How much, how fast?: A science review and outlook for research on the instability of Antarctica's Thwaites Glacier in the 21st century

Abstract

Constraining how much and how fast the West Antarctic Ice Sheet (WAIS) will change in the coming decades has recently been identified as the highest priority in Antarctic research (National Academies, 2015). Here we review recent research on WAIS and outline further scientific objectives for the area now identified as the most likely to undergo near-term significant change: Thwaites Glacier and the adjacent Amundsen Sea. Multiple lines of evidence point to an ongoing rapid loss of ice in this region in response to changing atmospheric and oceanic conditions. Models of the ice sheet's dynamic behavior indicate a potential for greatly accelerated ice loss as ocean-driven melting at the Thwaites Glacier grounding zone and nearby areas leads to thinning, faster flow, and retreat. A complete retreat of the Thwaites Glacier basin would raise global sea level by more than three meters by entraining ice from adjacent catchments. This scenario could occur over the next few centuries, and faster ice loss could occur through processes omitted from most ice flow models such as hydrofracture and ice cliff failure, which have been observed in recent rapid ice retreats elsewhere. Increased basal melt at the grounding zone and increased potential for hydrofracture due to enhanced surface melt could initiate a more rapid collapse of Thwaites Glacier within the next few decades. words

Ocean Tide Influences on the Antarctic and Greenland Ice Sheets

“…Jacobs et al (1992) described the various styles of ocean/ice shelf interactions, some of which are illustrated in Figure 3. Recent overviews of the complex interactions between the ocean, ice sheets, and atmosphere have been provided by Straneo et al (2013) for Greenland and Scambos et al (2017) and Turner et al (2017) for the Amundsen Sector, West Antarctica. Truffer and Motyka (2016) reviewed the thermodynamic and mechanical interactions between glaciers flowing into both the ocean and lakes.…”

Retreat of Thwaites Glacier, West Antarctica, over the next 100 years using various ice flow models, ice shelf melt scenarios and basal friction laws

“…The strengthening of westerlies around the Antarctic continent over the past decades has caused more warm, salty Circumpolar Deep Water (CDW) to intrude onto 5 the continental shelf, flow along troughs in the sea floor, reach the sub-ice-shelf cavities and glacier grounding lines and melt them from below (Schneider and Steig, 2008;Spence et al, 2014; Dutrieux et al, 2014; Li et al, 2015;Scambos et al, 2017). …”

Response to Reviewer 1

“…Increasing ice loss is presently occurring through these mechanisms in the Amundsen Sea sector of the WAIS (Fig. 1) (see review in Scambos et al, 2017), and numerical modeling suggests that an incipient collapse of the ice sheet is underway in this sector (e.g., Joughin et al, 2014). How much and how quickly future sea level will rise due to WAIS deglaciation remains unknown (Scambos et al, 2017), but continued ice loss could eventually increase global mean sea level by 3-4 m (Bamber et al, 2009).…”

“…1) (see review in Scambos et al, 2017), and numerical modeling suggests that an incipient collapse of the ice sheet is underway in this sector (e.g., Joughin et al, 2014). How much and how quickly future sea level will rise due to WAIS deglaciation remains unknown (Scambos et al, 2017), but continued ice loss could eventually increase global mean sea level by 3-4 m (Bamber et al, 2009). Knowledge of ice-sheet extent during interglacials warmer and more prolonged than the Holocene would be invaluable for understanding, and potentially predicting, the future stability or instability of the WAIS.…”