Strong ocean/sea-ice contrasts observed in satellite-derived ice crystal
number concentrations in Arctic ice boundary-layer clouds
Abstract
The Arctic climate changes at a faster rate than the rest of the globe.
Boundary-layer clouds may play an important role to this change. At
temperatures below 0°C, mixed-phase clouds exist and their phase and
longevity is influenced by the abundance of ice crystals, which in turn
is a function of aerosols serving as ice nucleating particles (INPs).
Previous in-situ studies suggested a local source of INPs due to
biological activity over open ocean. Here we investigate ice crystal
concentrations in clouds below 2km at a large scale, by exploiting a
newly-developed dataset - DARDAR-Nice - retrieved from active satellite
remote sensing. The dataset spans from 2006-2016. Contrary to previous
expectation, we find that at a given latitude and temperature, there are
more ice crystals over sea ice than over open ocean. This enhancement is
particularly found in clouds south of 70°N, but also at temperatures
between 0 and -10°C.