Ice Sheet and Sea Ice Ultrawideband Microwave radiometric Airborne eXperiment (ISSIUMAX) in Antarctica: first results from Terra Nova Bay

Abstract

Abstract. An airborne microwave wide-band radiometer (500–2000 MHz) was operated for the first time in Antarctica to better understand the emission properties of sea ice, outlet glaciers and the interior ice sheet from Terra Nova Bay to Dome C. The different glaciological regimes were revealed to exhibit unique spectral signatures in this portion of the microwave spectrum. Generally, the brightness temperatures over a vertically homogeneous ice sheet are warmest at the lowest frequencies, consistent with models that predict that those channels sensed the deeper, warmer parts of the ice sheet. Vertical heterogeneities in the ice property profiles can alter this basic interpretation of the signal. Spectra along the lengths of outlet glaciers were modulated by the deposition and erosion of snow, driven by strong katabatic winds. Similar to previous experiments in Greenland, the brightness temperatures across the frequency band were low in crevasse areas. Variations in brightness temperature were consistent with spatial changes in sea ice type identified in satellite imagery and in situ ground-penetrating radar data. The results contribute to a better understanding of the utility of microwave wide-band radiometry for cryospheric studies and also advance knowledge of the important physics underlying existing L-band radiometers operating in space.

Ice Shelf Water-influenced Fast Ice and Sub-Ice Platelet Layer Thickness Distributions beside the Campbell Ice Tongue in Terra Nova Bay, Antarctica

“…This was indicated by fast ice extent in winter, which formed a straight line from west to east, across the ice tongue terminus, which was also observed in winter of 2018 (Brogioni et al 2023). The coastal fringe, as described in section 4.1, reoccurred over winter in 2021, and was also observed in late spring of 2005 (Vacchi et al 2012), and in winter of 2018 (Brogioni et al, 2023). The coastline is likely the dominant influence on the reoccurrence of the fast ice fringe, but shallower bathymetry (<300 m) could also aid fast ice persistence by providing shelter from polynya-driven and open ocean circulation.…”

“…The coastline, including the southward protruding ice tongue and Cape Washington provided anchorage for fast ice as it forms, and once established, protection from katabatic winds and polynya dynamics. This was indicated by fast ice extent in winter, which formed a straight line from west to east, across the ice tongue terminus, which was also observed in winter of 2018 (Brogioni et al 2023). The coastal fringe, as described in section 4.1, reoccurred over winter in 2021, and was also observed in late spring of 2005 (Vacchi et al 2012), and in winter of 2018 (Brogioni et al, 2023).…”

“…McMurdo Sound, Brett et al, (2020, 2024) used a seawater conductivity of 2700 mS m -1 obtained from extensive oceanographic observations in the region (e.g., Robinson et al, 2014). In Gerlache Inlet, Brogioni et al, (2023) measured seawater salinity of 31.2-32.1 g kg -1 in the centre and near Tethys Bay on 18 November 2018, corresponding to a conductivity of ~2500 mS m -1 for a temperature of -1.91°C and pressure of 15 dbar (McDougall and Barker, 2011). This is slightly lower than the seawater conductivity of 2700 mS m -1 we obtained from EM measurements of the full study region.…”

Simulating 0.4–2.5 GHz Brightness Temperatures of the Ross Ice Shelf, Antarctica

“…Microwave radiometry at 1.4 GHz has recently proven successful in estimating inland ice sheet internal temperatures up to 1 km depth [10]. Ultrawideband radiometry over the 0.5-2 GHz range further extends this capability to the entire ice sheet depth [11], representing a significant potential for bridging existing knowledge gaps in ice rheology [12], [13], [14]. Because sub-2 GHz brightness temperature measurements for the RIS are available currently only at 1.4 GHz, this potential has yet to be tested on ice shelves, but a detailed analysis of relationships between RIS geophysical parameters and 1.4 GHz brightness temperature (Tb) observations is provided in [16].…”