Glacial Meltwater in the Current System of Southern Greenland

• Published in: Journal of geophysical research. Oceans Vol. 128; no. 12
• Main Authors: Beaird, Nicholas L., Straneo, Fiamma, Le Bras, Isabela, Pickart, Robert, Jenkins, William J.
• Format: Journal Article
• Language: English
• Published: 01.12.2023
• Subjects: coastal; freshwater; glacier; Greenland; meltwater; tracer
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2023JC019658

The Greenland Ice Sheet is losing mass at an accelerating pace, increasing its contribution to the freshwater input into the Nordic Seas and the subpolar North Atlantic. It has been proposed that this increased freshwater may impact the Atlantic Meridional Overturning Circulation by affecting the stratification of the convective regions of the North Atlantic and Nordic Seas. Observations of the transformation and pathways of meltwater from the Greenland Ice Sheet on the continental shelf and in the gyre interior, however, are lacking. Here, we report on noble gas derived observations of submarine meltwater distribution and transports in the East and West Greenland Current Systems of southern Greenland and around Cape Farewell. In southeast Greenland, submarine meltwater is concentrated in the East Greenland Coastal Current core with maximum concentrations of 0.8%, thus significantly diluted relative to fjord observations. It is found in water with density ranges from 1,024 to 1027.2 kg m−3 and salinity from 30.6 to 34, which extends as deep as 250 m and as far offshore as 60 km on the Greenland shelf. Submarine meltwater transport on the shelf averages 5.0 ± 1.6 mSv which, if representative of the mean annual transport, represents 60%–80% of the total solid ice discharge from East Greenland and suggests relatively little offshore export of meltwater east and upstream of Cape Farewell. The location of the meltwater transport maximum shifts toward the shelfbreak around Cape Farewell, positioning the meltwater for offshore flux in regions of known cross‐shelf exchange along the West Greenland coast. Plain Language Summary The Greenland Ice Sheet is losing a lot of ice very quickly and this is causing more lightweight freshwater to flow into the North Atlantic Ocean. This extra freshwater could possibly influence the way that the surface and interior of the ocean interact, impacting global ocean currents. We do not have enough information about how the ice that is melting from Greenland is affecting the ocean, in part because we do not have many tools to observe where the meltwater goes. In this work, we made measurements with the best tools available to follow the ice melted from marine terminating glaciers as it travels around Greenland. We were able to make some of the most comprehensive direct measurements of the oceanic pathways of glacial meltwater in coastal Greenland. We found that the freshwater from Greenlandic glacier's submarine melted ice is not very concentrated when it gets to the ocean, but it does go deep and, at first, not too far away from the shore. The Greenland meltwater stays close to shore along the east coast up to Cape Farewell. However, meltwater moves farther from shore after that and may mix out into the open ocean from there. Key Points Direct measurements of the pathways and fluxes of glacial meltwater in coastal Greenland Little offshore export of meltwater east and upstream of Cape Farewell Meltwater moves offshore toward shelfbreak around Cape Farewell