2009 Annual Science Report
University of Hawaii, Manoa Reporting | JUL 2008 – AUG 2009
Permafrost in Microclimates
Microclimates are small areas where climate conditions differ from the surrounding area. This can lead to the occurrence of permafrost in otherwise ice-free areas or to exceptionally long lasting ice. The reasons for the persistence of the ice or its age are inadequately understood. In this project, two study sites are investigated. One is an exceptionally old glacial remnant in Upper Beacon Valley, Antarctica. Paradoxically, tiny amounts of melt water may play a crucial role in the survival of the ice. The second study area includes extremely rare patches of permafrost on the Hawaiian Islands, in cinder cones near the summit of Mauna Kea.
The persistence of ice in terrestrial microclimates is investigated at two different locations.
Subsurface ice in cold hyperarid conditions retreats by sublimation and diffusion through the overlying soil layer. One such environment is Upper Beacon Valley, Antarctica, where precipitation is rare and a glacial remnant buried by only decimeters of sublimation till is of 'fossil’ age. In a recent publication by Schorghofer (2009) it is shown that even tiny amounts of percolating melt water can counterbalance sublimation loss effectively and thus increase the persistence time of the ice. Time-averaging of transport equations is used to evaluate the significance of percolation in an otherwise complex dynamical system. The reduction in sublimation loss is approximately given by the amount of melt water multiplied by the percolation depth and divided by the depth to the ice table. Since theoretical recession rates are less than a millimeter per year, this implies that percolation may play a major role. Results of this work have recently been published in the journal Permafrost and Periglacial Processes (Schorghofer, 2009).
Although the summit of Mauna Kea, Hawaii, is exceptionally dry, sporadic permafrost exists in cinder cones near the summit. In the time period 1972-1973, the only period of investigation, the annual mean temperature at permafrost locations was below the melting point of ice, but only by a few tenths of a degree centigrade. Theoretical models are used to illuminate microclimatic effects, estimate the degradation rate of the ice, and predict the response to climate warming. As an outcome of this work, a grant proposal 'Origin, Distribution, and Fate of Permafrost in Hawaii’ has been submitted to fund field studies and theoretical modeling. The potential for interdisciplinary work and for follow-up studies is exceptionally strong.
PROJECT INVESTIGATORS:Norbert Schorghofer