Pan-Arctic land surface hydrology: Patterns of change and global implications

Anthropogenic emissions of greenhouse gases are increasingly changing the global climate. The change will be most pronounced in the high northern latitudes, in the so called pan-arctic region. In this dissertation, we investigate several aspects of pan-arctic change. In particular, we analyze changes in land surface hydrology, how these changes interact with the ecosystem and ocean dynamics, and discuss how these interactions may moderate or enhance changes in global climate.; Our study of land surface hydrology investigates trends in cold-season low-flow. We observe two opposite patterns: cold-season low-flow decreases in East Canada, whereas it increases in the rest of the pan-arctic. On large scale the cold-season low-flow decreases are minor compared to the increases. The cold-season low-flow is related to the state and dynamics of subsurface hydrology; therefore, the increase in cold-season low-flow indicates widespread mobilization of subsurface stores, and substantial changes to climate and land surface hydrology.; Next, we analyze the interaction of land surface hydrology and ecology. Specifically, we focus on the control of precipitation variability on peatland dynamics. Using stochastic modeling, we find that enhanced variability of precipitation may eliminate peatland's inherent bistability. The elimination of bistability causes co-existing thin and thick peat to transition into peat of intermediate thickness. During the transition peatlands may either uptake or release greenhouse gases which ultimately affects global climate.; Finally, we examine how the interactions of land surface hydrology and the ocean system control the Atlantic meridional overturning circulation (AMOC). With an intermediate-complexity earth-system model we find that the regions with different cold-season low-flow trends also have different control on the AMOC. River discharge reductions from East Canada are more efficient in strengthening the AMOC, while river discharge increases from the rest of the pan-arctic aremore efficient in strengthening the AMOC. The long-term balance between river-flow trends in East Canada and the rest of the pan-arctic influences the strength of the AMOC, and the AMOC's control on global heat redistribution and climate.; Our findings show that large-scale changes in pan-arctic hydrology are taking place. Interactions of these changes with peatland dynamics and AMOC strength may moderate or enhance anthropogenic climate change.