Mid-Holocene pulse of thinning in the Weddell Sea sector of the West Antarctic ice sheet

Abstract

Establishing the trajectory of thinning of the West Antarctic ice sheet (WAIS) since the last glacial maximum (LGM) is important for addressing questions concerning ice sheet (in)stability and changes in global sea level. Here we present detailed geomorphological and cosmogenic nuclide data from the southern Ellsworth Mountains in the heart of the Weddell Sea embayment that suggest the ice sheet, nourished by increased snowfall until the early Holocene, was close to its LGM thickness at 10 ka. A pulse of rapid thinning caused the ice elevation to fall ∼400 m to the present level at 6.5–3.5 ka, and could have contributed 1.4–2 m to global sea-level rise. These results imply that the Weddell Sea sector of the WAIS contributed little to late-glacial pulses in sea-level rise but was involved in mid-Holocene rises. The stepped decline is argued to reflect marine downdraw triggered by grounding line retreat into Hercules Inlet.

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

“…Secondly, it is possible under a scenario of dynamic deglaciation during the LGT that rapid regional bedrock isostatic variations may have effectively masked rapid ice-sheet elevation changes that have occurred during deglaciation and subsequently during the Holocene (Supplementary Information). Therefore, terrestrial cosmogenic isotope reconstructions from mountains and nunataks across the WSE are only likely to robustly reconstruct ice-sheet surface elevation changes during Holocene deglaciation252930. This is an issue which requires future detailed analysis, with multiple lines of evidence pointing towards a dynamic history of ice-sheet change across the WSE during the Holocene293031, with significant implications for defining the pre-Holocene history of this sector of the AIS.…”

“…Therefore, terrestrial cosmogenic isotope reconstructions from mountains and nunataks across the WSE are only likely to robustly reconstruct ice-sheet surface elevation changes during Holocene deglaciation252930. This is an issue which requires future detailed analysis, with multiple lines of evidence pointing towards a dynamic history of ice-sheet change across the WSE during the Holocene293031, with significant implications for defining the pre-Holocene history of this sector of the AIS. Innovative reconstructions, such as that provided by the Patriot Hills BIA, are urgently required to define in detail dynamic Antarctic ice-climate feedbacks and better constrain the ice sheets contribution to global sea level rise during periods of rapid climate transition such as the LGT.…”

Major Ice Sheet Change in the Weddell Sea Sector of West Antarctica Over the Last 5,000 Years

“…Solid black line indicates Scenario MAX for LGM ice extent, dashed black line indicates Scenario MIN. Orange points indicate LGM ice thickness (m) difference relative to present (Bentley et al, ; Hein, Marrero , et al, ; Johnson et al, ; Nichols et al, 2019). GPS sites are shown by the blue triangles.…”

“…The exposure dating method has been used extensively in Antarctica to constrain past ice sheet elevation change by dating erratics deposited on the flanks of nunataks as the ice sheet thinned. In this way, the nunataks act as dipsticks that record the changing elevation of the ice sheet through time, and the approach has proved highly effective at many locations in Antarctica (Hein, Marrero et al, ; Jones et al, ; Balco, ; Mackintosh et al, ; Stone et al, ).…”

“…The preservation of striations also indicates minimal erosion of the rock surface after deposition. Exposure dates from locations where these sample characteristics are common can produce clear thinning histories with little geological scatter in exposure age results (e.g., Hein, Marrero , et al, ; Jones et al, 2015). In other settings, the success of the method is highly variable.…”