DR. DENNIS A. DARBY
Old Dominion University, Norfolk, VA 23529-0276

Dr. Darby has pioneered new approaches to trace sand back to its source. His “fingerprinting” technique can precisely determine sources and mixes of different sources, which provides new insights into contaminant dispersal, transport processes, and the history of changes in these and other phenomenon. He is using this technique to research the affect of the Arctic Ocean on global climate, the transport and spread of contaminants such as dangerous radionuclides from Russian processing plants, and the past history of large polar ice sheets.  He has received over $2 million in NSF and ONR grants in the last eight years and served on several national and international advisory committees.

What will the expedition attempt to do?

Should the expedition come across any heavy concentrations of mud on the ice surface, GPS position will be recorded and 5-10 grams of mud will be brought back to Dr. Darby so that he can analyze the dirt to determine its source (See Paper on Sources of Sediment).

The team will need to be aware that much of the "dirt" is algae that grows attached to the ice and becomes incorporated into it. Sediment is nearly black or dark brown and algae is lighter and looks like typical organic matter.

Any samples brought back can indicate where the sea ice formed and the type of sediment that sea ice entrains. Sediment transport by sea ice is probably the most important means by which sediment is transported around large distances in the Arctic today. It could potentially transport contaminated sediment far from its source. In a recent paper by Cota et al., in Science of the Total Environment, large doses of Cs-137 were found in sea ice near Resolute and it appears, based on the sediment that this ice may have come from the Laptev Sea and Russian rivers such as the Ob or Yenisey

What about low concentrations?

Low concentration cases would either require the team to transport a large volume (53-5 gallons) of ice or to melt such a volume and filter it through a coffee filter. Due to fuel and weight limitations, the team will bypass any attempt to gather this type of sample.

Why is the dirt sample important?

This is important for understanding the ice budget, diminishing sea ice coverage, and sediment transport, especially of sediment from possibly contaminated areas or rivers.

There are very few dirty sea ice samples from the central Arctic and only 10 usable samples from the 2-month trans-Arctic cruise on USCGC Healy was obtained last year (HOTRAX).  Any dirty ice samples with sufficient sediment for analyses are important.  The nice thing is that only the sediment is required and this can be melted and filtered even through ordinary lab filters (not 0.4 micron Millipore filters) to obtain the fine sand and silt down to 45 micron that we use.  This might be part of the routine ice melting that might be done to obtain water for the expedition for example.  The dirt is not harmful and would be filtered anyway.