Multi-decadal trends in Antarctic sea-ice extent driven by ENSO–SAM over the last 2,000 years

Crosta, Xavier; Etourneau, Johan; Orme, Lisa C.; Dalaiden, Quentin; Campagne, Philippine; Swingedouw, Didier; Goosse, Hugues; Massé, Guillaume; Miettinen, Arto; McKay, Robert; Dunbar, Robert B.; Escutia, Carlota; Ikehara, Masaaki

doi:10.1038/s41561-021-00697-1

Cited by 41 publications

(27 citation statements)

References 79 publications

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“…have been used to reconstruct the SAM back through time, presenting a long-term picture of the natural variability of the SAM prior to recent anthropogenic forcing (Abram et al, 2014;Dätwyler et al, 2018;Saunders et al, 2018;Villalba et al, 2012). Proxy-based reconstructions indicate that the SAM experiences a large amount of natural variability that may be intrinsic (unforced) or a response to natural external forcing, while SAM variability may also feed back to force climate changes through modulating CO 2 outgassing from the Southern Ocean (Saunders et al, 2018) and Antarctic sea ice extent (Crosta et al, 2021). During the last millennium, a minimum in the SAM index (i.e.…”

Section: Introductionmentioning

confidence: 99%

Influence of long-term changes in solar irradiance forcing on the Southern Annular Mode

Wright

Krause

Phipps³

et al. 2022

Clim. Past

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Abstract. The Southern Annular Mode (SAM) is the leading mode of climate variability in the extratropical Southern Hemisphere, with major regional climate impacts. Observations, reconstructions, and historical climate simulations all show positive trends in the SAM since the 1960s; however, earlier trends in palaeoclimate SAM reconstructions cannot be reconciled with last millennium simulations. There are also large differences in the magnitude of solar irradiance change between various solar reconstructions, although most last millennium climate simulations have relied on a low-amplitude solar-forcing scenario. Here we investigate the sensitivity of the SAM to solar irradiance variations using simulations with a range of constant solar-forcing values and last millennium transient simulations with varying amplitude solar-forcing scenarios. We find the mean SAM state can be significantly altered by solar irradiance changes and that transient last millennium simulations using a high-amplitude solar scenario have an improved and significant agreement with proxy-based SAM reconstructions. Our findings suggest that the effects of solar forcing on high-latitude climate may not be adequately incorporated in most last millennium simulations due to solar irradiance changes that are too small and/or the absence of interactive atmospheric chemistry in the global climate models used for these palaeoclimate simulations.

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Section: Introductionmentioning

confidence: 99%

Influence of long-term changes in solar irradiance forcing on the Southern Annular Mode

Wright

Krause

Phipps³

et al. 2022

Clim. Past

View full text Add to dashboard Cite

show abstract

“…Recently, the molecular remains of certain diatom taxa, i.e. specific organic geochemical lipids, have emerged as a potential proxy for reconstructing past Antarctic sea-ice cover (Barbara et al, 2013;Collins et al, 2013;Crosta et al, 2021;Denis et al, 2010;Etourneau et al, 2013;Lamping et al, 2020;Massé et al, 2011;Vorrath et al, 2019Vorrath et al, , 2020. Specifically, a di-unsaturated highly branched isoprenoid (HBI) alkene (HBI diene, C 25:2 ) has been detected in both sea-ice diatoms from the Southern Ocean and Antarctic marine sediments (Johns et al, 1999;Massé et al, 2011;Nichols et al, 1988).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of lipid biomarkers as proxies for sea ice and ocean temperatures along the Antarctic continental margin

et al. 2021

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Abstract. The importance of Antarctic sea ice and Southern Ocean warming has come into the focus of polar research during the last couple of decades. Especially around West Antarctica, where warm water masses approach the continent and where sea ice has declined, the distribution and evolution of sea ice play a critical role in the stability of nearby ice shelves. Organic geochemical analyses of marine seafloor surface sediments from the Antarctic continental margin allow an evaluation of the applicability of biomarker-based sea-ice and ocean temperature reconstructions in these climate-sensitive areas. We analysed highly branched isoprenoids (HBIs), such as the sea-ice proxy IPSO25 and phytoplankton-derived HBI-trienes, as well as phytosterols and isoprenoidal glycerol dialkyl glycerol tetraethers (GDGTs), which are established tools for the assessment of primary productivity and ocean temperatures respectively. The combination of IPSO25 with a phytoplankton marker (i.e. the PIPSO25 index) permits semi-quantitative sea-ice reconstructions and avoids misleading over- or underestimations of sea-ice cover. Comparisons of the PIPSO25-based sea-ice distribution patterns and TEX86L- and RI-OH′-derived ocean temperatures with (1) sea-ice concentrations obtained from satellite observations and (2) instrument measurements of sea surface and subsurface temperatures corroborate the general capability of these proxies to determine oceanic key variables properly. This is further supported by model data. We also highlight specific aspects and limitations that need to be taken into account for the interpretation of such biomarker data and discuss the potential of IPSO25 as an indicator for the former occurrence of platelet ice and/or the export of ice-shelf water.

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“…have been used to reconstruct the SAM back through time, presenting a long-term picture of the natural variability of the SAM prior to recent anthropogenic forcing (Abram et al, 2014;Dätwyler et al, 2018;Saunders et al, 2018;Villalba et al, 2012). Proxy-based reconstructions indicate that the SAM experiences a large amount of natural variability that may be intrinsic (unforced) or a response to natural external forcing, while SAM variability may also feedback to force climate changes through modulating CO2 outgassing from the Southern Ocean (Saunders et al, 2018) and Antarctic sea ice extent (Crosta et al, 2021). During the last millennium, a minimum in the SAM index (i.e., negative SAM) occurred during the 1400s and a positive trend in the SAM (with superimposed interannual to century-scale variability) is evident since this time (Fig.…”

Section: Introductionmentioning

confidence: 99%

Influence of long-term changes in solar irradiance forcing on the Southern Annular Mode

Wright

Krause

Phipps³

et al. 2021

Preprint

View full text Add to dashboard Cite

Abstract. The Southern Annular Mode (SAM) is the leading mode of climate variability in the extratropical Southern Hemisphere, with major regional climate impacts. Observations, reconstructions, and historical climate simulations all show positive trends in the SAM since the 1960s; however, earlier trends in palaeoclimate SAM reconstructions cannot be reconciled with last millennium simulations. Here we investigate the sensitivity of the SAM to solar irradiance variations using simulations with a range of constant solar forcing values, and last millennium transient simulations with varying amplitude solar forcing scenarios. We find the mean SAM state can be significantly altered by solar irradiance changes, and that transient last millennium simulations using a high-amplitude solar scenario have an improved and significant agreement with proxy-based SAM reconstructions. Our findings suggest that the effects of solar forcing on high-latitude climate may not be adequately incorporated in most last millennium simulations, due to solar irradiance changes that are too small and/or the absence of interactive atmospheric chemistry in global climate models.

show abstract

Multi-decadal trends in Antarctic sea-ice extent driven by ENSO–SAM over the last 2,000 years

Cited by 41 publications

References 79 publications

Influence of long-term changes in solar irradiance forcing on the Southern Annular Mode

Influence of long-term changes in solar irradiance forcing on the Southern Annular Mode

Evaluation of lipid biomarkers as proxies for sea ice and ocean temperatures along the Antarctic continental margin

Influence of long-term changes in solar irradiance forcing on the Southern Annular Mode

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