Distinct characteristics and mechanisms of two tidewater glaciers exhibiting velocity anomalies in western Svalbard

Svalbard hosts numerous tidewater glaciers whose dynamic responses are critical to polar environmental change and global sea-level rise. This study investigates Tunabreen glacier and Osbornebreen glacier in Svalbard using multi-source remote sensing data from Landsat, Sentinel, ArcticDEM, and other reanalysis data. We analyzed glacier surface velocity, terminus length change, and elevation evolution to assess their dynamic characteristics and driving mechanisms. Tunabreen glacier experienced a typical surge from 2016 to 2018, advancing 1.6 km, reaching a peak velocity of ~2073 m yr−1 , and thickening by up to 15.7 m in the receiving zone. The surge propagated from the terminus upstream and was likely driven by subglacial hydrodynamics. In contrast, Osbornebreen glacier showed terminus advance and acceleration between 2017 and 2021, advancing 1.6 km with a peak velocity of ~3143 m yr−1 in 2020. However, the sustained thinning of the glacier, combined with fjord water warming driven by the North Atlantic Current and a significant increase in air temperature and precipitation, suggests that the observed acceleration was more likely externally forced by oceanic and atmospheric forcing. These contrasting behaviors reveal distinct response patterns of tidewater glaciers to internal glacier dynamics and external forcing, offering new insights into glacier evolution under climate change.