¹⁰Be/⁹Be Ratios Reflect Antarctic Ice Sheet Freshwater Discharge During Pliocene Warming

Abstract

Along glaciated margins, ratios of meteoric cosmogenic beryllium‐10, 10Be, normalized to its stable isotope, 9Be, reflect an environmental signal, driven ultimately by climatic change. We explore the application of this isotopic pair as a proxy for East Antarctic Ice Sheet dynamics. We analyze 10Be/9Be in middle Pliocene glaciomarine sediments offshore the Wilkes Land Region (Integrated Ocean Drilling Program (IODP) Site U1361A) and examine our new record alongside existing biochemical/geochemical records (Ba/Al, opal %wt, εNd, and 87Sr/86Sr). 10Be/9Be ratios reach local maxima during pulsed, mild warming events and are strongly correlated with existing records that indicate concurrent ice sheet retraction and increased bioproductivity. We suggest climate change as the primary driver of the 10Be/9Be record near glaciated margins, whereby increased warming drives ice sheet retraction, discharging freshwaters and diluting the open ocean 10Be/9Be signal recorded in authigenic minerals.

Enhanced iceberg discharge in the western North Atlantic during all Heinrich events of the last glaciation

“…While most HE modeling studies have focused on meltwater (Ganopolski and Rahmstorf, 2001;Prange et al, 2004;Roberts et al, 2014) and iceberg calving (Alvarez-Solas et al, 2013Bassis et al, 2017;Marshall and Koutnik, 2006), the absolute fluxes of meltwater and iceberg calving are challenging to reconstruct with paleo proxies. Meltwater proxies, including d 18 O (Cortijo et al, 1997;Roche et al, 2004), %C37:4 (Naafs et al, 2011;Rodrigues et al, 2017;Stein et al, 2009), and 10 Be/ 9 Be (Valletta et al, 2018), while valuable, are currently only qualitative. IRD grain concentration can only provide a relative measure of the magnitude of iceberg calving (e.g., Bond et al, 1992).…”

The Sensitivity of the Antarctic Ice Sheet to a Changing Climate: Past, Present, and Future

“…Observational evidence for retreat into the marine-based portions of the EAIS includes geochemical proxy data in marine sediment records offshore Adelie Land that suggest significant ice retreat inland of the Wilkes Subglacial Basin, one of the largest subglacial basins of the EAIS, which may have contributed 3-4m to Pliocene sea levels (Bertram et al, 2018;Cook et al, 2013;Patterson et al, 2014;Valletta, Willenbring, Passchier, & Elmi, 2018) (Figure 20). Quantification of the subglacial sediment thickness of the northern Wilkes Subglacial Basin by airborne gravity and geophysical data reveals thin sediment deposits influenced by glacial erosion (Frederick et al, 2016;Paxman et al, 2018) that may suggest more frequent Pliocene to Pleistocene ice sheet retreat and advance.…”

Holocene melting of the West Antarctic Ice Sheet driven by tropical Pacific warming

“…Relative Be isotope values from offshore Wilkes Land 37 and Baffin Bay 36 are presented using light blue diamonds and dark blue squares, respectively. The dashed black line, light blue line, and dark blue line represent the relationship for samples from this study, Wilkes Land 37 , and Baffin Bay 36 , respectively. …”