Identifying Glacial Meltwater in the Amundsen Sea

Abstract Pine Island Ice Shelf (PIIS), in the Amundsen Sea, is losing mass due to warm ocean waters melting the ice from below. The glacial meltwater appears as a warmer and more saline water mass (with lower O2 concentration) than theWinterWater. Tracing meltwater pathways from ice shelves is important for identifying the regions most affected by the increased input of this water type. Water mass characteristics (temperature, salinity, O2 concentration) are used to calculate glacial meltwater fractions (MW). The observations from the Amundsen Sea show a plume of MW travelling away from PIIS along ¾ = 27.7 kg m¡3, out to the continental shelf edge. We investigate the reliability of the interpretation of the observations as a signature of MW. Physical and biological processes can affect the calculated apparentMWby causing variations in the water mass characteristics. In theWeddell Sea, iceberg meltwater was found to enhance biological productivity. In the Amundsen Sea, the biological productivity was seen to artificially decrease the apparentMWsignature. We analyse the effects of these processes on the reliability of the calculated meltwater fractions using a modified one-dimensional ocean model. The model simulates the effects of an increase in sea ice production and an influx of Lower CDW, as well as biological activity. These processes are found to result in an observation that can conventionally be interpreted as a meltwater signature, similar to the plume observed at the continental shelf edge. Recommendations are made to improve the reliability of MW calculations, including the identification of a ‘pseudo’-CDW endpoint and to increase the uncertainty associated with the O2 concentrations. A meltwater pathway leading to the west of PIIS, along the coastline, is observed. This has implications for water mass characteristics further to the west and ultimately AABW formation in the Ross Sea.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2016

Author dc:creator

• Biddle, Louise

Language dc:language

en