Fig. 5: Temporal changes in sea ice production and cross-slope water properties.
From: Emerging outflow of not-so-dense shelf water from an East Antarctic polynya
a Timeseries of annual sea ice production (m³ yr−1) in the Dibble Polynya (66.3–64.8°S, 132.0–135.0 °E), derived from SSM/I (solid), AMSR-E (dashed), and AMSR-2 (dotted) satellite data. b Time series of annual sea ice production (m³/yr) in the Mertz Polynya (67.3–65.7°S, 141.0–147.4 °E). Black lines represent the eastern area (143–147.4 °E) and blue lines represent the western area (141–143 °E). c Mean annual sea ice production in the Mertz Polynya derived from AMSR-E (2003–2010). Labels indicate Adélie Sill (AS), Adélie Depression (AD), and Mertz Glacier Tongue (MGT). d Same as (c) but derived from AMSR-2 (2013–2021), showing the location of the B9B iceberg calved from the MGT grounded near the AS. Timeseries of (e) Absolute Salinity (g kg−1) within the upper AABW 28.27–28.30 γn, f thickness (m) by the depth of 28.27 γn, and (g) Conservative Temperature (°C) at 300 dbar (as the Antarctic Slope Front proxy) in the area of interest are plotted against slope bottom depth (m). CCHDO data is shown by large circle with black edge colour (MEOP data are used only in (g)). Dashed lines represent the linear regression of the labelled values calculated using the surface data, which is first regressed as a function of depth for each year, and then linearly interpolated across the years. These panels are projected onto the bottom depth–property space in (h), (i) and (j) to reveal changes in the cross-slope gradient between 1996–2010 (blue) and 2011–2024 (red). Linear regressions are calculated for the 500–3000 m (solid), 500–2000 m (dashed), and 750–3000 m (dotted) depth ranges.
