Roger G. Barry (email@example.com), University of Colorado
We propose to investigate the response of soil thermal, freeze-thaw, and permafrost dynamics to climatic change, and their impact on the hydrologic cycle in the Russian arctic drainage basin over the past 50 years. Specifically, we will:
The proposed research will be accomplished mainly through data analysis and synthesis, with the use of a one-dimensional heat transfer numerical model with phase change. We will collect and rescue soil temperature data (up to 3.2 m) and freeze-thaw data from 400 stations distributed over the former Soviet Union. About half of these data (240 stations with data up to 1990) have been transferred to the National Snow and Ice Data Center through our prior NSF support. We will update the time series of 240 stations to 2000 and add to our database an additional 160 stations (110 of them up to 2000) within the Russian arctic drainage basin. The average density of station within a 5o by 5o grid is 2.6, with a range from 1 to 23. Freezing and thawing indexes will be estimated based on mean monthly air temperature using data from individual stations and from gridded fields. Maximum thaw depth will also be estimated using simple Stefan solution and estimated thawing index over the entire Russian arctic drainage basin. We will use data from the 400 stations and other sources to define climatologies, trends, and variabilities of monthly and annual soil temperature at various depths, and to determine the timing, duration and number of days, area extent, and depth of the active layer and seasonally frozen ground. Comprehensive statistical methods will be applied to identify the major spatial variation patterns. Combining these data with other available climatic variables, such as air temperature, precipitation, and snow cover, we will investigate the response of soil temperature, freeze-thaw cycle, and permafrost to climatic change at local and regional scales. We will also compare the measured long-term near-surface soil temperatures with the constructed surface temperature history from deep borehole temperature profiles. The key question to answer is why does the surface temperature, obtained by extrapolating the deep portions of temperature profiles to the surface, show that some areas have warmed a few degrees (but with varying magnitudes and timing), some areas show little or no change, and some areas even show a recent cooling?
Recent studies indicate that runoff has increased 25 to 90 percent during the cold season (October-April) and there is imbalance between runoff and precipitation minus evapotranspiration (P-ET) over the Russian arctic drainage basin during the past several decades. The cause of the imbalance between runoff and P-ET, and the increase in winter runoff is poorly understood. Studies also indicate that soil temperature has increased substantially, especially in the high arctic regions, and active layer thickness increased about 30 cm in the Lena river basin during the past two decades. We will investigate the linkage between the arctic hydrological regime and the dynamics of permafrost and the freeze-thaw cycle to better comprehend the arctic hydrological cycle. We hypothesize the sequence of impacts of and response to changes in seasonal freeze-thaw dynamics over the Russian arctic drainage basin as follows. Climatic warming results in higher permafrost temperature, a deeper active layer, and a longer thaw season. The thicker active layer (having a greater ground water storage capacity) has more ground water storage due to increased precipitation input, and perhaps some snowmelt water contribution in early winter. The deeper active layer delays its freeze-up date in winter. The late active layer freeze-up and increased ground water storage result in greater contribution of subsurface water to the river system, and hence to the winter season runoff. We further hypothesize that meltwater of excess ground ice near the permafrost surface due to thickening of the active layer and permafrost degradation contributes to river runoff.
This project will produce a series of new data products for individual stations, for river basins, and for the entire Russian arctic drainage basin. These include monthly mean soil temperature at various depths and freeze-thaw cycle variables from 400 stations, dating back as far as 1900's to 2000. We will also provide gridded products at 5o x 5o resolution. Freeze-thaw cycle variables include timing, duration, number of days, area extent, and thickness of seasonal frozen and thawed soils. Estimated time series of freezing/thawing index and maximum thaw depth from both individual station and 25 km by 25 km gridded pixels will be products.
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