Abstract
Abstract. The quantity and quality of river discharge in Arctic regions is influenced by many processes including climate, watershed attributes and, increasingly, hydrological cycle intensification and permafrost thaw. We used a hydrological model to quantify baseline conditions and investigate the changing character of hydrological elements for Arctic watersheds between Utqiagvik (formerly known as Barrow)) and just west of Mackenzie River over the period 1981–2010. A synthesis of measurements and model simulations shows that the region exports 31.9 km3 yr−1 of freshwater via river discharge, with 55.5 % (17.7 km3 yr−1) coming collectively from the Colville, Kuparuk, and Sagavanirktok rivers. The simulations point to significant (p<0.05) increases (134 %–212 % of average) in cold season discharge (CSD) for several large North Slope rivers including the Colville and Kuparuk, and for the region as a whole. A significant increase in the proportion of subsurface runoff to total runoff is noted for the region and for 24 of the 42 study basins, with the change most prevalent across the northern foothills of the Brooks Range. Relatively large increases in simulated active-layer thickness (ALT) suggest a physical connection between warming climate, permafrost degradation, and increasing subsurface flow to streams and rivers. A decline in terrestrial water storage (TWS) is attributed to losses in soil ice that outweigh gains in soil liquid water storage. Over the 30-year period, the timing of peak spring (freshet) discharge shifts earlier by 4.5 d, though the time trend is only marginally (p=0.1) significant. These changing characteristics of Arctic rivers have important implications for water, carbon, and nutrient cycling in coastal environments.
Highlights
The Arctic water cycle is central to a range of climatic processes and to the transfer of carbon, energy, and other materials from the land mass to coastal waters of the Arctic Ocean
Freshwater export to the Arctic Ocean is high relative to the ocean’s area (Shiklomanov et al, 2000), and dominated by river discharge (Serreze et al, 2006), which serves as a conveyance for carbon and heat across the land–ocean boundary
Agreement between Pan-Arctic Water Balance Model (PWBM) and GIPL is strongest in coastal areas and differ most near the center of the domain, where PWBM produces relatively smaller active-layer thickness (ALT) compared to GIPL
Summary
The Arctic water cycle is central to a range of climatic processes and to the transfer of carbon, energy, and other materials from the land mass to coastal waters of the Arctic Ocean. An increase in river discharge from Eurasia to the Arctic Ocean was noted in simulations with the HadCM3 general circulation model (Wu et al, 2005), illustrating the potential for increased winter net P to influence freshwater export. The model domain contains 312 grid cells (total area = 196 060 km2) that define the North Slope drainage of northern Alaska and NW Canada. It is defined by the drainage basins of rivers (42 total, Table S1 in the Supplement) with an outlet along the coast from just west of the Mackenzie River to Utqiagvik (formerly Barrow) to the west. Many North Slope rivers are oriented roughly north–south, and the region is underlain by continuous permafrost, approximately 250–300 m thick in the Brooks Range and, locally, up to nearly 400 m thick near the coast (Jorgenson et al, 2008)
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