Seasonal Cycle of the Fram Strait Freshwater Export: A Model Perspective

Fram Strait is an important pathway for the liquid freshwater (FW) transport from the Arctic to the North Atlantic, but the seasonal and long-term variability of this FW export is not well known, due to the limited available observations of this transport. To better understand the seasonal variability of the liquid Fram Strait FW export, we present an analysis of a simulation from the Community Climate System Model (CCSM), Version 3, which includes passive tracers that track FW from different sources (e.g., river runoff, Pacific FW, and sea ice melt). The results from this simulation show that the seasonal cycle of the FW export through Fram Strait is mainly driven by salinity changes caused by sea-ice melt upstream of Fram Strait. Seasonal velocity-driven FW export changes have a smaller amplitude, and only delay the maximum and minimum FW export by one month compared to the seasonal cycle of the FW concentration in Fram Strait. Furthermore, we show that in the model seasonal concentration changes of Pacific FW and meteoric FW in Fram Strait are small, and the seasonal cycle of their export is controlled by velocity changes. This means that measurements of meteoric and Pacific FW concentrations obtained during different months of different years can be used to analyze the interannual variability of their concentrations in Fram Strait. In contrast, measurements of sea-ice melt concentrations are strongly influenced by seasonal changes, and measurements during different parts of the year are necessary to analyze interannual changes of the sea-ice melt concentration in Fram Strait.