A study examines mixing and heat transport processes under the world's largest ice shelf. Ocean water in the cavities beneath ice shelves contributes to ice shelf melting. Craig Stevens and colleagues measured water column properties, including temperature, salinity, and oxygen isotope ratios, in the cavity beneath the center of the Ross Ice Shelf in Antarctica, the world's largest ice shelf by area, in December 2017. Water in this cavity had been previously sampled in the mid-1970s. The authors identified four distinct regions in the water column: a 20-40-m homogenized benthic boundary layer, a 150-m linearly stratified region, a 150-m region of highly variable temperature and salinity structures, and a 30-m basal boundary layer just beneath the ice. Imaging revealed a thin, ephemeral layer of ice crystals on the underside of the shelf. This finding, combined with temperature and salinity measurements in the basal boundary layer, suggests that this layer is close to the melting/freezing threshold. Below the basal boundary layer, interleaving salinity and temperature structures imply the existence of enhanced diffusion, which may have the potential to modify the expected cavity circulation and which appeared to be tidally modulated. The results provide insight into ice shelf cavity circulation and emphasize the importance of in situ measurements, according to the authors.
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Article #19-10760: "Ocean mixing and heat transport processes observed under the Ross Ice Shelf control its basal melting," by Craig Stevens et al.
MEDIA CONTACT: Craig L. Stevens, National Institute of Water and Atmospheric Research, Wellington, NEW ZEALAND; tel: +64-4-386-0476, +64-27-419-1855; e-mail: craig.stevens@niwa.co.nz
Proceedings of the National Academy of Sciences