Arctic slope hydrology studies suggest that water follows preferential subsurface flow paths known as water tracks. While subsurface flow is usually expected to transport only dissolved solids, periglacial studies have indicated some evidence of lessivage associated with flow through sorted patterned ground. We investigated the transport of dissolved and suspended sediments in water tracks on a polar desert slope, and linked this transport to slope and flow path geomorphology. Solute transfer was dominated by carbonate weathering products, and concentrations of other ions increased disproportionately when the active layer thawed. Suspended sediment transport occurred in water tracks, but fluxes were supply-limited, indicating competent subsurface mechanical erosion. Solute mass fluxes were 5-10 times greater than sediment fluxes. In this dry landscape dominated by snowmelt, surface seepage leads to sediment deposition, while subsurface flow promotes lessivage. A conceptual model of nivation slopes is presented, taking into consideration the influence of flow path morphology and adaptation of the hydrological system to localized water sources from wind-drifted snowbanks. Climate-driven permafrost degradation and the increased frequency of rainfall events may result in new sediment sources and changes in flow pathways, modifying the physico-chemical properties and ecology of downstream receiving waters.

The Arctic hydrologic cycle is intensifying, as evidenced by increased rates of precipitation, evapotranspiration, and riverine discharge. However, the controls on water fluxes from terrestrial to aquatic systems in upland Arctic landscapes are poorly understood. Upland landscapes account for one third of the Arctic land surface and are often drained by zero-order geomorphic flowpath features called water tracks. Previous work in the region attributed rapid runoff response at larger stream orders to water tracks, but models suggest water tracks are hydrologically disconnected from the surrounding hillslope. To better understand the role of water tracks in upland landscapes, we investigated the surface and subsurface hydrologic responses of 6 water tracks and their hillslope watersheds to natural patterns of rainfall, soil thaw, and drainage. Between storms, both water track discharge and the water table in the hillslope watersheds exhibited diel fluctuations that, when lagged by 5hr, were temporally correlated with peak evapotranspiration rate. Water track soils remained saturated for more of the summer season than soils in their surrounding hillslope watersheds. When rainfall occurred, the subsurface response was nearly instantaneous, but the water tracks took significantly longer than the hillslopes to respond to rainfall, and longer than the responses previously observed in nearby larger order Arctic streams. There was also evidence for antecedent soil water storage conditions controlling the magnitude of runoff response. Based on these observations, we used a broken stick model to test the hypothesis that runoff production in response to individual storms was primarily controlled by rainfall amount and antecedent water storage conditions near the water track outlet. We found that the relative importance of the two factors varied by site, and that water tracks with similar watershed geometries and at similar landscape positions had similar rainfall-runoff model relationships. Thus, the response of terrestrial water fluxes in the upland Arctic to climate change depends on the non-linear interactions between rainfall patterns and subsurface water storage capacity on hillslopes. Predicting these interactions across the landscape remains an important challenge.