Bottom water temperatures in lakes and the near-shore Arctic Ocean are usually below 4°C. If the water depth is shallow enough, the sea/lake ice freezes to the sea/lake bed and may significantly shift the mean annual temperature below zero. Thus, pre-existing permafrost may survive inundation but undergoes a rapid warming of up to 10°C. Taliks form and grow deeper over time. The temperature regime below the water is therefore directly dependent on the water depth and small changes can have a huge impact. Measurements of the sediment temperature below shallow water bodies are scarce, and single temperature-chains in boreholes are not sufficient to map spatial variability. We are using a new temperature lance to measure temperature profiles in lake sediments. The device is a 1.5m steel lance with 30 sensors at 5cm spacing that can be pushed or hammered into the sediment. The sensors equilibrate to sensor accuracy within 10min, allowing for repeat measurements to cover the spatial variability. As part of the “MOSES 2021 Canada” expedition temperature-depth profiles have been measured at three different sites: “Swiss Cheese Lake” in the outer Mackenzie Delta, “Lake 3” east of the Inuvik-Tuktoyaktuk-Highway north of Trail Valley Creek and at Tuk Island in the harbour of Tuktoyaktuk.