Collaborative Research: A field and laboratory study of the melting processes of icebergs in a Greenland fjord

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Iceberg calving accounts for half of the mass discharge from the Greenland and Antarctic ice sheets, which has increased dramatically over the last two decades. Through their displacement and progressive melt, these icebergs impact the regional ocean and its ecosystem by affecting its stratification, nutrient and carbon cycling. Freshwater input due to iceberg melt has the potential to impact regional sea-ice distribution and the global overturning circulation. In addition, they pose a threat to local infrastructure and navigation. Notwithstanding their importance, our understanding of where and how icebergs melt is limited and their representation in ocean and climate models is over-simplistic, in part because informed by only a handful of observations. As a result, model-based predictions of iceberg melt rates, of the fate of the melt water, and of its impact on the ocean are highly uncertain. Improved iceberg parameterizations will reduce uncertainties in model-based predictions of the impact of shrinking polar ice caps on the large-scale ocean circulation and marine ecosystems. This is an urgent issue given the projected increase in iceberg discharge from both ice sheets. While the field experiment will take place in Greenland, it is expected that the results will be applicable to Antarctica?s tabular icebergs. One student supported by this project will be exposed to a cutting-edge problem and a multidisciplinary team of researchers. A video package, created by professional producers with experience in educational/environmental material, will be developed as part of this project to illustrate the different methodologies used to address a complex scientific problem and engage a broad audience. The package produced here will include a similar video-documentary, a 360-degree virtual reality video and clips to be distributed to various media venues including social media. In general, the diverse scientific team engaged in this project has an extensive track record of public outreach through media engagement.Current parameterizations of iceberg motion and melt in ocean models typically utilize only surface ocean velocities and properties. This is inconsistent with the notion that much of the iceberg mass flux is concentrated in large icebergs with drafts of several hundred meters. Indeed, recent work by the investigators and others, based on observations, theory and laboratory experiments, has shown that both the motion and the melting of deep-keeled icebergs in a stratified ocean characterized by a vertically sheared flow are not well represented by current parameterizations. While incorporating the impact of sheared flows on parameterizations of iceberg motion is fairly straightforward, the impact of sheared flows on iceberg melt is not. In particular, preliminary laboratory experiments show that the interaction of the sheared flow with the melt plumes that rise at the edge of icebergs is complex - giving rise to non-linear melt responses. Similarly, observations and models of glaciers melting in a stratified ocean have shown that the melt dynamics is strongly affected by the ambient stratification. Based on these recent studies, the hypothesis that melting of icebergs and the distribution of melt water, in the vicinity of the iceberg, are strongly affected by the ambient stratification and vertical shear will be tested. Through a multi-faceted approach that includes field measurements in Greenland and laboratory modeling, this project seeks to identify the leading parameters that impact the distribution of subsurface melt of an iceberg and the release of melt water into the surrounding ocean. An autonomous surface vehicle, the jetyak, and an unmanned aerial vehicle will be used to quantify iceberg melt and map the circulation and distribution of melt water around the iceberg. Idealized laboratory experiments will complement the field measurements and provide quantitative and comprehensive descriptions of the melt. Together, these results will be used to improve iceberg parameterizations to be used in ocean and climate models.