Ocean Stratification Causes Submarine Melting in a Major Greenland Outlet Glacier

Submarine melting is said to be a potential cause for the widespread acceleration and mass loss of outlet glaciers<!–[if supportFields]> XE “glaciers” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “glacier” <![endif]–><!–[if supportFields]><![endif]–>. Since 2000, the retreat and acceleration of outlet glaciers accounts for 50% of Greenland’s net mass loss. To further explore this phenomenon, Straneo et al. (2011) conducted surveys of the Sermilik Fjord, which is a major outlet of the GrIS, in August 2009 and in March 2010. Their data revealed that both the cold, fresh Arctic<!–[if supportFields]> XE “Arctic” <![endif]–><!–[if supportFields]><![endif]–> waters (PW) and the warm, salty subtropical waters from the North Atlantic (STW) cause submarine melt in the summer, while only the STW drives the melt in the winter. Thus, due to the stratification of the waters, the ice edge is organized into multiple overturning cells, which increases the rate of fjord melting with depth. —Sachi Singh
Straneo, F., Curry, R. G., Sutherland, D. A., Hamilton, G. S., Cenedese, C., Våge, K., Stearns, L. A. 2011. Impact of ocean stratification on submarine melting of a major Greenland outlet glacier<!–[if supportFields]> XE “glacier” <![endif]–><!–[if supportFields]><![endif]–>. <http: 10101="" hdl.handle.net="" npre.2011.5670.1

Ocean-driven melting has important implications for ice sheet<!–[if supportFields]>XE “ice sheet”<![endif]–><!–[if supportFields]><![endif]–> variability and sea-level rise<!–[if supportFields]> XE “sea-level rise (SLR)” <![endif]–><!–[if supportFields]><![endif]–>. Typically, submarine melt rates are estimated from mass-balance calculations using ice-flow and ice-thickness data, however, these calculations do not provide any information on the water mass and circulation responsible for the melting. In this study, the authors surveyed a major outlet glacier<!–[if supportFields]> XE “glacier” <![endif]–><!–[if supportFields]><![endif]–> of the Greenland ice sheet and collected measurements for the summer and winter conditions in the fjord. They determined that the thermal forcing of ambient waters (the heat available to melt the ice) and the circulation at the ice edge are the main factors that drive submarine circulation. They found that in the summer, both PW and STW cause submarine melting in the fjord, leading to large seasonal changes in stratification of the waters. Temperature and salinity<!–[if supportFields]> XE “salinity” <![endif]–><!–[if supportFields]><![endif]–> data along the fjord show that the PW and STW layering is preserved even at the glacier’s terminus. Analysis of the summer data reveals that there are multiple overturning cells along the fjord, which give rise to non-uniform heat transport and increase the rates of melting with depth. These two observations reinforce the hypothesis that the PW and STW strongly influence circulation and melting at the ice edge.
Thus, the authors conclude that the single overturning cell model is not sufficient to understand the submarine melting rates of the Greenland ice sheet<!–[if supportFields]> XE “ice sheet” <![endif]–><!–[if supportFields]><![endif]–>. They believe that the Greenland glacier<!–[if supportFields]> XE “glacier” <![endif]–><!–[if supportFields]><![endif]–> dynamics are the complex consequence of the interface of the Atlantic/Arctic<!–[if supportFields]>XE “Arctic” <![endif]–><!–[if supportFields]><![endif]–> waters, as well as the changes in large-scale ocean circulation. 

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