On the remote Arctic archipelago of Svalbard, there is increasing evidence of environmental impacts from climate change. The analysis of lake sedimentary records can be used to assess how strongly these recent changes have altered lake ecosystems. Sediments deposited during the last millennium from Lake Blokkvatnet, Prins Karls Forland, were analysed using a multiproxy approach, including stable isotope and X-ray fluorescence analysis. The results were interpreted as reflecting variability of (1) soil organic matter inwash, and potentially catchment and lake primary production, and (2) catchment weathering and erosion. Organic content began increasing after 1920 AD to the present, likely in response to warming. Earlier peaks of a similar magnitude occurred on three occasions since 1300 AD, with evidence indicating that these may have coincided with multidecadal-scale periods with higher temperatures, reduced sea ice and negative phases of the North Atlantic Oscillation. Catchment weathering and fluvial erosion began to increase around 1800 AD and peaked during the early twentieth century, potentially due to rising temperatures in autumn and winter causing increased liquid water availability. The records suggest that similar levels of erosion and weathering occurred between approximately 1300 and 1600 AD, spanning the transition from the Medieval Climate Anomaly to the Little Ice Age.