A Dataset of Arctic Ocean Water Masses from 40 Years of Hydrographic Observations

The Arctic Ocean is changing significantly and rapidly in a warming climate. To monitor these changes, it is useful to classify the Arctic Ocean into water masses containing waters of same origin and similar physical and biogeochemical properties. However, there are significant barriers to Arctic Ocean water mass classification: observations of seawater properties are sparsely and heterogeneously sampled in space and time, and traditional water mass classification relies on extensive knowledge of water mass characteristics and circulation and mixing. We propose a tool for estimating relative fractions of Arctic Ocean water masses (0-1) from observations of seawater temperature and salinity, and share the classification tool and water mass dataset. Our estimates of relative fractions of water masses broadly reproduce the spatial and temporal distribution of Arctic Ocean water masses reported in the literature, most notably the key Atlantic Water (AW) and Pacific Water (PW) pathways within the Arctic Ocean and the increasing influence of AW and PW in the Arctic Ocean over the last few decades. Our classification tool and water mass dataset will help improve understanding of Arctic Ocean dynamics and changes, and provides an accessible framework for assessing the accuracy of models in representing Arctic Ocean properties.