NSFGEO-NERC:Collaborative Research: Chemistry and Biology under Low Flow Hydrologic Conditions Beneath the Greenland Ice Sheet Revealed through Naturally Emerging Subglacial Water

This project is jointly funded by the National Science Foundation's Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (UKRI/NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own component of the work.

Weathering is an important process that releases nutrients that are essential for life from rocks and minerals in the Earth's surface. This project seeks to understand the effect of large glaciers on weathering processes beneath the Greenland Ice Sheet and the consequences for life. During summer, nutrients and other products are flushed out of the Greenland Ice Sheet with water from melting ice. While these products have been sampled in spring and summer, it is not known how weathering processes are different during winter. In this project, researchers will sample the seasonal ice that forms in front of two of Greenland's glacial outlets, Isunnguata Sermia and Leverett Glacier, during the freezing months to assess the chemistry and microbiology processes that reflect wintertime conditions beneath the ice sheet – periods when input of fresh meltwater is minimal. These samples will increase knowledge of winter conditions under the Greenland Ice Sheet and help better understand the interior portions of the ice sheet which are largely inaccessible. Such information will help in assessing past conditions, when colder atmospheric conditions resulted in minimal meltwater input through the ice sheet and to the glacial bed. These analyses will inform understanding of the role of glaciers on earth's nutrient cycles presently, under past ice age conditions, and in a future deglaciating world.

The Greenland Ice Sheet is a major exporter of biologically important elements to the world's oceans. However, most of our knowledge of chemical and biological fluxes from the ice sheet comes from the summer outflux of outlet glaciers whose channelized waters contact only a limited portion of the glacier bed. The majority of the glacier-bed interface contains slow-flowing, distributed waters not representative of this flux. The project will test the hypothesis that overwinter chemical and biological processes under outlets of the Greenland Ice Sheet differ substantially from summer outflow and represent a window into widespread, but typically inaccessible, distributed flow. The principal sample collection method will be early spring coring of naled ice that forms at glacial termini from wintertime subglacial flow. Chemical, mineralogical, and biological constituents of this flow will be compared to material emerging from the initial, peak, and terminal phases of the melt season. Elsewhere in the Arctic, the chemistry of frozen overwinter subglacial material shows significant limitation in oxygen or sediment supply compared with even the first spring melt, supporting the idea that naled ice reveals a unique overwinter system. The naled ice and outflow of Isunnguata Sermia and Leverett Glacier will be sampled over two years. These West Greenland outlets differ by more than an order of magnitude in the size of the catchments they drain, thereby testing the effect of scale on biogeochemistry. Naled ice structure will be characterized by ground penetrating radar and ice borehole temperature profiles. The aqueous geochemistry, stable isotopes of carbonate and sulphate, and mineralogy of the suspended sediment of ice and water will be assessed. These analyses will document changes in the mineral flux and supply of atmospheric gases at the glacial bed between winter low flow conditions and peak summer melt. Microbial abundance, diversity, metagenomics, and stable isotopes of biomass will also be measured to understand the concomitant relationship between geochemical conditions and biological communities. Researchers will incorporate findings into a number of outreach efforts including developing a new curriculum module for the Center for Earth and Environmental Sciences, providing research opportunities for underrepresented students as part of the Bridge to Research Program and preparing hands-on activities for the Market Science Program.

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.