Surface albedo and spring snow melt variations at Ny-Ålesund, Svalbard

The monitoring of surface albedo using radiometric measurements is a simple but effective way to study variations in snow cover and melt timing in the high northern latitudes, where there is a clear indication of warming in response to the changing global climate. In this paper, we investigate these phenomena in the Northwest region of Svalbard using a 40-year record, combining previous data from 1981 to 1997, radiation measurements from the Baseline Surface Radiation Network (BSRN) station since 1993, and the Amundsen Nobile Climate Change Tower (CCT) since 2009. A methodology has been developed to estimate the start, duration, and end date of the spring snow melt. This has been applied to the integrated dataset for the period 1981 to 2019. Our results are in good agreement with qualitative information on snow persistence provided by webcam images archived since 2000. The date of snow melt has advanced at a rate of about 3 days per decade during the period of study, from Julian calendar date (doy) 180 in the early 1980s to 165-170 in the late 2010s. There is indication the trend has accelerated since 2010. The footprint of the radiation measurements is a crucial factor in the evaluation of surface albedo; the larger the area within the field of view of the instrument, the more representative is the measure. The assimilated 40-year dataset will provide a base for future monitoring of snow persistence at Ny-Ålesund as the climate continues to change in the region. Our work highlights the importance of technical improvements made in measurement systems and combining different techniques to monitor surface albedo. In particular, terrestrial photography, combined with broadband radiation measurements, will contribute to increased knowledge of underlying processes that determine the surface energy budget in the Arctic region. In addition, the combined ground-based measurements can be used to validate those derived from space-born platforms.