Collaborative Research: Improving estimates of Greenland’s freshwater flux: Where do icebergs form and where do they melt?

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Greenland is a large reservoir of fresh, frozen water that flows downhill until it reaches the ocean. Some of this frozen reservoir melts at the surface and directly enters the ocean. Some of the ice instead breaks off, making icebergs that melt as they float around the ocean like ice cubes in a glass of water. Where and when this freshwater enters the ocean can influence the ocean currents that carry heat, salt, and vital nutrients for marine life. However, we cannot tell if recent changes to the amount of Greenland ice that is melted and mixed into the ocean are important because we don’t yet have accurate maps of where exactly this freshwater enters the ocean. In this project, we will combine 1) photos of Greenland’s coastline taken from satellites and 2) measurements of the warm, salty, and fast coastal waters taken from ships and instruments in the ocean. From these observations we will create new maps of how much Greenland icebergs melted from 2010 to 2023. Our science team will develop outreach activities that focus on iceberg melting and will work with an artist to educate the public about the importance of iceberg melt and inspire them to think more about the Earth’s fascinating icy features. Increasing freshwater flux from the Greenland Ice Sheet influences ocean properties, with potentially large consequences for circulation, marine ecosystems, and climate at local-to-global scales. The severity of the downstream effects depends on: the fingerprint of meltwater runoff from the ice-sheet surface, meltwater produced where the ice sheet flows into the relatively warm and salty ocean, and meltwater injected into the ocean by the gradual decay of icebergs. Variations in freshwater produced by iceberg melt are poorly mapped and yet may be incredibly important since icebergs can transport cold, fresh meltwater far from the ice-sheet margins to remote ocean basins. In this project, we will combine independent iceberg melt rate estimation methods using satellite and ocean observations. We will investigate the drivers of iceberg melt and also quantify potential errors and the uncertainty in each of our methods. We will pair the iceberg melt rate estimates with observations of iceberg production from the Greenland Ice Sheet to construct time series of iceberg freshwater flux from 2010 to 2023. The project will yield time series of iceberg meltwater flux maps and determine how iceberg meltwater compares to other freshwater sources, such as surface and subglacial meltwater runoff from the ice sheet. We will also produce several novel datasets (e.g., spatially distributed iceberg size distributions, melt rates, and freshwater flux time series) that will be valuable for studies focused on ice sheet-ocean interactions. We will incorporate data products produced by the project into the open-source QGreenland geographic information system package as part of efforts to increase data accessibility and use. The project also provides an opportunity for two female early career scientists to strengthen their research programs, and we will emphasize recruitment of underrepresented groups for junior personnel. Finally, the project team will develop K–12 outreach activities that demonstrate iceberg melting in a fish-tank fjord and will work with an artist who has experience in creatively disseminating polar research to a broad range of audiences; this will enable us to communicate our project findings more effectively to the public.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.