Arctic Sea-Ice-Zone Blowing Snow - Contribution to Sea Salt Aerosol (ABSCISSA)

The Arctic sea ice zone (SIZ) affects atmospheric composition and climate, and it is responding rapidly to climate change. We urgently need to quantify its influence on the regional/global atmosphere so we can predict how this may change in the future. Arctic research is logistically and scientifically challenging, and continually relies on new international partnerships, shared science expertise, data, and logistics. This scientific context and modus operandi entirely reflects our focus and approach within the proposed ABSCISSA project.

Our scientific focus is the potential of the Arctic SIZ to be a source of sea salt aerosol (SSA). Aerosols are small particles in the atmosphere which play several critical roles. They affect the transmission of sunlight and the formation of clouds. They host the production of halogen compounds to the atmosphere which in turn affect atmospheric oxidation chemistry and the availability of mercury to the food chain - a major current health concern for Arctic people. When they are deposited on polar ice caps, sea salt aerosols leave a record of past conditions that can be accessed by drilling ice cores. So it's important to pinpoint and quantify sources of SSA. There is strong evidence that in the polar regions, the source is the effect of wind blowing on salty snow on the sea ice surface. If this is right, it opens the possibility of using ice core data to derive changes in sea ice extent over long time periods. It is therefore important to understand the sources of polar sea salt aerosol and to be able to predict how they may vary with, and feedback to, climate.

Field work within the SIZ is challenging - the area is hard to access and very few ship-based programmes operate there, particularly during the winter. However in winter 2015, the Norwegian Polar Institute (NPI) will host a cruise on their research ship, Lance, deep within the Arctic SIZ. We have negotiated a chance to participate but need funding for the mandatory financial contribution. We have established new project partners in NPI with whom to work. Our scientific aim is to determine whether wind-blown snow on sea ice really is the dominant source of Arctic sea salt aerosol, and to make a series of measurements needed to parameterise this process in numerical models. We will use the same methodology, equipment and personnel deployed by us during a previous successful winter cruise to the Antarctic SIZ (funded by NERC), thus using previous NERC investment as a springboard for this Arctic research. The Arctic SIZ is substantially different from that of the Antarctic so to assess sea salt sources and impacts in the Arctic, we must have data derived directly from the Arctic SIZ. The collaboration with NPI is highly mutually beneficial: NPI logistics will enable access to an otherwise inaccessible region; we will make novel measurements, needed, but not made by our NPI partners; similarly, their data will fill gaps in our measurement suite; we will all contribute expertise for data interpretation. Such working practices provide considerable leverage, and build strong collaborations for the future.

Strategically, the project fits within a government-level MoU that aims to increase scientific collaboration between the UK and Norway. The project fits NERC aspirations for BAS to assume an increased role in the Arctic. In the longer-term, we will use our data i) to scale up to derive an Arctic regional source, ii) to compare with sea salt production over Antarctica, iii) to assess the impact on chemical composition of the atmosphere, and iv) to assess the suitability of sea salt aerosol as a sea ice proxy. Our results thus contribute to a range of different academic groups, raise the profile and momentum of UK science within the Arctic, and contribute to an area of intense scientific, political and public interest: the socio-economic and climatic implications and feedbacks associated with reducing Arctic sea ice extent.

Our ABSCISSA project has 2 immediate outcomes: i) a unique set of measurements from the Arctic winter sea ice zone from which we can parameterise, in numerical models, the source of sea salt aerosol (SSA) from blowing snow; ii) a firm basis of partnership with scientists at the Norwegian Polar Institute which will act as a springboard for future collaborations.

Potential beneficiaries of the project, in the long- and short-term, would gain in the following ways:

* Those who need to access the ice-covered areas of the polar regions, with obvious economic (shipping, resources, insurance) and geopolitical implications, benefit from improved (confidence in) models of current sea ice and future predictions. Such improvements can be achieved through learning about palaeo sea ice, e.g. from a quantitative proxy of sea ice extent. While such a proxy potentially lies in the sea salt record in ice cores, its development needs input regarding sources of sea salt, and its link to sea ice surfaces - data we aim to generate within ABSCISSA.

* The same beneficiaries gain from improved understanding of sea ice zone processes, including its mass and radiative balance. Such improved understanding will ultimately come from the work of cryosphere/atmosphere scientists, such as our PPs at NPI, with whom we will share our field data and parameterisations.

* The chemical environment in which people live, in terms of air quality and exposure to contaminants, is a key concern for policy makers. In the Arctic, mercury is already a serious health issue, and improved estimates of factors affecting its production, such as sources of SSA, are urgently required. With Arctic-specific parameterisations of SSA sources, models would be primed to predict the impact on halogen chemistry (and consequently on surface ozone and mercury) of changing Arctic sea ice characteristics (e.g. in terms of changing salinity), and extent.

* Reducing uncertainty in assessments of atmospheric radiative forcing is critical for policy makers dealing with adaptation/mitigation strategies for climate change. The effect of aerosols on the global radiation balance, including its direct and indirect radiative effects, is a key uncertainty in climate models. A recent publication identified the large contribution of natural aerosols to uncertainty in radiative forcing, concluding that reductions in this uncertainty must include improved assessments of natural aerosol sources. Our assessment of SSA production from Arctic blowing snow would directly contribute to reducing this uncertainty.

* Given the pace of change observed over recent years, understanding the Arctic environment, the drivers of change, and predicting future impacts, has risen considerably on the UK science agenda. ABSCISSA would contribute to these strategic ambitions, both from the research we would carry out, but also from the strong links to the Norwegian Polar Institute that we would build. These links would provide a foundation for further UK-Norway collaborations, through establishing a model for scientific co-operation, sharing data, expertise, and logistics.

* As scientists, we have a role in making science exciting and accessible to the public and to students. Like many projects in the Arctic, ABSCISSA has considerable potential as an exemplar of how science is done and how exciting it can be. BAS and the PI's group have a strong record of public outreach, and we will use our usual channels (e.g. public lectures, visits to BAS by groups such as the Cambridge Programme for Industry, visits to schools and web material) to convey this exciting science and the benefits of science collaborations.