Loess origin, transport, and deposition over the past 10,000years, Wrangell-St. Elias National Park, Alaska

Abstract

a b s t r a c tContemporary glaciogenic dust has not received much attention, because most research has been on glaciogenic dust of the last glacial period or non-glaciogenic dust of the present interglacial period. Nevertheless, dust from modern glaciogenic sources may be important for Fe inputs to primary producers in the ocean. Adjacent to the subarctic Pacific Ocean, we studied a loess section near Chitina, Alaska along the Copper River in Wrangell-St. Elias National Park, where dust has been accumulating over the past $10,000 years. Mass accumulation rates for the fine-grained (<20 lm) fraction of this loess section are among the highest reported for the Holocene of high-latitude regions of the Northern Hemisphere. Based on mineralogy and geochemistry, loess at Chitina is derived from glacial sources in the Wrangell Mountains, the Chugach Mountains, and probably the Alaska Range. Concentrations of Fe in the silt-plus-clay fraction of the loess at Chitina are much higher than in all other loess bodies in North America and higher than most loess bodies on other continents. The very fine-grained (<2 lm) portion of this sediment, capable of long-range transport, is dominated by Fe-rich chlorite, which can yield Fe readily to primary producers in the ocean. Examination of satellite imagery shows that dust from the Copper River is transported by wind on a regular basis to the North Pacific Ocean. This Alaskan example shows that high-latitude glaciogenic dust needs to be considered as a significant Fe source to primary producers in the open ocean.Published by Elsevier B.V. IntroductionDust is an integral part of the Earth's environmental systems, including the atmosphere, geosphere, hydrosphere, and biosphere. A number of reviews in the past decade or so have emphasized the importance of dust with its influence on planetary radiation balance, effects on clouds and precipitation, its role in adding nutrients to soils and the biosphere, and the importance of dust as a source of iron to primary producers (such as phytoplankton) in the world's oceans (Kohfeld and Harrison, 2001;Tegen, 2003;Goudie and Middleton, 2006;Mahowald et al., 2005Mahowald et al., , 2006Kohfeld and Tegen, 2007;Maher et al., 2010;Shao et al., 2011;Muhs, 2013a). These reviews also show that the emphasis of dust research has been on either contemporary dust sources, dominantly in low-latitude arid regions, or enhanced dust production at higher latitudes during the last glacial period. There has been a focus on contemporary dust sources at low latitudes because satellite-based global studies show that such regions are unquestionably the most important dust sources at the present time (Prospero et al., 2002). Concentration of studies on mid-latitude and high-latitude dust sources during the last glacial period is also understandable, because dust production globally during this time was much greater than at present, as seen in ice core records (EPICA Community Members, 2004;Ruth et al., 2007), deep-sea core records (Rea, 1994(Rea, , 2007, and loess r...

Quantification of iron-rich volcanogenic dust emissions and deposition over the ocean from Icelandic dust sources

“…There is evidence that the oceans south of Iceland are Felimited during and after peak bloom, and the Irminger Basin waters have been identified as an area of low dissolved Fe (Nielsdóttir et al, 2009;Ryan-Keogh et al, 2013). Achterberg et al (2013) found elevated Fe levels in surface waters south of Iceland during the 2010 Eyjafjallajökull eruption, indicating that volcanic activity can raise the oceanic Fe numbers.…”

“…Bullard, 2013), as was witnessed after the 2010 Eyjafjallajökull eruption (Thorsteinsson et al, 2012). Furthermore, some glaciogenic Arctic dust sources are composed of ironrich volcanic deposits, such as in Iceland (Baratoux et al, 2011;Dagsson-Waldhauserova et al, 2013b) and some parts of Alaska (Muhs et al, 2013). In Iceland, these aeolian materials are primarily poorly crystallized basaltic materials (glass) containing high quantities of iron, which can have a substantial impact on the ocean chemistry and fertility.…”

“…Dust production is mainly attributed to unstable barren areas in dry climates, with northern Africa being the largest contributor of dust to the atmosphere (Engelstaedter et al, 2006). Other commonly cited dust sources include Mongolia (e.g., Natsagdorj et al, 2003), the Aral Sea basin (Singer et al, 2003), the Middle East (Jamalizadeh et al, 2008), Australia (Ekström et al, 2004;Leys et al, 2011) and the southern USA (e.g., Sweeney et al, 2011). However, dust emissions from the Arctic and Antarctic have received increased attention (Arnalds, 2010;Bullard, 2013;Gillies et al, 2013;Muhs et al, 2013).…”

“…Other commonly cited dust sources include Mongolia (e.g., Natsagdorj et al, 2003), the Aral Sea basin (Singer et al, 2003), the Middle East (Jamalizadeh et al, 2008), Australia (Ekström et al, 2004;Leys et al, 2011) and the southern USA (e.g., Sweeney et al, 2011). However, dust emissions from the Arctic and Antarctic have received increased attention (Arnalds, 2010;Bullard, 2013;Gillies et al, 2013;Muhs et al, 2013). Research shows frequent dust storms in South Iceland moving into the North Atlantic Ocean (Arnalds and Metúsalemsson, 2004; and into the Arctic from Northeast Iceland (Dagsson-Waldhauserova et al, 2013a), and it has been suggested that Iceland is among the world's most active dust sources (Arnalds, 2010;Blechschmidt et al, 2012;Bullard, 2013).…”

Geochemical evidence for seasonal controls on the transportation of Holocene loess, Matanuska Valley, southern Alaska, USA

“…1b) and abundant production of glaciogenic silt. Holocene loess accumulation has been observed at numerous locations within central and southern Alaska (Péwé, 1975;Muhs et al, 2003Muhs et al, , 2004Muhs et al, , 2013Crusius et al, 2011).…”