Relationships between synoptic‐scale transport and interannual variability of inorganic cations in surface snow at Summit, Greenland: 1992–1996

Abstract

Abstract. To fully utilize the long-term chemical records retrieved from central Greenland ice species in the records need to be better understood. This research examines associations between the variability of surface snow inorganic cation chemistry at Summit, Greenland (collected during 1992-1996 summer field seasons) and changes in air mass transport pathways and source regions, as well as variations in aerosol source strength. Transport patterns and source regions are determined through 10-day isentropic backward air mass trajectories during a 1 month (late May to late June) common season over the 5 years. Changes in the extent of exposed continental surfaces in source regions are evaluated to estimate aerosol-associated calcium and magnesium ion source strength, while forest fire activity in the circumpolar north is investigated to estimate aerosol ammonium ion source strength. During the 1995 common season, 3 times more calcium and magnesium accumulated in the snowpack than the other study years. Also, an increasing trend of ammonium concentration was noted throughout the 5 years. Anomalous transport pathways and velocities were observed during 1995, which likely contributed to the high levels of calcium and magnesium. Increased forest fire activity in North America was concurrent with increased levels of ammonium and potassium, except for 1996, when ion levels were above average and forest fire activity was below average. Because of the ubiquitous nature of soluble ions, we conclude that it is very difficult to establish a quantitative link between the ion content of snow and firn at Summit and changes in aerosol source regions and source strength.

Possible deposit of soil dust from the 1930's U.S. dust bowl identified in Greenland ice

“… Dibb et al [1996] tracked the transport of a biomass burning plume from the Hudson Bay lowlands region of Canada to Summit, Greenland. Slater et al [2001] showed that at least 50% of the air masses transported to Summit during May/June of 1992–1996 had origins in the North American sector, which included regions down to 40°N latitude. Their evidence included increased soil dust aerosols (as represented by Ca and Mg soluble ions) during 1995 that could only have come from snow‐free areas south of 60°N latitude.…”

Chemical and optical properties of 2003 Siberian forest fire smoke observed at the summit of Mt. Fuji, Japan

“… Owega et al [2004] and Hudson et al [2004] reported that K can be one of the specific markers of forest fire aerosols from midlatitude and high‐latitude regions. Slater et al [2001] showed that an increased level of K + in surface snow at Greenland was concurrent with an increased forest fire activity in North America. Although increases in K + concentration in aerosols during 21 and 24 May and 5–10 June events are recognizable (Figure 3c) in our measurements, the difference in value between smoke and nonsmoke days (e.g., 0.42 μ g m −3 on 21 May versus 0.09 μ g m −3 on 1 May) was not as prominent as that of BC (1948 ng m −3 versus 41 ng m −3 for the corresponding days).…”

A three-dimensional residence-time analysis of potential summertime atmospheric transport to Summit, Greenland

“…5c). for 1996, Slater and others (2001) found that >20% of 10 day trajectory origins were located in theYukon and Siberia.…”

“…Dibb and others (1996) used three-dimensional trajectories to investigate chemical signatures associated with the transport of biomass-burning emissions from North America. More recently, Slater and others’ (2001) analysis of three-dimensional back trajectories again revealed the importance of transport from North America. Although Slater and others’ work considered three-dimensional transport to Summit, the vertical component of transport was not considered in a comprehensive or systematic manner.…”

“…Meeker and others, 1997) and air/snow transfer processes (Dibb and Jaffrezo, 1997). the sources of airborne material reaching the Greenland ice sheet have also been studied (Davidson and others, 1993; Kahl and others, 1997, 1999; Slater and others, 2001). the general conclusion of studies like these is that long-range transport is an important determinant of the content of the air and surface snow at the receptor, and thus is a significant air/snow transfer process.…”