Salinity profiles of snow on sea ice in the Weddell Sea (Antarctica) during austral winter 2013

Small particles (known as aerosol) in the atmosphere play several critical roles. They affect the transmission of sunlight
to the underlying surface; they affect the formation of clouds, and they host and enhance important chemical reactions.
When they are deposited on ice they leave a record of past conditions that can be accessed by drilling ice cores. The most
significant aerosol component over marine areas is sea salt aerosol. Over most of the world's oceans this is created by
bubble bursting in sea spray. However there is strong evidence that another source of sea salt aerosol is important in the
polar regions, and that this ultimately derives from the surface of sea ice. The existence of this source forms the basis
for a proposed method using ice core data for determining changes in sea ice extent over long time periods. Additionally sea
salt aerosol, along with salty sea ice surfaces, is the host for the production of halogen compounds which seem to play a key
role in the oxidation chemistry of the polar regions. It is therefore important to understand the sources of polar sea salt
aerosol and therefore to be able to predict how they may vary with, and feedback to, climate.

It was recently proposed that the main source of this polar sea salt aerosol was the sublimation of salty blowing snow. The
idea is that snow on sea ice has a significant salinity. When this salty snow is mobilised into blowing snow, sublimation from
the (top of) the blowing snow layer will allow the formation of sea salt aerosol above the blowing snow layer, that can remain
airborne after the blowing snow has ceased. First calculations suggested that this would provide a strong source of aerosol
(greater than that from open ocean processes over an equivalent area). It was proposed that this would have a strong influence
on polar halogen chemistry and a noticeable influence on halogens at lower latitudes. However, this was based on estimates of
the relevant parameters as there were no data about aerosol production from this source, and almost no data about blowing snow
over sea ice in general.

Participation in a rare sea ice cruise onboard the German ice breaker Polarstern operated by Alfred-Wegener-Institut (AWI) provided
the opportunity to access the sea ice covered Weddell Sea during Austral winter 2013. Snow on sea ice was sampled at various locations,
and the snow salinity was subsequently measured in the ship's laboratory.