Investigation of mass balance parameters on the Greenland ice sheet using passive microwave satellite data.

摘要

The Greenland ice sheet is an integral part of the Earth system, and this barren expanse is intimately linked with the climate both within, and far beyond, its borders. This research seeks to improve our understanding of the role of the ice sheet both in response to and as a contributing factor to changes in the climate. One means of response studying such a large and remote area is with the use of satellite data. In this investigation passive microwave satellite data are used to assess the melt characteristics of the ice sheet, and a microwave radiative transfer model is developed to investigate the effects of accumulation and hoar development on the microwave emission. In addition, the relationships between accumulation, melt, and coastal temperatures are assessed.; The analyses shows that there are significant links between regional temperatures, the extent of melt, and the snow accumulation characteristics. A melt signal is identified in the microwave emission, which enables the classification of dry and wet snow. Based on this melt signal, the spatial extent of snowmelt on the ice sheet was observed to increase at a rare of 4.5% per year for the years 1979-1991. At the same time, regional air temperatures along the coast showed a strong correlation and increased by approximately 1.1{dollar}spcirc{dollar}C over the 12 year period. Following the eruption of Mt. Pinatubo in 1991, both the melt extent and regional temperatures dropped to nearly their lowest levels in the 1978-1994 coverage period of the passive microwave data set.; In addition to the melt effects in the ablation zones of the ice sheet, changes in accumulation rates impact the microwave emission in the dry snow zones, but they are only secondary effects. Of much greater significance is the development of hoar during the summer months. These large crystals, with their high scattering characteristics reduce the microwave emission by almost 3% (which translates to almost 5 K). They are nearly an order of magnitude more effective in altering the emission than are changes of accumulation. Thus identification of accumulation variations requires successful parameterization of hoar characteristics.; Finally, a comparison between temperatures, melt assessments, and accumulation estimations shows that under conditions of warming, the amount of melt (mass loss) increases by approximately 49% of the current value per 1{dollar}spcirc{dollar}C air temperature rise while the amount of accumulation (mass gain) decreases by about 7%. The result is an expected negative mass balance which is estimated to be approximately {dollar}-{dollar}200 Gt (or km{dollar}sp3{dollar} water equivalent). This corresponds to a 0.5 mm sea level rise.; Understanding the interactions between the Greenland ice sheet and the Arctic and global climates is an ongoing process. Through the analysis of passive microwave satellite data, this research address some of the important issues and provides insight into these complex interactions. As a result, our understanding of the behavior of the Ice sheet in the changing climate is improved.