Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the Last Glacial Termination

Abstract

Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT; 18,000–11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well-known, relatively poor chronological control has precluded precise alignment of ice, atmospheric and marine records, making it difficult to assess relationships between Antarctic ice-sheet (AIS) dynamics, climate change and sea level. Here we present results from a highly-resolved ‘horizontal ice core’ from the Weddell Sea Embayment, which records millennial-scale AIS dynamics across this extensive region. Counterintuitively, we find AIS mass-loss across the full duration of the Antarctic Cold Reversal (ACR; 14,600–12,700 yrs ago), with stabilisation during the subsequent millennia of atmospheric warming. Earth-system and ice-sheet modelling suggests these contrasting trends were likely Antarctic-wide, sustained by feedbacks amplified by the delivery of Circumpolar Deep Water onto the continental shelf. Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections. With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise.

Spatial pattern of accumulation at Taylor Dome during Marine Isotope Stage 4: stratigraphic constraints from Taylor Glacier

“…The ablation zone extends approximately 80 km from the terminus (Kavanaugh et al, 2009b). The close proximity to Mc-Murdo Station provides excellent logistical access to the site (e.g., Fountain et al, 2014;Petrenko et al, 2017;Baggenstos et al, 2017;Marchant et al, 1994;Aarons et al, 2017).…”

“…A number of blue ice areas have provided useful paleoclimate archives including Pakitsoq, Greenland, for the Younger Dryas-Preboreal transition Schaefer et al, 2009Schaefer et al, , 2006, Allan Hills, Victoria Land, Antarctica, for ice 90-250 ka and > 1 Ma (Spaulding et al, 2013;Higgins et al, 2015), Mt. Moulton, Antarctica, for the last interglacial (Korotkikh et al, 2011), the Patriot Hills, Horseshoe Valley, Antarctica, for ice from the last glacial termination (Fogwill et al, 2017), and Taylor Glacier, McMurdo Dry Valleys, Antarctica, for ice spanning the last glacial termination and MIS 3 Schilt et al, 2014;Baggenstos et al, 2017;Petrenko et al, 2017). Taylor Glacier is particularly well suited for paleoclimate reconstructions because of the excellent preservation of near-surface ice, large age span, and continuity of the record (Buizert et al, 2014;Baggenstos, 2015;Baggenstos et al, 2017).…”

Atmospheric gas records from Taylor Glacier, Antarctica, reveal ancient ice with ages spanning the entire last glacial cycle

“…In Antarctica, this includes sites at Scharffenbergbotnen (Sinisalo et al, 2007), Allan Hills (Spaulding et al, 2013), Mount Moulton (Custer, 2006;Korotkikh et al, 2011), Yamato Mountain (Moore et al, 2006), Taylor Glacier (Aciego et al, 2007), and Patriot Hills (Turney et al, 2013;Fogwill et al, 2017). Depending on the initial accumulation rate and the ice dynamics at a specific site, such records can span anywhere from a few thousand years at Yamato Mountain to 1 million years at Allan Hills (Higgins et al, 2015).…”

Expedition 382 Preliminary Report: Iceberg Alley and Subantarctic Ice and Ocean Dynamics

“…This interpretation is supported by novel modeling and ice-core studies (Fogwill et al, 2017;Golledge et al, 2014) but is in marked contrast to reconstructions arguing for a minor and later (after ~14 ka) AIS retreat (e.g., Bentley et al, 2010;Conway et al, 1999;Mackintosh et al, 2011Mackintosh et al, , 2014Peltier, 2004). However, those studies rely on temporally and geographically restricted terrestrial and shallowmarine, near-field sequences Heroy and Anderson, 2007;Hillenbrand et al, 2013).…”

“…Fogwill et al (2014) modeled a 9° poleward shift of the SHW and a 0.2°-0.9°C warming in the upper 500 m of the subpolar gyres that persisted for millennia during deglaciation. Associated AIS drawdown might also have induced large-scale sea ice expansion and IBRD increase (Fogwill et al, 2017). Reconstructing these Antarctic sea ice conditions and dust-climate couplings will provide much needed empirical data to assess whether changes in sea ice cover are driven by the position of the southern SHW and/or flux of glacial meltwater.…”