
D. Langgut ◽  
T. Litt
Keyword(s):  
North Atlantic ◽  
Environmental Changes ◽  
Environmental Variability ◽  
Ice Cores ◽  
Eastern Anatolia ◽  
Lake Van ◽  
Last Glacial ◽  
The North ◽  
The Last Glacial ◽  
Millennial Scale

Abstract. Detailed analyses of the Lake Van pollen and stable oxygen isotope record allow the identification of millennial-scale vegetation and environmental changes in eastern Anatolia throughout the last glacial. The climate within the last glacial period (∼75–15 ka BP) was cold and dry, with low arboreal pollen (AP) levels. The driest and coldest period corresponds to Marine Isotope Stage (MIS) 2 (∼28–14.5 ka BP) dominated by the highest values of xerophytic steppe vegetation. Our high-resolution multi proxy record shows rapid expansions and contractions that mimic the stadial-interstadial pattern of the Dansgaard–Oeschger (DO) events as recorded in the Greenland ice cores, and thus, provide a linkage to North Atlantic climate oscillations. Periods of reduced moisture availability characterized at Lake Van by enhanced xerophytic species correlates well with increase in ice-rafted debris (IRD) and a decrease of sea surface temperature (SST) in the North Atlantic. Furthermore, comparison with the marine realm reveals that the complex atmosphere–ocean interaction can be recognized by the strength and position of the westerlies in eastern Anatolia. Influenced by rough topography at Lake Van, the expansion of temperate species (e.g. deciduous Quercus) was stronger during interstadials DO 19, 17–16, 14, 12 and 8. However, Heinrich events (HE), characterized by highest concentrations of ice-rafted debris in marine sediments, are identified in eastern Anatolia by AP values not lower and high steppe components not more abundant than during DO stadials. In addition, this work is a first attempt to establish a continuous microscopic charcoal record over the last glacial in the Near East, which documents an initial immediate response to millennial-scale climate and environmental variability and enables the shed light on the history of fire activity during the last glacial.

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