Abstract
AbstractPine Island Ice Shelf, in the Amundsen Sea, is losing mass because of warm ocean waters melting the ice from below. Tracing meltwater pathways from ice shelves is important for identifying the regions most affected by the increased input of this water type. Here, optimum multiparameter analysis is used to deduce glacial meltwater fractions from water mass characteristics (temperature, salinity, and dissolved oxygen concentrations), collected during a ship-based campaign in the eastern Amundsen Sea in February–March 2014. Using a one-dimensional ocean model, processes such as variability in the characteristics of the source water masses on shelf and biological productivity/respiration are shown to affect the calculated apparent meltwater fractions. These processes can result in a false meltwater signature, creating misleading apparent glacial meltwater pathways. An alternative glacial meltwater calculation is suggested, using a pseudo–Circumpolar Deep Water endpoint and using an artificial increase in uncertainty of the dissolved oxygen measurements. The pseudo–Circumpolar Deep Water characteristics are affected by the under ice shelf bathymetry. The glacial meltwater fractions reveal a pathway for 2014 meltwater leading to the west of Pine Island Ice Shelf, along the coastline.
Highlights
The West Antarctic Ice Sheet holds up to 3.3 m of potential sea level rise (Bamber et al 2009) and has been observed to contain some of the fastest thinning ice shelves around Antarctica, with up to 7 m a21 thinning (Pritchard et al 2012)
By defining the modified CDW (mCDW) endpoint as the warmest and the Winter Water (WW) endpoint as the coolest below the surface layer in each conductivity– temperature–depth (CTD) profile, variations in the characteristics of these water masses are seen across the continental shelf of the Amundsen Sea, similar to methods used by Nakayama et al (2013)
The development of a one dimensional model revealed that the combination of varying WW properties and a switch between Upper CDW (UCDW) and Lower CDW (LCDW) endpoints for mCDW can replicate the curvature observed in Q–SA space
Summary
The West Antarctic Ice Sheet holds up to 3.3 m of potential sea level rise (Bamber et al 2009) and has been observed to contain some of the fastest thinning ice shelves around Antarctica, with up to 7 m a21 thinning (Pritchard et al 2012). By defining the mCDW endpoint as the warmest (and most saline) and the WW endpoint as the coolest below the surface layer in each CTD profile, variations in the characteristics of these water masses are seen across the continental shelf of the Amundsen Sea, similar to methods used by Nakayama et al (2013). Using this endpoint identification, CTD stations were grouped into regions with similar properties The overdetermined system used in OMPA results in a larger water mass fractions matrix (A, where A1,k signifies the value of tracer 1 for water mass k) and observations array (b, where b1 signifies the observational value of tracer 1) than the water mass fractions array (x, where k, l, and m are the three water masses): BBB@
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
