Assessment of high-latitude Arctic lake dynamics in representative areas on continuous permafrost

Recent evidences of Arctic lake dynamics display consistent trends linked to climatic changes. Primary control on local hydrological processes in high-latitude regions is dictated by the presence or absence of permafrost. Though our understanding of permafrost hydrologic processes has advanced considerably in the past decades, the potential linkage between permafrost and the rate and direction of recent (∼30 years) lake area change is the subject of ongoing debate. In Arctic regions with continuous permafrost, most studies have found insignificant long-term trend in lake change, whereas studies in some parts of Alaska and Siberia reported substantial increase in the areal extent of continuous permafrost lakes as a response to accelerated climatic warming. The results from these earlier studies raise an important question that if permafrost type is the key factor driving the direction of lake area changes, then how is it possible that the continuous permafrost lakes in some parts of the Arctic are expanding, whereas those in the other parts of the Arctic are shrinking. Hence, the proposed research sought to identify the cause of opposing directions of continuous permafrost lake area changes in different parts of the Arctic. Study regions were chosen in continuous permafrost regions of West Siberia, Western Arctic Coastal Plain of Alaska, and Northern Canada. For estimating lake area and their changes, Landsat satellite images were chosen for the summer season of ∼1970s (MSS) and ∼2000s (ETM+). An image processing chain was proposed for processing these satellite images, and novel techniques were developed for each of its components including image registration and orthorectification, lake shoreline mapping, and change detection. Contrary to the earlier studies, the findings of the research presented in this dissertation reveal a net decline in lake area over all the three study regions. A net increase in lake counts suggests that over the past three decades, many of these lakes have disintegrated into more than one smaller lake. Also. there existed a correlation between the summer thaw degree days and the magnitude of lake area changes. Hence, if permafrost is the primary factor driving lake dynamics in these regions as reported in earlier studies, then these negative lake area changes suggest that the recent (∼30 year) rate of permafrost degradation is much higher than currently presumed. An alternative explanation for these negative trends on continuous permafrost consistent with lake area changes observed in warmer (discontinuous, isolated, and sporadic) permafrost zones could be that the variability in regional hydro-climatic processes is driving the observed changes.