Model insights into dust variability at high latitudes and their impacts

Abstract:

High latitude variability in dust is archived in ice cores and represents one of our best records of dust variability over different time scales. As high latitudes respond to change in the current climate, paleo records provide insight into the importance of these new sources for Earth system processes. Any changes in dust sources at high latitudes will be combined with variability in long range transport from the much larger dust sources in the tropics, sub-tropics and mid-latitudes as well as other aerosols. In addition, studies show that other sources of soluble iron, besides dust, may be important for high latitudes: for example, wild fires or industrial sources. In this presentation, we discuss the relative importance of high-latitude sources of dust. For example, new studies suggest that high latitudes provide more dust than previously suggested, with properties that are different than from lower latitude (desert) regions: the iron in high latitude dust from glaciogenic sources tends to be more soluble, and high latitude dust appears to act as a better ice nuclei than other sources of dust. The circulations raising dust at high-latitudes may differ from their subtropical counterparts. The mineral composition of dust is very important for the impacts of dust either on climate directly through radiation in the atmosphere or when deposited on snow, through interactions with clouds, or through deposition of iron into the ocean. Indeed, the shape of the dust itself, and thus its rate of deposition, changes with different sources of dust. Recent studies have suggested that the direct role of dust on the global radiation budget is less important than previously thought, due to improved understanding of both the optical properties of dust, and the size distribution, but the regional impacts may be very important. Here we review some of the recent studies showing the relative role of high-latitude dust sources compared to other sources of dust and aerosols in modulating climate and biogeochemistry.