BG3-1: Climate warming and disturbance that initiate thermokarst lead to (1) release of soil organic matter and N from frozen soils, (2) significant landscape evolution, and (3) inputs of sediments, old soil carbon, and nutrients into aquatic ecosystems, causing a net loss of these materials from watersheds.

Caribou-Poker Creeks Research Watershed is located in the discontinuous permafrost region. Permafrost is confirmed mainly to valley bottoms and north facing slopes. From our modeling analyses we see there is large change in the amount of frozen ground between early 1900s and end of the 1900s. The end of the Little Ice Age is not only the influence on thawing of permafrost. Human activity is also important through such anthropogenic processes as mining or burning. Many of the wildfires happened after 1900 (and initiation of mining activity) in this watershed. Ground surface conditions strongly impact the ground freezing process after burning the moss layer. Recent warming of the climate will affect the ground thawing process too. The purpose of this study is to monitor permafrost temperature and periglacial geomorphology. We will monitor permafrost degradation to see how that influences sediment output and stream chemistry.

We have observed permafrost temperatures using boreholes established in 1985. Currently, there are 14 boreholes for collecting ground temperature in the watershed. Some of the boreholes are in areas free of permafrost and some others are located in permafrost in the coldest parts of the watershed. Two of the sites were in the experimental forest fire in 1999. We are planning to calculate heat flow and thermal budget in the ground and calibrate our numerical models using these data (Romanovsky et al., 1997; Osterkamp and Romanovsky, 1999). Using the calibrated models and several available scenarios of future climatic changes, we will calculate active layer thicknesses and permafrost temperature dynamics at each of the chosen sites for the next 50 to 100 years. An intensive sensitivity analysis will allow assessment of the relative importance of the specific climatic components (such as air temperature and precipitation), snow cover and vegetation characteristics, and the soil properties (such as moisture content) on the future active layer and permafrost temperature dynamics, permafrost degradation and thermokarst development.

Thermokarst depressions and pingos are significant landforms for permafrost dynamics in the watershed. Thermokarst is especially responsive to climatic change. We established five transects for surveying ground uplifting and subsidence at pingos and thermokarst sites. The topographic surveys are carried out every year. We will establish additional transects with control points in several thermokarst sites in the summer of 2004. Permanent surveying stakes were installed on 3m intervals and anchored in the permafrost. Ground temperature and active layer thickness are also measured at the thermokarst site, and other sites. We established 30 sites where we measure ground temperature up to 1.5m deep for active layer and permafrost mapping. A thaw depth probe is used for active layer thickness measurements. Sediment flux from actively growing thermokarsts will be monitored using sediment traps and autosamplers.

Our aufeis (icing) survey is also an important component for permafrost hydrology analyses. We measure the area covered by ice every spring. Several sites along the Caribou Creek have aufeis monitoring stakes for estimating the total volume of the ice and accumulation throughout the winter. We will take ice core samples for studying base flow chemistry in the spring. We are planning to collect ground-penetrating radar (GPR) and Electric resistivity meter measurements for mapping ice content and permafrost extent in the sediment this spring. This mapping is not only for permafrost research, but also we hope to learn how thick the sediment and soil is above the bedrock. The amount of ice in the permafrost exerts significant controls on most of the periglacial landforms in this area. Thermokarst is especially strongly impacted by the ice content in the upper part of the permafrost.