Changes in sea ice cover and ice sheet extent at the Yermak Plateau during the last 160 ka – Reconstructions from biomarker records

Abstract

The Yermak Plateau is located north of Svalbard at the entrance to the Arctic Ocean, i.e. in an area highly sensitive to climate change. A multi proxy approach was carried out on Core PS92/039-2 to study glacial-interglacial environmental changes at the northern Barents Sea margin during the last 160 ka. The main emphasis was on the reconstruction of sea ice cover, based on the sea ice proxy IP 25 and the related phytoplankton-sea ice index PIP 25. Sea ice was present most of the time but showed significant temporal variability decisively affected by movements of the Svalbard Barents Sea Ice Sheet. For the first time, we prove the occurrence of seasonal sea ice at the eastern Yermak Plateau during glacial intervals, probably steered by a major northward advance of the ice sheet and the formation of a coastal polynya in front of it. Maximum accumulation of terrigenous organic carbon, IP 25 and the phytoplankton biomarkers (brassicasterol, dinosterol, HBI III) can be correlated to distinct deglaciation events. More severe, but variable sea ice cover prevailed at the Yermak Plateau during interglacials. The general proximity to the sea ice margin is further indicated by biomarker (GDGT)-based sea surface temperatures below 2.5°C.

Late Pleistocene Chronology of Sediments From the Yermak Plateau and Uncertainty in Dating Based on Geomagnetic Excursions

“…The MIS 5/4 boundary was identified by similar means and is supported by the occurrence of Pullenia bulloides (stratigraphic marker for MIS event 5.1) in Core 39 just below the boundary (Kremer et al, 2018). We found a gradual grain size coarsening during MIS 5 with a more abrupt drop at the MIS 5/4 boundary.…”

“…Black solid lines are based on ARM ∕ tuning to LR04. Red dotted lines are previously published age models: Core 39 Kremer et al (2018), JPC 22 (Myers & Darby, 2015), PS1533-3 and PS2212-3 (Nowaczyk et al, 1994), and PS2138-1 (Nowaczyk & Knies, 2000). The panel on the right shows the extent of the Svalbard Barents Sea Ice Sheet (SBIS; hatched area, based on Mangerud et al, 1998;Winkelmann et al, 2008), terrigenous input events (blue shaded area, Winkelmann et al, 2008), and the intensity of inflowing Atlantic water (Spielhagen et al, 2004) of the oldest radiocarbon age at 2.98 m in Core 39 (dated at 43.6->50.0 cal ka BP) exceeds the limits of the calibration curve and might be much older.…”

Wahlenbergfjord, eastern Svalbard: a glacier‐surrounded fjord reflecting regional hydrographic variability during the Holocene?

“…These comparably warm surface temperatures most likely resulted in a reduced sea ice cover during summer (Fig. during MIS 6; Knies et al 1999;Kremer et al 2018). The trend of increasing phytoplankton biomarker data (dinosterol and brassicasterol; Figs 5F, 6) in the course of the early Holocene also points to temporarily open water conditions during summer.…”

“…Open water conditions may also have been caused by katabatic winds as it was assumed at the northern Barents Sea margin during previous glacial periods (e.g. during MIS 6; Knies et al 1999;Kremer et al 2018).…”

Western Mediterranean Sea Paleothermometry Over the Last Glacial Cycle Based on the Novel RI‐OH Index

“…Lü et al (2015) have also developed RI-OH′, which is an alternative version of RI-OH for temperature estimates in polar oceans. To date, de Bar et al (2019) and Kremer et al (2018) alone have used RI-OH and RI-OH′, respectively. In addition, only a few studies have assessed potential biases for RI-OH and RI-OH′, such as inputs of terrestrial OH-GDGTs, seasonal biases, and OH-GDGT production in subsurface waters (Kang et al, 2017;Lü et al, 2015Lü et al, , 2019Yang et al, 2019;Zhu et al, 2016).…”