Field Campaign march 8-16, 2012
Scientists: Jeff White, Seth Young, Jacob Rebholz
Results from First-Year Winter Field Campaign
During March 2012, we conducted a comprehensive survey of under-ice conditions in two cryo-karst lakes located near the margin of the Greenland ice sheet. We measured an array of physical and chemical parameters within the water column, including temperature, pH, dissolved oxygen, redox potential, and conductivity. Thermal stratification was very weak (0.4-1.8°C) with no evidence of chemical stratification. Water was also pumped from mid-depth at several locations in each lake and subsampled for ion and trace gas analysis. Sediment cores were also collected at each of the water sampling sites. Cores were sub-sectioned in the field lab and frozen for sulfur and organic carbon analyses. Water samples were preserved and returned to the laboratory at Indiana for ion chemistry, dissolved organic carbon (DOC), alkalinity, hydrogen isotope, and sulfur isotope analyses. All samples shipped frozen and moved into appropriate storage upon return. Both lakes were found to be hypoxic to anoxic (DO ≤ 5 mg L-1), and highly reducing, with negative redox potentials in Upper Lake (-60 to -95 mV), and low values (4 to 160 mv) in Lower Lake. There was also evidence of accumulation of dissolved sulfides in Upper Lake. Dissolved methane concentrations were more than twice as high in Lower Lake (9,000 mg CH4/L) than in Upper Lake (4,000 CH4/L). Both ion chromatography, and sulfur isotope analyses showed sulfate levels significantly lower than summertime concentrations for Upper Lake (≤15 µmols SO4= L-1). Lower Lake may support higher rates of methanogenesis under ice due to the more limited sulfur cycling (lower sulfate concentrations). A higher proportion of labile carbon substrates may flow to methanogenesis in Lower Lake, while sulfate reduction co-opts a greater proportion of labile substrates in Upper Lake. Early results suggest that the seasonal extremes in temperature, negative water balance, and winter ice thickness and duration of ice cover, drive significant shifts in redox conditions, and chemical composition controlled by in-lake microbial processes.
notes from the field
Friday, March 9th "We are settled into KISS. Beautiful sunny afternoon with clear blue sky, but just a bit cold. Temp here is -37oF. Thankfully no wind chill. Even the locals are saying, "Boy it is COLD." Glad for our warm layers!!! Had great pasta dinner by Seth Young. Going to try and catch Aurora borealis this eve. Will send pics if we get good look. Take care. More news as it comes. JW"
Saturday, March 10th "Greetings folks. We are off to a good start, most all of our equipment is functioning as planned, and Lower Lake has liquid water under the ice! We will drill Upper Lake tomorrow and see what it has. As you can see in the attached pictures, this Kentucky boy is handling his first experience at -20 quite well! Also included is a picture of our lovely valley covered in snow for everyone's viewing pleasure. Please feel free to pass on to anyone who may wish to see.
Keep warm for me! Jake "
Sunday, March 11th "Greetings from above the Arctic Circle.
Getting things done despite cold temps (-37 to -20oF every day). We move slowly as each step requires thawing out. The heat gun is a critical tool – without it we would be dead in the water (the frozen kind). More to follow in days to come. Warmly, Jeff"
Monday, March 12th "Hello from Kanger. Lab work in the morning and a tour to the edge of the glacier this afternoon. Today was a sunny and calm -28oF. But the evidence of wind is everywhere. Katabatic winds off of the Russell Glacier sculpt so much on this landscape. Even the snow highlights the prevailing wind direction. The dynamics of glacial melt are at full stop until spring comes to this landscape. Locals expect the deep freeze to end within the next 3 weeks – not a hint at the moment. JW "
Tuesday March 13th "Today was our last day in the field. A cold snow fell all day. But we were able to complete all of our sampling with no major setbacks. We have a full day of lab work tomorrow to prep samples for shipment back to IU. Then it is back to the USA in time for spring weather. It will be a thermal shock for sure. We will adjust. JW"
Wednesday, March 14th "Greetings from Kalaallit Nunaat ("Greenlander Country" in Kalaallisut – the local Inupik dialect spoken here). We finished lab work today and packed everything up for our return to USA via a stop–over in Copenhagen. We hope our samples beat us back to Bloomington given what we paid to have them air mailed! The temperature differential will be interesting to experience – from a crunching -37oF this evening to a balmy +83oF this weekend. The 120oF differential will surely melt the skin off of our bones. JW"