Diurnal and seasonal source-proximal dust concentrations in complex terrain, West Greenland

Diurnal and seasonal cycles of aeolian activity are well-constrained for low latitude dust source regions and provide valuable insights into relationships between dust emissions and environmental drivers. Such cycles have received little systematic attention in high latitude dust source areas (& GE;50 & DEG;N and & GE;40 & DEG;S), and understanding them will aid the modelling of atmospheric dust over different timescales. This paper examines the timing and drivers of atmospheric dust concentration close to source at ice-free locations c. 6 km and c. 37 km from the Greenland Ice Sheet margin. Dust concentration, and associated environmental drivers including wind speed and velocity, air temperature and humidity, was measured from April-October 2018 and April-August 2019. Measured dust concentrations were a similar order of magnitude to source-proximal values measured globally and varied from 0 to & GE;1000 & mu;g m(-3). Diurnal cycles in the environmental drivers of dust emission were similar to those observed in low latitudes, but unlike in the low latitudes, there was no clear diurnal pattern of dust concentration. Only 3 out of 17 recorded dust events showed a significant positive relationship between wind speed and dust concentration, and factors such as wind direction, humidity and sediment availability are the over-riding controls on dust activity at the event and seasonal scales. Whereas 7 dust events are attributed to down-valley katabatic winds, 10 events were associated with a westerly sea breeze blowing up-valley towards the ice sheet and high atmospheric moisture content. If deposited on the ice, this dust will alter ice albedo both directly and indirectly, (e.g. through the promotion of algal blooms) affecting cryospheric melt rates. Our results demonstrate an intricate relationship between first-order controls and dust concentration that raises challenges for modelling the uplift and subsequent dust transport from high latitude sources, especially the appropriateness of assumptions based on emissions behaviour at low latitudes.