85th AMS Annual Meeting

Tuesday, 11 January 2005
SEARCH Climate Indicators: Melt Onset and Other Cryospheric Data Products
Bruce Raup, University of Colorado/CIRES, Boulder, CO; and F. M. Fetterer, M. Parsons, M. Savoie, and K. Knowles
The surface of Earth is warming, and this global signal is amplified in the Arctic. The details of patterns in climate change (such as surface atmospheric pressure, temperature, and surface heat balance) can be complicated and involve many geophysical processes. Therefore, it is desirable to find signals that are the products of natural processes that integrate these variables into something more easily interpreted. NSIDC, through the Study of Environmental Arctic Change (SEARCH) program, has developed some prototypes of climate indicators with the goal of providing easily understood climate trend information to scientists, policy makers, and the general public. This poster presents initial results of the development of the following indicator products: date of onset of snow melt in the Arctic; a sea ice index; normalized difference vegetation index (NDVI); and soil temperature. The melt onset product uses data from passive microwave satellite instruments to detect the presence of wet snow on the surface, using the Goodison-Walker algorithm over snow-covered soil above tree-line, and the Abdalati-Steffen algorithm over ice sheets and ice caps. For each pixel, the time series of daily "wet snow" flags is smoothed, and a threshold is applied to the result to derive a melt onset date. The sea ice index provides at-a-glance trends and anomalies in ice extent and concentration by month using passive microwave satellite data, beginning in 1979. For NDVI, continuity between the NOAA/NASA Pathfinder AVHRR-derived NDVI and the newer, higher resolution MODIS NDVI product is being evaluated as a first step. With NDVI as with all climate data records, consistency in the record is key if trends are to be derived. Soil temperature records from boreholes in Alaska, in Canada, and in Russia show unambiguous warming trends. Here the challenge in presenting the data to the public is to simply interpret differences in trends from place to place in terms of differences in snow cover, soil type, and other factors in addition to changes in air temperature.

These indicators and others developed elsewhere are the operational (near real time or updateable) data streams that underlie the Arctic Change Detection product developed by NOAA's Pacific Marine Environmental Laboratory (PMEL). The NOAA Arctic Research Office sponsors this work.

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