Mercury Deposition to the Arctic over the Last Glacial Cycle
Arctic Research Initiative
2009 Funded Project
Analysis of mercury (Hg) in Antarctic ice in the early 1990’s indicated that large increases in Hg deposition occurred in that region during the last glacial maximum relative to the Holocene (Vandal et al., 1993). In an on-going effort to understand the mechanism behind this increase, a WHOI Post-doctoral Scholar, Dr. Paul Drevnick, and I have been exploring reconstruction of trends in Hg deposition across glacial/interglacial transitions using a number of archives. To date, these most notably include non-glaciated lakes (Titicaca and Baikal) as well as marine sediments. Fascinating trends have been revealed which challenge the proposed explanation for Hg cycling in the past, and provide the basis for using Hg as paleoproxy of large-scale geophysical/climate change over millennial timescales.
To further this effort, I propose here to construct a timeline of Hg depositional changes in an Arctic analog to that of the Antarctic. A number of Arctic ice cores of suitable age/length were recovered during the Greenland Ice Sheet Project #2 (GISP2), and these samples are available to outside scientists through collaboration with the National Ice Core Laboratory. Thus, I request support to travel to the Core Repository in Denver, set up a small clean lab space within the frozen archive warehouse and subsample the ice cores for Hg analysis. The techniques for ultratrace metal clean sample processing of ancient glacial ice have been established during the Antarctic work, and my lab here at WHOI is outfitted with the necessary instrumentation to successfully measure Hg at the very low levels I anticipate will be found.
In addition to the long-time scale investigations of Hg cycling, the material stored in the National Ice Core Laboratory offers an opportunity to determine Hg loadings from the atmosphere in the recent past (last few hundred years). This is particularly relevant for the Arctic as the atmosphere is the principal way in which this toxic metal is transported to high latitudes, and unique conditions at polar sunrise can result in large “Mercury Depletion Events” that result in alarmingly high loadings during an ecologically sensitive time of year. Work in Arctic lakes has already indicated that Hg deposition has roughly tripled since the Industrial Revolution and in lock-step with atmospheric increases in CO2, but this trend remains to be confirmed for other Arctic locations.