With the Greenland Ice Sheet losing mass at an accelerating rate, a poor understanding of ocean-glacier interactions contributes to the uncertainties in sea level rise projections. Although fjords cannot be resolved in global climate models, fjord processes must be understood ? and eventually parameterized ? in order to study the global impacts of both ocean warming on glacier retreat and increased glacial freshwater on ocean circulation. Fjords connect Greenland?s marine-terminating glaciers to the continental shelf ocean, forming long, narrow conduits for the export of glacial freshwater and the import of oceanic heat to melt ice. As such, fjord dynamics modulate the exchange of heat and freshwater between the ocean and glaciers, and processes of climatic relevance are affected by both directions of this ocean-ice interaction. In terms of the cryosphere?s impact on the ocean, the Greenland Ice Sheet is losing mass at an accelerating pace, and ocean warming has been implicated as a trigger for recent glacier changes via submarine melting in fjords. In the other direction, increased freshwater from Greenland can impact ocean dynamics and ecosystems ? locally within fjords, regionally in coastal currents, and potentially globally by altering the deep-convection in basins of the North Atlantic. Despite the importance of fjord circulation to ocean-glacier interactions, we have a limited understanding of the fjord processes that transport heat, salt and freshwater between the shelf ocean and glaciers. Recent observations have demonstrated the importance of two primary modes of circulation: freshwater buoyancy forcing from subglacial discharge at the glacier, and synoptic external forcing from winds and coastal trapped waves on the shelf. Drawing on these observations, the investigators will carry out numerical simulations of a fjord and its adjacent shelf, for both a quasi-realistic fjord and an idealized set of simulations. The goal of the project is to investigate the dynamics of the buoyancy-driven flow at the fjord-scale, and how this circulation interacts with synoptic external forcing to drive a net transport of heat, salt and freshwater. The relative contributions of these modes of circulation to mixing and the total exchange flow will be assessed spatially within fjords with characteristics representative of Greenland?s major fjords. This project will support K-12 education outreach, in close collaboration with two educational specialists at Rutgers. The PIs will help develop polar data kits with fjord observations and idealized model output for students to use in the Rutgers? Data Jam Program, an opportunity for students to get hands-on experience working with data and developing scientific skills. The project will involve participation in Data Jam activities and also the 4-H STEM Ambassador program at Rutgers, where the PIs will engage with 9th graders from underserved schools and develop an educational component focused on melting of glaciers, sea level rise, and climate change. Additionally, this project, which brings together scientists across a wide range of career stages, will train a PhD student and support an early career researcher.
New observations from near-glacier surveys and downstream moorings in fjords have been instrumental for understanding fjord exchange flow. Dynamical frameworks have recently been developed for external (shelf and wind) forcing in isolation, but no theory exists to describe the buoyancy-driven flow that transports tracers through the fjord or the impact of external forcing on this exchange. A realistic fjord model could untangle these intertwined dynamics and provide new insights into processes driving ocean-cryosphere exchange. While glacial fjords are fundamentally estuaries ? coastal embayments where terrestrial freshwater mixes into seawater ? they do not fit easily into traditional estuarine paradigms. However, there are many useful frameworks to build on from the coastal and estuarine world. This project will investigate fjord dynamics through an estuarine lens, drawing on better-studied processes in standard estuaries, and will attempt to expand estuarine paradigms to include glacial fjords. These questions will be addressed by a team of investigators with complementary expertise in fjord dynamics and ocean-ice interactions, estuarine dynamics, and coastal modeling and shelf processes.
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.
