Upper ocean distribution of glacial meltwater in the Amundsen Sea, Antarctica

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Biddle, Louise C., Loose, Brice, Heywood, Karen J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: Amundsen Sea; Antarc*; Antarctica; Antarctica Journal; Ice Shelf; Pine Island
• Online Access: https://ueaeprints.uea.ac.uk/id/eprint/72135/; https://ueaeprints.uea.ac.uk/id/eprint/72135/1/Biddle_et_al_2019_Journal_of_Geophysical_Research_Oceans.pdf; https://ueaeprints.uea.ac.uk/id/eprint/72135/4/Biddle_et_al_2019_Journal_of_Geophysical_Research_Oceans.pdf; https://doi.org/10.1029/2019JC015133

Pine Island Ice Shelf, in the Amundsen Sea, is losing mass due to increased heat transport by warm ocean water penetrating beneath the ice shelf and causing basal melt. Tracing this warm deep water and the resulting glacial meltwater can identify changes in melt rate and the regions most affected by the increased input of this freshwater. Here, optimum multi‐parameter analysis is used to deduce glacial meltwater fractions from independent water mass characteristics (standard hydrographic observations, noble gases and oxygen isotopes), collected during a ship‐based campaign in the eastern Amundsen Sea in February‐March 2014. Noble gases (neon, argon, krypton and xenon) and oxygen isotopes are used to trace the glacial melt and meteoric water found in seawater and we demonstrate how their signatures can be used to rectify the hydrographic trace of glacial meltwater, which provides a much higher resolution picture. The presence of glacial meltwater is shown to mask the Winter Water properties, resulting in differences between the water mass analyses of up to 4 g kg−1 glacial meltwater content. This discrepancy can be accounted for by redefining the ”pure” Winter Water endpoint in the hydrographic glacial meltwater calculation. The corrected glacial meltwater content values show a persistent signature between 150 ‐ 400 m of the water column across all of the sample locations (up to 535 km from Pine Island Ice Shelf), with increased concentration towards the west along the coastline. It also shows, for the first time, the signature of glacial meltwater flowing off‐shelf in the eastern channel.