Paleoceanography of the Northwestern Greenland Sea and Return Atlantic Current evolution, 35–4 kyr BP

The flow of the Atlantic Water (AW) via the Return Atlantic Current (RAC) regulates the oceanographical conditions in the Northwestern (NW) Greenland Sea in the Fram Strait. As the intensity of the RAC might significantly influence both deep-water formation in the area and the stability of the Northeast Greenland Ice Sheet (NE GIS), knowledge of its variability in the past is important. Here we present a reconstruction of the paleoceanographic forcing of the AW on climatic conditions and associated environmental changes in the NW Greenland Sea by means of foraminiferal assemblages, stable (oxygen and carbon) isotopes, and various sedimentological parameters from sediment core GR02-GC retrieved from NE Greenland continental slope (1170 m water depth). Our data indicate an almost continuous presence of AW in the NW Greenland Sea during the last 35 kyr BP. Two peaks of low planktic δ18O values at ~34.5 and 33 kyr BP are interpreted as meltwater signals associated with warm AW-induced melting of the adjacent NE GIS. The NE GIS advanced between 32 and 29 kyr BP, resulting in reduced meltwater influx to the NW Greenland Sea. Increased iceberg calving and melting after 29 kyr BP, were probably linked to surface warming and glacier advance to the shelf-break lasting until 23.5 kyr BP. During the Last Glacial Maximum, the extensive sea ice cover was associated with the presence of subsurface AW at the study site. During the Bølling–Allerød (B/A, ~14.6–12.7 kyr BP) strong melting of glaciers and sea ice was probably caused by the combined effect of the B/A warming and the flow of warm AW. The RAC was weakened during the Younger Dryas (~12.8–11.7 kyr BP), which reduced the advection of warm AW to the NW Greenland Sea. After 11.7 kyr BP, the RAC reached its modern strength, whereas, during the Holocene Thermal Maximum, it reached its maximum strength for the study period. In addition, short-term weakening of AW inflow to the core site was observed, especially at 10.5, 8.5, and 5.8 kyr BP

Sediment Provenance of the Nansha Trough Since 40 ka B.P. in the South China Sea: Evidence From δ13Corg, TOC and Pollen Composition

Geochemical proxies in organic matter (OM) are considered to be reliable proxies for deciphering types of paleo-vegetation (C3 plants and C4 plants) and their abundance. The contributions of total organic carbon (TOC), stable carbon isotopes (δ13Corg), total nitrogen (TN) and organic carbon to total nitrogen ratios (C/N) were obtained from a gravity core NS07-25 (6°39.945′ N, 113°32.936′ E, water depth 2006 m), extracted from the southern South China Sea (SCS). These data were used to reconstruct the climate changes of the Nansha Trough since 40 ka B.P. by comparing them with pollen data from the same core, and this comparison provides better sediment provenance details in the study area. During the periods between 37 and 27 ka, and from 12.5 ka to modern day, the majority of terrestrial sediment received from Borneo, and some climatic events have been governed by aeolian fluxes from mid-latitude areas (mainland China). These periods were relatively humid, compared to 27–12.5 ka, where the majority of terrestrial sediment came from the Sunda Shelf through riverine pathways. This study serves as the first study to correlate deep oceanic pollen and geochemical proxies in order to identify the weaken terrestrial OM signals in the deep ocean

Sedimentary ancient DNA: a new paleogenomic tool for reconstructing the history of marine ecosystems

Sedimentary ancient DNA (sedaDNA) offers a novel retrospective approach to reconstructing the history of marine ecosystems over geological timescales. Until now, the biological proxies used to reconstruct paleoceanographic and paleoecological conditions were limited to organisms whose remains are preserved in the fossil record. The development of ancient DNA analysis techniques substantially expands the range of studied taxa, providing a holistic overview of past biodiversity. Future development of marine sedaDNA research is expected to dramatically improve our understanding of how the marine biota responded to changing environmental conditions. However, as an emerging approach, marine sedaDNA holds many challenges, and its ability to recover reliable past biodiversity information needs to be carefully assessed. This review aims to highlight current advances in marine sedaDNA research and to discuss potential methodological pitfalls and limitations

Sediment provenance of the Nansha trough since 40 ka B.P. in the south China sea: evidence from δ13Corg, TOC and Pollen composition

Geochemical proxies in organic matter (OM) are considered to be reliable proxies for deciphering types of paleo-vegetation (C3 plants and C4 plants) and their abundance. The contributions of total organic carbon (TOC), stable carbon isotopes (δ13Corg), total nitrogen (TN) and organic carbon to total nitrogen ratios (C/N) were obtained from a gravity core NS07-25 (6°39.945′ N, 113°32.936′ E, water depth 2006 m), extracted from the southern South China Sea (SCS). These data were used to reconstruct the climate changes of the Nansha Trough since 40 ka B.P. by comparing them with pollen data from the same core, and this comparison provides better sediment provenance details in the study area. During the periods between 37 and 27 ka, and from 12.5 ka to modern day, the majority of terrestrial sediment received from Borneo, and some climatic events have been governed by aeolian fluxes from mid-latitude areas (mainland China). These periods were relatively humid, compared to 27–12.5 ka, where the majority of terrestrial sediment came from the Sunda Shelf through riverine pathways. This study serves as the first study to correlate deep oceanic pollen and geochemical proxies in order to identify the weaken terrestrial OM signals in the deep ocean

Paleoceanography of the NW Greenland Sea and Return Atlantic Current evolution, 35–4 kyr BP

We present benthic and planktonic census data, carbon and oxygen stable isotope, Total organic carbon and Total carbon, IRD, and grain size data for the last 35 kyr BP from sediment core retrieved from a plateau on the NE Greenland continental slope (77°05.192N, 5°13.896W, 1170 m water depth) during the AREX expedition, with RV Oceania in 2017. Benthic stable isotopes were measured dominantly on Cassidulina neoteretis, and planktonic were measured on Neogloboquadrina pachyderma. Data is presented against age