2018-2019 USAP Field Season
Estimation of Antarctic ice melt using stable isotopic analyses of seawater
Dr. Robert Dunbar
Supporting Stations: RV/IB Nathaniel B. Palmer
Current estimations of ice-sheet mass balance in Antarctica and Greenland rely directly on satellite-based observations of the ice-sheet surface, ice margins, and ice shelves. The extent of melting ice sheets as a driver of sea level rise is not yet well understood. This project will use independent tracers of freshwater introduction from the ice sheets to the surrounding ocean to improve the ability to track how fast and where continental ice is melting. Polar ice is greatly depleted in two stable isotopes, O-18 and deuterium, relative to Southern Ocean seawater and precipitation. Using these as tracers of freshwater introduction from the ice sheet, in conjunction with precise observations of seawater temperature and salinity, the inputs of freshwater derived from melting glacial ice can be discriminated from regional precipitation.
Field Season Overview
To collect the necessary samples for this work, one scientist on the RV/IB Nathaniel B. Palmer will conduct near-real-time isotopic and salinity analyses of conductivity-temperature-depth (CTD) samples. Samples collected near Thwaites Glacier and Pine Island Glacier are of particular interest. For each sample taken for isotopic analyses (O-18 and deuterium), high-quality salinity data must be collected on the same sample. Analyzing samples with a salinometer, especially in highly stratified areas, will be essential for post-processing comparisons with CTD data. The USAP salinometer will be used in conjunction with a Picarro cavity ring down spectroscopy (CRDS) system. The principal investigator may also bring a Guildline Portasal salinometer on the cruise. Samples will also be collected on ships of opportunity with the USAP and other national programs from Italy, South Korea, China, New Zealand, and the United Kingdom.
Deploying Team Members