Did Holocene climate changes drive West Antarctic grounding line retreat and readvance?

• Published in: The Cryosphere
• Main Authors: S. U. Neuhaus, S. M. Tulaczyk, N. D. Stansell, J. J. Coenen, R. P. Scherer, J. A. Mikucki, R. D. Powell
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2021
• Subjects: geo; envir; Antarctic; Bindschadler Ice Stream; Conway; Kamb Ice Stream; Lowry; Ross Sea; West Antarctic Ice Sheet; Whillans; Whillans Ice Stream; Antarc*; Antarctica; Ice Sheet; Ice Shelf; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-15-4655-2021; https://tc.copernicus.org/articles/15/4655/2021/tc-15-4655-2021.pdf; https://doaj.org/article/40f0e2baba564659bd64d8f1999e3019

Knowledge of past ice sheet configurations is useful for informing projections of future ice sheet dynamics and for calibrating ice sheet models. The topology of grounding line retreat in the Ross Sea sector of Antarctica has been much debated, but it has generally been assumed that the modern ice sheet is as small as it has been for more than 100 000 years (Conway et al., 1999; Lee et al., 2017; Lowry et al., 2019; McKay et al., 2016; Scherer et al., 1998). Recent findings suggest that the West Antarctic Ice Sheet (WAIS) grounding line retreated beyond its current location earlier in the Holocene and subsequently readvanced to reach its modern position (Bradley et al., 2015; Kingslake et al., 2018). Here, we further constrain the post-LGM (Last Glacial Maximum) grounding line retreat and readvance in the Ross Sea sector using a two-phase model of radiocarbon input and decay in subglacial sediments from six sub-ice sampling locations. In addition, we reinterpret high basal temperature gradients, measured previously at three sites in this region (Engelhardt, 2004), which we explain as resulting from recent ice shelf re-grounding accompanying grounding line readvance. At one location – Whillans Subglacial Lake (SLW) – for which a sediment porewater chemistry profile is known, we estimate the grounding line readvance by simulating ionic diffusion. Collectively, our analyses indicate that the grounding line retreated over SLW 4300-2500+1500 years ago, and over sites on Whillans Ice Stream (WIS), Kamb Ice Stream (KIS), and Bindschadler Ice Stream (BIS) 4700-2300+1500, 1800-700+2700, and 1700-600+2800 years ago, respectively. The grounding line only recently readvanced back over those sites 1100-100+200, 1500-200+500, 1000-300+200, and 800±100 years ago for SLW, WIS, KIS, and BIS, respectively. The timing of grounding line retreat coincided with a warm period in the mid-Holocene to late Holocene. Conversely, grounding line readvance is coincident with cooling climate in the last 1000–2000 years. Our estimates for the ...