Abstract
Abstract. The Totten Glacier is rapidly losing mass. It has been suggested that this mass loss is driven by changes in oceanic forcing; however, the details of the ice–ocean interaction are unknown. Here we present results from an ice shelf–ocean model of the region that includes the Totten, Dalton and Moscow University ice shelves, based on the Regional Oceanic Modeling System for the period 1992–2007. Simulated area-averaged basal melt rates (net basal mass loss) for the Totten and Dalton ice shelves are 9.1 m ice yr−1 (44.5 Gt ice yr−1) and 10.1 m ice yr−1 (46.6 Gt ice yr−1), respectively. The melting of the ice shelves varies strongly on seasonal and interannual timescales. Basal melting (mass loss) from the Totten ice shelf spans a range of 5.7 m ice yr−1 (28 Gt ice yr−1) on interannual timescales and 3.4 m ice yr−1 (17 Gt ice yr−1) on seasonal timescales. This study links basal melt of the Totten and Dalton ice shelves to warm water intrusions across the continental shelf break and atmosphere–ocean heat exchange. Totten ice shelf melting is high when the nearby Dalton polynya interannual strength is below average, and vice versa. Melting of the Dalton ice shelf is primarily controlled by the strength of warm water intrusions across the Dalton rise and into the ice shelf cavity. During periods of strong westward coastal current flow, Dalton melt water flows directly under the Totten ice shelf further reducing melting. This is the first such modelling study of this region to provide a valuable framework for directing future observational and modelling efforts.
Highlights
Understanding how changing ocean circulation and properties are causing increased basal melt of Antarctic ice shelves is crucial for predicting future sea level rise
Most of the ice sheet that drains through the Totten Glacier is from the Aurora Subglacial Basin (Young et al, 2011) and is marine based making the region potentially vulnerable to rapid ice sheet collapse
The Totten ice shelf areaaveraged melt rate averaged over the period 1992–2007 is modelled as 9.1 m ice yr−1 (44.5 Gt ice yr−1), which compares well to the most recent estimate of areaaveraged melt rate of 10.5 ± 0.7 m yr−1 (Rignot et al, 2013)
Summary
Understanding how changing ocean circulation and properties are causing increased basal melt of Antarctic ice shelves is crucial for predicting future sea level rise. Most of the ice sheet that drains through the Totten Glacier is from the Aurora Subglacial Basin (Young et al, 2011) and is marine based (i.e. the ice base is grounded below sea level; Roberts et al, 2011) making the region potentially vulnerable to rapid ice sheet collapse. Weertman (1974) showed that ice grounded below sea level is inherently unstable, where the bedrock slopes downwards, away from the ocean, as is the case in the Aurora Subglacial Basin (Young et al, 2011). Observations of global mean sea level rise over the period 1993–2008, indicate an average rate of 2.61 ± 0.55 mm yr−1, with an Antarctic contribution of 0.43 ± 0.2 mm yr−1 (Church et al, 2011). Projections of sea level rise have a large uncertainty in the contribution of Antarctica, due to lack of observations of ice discharge rates and surface mass balance (Gregory et al, 2013)
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