Abstract
Rapid Arctic warming results in increased winter rain frequencies, which may impact glacial systems. In this paper, we discuss climatology and precipitation form trends, followed by examining the influence of winter rainfall (Oct–May) on both the mass balance and dynamics of Hansbreen (Svalbard). We used data from the Hornsund meteorological station (01003 WMO), in addition to the original meteorological and glaciological data from three measurement points on Hansbreen. Precipitation phases were identified based on records of weather phenomena and used—along with information on lapse rate—to estimate the occurrence and altitudinal extent of winter rainfall over the glacier. We found an increase in the frequency of winter rain in Hornsund, and that these events impact both glacier mass balance and glacier dynamics. However, the latter varied depending on the degree of snow cover and drainage systems development. In early winter, given the initial, thin snow cover and an inefficient drainage system, rainfall increased glacier velocity. Full-season winter rainfall on well-developed snow was effectively stored in the glacier, contributing on average to 9% of the winter accumulation.
Highlights
Water circulation within a glacier’s body governs numerous glacial processes, including mass and material transport, dynamics, and thermal state [1,2,3,4]
We found that 62% of winter rain events occurred after the beginning of the accumulation period, after the snow cover formed on the glacier, which may have accumulated in the snow cover
We examined all days with mixed precipitation to identify those with the greatest precipitation totals due to rain according to the criterion that the occurrence of snowfall may be recorded within one observational term for current weather or two observational terms for past weather
Summary
Water circulation within a glacier’s body governs numerous glacial processes, including mass and material transport, dynamics, and thermal state [1,2,3,4]. Summer rainfall is more frequent; its significance for glacier mass balance, dynamics, surface energy balance, water drainage system, and other glacial processes has been widely acknowledged, e.g., [9,10,11]. The importance of rainwater in glacial processes during cold seasons will increase. In early winter, when snow cover has not yet developed, rainwater is rapidly drained into the englacial system or firn aquifer. This water exerts a considerable influence on both the glacier’s hydroglaciological system and dynamic behavior. The paper assesses the contribution of rainfall to winter mass balance, and investigates the dynamic response of the glacier to rainfall in the cold season (Oct–May). In the following parts of the paper, terms “liquid precipitation” and “rainfall” are used in the context of the entire year and winter, respectively; while “rainwater” is used in the context of glaciers
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