Estimates of iceberg submarine melting from high-resolution digital elevation models: application to Sermilik Fjord, East Greenland

Abstract

ABSTRACT. Observed increases in iceberg discharge from Greenland's marine-terminating glaciers over the past two decades have altered the freshwater flux from glacial fjords into surrounding ocean basins. Although variations in freshwater flux due to ice-sheet discharge change have been investigated on a broad scale, the distribution of the freshwater flux due to melting of calved glacier ice (i.e. icebergs) has not been examined. Logistical challenges to collecting in situ data in glacial fjords have so far prevented a detailed examination of freshwater fluxes arising from melting beneath the waterline (i.e. submarine melting). Here we demonstrate that submarine melting of icebergs can be quantified using repeat digital elevation models derived from very high-resolution stereo satellite images. Analysis of volume changes for icebergs in Sermilik Fjord, East Greenland, yield area-averaged submarine melt rates of �0.39 m d -1. These rates are in relatively good agreement with simulated winter melt rates along the submerged portion of the Helheim Glacier terminus, providing independent validation of the applied technique. Further, the volume flux of fresh water from iceberg melting scales with surface and submerged iceberg areas, which suggests that iceberg meltwater may be an important freshwater component in fjords with high iceberg concentrations and/or expansive ice melange.

Icebergs and Sea Ice Detected with Inverted Echo Sounders

“…Since little is known about the temporal and spatial variability of melt rates and residence times, the histories of iceberg discharge reconstructed from sediment studies are not yet very well constrained. Although iceberg residence times can be estimated from Lagrangian trackers mounted on individual icebergs and basal iceberg melt rates have been estimated using repeat high-resolution stereo images from satellites (Enderlin and Hamilton 2014), these studies have examined relatively few icebergs.…”

“…Evidence suggests that the rate of freshwater discharge from Greenland, including that carried by icebergs exported from fjords in northwestern and southeastern Greenland, accelerated in the early 2000s (e.g., Enderlin et al 2014). To put the recent acceleration into context, deposits of ice-rafted debris, which has accumulated on the fjord bed (Boldt et al 2013 and references therein), have been used to infer the history of calving and iceberg discharge rate (e.g., Andresen et al 2012).…”

Dynamics of Greenland�s glacial fjords

“…However, it is contrary to the assumption of most previous studies that iceberg melting is small compared to glacier melting. New techniques, such as inferring iceberg melt-rates from satellites (Enderlin and Hamilton, 2014) or tracking icebergs (Sutherland et al, 2014a), are opening many possibilities for studying the role of icebergs in glacial fjords and for isolating their meltwater contribution. The fjord circulation, mixing, and heat transport from this distributed buoyancy source has not been examined and could have very different impacts than a localized freshwater input at the glacier.…”

An Empirical Approach for Estimating Stress-Coupling Lengths for Marine-Terminating Glaciers

“…A total of 18 DEMs were compiled for each glacier ( Table 1) in DEM-derived surface elevations were estimated as ∼7 m for the ASTER products (Stearns and Hamilton, 2007) and ∼3 m for WorldView DEMs (Enderlin and Hamilton, 2014). Systematic biases in DEM-derived elevations were minimized through vertical co-registration of overlapping DEMs using exposed bedrock elevations (Nuth and Kääb, 2011).…”