The Arctic Ocean has experienced rapid alterations in recent decades. Significant reductions in sea ice extent and thickness and enhanced runoff from the surrounding continents have occurred in response to climate warming. Atmospheric transport and deposition of aerosols (tiny particles suspended in the air) is an important mechanism for trace elements from natural and anthropogenic sources from the surrounding continents to enter the Arctic Ocean, affecting the region's changes. While many studies on aerosols over the Arctic have focused on the winter and springtime Arctic haze, fewer studies on aerosols have been conducted over the central Arctic Ocean in summer and fall. During these times, the polar front retreats northwards, reducing the transport of polluted air from mid-latitude sources. Therefore, this period provides a unique window to explore the background composition of the marine atmosphere over the Arctic Ocean. This study aims to characterize trace elements (TEs) in aerosols, particularly iron (Fe), a limiting micronutrient for phytoplankton growth in the ocean, in the marine atmosphere over the Arctic Ocean. Atmospheric sampling was carried out during the US GEOTRACES Western Arctic Cruise (GN01) along a transect of 56ºN-90ºN during August - October 2015 (Figure 1) on the US icebreaker, US Coast Guard Cutter Healy. Among air samples collected on this cruise were size-segregated aerosol particles by a MOUDI sampler, and each MOUDI sample contained ten size-fractions from 0.056 μm to 18 μm in diameter. A total of eight sets of MOUDI samples were collected (M1-M8). The data derived from these size-segregated aerosol samples are crucial for exploring the processes affecting aerosol TEs properties and for estimating atmospheric fluxes of TEs by the dry deposition process. Results from this study show that aerosol Fe concentrations varied with aerosol particle size with a single-mode size pattern, peaking at 4.4 μm in diameter (Figure 2), suggesting that aerosol Fe was from the continental sources around the Arctic Ocean. The input of aerosol Fe through the dry deposition process decreased from 6.1 μmol m-2 yr-1 in the areas of ~56ºN-80ºN to 0.73 μmol m-2 yr-1 in the regions north of 80ºN. Aerosol Fe solubility was higher in fine particles (<1 μm), which were observed mainly north of 80ºN. This study also shows a significant enrichment of calcium (Ca) in sea spray aerosol (SSA) particles relative to seawater. The extent of this calcium enrichment generally increased with decreasing aerosol particle size in fine particles (defined as particle size < 1.8 μm in diameter). Calcium bound to certain organic compounds and possibly calcareous debris from marine organisms may have contributed to the calcium enrichment in aerosols (Figure 3), reflecting the atmosphere-marine ecosystem interactions in the Arctic Ocean. This project has filled the critical data gap in this region. New measurement data from this study can be used in atmospheric and ocean models to understand better the Arctic Ocean's biogeochemical cycles. This project has provided excellent opportunities for graduate and undergraduate students to participate in research. The students have gained new experiences and skills that are valuable for their professional development. Last Modified: 12/23/2020 Submitted by: Yuan Gao
©2020 Biological and Chemical Oceanography Data Management Office.