Surface water conditions and calcium carbonate preservation in the Fram Strait during marine isotope stage 2, 28.8-15.4 kyr

Abstract

[1] We present a high-resolution record of calcium carbonate preservation alongside the distribution pattern of planktic foraminifera from the Fram Strait. The record covers the marine isotope stage (MIS) 2, 28.8 to 15.4 kyr, including the Last Glacial Maximum (LGM) and the early deglaciation in multidecadal temporal resolution. The investigation is based on the distribution patterns of planktic foraminifera, stable isotopes, mean shell weight of Neogloboquadrina pachyderma, the degree of fragmentation of planktic shells, CaCO 3 content, and geochemical and sedimentological data. The dissolution proxies indicate long-lasting periods of markedly reduced preservation of calcium carbonate at~28.8-27.2,~24.1-23.2, and 16.6-15.4 kyr in addition to a number of short-lasting periods (< 300 year) during the LGM. These periods are accompanied by a simultaneous and significant reduction in specimens of subpolar planktic foraminifera indicating a southward expansion of Arctic surface water masses. Prolonged periods with high abundances of subpolar foraminiferal species and good preservation of calcium carbonate are attributed to increased influence of Atlantic water masses, which appears to persist throughout most of the MIS 2. Comparison to Holocene (MIS 1) shell weight records shows that the preservation during MIS 2 was overall better, even during the events of dissolution. This was probably a reflection of the low concentration of atmospheric CO 2 at the time.

High-resolution record of late glacial and deglacial sea ice changes in Fram Strait corroborates ice–ocean interactions during abrupt climate shifts

“…Recently, a potential sea ice origin of brassicasterol (but not dinosterol) has been discussed by (Fig. 3) concur with the maximum abundance of the subpolar foraminifer T. quinqueloba in this core (Zamelczyk et al, 2014), which also points to a temporary retreat of sea ice. Coincident with this reduction in sea ice, a short but intensive discharge of glacial meltwater is recorded at various sites along the western continental slope of Svalbard, which caused a high accumulation of (terrigenous) organic matter (S1) and ice rafted detritus (Knies and Stein, 1998;Vogt et al, 2001;Jessen et al, 2010).…”

“…3). Further, Zamelczyk et al (2014) observed a drop in the total foraminifer flux and a high shell fragmentation in the respective sediments of core MSM5/5-712-2 at about 19 ka BP which they attribute to a cooling of the sea surface. This onset of a perennial sea ice cover in eastern Fram Strait seems to coincide with the final expansion (according to Andersen et al, 1996) or retreat (see Jessen et al, 2010 for further references and discussion) of the SBIS at the western shelf edge of Svalbard.…”

“…Following Zamelczyk et al (2014), we correlated the magnetic susceptibility values of core MSM5/5-712-2 with the Western Svalbard slope MS stack by Jessen et al (2010) and the susceptibility values of core PS2837-5 from the Yermak Plateau (Niessen et al, 1997; see S1). Further, by means of correlating the TOC contents of core MSM5/5-712-2 and core PS2837-5 from the Yermak Plateau (S1; Birgel and Hass, 2004) we identified several tie points and selected three AMS 14 C ages of core PS2837-5 (Nørgaard-Pedersen et al, 2003 Table S2) that we adopted to improve the herein presented age model of core MSM5/5-712-2 (Fig.…”

“…The often lowered preservation potential of sea ice associated diatoms and foraminifera (due to silica or carbonate dissolution) in the Arctic Ocean and subpolar North Atlantic (e.g. Scott and Vilks, 1991;Schlüter and Sauter, 2000;Zamelczyk et al, 2014), however, often hamper the reconstruction of the spatial and temporal distribution of sea ice in the past. The sea ice biomarker proxy IP 25 , a highly branched isoprenoid (HBI) monoene with 25 carbon atoms (C 25 ) derived from sea ice diatoms (Belt et al, 2007;Brown et al, 2014), has been found stable within Arctic Ocean sediments for at least the entire Quaternary and thus enables the assessment of sea ice changes in the High Northern Latitudes even during the distant past.…”

Geochemical characterisation of northern Norwegian fjord surface sediments: A baseline for further paleo-environmental investigations

“…The CaCO 3 content in surface sediments usually reflects the modern surface water oceanography and was, for example, successfully applied as a paleoceanographic tool to reconstruct northern Hemisphere glacial/interglacial cycles (e.g. Bond et al, 1992;Ruddiman and McIntyre, 1981;Zamelczyk et al, 2014). Furthermore, Faust et al (2016) recently revealed that Ca/Si and CaCO 3 in fjord sediments can provide detailed reconstructions of atmospheric circulation changes.…”