High Latitude and Cold Climate Dust: observations, impacts and characteristics
Joanna Bullard, Eleanor Darlington
Loughborough University, Leicestershire, UK
Natural dust is often associated with hot, subtropical deserts, but significant high latitude dust events have been reported from Alaska, Canada, Iceland and Greenland in the northern hemisphere (≥50°N), and Antarctica, New Zealand and Patagonia in the southern hemisphere (≥40°S). These regions are not all ‘deserts’ due to high humidity and rainfall (e.g. Iceland >1000 mm yr-1), but they are all areas with strong winds and sparse vegetation. High latitude contemporary dust sources are conservatively estimated to cover c.600 000 km2.
Meteorological stations record over 50 dust events per year in parts of the Arctic and Patagonia and satellite observations reveal that individual high latitude dust storms can be extensive, covering areas >50,000 km2. Field campaigns suggest dust emission rates can exceed those in some hot desert regions and that short-term high latitude dust deposition rates are amongst the highest in the world. High latitude dust storms affect natural and anthropogenic activities. For example, in 2008 in Reykjavík, Iceland, one third of all air quality exceedences were caused by dust storms. In south central Alaska air quality regularly exceeds recommended limits (>150 μg m3) due to dust storms from glacial river plains, with some dust concentrations >500 μg m3. Dust travelling over oceans can contribute nutrients to the marine system; one event in 2006 is estimated to have input 60-400 tons of soluble iron to the Gulf of Alaska. Dust redistribution in the landscape via dust storms can affect rates of soil formation and contribute nutrients to lakes. In southwest Greenland, the rate of organic carbon input to lakes from dust deposition is estimated to be 50 mg C m-2a-1. However observations of high latitude, cold climate dust (HL-CCD) events are sparse. Cloud cover restricts satellite coverage in spring and autumn, which are the typical high latitude dust storm seasons, and most field campaigns last only a few weeks.
To date there has been no attempt to quantify systematically the expanse, characteristics or dynamics of high latitude, cold climate dust sources, and this limits our ability to assess their current and future geomorphological significance. For example, the global expanse of potential HL-CCD sources is expected to expand rapidly in the next 100 years as ice retreat exposes fresh sediments. To consolidate current understanding of high latitude dust emissions and impacts, the High Latitude and Cold Climate Dust Network (www.hlccd.org) has created a comprehensive database of contemporary high latitude dust sources. The database, presented here, integrates diverse sources of data and is being used to determine the global scale climatic, sedimentological, and geomorphological characteristics of high latitude dust storms.