Temperature time-series in Svalbard fjords. A contribution from the "Integrated Marine Observatory Partnership"

This is chapter 4 of the State of Environmental Science in Svalbard (SESS) report 2018 (https://sios-svalbard.org/SESS_Issue1). Many observations around Svalbard have tended to be biased towards summer and autumn and we don't always have a full picture of the annual cycles. However, some marine measurements have been sustained over many years; these are exceptionally valuable, as they enable us to quantify the environmental change. One rich source of data is the network of observatories in the coastal and offshore waters of Svalbard. Some of these observatories have been in operation for more than 15 years with instruments continuously recording data for a variety of parameters. As the data series builds up we reveal both the seasonality of the marine environment and the long term change. The Integrated Marine Observatory Partnership (iMOP) has studied water temperature records from three fjords. Kongsfjorden and Isfjorden are west-facing and influenced by the West Spitsbergen Current, which carries warm Atlantic Water to the Arctic Ocean. Rijpfjorden is north-facing and is influenced by the colder, fresher Arctic waters. The records come from contrasting locations which experience different oceanographic conditions during their seasonal cycles. The west-facing, Atlantic fjords are both warming. Water temperatures are increasing in both the warmest months (September, October and November) and the coldest (March, April and May). The rate of change is up to 2°C per decade for the warmest months and around 1°C per decade for the coldest. The impact of warming means that the fjords experience fewer years where the water cools to the freezing point: this limits the formation of sea ice. The warming is related to both the temperature of the West Spitsbergen Current and the pattern of winds that help drive water towards the coast. In contrast, Rijpfjorden does not show any significant warming and sea ice regularly forms in the fjord