Research paperAntarctic sea-ice and palaeoproductivity variation over the last 156,000 years in the Indian sector of Southern Ocean
Introduction
Antarctic sea ice is the most seasonal feature on Earth. Its annual cycle modulates the radiative balance of the Southern Ocean (SO) (Comiso, 2010), the heat-gas exchange between the ocean and the atmosphere (Delille et al., 2014; Ferrari et al., 2014), the global oceanic circulation (Abernathey et al., 2016) along with the SO productivity (Arrigo and Thomas, 2004). Of special interest is that all these processes affect the partitioning of carbon between the ocean and the atmosphere (Kohfeld and Chase, 2017). More precisely, Antarctic sea-ice expansion during glacial periods is thought to be the main process lowering atmospheric CO2 concentration via its direct insulation effect (Ferrari et al., 2014), its impact on the carbon storage in abyssal SO waters (Bouttes et al., 2011) and on the regional and distal productivity (Moore et al., 2000; Matsumoto, 2007; Jaccard et al., 2013). Hence, it is necessary to document the past changes in Antarctic sea-ice extent in all SO basins to better understand its interactions with climate drivers on a multi-millennial timescale.
Most reconstructions of past Antarctic sea-ice dynamic are either qualitative or restricted to the last 30,000–40,000 years (Burckle and Mortlock, 1998; Crosta et al., 1998a, Crosta et al., 1998b; Gersonde and Zielinski, 2000; Gersonde et al., 2005; Collins et al., 2012; Ferry et al., 2015; Xiao et al., 2016). Only few quantitative studies cover the last glacial-interglacial cycle (Kunz-Pirrung et al., 2002; Crosta et al., 2004; Esper and Gersonde, 2014a; Nair et al., 2019). These studies suggested that the winter sea-ice (WSI) limit was located 5–10 degrees of latitude northward during the last glacial stage relative to its modern position. Although still under debate, this northward shift probably resulted from a congruent shift in the Southern Hemisphere Westerlies Winds (SWW) and Antarctic Circumpolar Current (ACC) along with a drop in atmospheric and oceanic temperatures (Martinson, 2012; Kohfeld et al., 2013; Bostock et al., 2015; Nair et al., 2019). However, there are currently not enough studies to document potential regional differences and therefore robustly assess drivers of past sea-ice dynamic and its feedbacks on the climate system.
Here we used the narrow ecological preferences of diatoms to infer past oceanographic conditions such as sea-surface temperature (SST) and winter sea-ice concentration (WSIC) and duration (WSID), and compared these with palaeoproductivity records in the under-studied Indian sector of the SO over the past 156,000 years. Quantitative estimates of both SST and WSIC-WSID are provided through the Modern Analogue Technique (MAT) and are compared to similar records from the Atlantic and southwestern (SW) Pacific to evaluate whether sea-ice dynamic was comparable in each SO basin over the past ~156,000 years.
Section snippets
Study area and core details
Sediment core SK 200/33 was obtained on-board ORV Sagar Kanya in 2004 from 55°01′S-45°09′E, at a water depth of 4204 m. The core site is located in the SW Indian sector of the SO within the Permanently Open Ocean Zone (POOZ), sea-ice free region, where mean summer SST is ~2 °C which was derived from World Ocean Atlas 2013 (Locarnini et al., 2013) (Fig. 1). The present core site is bound by the Antarctic Polar Front (APF) to the north and Southern ACC Front (SACCF) and WSI limit to the south
Down-core variations in diatom assemblages
The sea-ice diatom group represents the second most abundant group in the core SK 200/33 with the relative abundances ranging from 0 to 8% over the last 156 ka (Fig. 3a). The highest occurrences (> 3%) of this group were observed during the glacial stages (MIS 2–4 and 6) and the lowest abundances (0–2%) were found during the interglacial periods (MIS 1 and 5). Similarly, the water stratification group was more present during the glacial stages, when abundances were 0–5% than in the interglacial
Latitudinal shifts in Antarctic winter sea-ice extent and hydrological fronts in the Indian sector
At present time, core SK 200/33 is located in the POOZ, north of the SACCF and WSI edge but 2–3° of latitude to the south of the southern APF (Fig. 1). The most recent diatom assemblages, dated from the early-mid Holocene, preserved in the core are strongly dominated by the POOZ diatom group (Fig. 3c), with few percent of SAZ diatoms (Fig. 3d), and the absence of sea-ice diatoms (Fig. 3a). These assemblages resulted in SST estimates of ~4 °C (Fig. 3g), which are ~2 °C higher than the modern
Conclusion
The diatom assemblages preserved in sediment core SK 200/33 allowed to estimate SST and WSI conditions in the POOZ of the SW Indian sector of the SO over the past 156 ka. The new records suggest SST of ~1–2 °C and WSID of ~2 months/year during each glacial period, with very little difference in between the mean values during each glacial period. The combination of the new data with published regional SST and WSI data suggests that all hydrological features migrated northward by a few degrees of
Author statement
Pooja Ghadi: Prepared diatom slides, performed diatom counts, graphs and schematic preparation, conceptualization, writing-original draft, reviewing and editing.
Abhilash Nair: Conceptualization, plotting graphs, writing-original draft, reviewing and editing, providing supporting data.
Xavier Crosta: Estimated the sea-surface temperature and sea ice extent records, revising and drafting the manuscript.
Rahul Mohan: Project administration, core collection, obtaining the radiocarbon dates for core
Declaration of Competing Interest
The authors declare no competing interests.
Acknowledgement
The authors wish to thank the Director, ESSO-NCPOR, Ministry of Earth Sciences (MoES), India, and Council of Scientific and Industrial Research (CSIR) for providing the funds for the research program at NCPOR. Pooja Ghadi thanks CSIR , New Delhi, India for the award of Junior Research Fellowship [Ref No. 18/12/2016(ii)EU-v]. We would also like to express our sincere gratitude toward the members of the pilot expedition to the Southern Ocean and Polar Micropaleontology and Past Climate Section,
References (108)
- et al.
Late-Quaternary changes in productivity of the Southern Ocean
J. Mar. Syst.
(1998) - et al.
Problems and possible solutions concerning radiocarbon dating of surface marine sediments, Ross Sea, Antarctica
Quat. Res.
(1999) - et al.
Fronts, water masses and heat content variability in the Indian Sector of Southern Ocean during Austral Summer
J. Mar. Syst.
(2006) - et al.
The biogeography of major diatom taxa in Southern Ocean sediments: 1. Sea ice related species
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(2005) - et al.
Glacial–interglacial changes in the accumulation rates of major biogenic components in Southern Indian Ocean sediments
J. Mar. Syst.
(1998) - et al.
Last Glacial Maximum sea surface temperature and sea-ice extent in the Pacific sector of the Southern Ocean
Quat. Sci. Rev.
(2016) - et al.
Climate evolution at the last deglaciation: the role of the Southern Ocean
Earth Planet. Sci. Lett.
(2004) - et al.
Temporal and spatial structure of multi-millennial temperature changes at high latitudes during the Last Interglacial
Quat. Sci. Rev.
(2014) - et al.
Analysing the timing of peak warming and minimum winter sea-ice extent in the Southern Ocean during MIS 5e
Quat. Sci. Rev.
(2020) - et al.
Accumulation of biogenic and lithogenic material in the Pacific sector of the Southern Ocean during the past 40,000 years
Deep-Sea Res. II Top. Stud. Oceanogr.
(2003)
Morphometric variability in the diatom Fragilariopsis kerguelensis: Implications for Southern Ocean paleoceanography
Earth Planet. Sci. Lett.
Abrupt climate warming in East Antarctica during the early Holocene
Quat. Sci. Rev.
Late Quaternary Sea ice history in the Indian sector of the Southern Ocean as recorded by diatom assemblages
Mar. Micropaleontol.
The biogeography of major diatom taxa in Southern Ocean sediments: 2. Open Ocean related species
Palaeogeogr. Palaeoclimatol. Palaeoecol.
Sea ice seasonality during the Holocene, Adélie Land, East Antarctica
Mar. Micropaleontol.
New tools for the reconstruction of Pleistocene Antarctic Sea ice
Palaeogeogr. Palaeoclimatol. Palaeoecol.
Quaternary surface water temperature estimations: New diatom transfer functions for the Southern Ocean
Palaeogeogr. Palaeoclimatol. Palaeoecol.
The role of Southern Ocean processes in orbital and millennial CO2 variations–a synthesis
Quat. Sci. Rev.
The reconstruction of late Quaternary Antarctic Sea-ice distribution—the use of diatoms as a proxy for sea-ice
Palaeogeogr. Palaeoclimatol. Palaeoecol.
Sea-surface temperature and sea ice distribution of the Southern Ocean at the EPILOG last Glacial Maximum—a circum-Antarctic view based on siliceous microfossil records
Quat. Sci. Rev.
Is spatial autocorrelation introducing biases in the apparent accuracy of paleoclimatic reconstructions?
Quat. Sci. Rev.
The climate of western Europe during the last Glacial/Interglacial cycle derived from pollen and insect remains
PPP
Marine diatoms
Temporal evolution of mechanisms controlling ocean carbon uptake during the last glacial cycle
Earth Planet. Sci. Lett.
Southern Hemisphere westerly wind changes during the Last Glacial Maximum: paleo-data synthesis
Quat. Sci. Rev.
Mid-Brunhes century-scale diatom sea surface temperature and sea ice records from the Atlantic sector of the Southern Ocean (ODP Leg 177, sites 1093, 1094 and core PS2089-2)
Palaeogeogr. Palaeoclimatol. Palaeoecol.
Upper-ocean hydrodynamics along meridional sections in the southwest Indian sector of the Southern Ocean during austral summer 2007
Polar Sci.
Southern Ocean thermal fronts south of Africa
Deep Sea Research I
Shifting frontal regimes and its influence on bioproductivity variation during the Late Quaternary in the Indian sector of Southern Ocean
Deep Sea Res., Part II
Antarctic circumpolar current's role in the Antarctic ice system: an overview
Palaeogeogr. Palaeoclimatol. Palaeoecol.
A simple method for the rapid determination of biogenic opal in pelagic marine sediments
Deep-Sea Res. Part A
Southern Ocean sea ice and frontal changes during the Late Quaternary and their linkages to Asian summer monsoon
Quat. Sci. Rev.
Sediment waves on the Conrad Rise, Southern Indian Ocean: Implications for the migration history of the Antarctic Circumpolar current
Mar. Geol.
On the meridional extent and fronts of the Antarctic Circumpolar current
Deep-Sea Res. I Oceanogr. Res. Pap.
A review of the Si cycle in the modern ocean: recent progress and missing gaps in the application of biogenic opal as a paleoproductivity proxy
Glob. Planet. Chang.
The biogeography of major diatom taxa in Southern Ocean surface sediments: 3. Tropical/Subtropical species
Palaeogeogr. Palaeoclimatol. Palaeoecol.
Potential and limitations of marine and ice core sea ice proxies: an example from the Indian Ocean sector
Quat. Sci. Rev.
Carbon export fluxes in the Southern Ocean: results from inverse modeling and comparison with satellite-based estimates
Deep-Sea Res. II Top. Stud. Oceanogr.
Water-mass transformation by sea ice in the upper branch of the Southern Ocean overturning
Nat. Geosci.
Large scale importance of sea ice biology in the Southern Ocean
Antarct. Sci.
Correction of accelerator mass spectrometry 14C ages measured in planktonic foraminifera: paleoceanographic implications
Paleoceanography
Southern Ocean fronts from the Greenwich meridian to Tasmania
J. Geophys. Res.
Pre-bomb radiocarbon and the reservoir correction for calcareous marine species in the Southern Ocean
Geophys. Res. Lett.
Holocene ice dynamics and bottom-water formation associated with Cape Darnley polynya activity recorded in Burton Basin, East Antarctica
Mar. Geophys. Res.
Changes in the position of the Subtropical Front south of New Zealand since the last glacial period
Paleoceanography
Last Glacial Maximum CO2 and d13C successfully reconciled
Geophys. Res. Lett.
A switch from Si (OH) 4 to NO3− depletion in the glacial Southern Ocean
Geophys. Res. Lett.
Sea-ice extent in the Southern Ocean during the Last Glacial Maximum: another approach to the problem
Ann. Glaciol.
Change in the Southern Ocean: responding to Antarctica
Antarctic sea ice variability and trends, 1979–2006
J. Geophys. Res.
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