Project Title: Exploring the Relationship Between Past Atmospheric Dust Deposition, Climate, and Biological Productivity in the North Pacific Ocean
Mendenhall Fellow: Christopher M. Moy, (508) 457-2283, firstname.lastname@example.org
Duty Station: Woods Hole, MA
Start Date: March 30, 2010
Education: Ph.D. (2010), Geological and Environmental Sciences, Stanford University
Research Advisors: John Crusius (email@example.com); Dorothy Peteet (firstname.lastname@example.org); Timothy Eglinton (email@example.com)
Project Description: Atmospheric dust plays an important role in the global climate system by directly altering the Earth’s radiation budget and by influencing biogeochemical cycling in the ocean. Although dust has been emphasized as an important driver of global climate change, there are very few well-dated and highly resolved records of dust deposition that can be used to examine the influence on the global carbon cycle over millennial timescales. We are developing high-resolution records of dust deposition from ombrotrophic peat bogs in southern Alaska that span the Holocene and can be compared to established North Pacific records of primary productivity derived from an Fe-limited part of the Pacific Ocean. Southern Alaska is an ideal location to investigate past changes in dust flux because a significant portion of global dust deposition occurs in the northern Pacific Ocean and the region is situated “downstream” of the major Northern Hemisphere dust producing areas in Asia. In addition, coastal Alaskan glacial outwash and fluvial floodplains are a significant local dust source that can potentially play a very large role in biogeochemical cycling in the North Pacific but that, as of yet, has not been extensively examined (fig. 1). Results from this study will be used to answer the following research questions:
- How have the timing and nature of dust accumulation in southern Alaska changed during the past 16,000 years?
- What are the important climate controls on past dust deposition?
- How do records of dust deposition compare to regional paleoclimate studies and can we identify a link between dust deposition and productivity reconstructions from the northern Gulf of Alaska?
We collected a series of peat cores from Middleton Island in the Gulf of Alaska and from alpine bogs in the Copper River delta region (fig. 1) during July and August 2010. MODIS satellite imagery indicates that these locations are commonly influenced by dust events that originate primarily from the Copper River Delta and typically occur in fall and early winter months when river levels are low and snow cover is less extensive. These events have the ability to transport significant amounts of dust and bioavailable Fe beyond the continental shelf and into Fe-limited waters. We will employ radiocarbon, scanning XRF, and other geochemical methods to accurately date and reconstruct past dust deposition to the northern Gulf of Alaska from these sites.
(LEFT) Figure 1. MODIS satellite image captures a Copper River dust event on November 11, 2005. Gray dust is emitted from the Copper River and transported >100 km over Middleton Island and beyond the continental shelf. Yellow star denotes the location of the automated weather station near the Million Dollar Bridge (fig. 2).
(RIGHT) Figure 2. Automated weather station collects wind speed and standard meteorological measurements. The elevated station is placed on a shipping container and is located along the Copper River (Million Dollar Bridge in background). The mounted camera faces southeast and captures images of the river and bridge at hourly intervals.
In addition, we have established an automated weather station in the Copper River valley near the Million Dollar Bridge to monitor dust and examine the meteorological controls on dust events (Figure 2). Meteorological data is sent via satellite every hour and provides near real time weather conditions. In addition, dust activity in the valley is monitored by an automated camera pointed at the Million Dollar Bridge. The camera collects hourly images during daylight hours and can be used to provide qualitative estimates of dust concentration (figs. 3, 4). Hourly meteorological data can be viewed at http://denali.micro-specialties.com/CopperRiver/Index.htm.
(LEFT) Figure 3. Clear day image taken on September 14, 2010, from camera mounted on the Copper River weather station.
(RIGHT) Figure 4. “Dusty” image collected during a Copper River dust event on September 25, 2010. Note lower river levels, yellow haze, and absence of mountains beyond bridge in this photo.
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