Figure 3: Dense shelf water around Prydz Bay.
From: The suppression of Antarctic bottom water formation by melting ice shelves in Prydz Bay
(a) Spatial distribution of bottom-of-dive salinity (coloured circles) corresponding to dense shelf water (DSW, γn>28.27 kg m−3, θ<−1.8, salinity>34.4) from all seal data post-April 2011 to 2012. Cyan and dark green contours show fast ice and polynya regions, as in Fig. 1. Instrumented mooring locations M3, M4 (ref. 10) (black squares) and PBM7 (black circle) are shown. Inverted triangles show the locations of bottom modified Shelf Water (mSW) values from seal data post-September on the continental slope north of Cape Darnley (depth>800 m, θ<−0.8), split into saline (>34.6) values west of 69° E (cyan) and fresher (<34.6) values east of 69° E (blue). Coloured boxes with dashed lines show regional polynyas areas (light green, yellow, blue and red) used for subsequent time series analysis in b. Zonal black dashed box shows data region used for vertical section of export in c. (b) Time series of salinity at 300 m from seal occupations in key polynya areas (Barrier—dark green, Davis—yellow, MacKenzie—blue (2012) and light blue (2013) and Cape Darnley—red) demonstrating the regional variability in the formation of DSW. Time series presented as the 8-day running mean of available data around the 300 m layer, gridded at a half-day resolution. Additional time series are presented from oceanographic moorings in the western corner of the Amery Ice Shelf (PBM7—light green dashed line) and from the Adélie Sill of the Adélie Land region8 (light blue dashed line). Additional bottom-of-dive DSW data (from a) is shown for the Cape Darnley region (red dots) and along the western flank of the Prydz Channel (black squares). (c) Vertical section of salinity across the shelf break from 68 to 76° E in October highlighting DSW export from Prydz Bay east of 70° E. The primary outflow from Prydz Bay is in the bottom layer on the western flank of Prydz Channel, with some DSW on the western flank near the Cape Darnley ice barrier at 70.5° E. The most saline DSW, from Cape Darnley, is found west of 70° E.
