Abstract. Icebergs account for half of all ice loss from Antarctica
and, once released, present a hazard to maritime operations. Their melting
leads to a redistribution of cold fresh water around the Southern Ocean
which, in turn, influences water circulation, promotes sea ice formation,
and fosters primary production. In this study, we combine CryoSat-2
satellite altimetry with MODIS and Sentinel-1 satellite imagery and
meteorological data to track changes in the area, freeboard, thickness, and
volume of the B30 tabular iceberg between 2012 and 2018. We track the
iceberg elevation when it was attached to Thwaites Glacier and on a further
106 occasions after it calved using Level 1b CryoSat data, which ensures
that measurements recorded in different acquisition modes and within
different geographical zones are consistently processed. From these data, we
map the iceberg's freeboard and estimate its thickness taking snowfall
and changes in snow and ice density into account. We compute changes in
freeboard and thickness relative to the initial average for each overpass
and compare these to estimates from precisely located tracks using the
satellite imagery. This comparison shows good agreement (correlation
coefficient 0.87) and suggests that colocation reduces the freeboard
uncertainty by 1.6 m. We also demonstrate that the snow layer has a
significant impact on iceberg thickness change. Changes in the iceberg area
are measured by tracing its perimeter, and we show that alternative estimates
based on arc lengths recorded in satellite altimetry profiles and on
measurements of the semi-major and semi-minor axes also capture the trend,
though with a 48 % overestimate and a 15 % underestimate,
respectively. Since it calved, the area of B30 has decreased from 1500±60 to 426±27 km2, its mean
freeboard has fallen from 49.0±4.6 to 38.8±2.2 m, and its
mean thickness has reduced from 315±36 to 198±14 m. The
combined loss amounts to an 80 %±16 % reduction in volume, two
thirds (69 %±14 %) of which is due to fragmentation and the
remainder (31 %±11 %) of which is due to basal melting.