What triggers the opening of large open-ocean polynyas (holes in the winter pack ice) is still debated as we do not have in-situ observations. The main motivation for our SNSA-funded project “WINDOWS” is to find signatures of upcoming polynya events in widely available remote sensing products, in order for example to re-route autonomous instruments or optimise expeditions.
In a preliminary study , we could predict a polynya 5-day ahead of its opening using thermal infrared. In , still using thermal infrared, we increased to two weeks. In this study, we use microwave-based retrievals and can predict the opening four months ahead.
We also find that the polynya opens because of both dynamics effects (anomalous wind and ocean currents’ stresses on the sea ice) and thermodynamics, notably anomalous entrainment of heat into the mixed layer.
We’re currently working on
- estimating energy fluxes and sea ice production in polynyas, both open-ocean and coastal;
- and improving the sea ice retrievals.
So stay tuned for more polynya results!