Oceanographic variability on the West Antarctic Peninsula during the Holocene and the influence of upper circumpolar deep water

Abstract

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. along the WAP to past changes in SWW by analysing the exceptionally well preserved 22 planktonic and benthic foraminifera, diatoms and pigments in marine sediment core TPC522, 23Marguerite Bay (Fig. 1). These biogenic components provide proxies for reconstructing past METHODS 2The chronology of TPC522 is based on twelve acid insoluble organic matter (AIOM), 3and one monospecific benthic foraminifera (Globocassidulina biora) radiocarbon dates. 4Dates were calibrated using CALIB 6.0 using the MARINE09 calibration curve (Stuiver & 5 Reimer, 1993). R was set at 1353 years based on a local mean surface sample radiocarbon Table 1). Classical radiocarbon age-depth modelling was undertaken 10 using CLAM v, 2.1 software in R (Blaauw, 2010) using a smooth spline curve fit, running 11 1000 iterations at 1 cm intervals (Fig. 3A). To independently date the surface sediments, 4For diatom counts the quantitative slide preparation method of Scherer (1994) was 5 used and counting was carried out at ×1000 magnification on an Olympus BX42 microscope. for >2 % of the CRS-free assemblage within at least one sample were included. 16Correspondence analysis (CA) was performed on both the diatom and benthic foraminferal 17 assemblage counts using the software of Hammer et al. (2005). 18For pigment analysis, bulk sediment samples were freeze-dried and homogenised. 19Approximately 2 g of sample was extracted with an organic solvent mixture of 24Samples were redissolved in a known volume of acetone and transferred to a 2 ml quartz 25 7 cuvette for analysis in a WPA spectrophotometer. Absorbance was recorded by 1 measurements in triplicate at the wavelengths 410 nm and 665 nm, which correspond to the 2 diagenetic transformation products of chlorophyll, the chlorins (Harris et al., 1996).The excess 210 Pb activity profile confirmed that the upper sediments were deposited 7 within recent decades (Fig. 3B). The surface sediment radiocarbon ages are therefore STATISTICAL ANALYSIS OF ASSEMBLAGES 23The first three axes of the CA accounted for 57% and 66% of the variance in the 24 diatom and foraminifera assemblages respectively (Fig. 4) (Fig. 5F), 18Thalassiosira gracilis and Proboscia truncata, is indicates reflect relatively warm surface (Fig. 5N). , 2010; Grossman, 1987). 9The stable and consistently offset benthic and planktonic 18 O values throughout the 10 early Holocene interval are consistent with a persistent density structure between the 11 pycnocline and sea floor, at least during the ...

Holocene glacial activity in Barilari Bay, west Antarctic Peninsula, tracked by magnetic mineral assemblages: Linking ice, ocean, and atmosphere

“…Signals of UCDW have been reported as consistently present on the western AP shelf during the early to mid‐Holocene [ Shevenell and Kennett , ; Peck et al ., ], coincident with a more southerly position of the westerly winds reconstructed from the southern Chilean margin [ Lamy et al ., ] suggesting upwelling favorable conditions (Figure b). The mid‐Holocene shift to a more northerly position in the westerly winds documented on the southern Chilean margin is roughly coincident with the large increase in magnetic susceptibility at Palmer Deep [ Domack et al ., ] and an increase in magnetic susceptibility at Barilari Bay (Figures c and e).…”

“…Barilari Bay, a western AP fjord visited during the LARISSA NBP10‐01 cruise, is located upwind of and at the same latitude as the former Larsen B ice shelf, allowing for east‐west comparison of Holocene glacial response to oceanic and atmospheric forcing (Figure ). Historical and geologic studies both indicate that while eastern AP changes are driven by atmospheric forcing, as demonstrated by the Holocene history and unprecedented breakup of the Larsen B ice shelf [ Scambos et al ., ; Domack et al ., ; Rebesco et al ., ], the western AP is particularly sensitive to oceanographic forcing [ Cook et al ., ], with high resolution records suggesting variable and episodic incursion of UCDW in the late Holocene [ Ishman and Sperling , ; Shevenell and Kennett , ; Bentley et al ., ; Peck et al ., ].…”

“…A constant 5 cm offset was used for JTC-127 relative to JKC-55. The Analyseries 2.0.4 software [Paillard et al, 1996] was used to adjust the depth scale of JPC-127 relative to JKC-55 (composite depth scale in supporting information Tables S12 and S13).…”

Subdividing the Holocene Series/Epoch: formalization of stages/ages and subseries/subepochs, and designation of GSSPs and auxiliary stratotypes

“…It has been termed the "Holocene Turnover" (Paasche et al, 2004) that subsequently resulted in the establishment of a new climatic regime or mode (Paasche and Bakke, 2009), or the "4.07 ka BP climatic anomaly" in southern Africa (Railsback et al, 2018). The event appears to be global in nature, occurring in proxy records across seven continents from North America and northern Europe, through the Mediterranean, Middle East (Weiss, 2017b(Weiss, , 2017a and India Kathayat et al, 2018) to China (Cai et al, 2017;Zhang et al, 2018) and Australia (Denniston et al, 2013); and across Africa (Chase et al, 2015b;Ruan et al, 2016), Andean-Patagonian South America (Schimpf et al, 2011), and Antarctica (Peck et al, 2015). In the North Atlantic and western Canada, the event is reflected in atmospheric and oceanic cooling ( GICC05 timescales during the Holocene (Adolphi and Muscheler, 2016).…”

“Live” (stained) benthic foraminiferal living depths, stable isotopes, and taxonomy offshore South Georgia, Southern Ocean: implications for calcification depths

“…The abundance of opportunistic infaunal species, however, can increase dramatically by accelerating growth and/or reproduction during eutrophic episodes (e.g. Gooday, 1988;Gooday and Hughes, 2002;Fontanier et al, 2006a;Peck et al, 2015) due to greater organic carbon availability and their tolerance of lower oxygen concentrations (Piña-Ochoa et al, 2010). Downcore epifaunal δ 13 C is potentially a more sensitive indicator of variable C org flux and bottom water conditions (oxygenation).…”