Climate and Hydrological Influences on Riverine Dissolved Organic Carbon Exports in a Changing Arctic

Authors

Michael A. Rawlins¹* (mrawlins@umass.edu),  Ambarish V. Karmalkar¹, James W. McClelland², Vladimir A. Alexeev³

Institutions

¹Climate System Research Center, University of Massachusetts–Amherst, MA; ²Marine Biological Laboratory, Woods Hole, MA; ³International Arctic Research Center, University of Alaska–Fairbanks, AK

Abstract

This project aims to advance understanding of lateral land-ocean flows of freshwater and dissolved organic carbon (DOC) to coastal zones in Arctic regions. Hydrological cycle intensification and permafrost thaw are among a myriad of changes unfolding across Arctic regions that are impacting riverine freshwater and DOC exports. Recent progress and project results have contributed to a growing body of evidence documenting increases in exports of DOC, cold season discharge, and associated subsurface flows. Building on these efforts, researchers used meteorological data from atmospheric reanalysis and two global climate models to drive simulations with the Permafrost Water Balance Model across the pan-Arctic drainage basin over the period 1980 to 2100 to better understand likely impacts of the changes. Model simulations were validated with observations of active-layer thickness, snow sublimation, evapotranspiration, and river discharge. An acceleration in simulated river discharge over the recent past is commensurate with trends drawn from observations and reported in other studies. Increased seasonal maximum active-layer thickness in northwest Alaska during this century is congruent with simulations by the Advanced Terrestrial Simulator, which show a deepening from approximately 50 to 160 cm. Permafrost extent in the simulations declines by 42 to 63% between early (2000 to 2019) and late (2080 to 2099) century periods, while annual total runoff increases by 21 to 33%. Also consistent with other recent studies, the fraction of subsurface to total runoff increases by 29 to 44% during this century. Soil moisture tends to decline, despite the runoff increases, influenced by higher evapotranspiration rates and drainage through more thawed soils. These manifestations of hydrological cycle intensification and permafrost thaw have profound implications for Arctic-terrestrial and coastal environments influenced by river flows and the materials they convey.