How and when can submarine melting be inferred from estimates of ocean heat transport?

Abstract:

Submarine melting of Greenland’s outlet glaciers has been implicated as a driver of dynamic glacier changes in the past decade. Yet, we have a limited understanding of this melting, with no direct measurements of it. A growing number of studies attempt to infer submarine melting from measurements of ocean heat transport in the fjords where outlet glaciers terminate. Water properties and velocity are measured at some distance from the glacier to calculate heat transport through the fjord, which is then assumed to be deposited at the glacier and used to infer a submarine melt rate. However, the prevalent equations of this method are oversimplified and the implicit assumptions are typically untested. Here, we develop a more thorough framework for assessing fjord heat and salt budgets. We assess the validity of common approximations and the measurements needed for an adequate heat budget. We find that the feasibility of inferring submarine melting from oceanic measurements will vary with certain parameters and properties of the glacier/fjord system. Two years of moored ocean measurements from Sermilik Fjord, near the terminus of Helheim Glacier, are used to inform the discussion, though many of the results are generalizable to any glacier/fjord system.