The Arctic Ocean is sensitive to freshwater fluxes in terms of ocean stratification, circulations and the nutrient balance. The main input to the freshwater budget is river discharge, ice and snow discharge, net precipitation, and inflow of low-salinity water through Bering Strait.

The main objective of Arcflux is to determine the freshwater budget of the Arctic Ocean, by maximizing the use of EO data in the determination of the individual freshwater fluxes .

To solve this task we focus on those freshwater fluxes where Earth observation data together with in-situ data is expected to improve the final estimation of the Arctic Ocean freshwater budget. These are
Inflow of freshwater related to discharge from rivers
We use missions such as Envisat, SARAL, T/P, Jason, -2, CryoSat-2, and potentially Sentinel-3 data, to estimate water level variations, which can be converted into discharge through a rating curve. Feasibility studies will be carried out to assess the ability to track water heights on medium sized rivers.

Inflow of ice and melt run off
The Freshwater flux from ice discharge (calving) is estimated from evaluating ice velocities derived from SAR data at the grounding line of the outlet glacier. We use state of the art velocity maps and combine these with models/measurements of ice thickness to derive ice discharge. The run-off from the ice is estimated from regional climate model runs, as this cannot be measured from satellites.
Outflow of sea ice.
In ArcFlux existing products of sea ice thickness will be used to estimate the flux of freshwater caused by outflow of sea ice from the Arctic Ocean. The ice thickness will be combined with ice drift information coming from SAR imagery.
Ocean Inflow/outflow
In this project we attempt to apply a new approach to ocean currents under the geostrophic assumption through deriving an accurate mean dynamic topography. This has previously been hampered by the presence of sea ice in the Arctic Ocean, but the SAR mode on CryoSat offers a much smaller footprint, hence being less sensitive to sea ice.

With Arcflux we aim to identify, and document the major challenges associated with estimation of the Arctic Freshwater budget. This includes identifying gaps in our current knowledge and capabilities.

As part of this we will explore, develop and validate different approaches to address the identified challenges and enhance current approaches to compute the freshwater budget in the Arctic.

Finally, a multi-year assessment of the Arctic freshwater budget based on the developed methodology will be computed.

The results will be validated uncertainties estimated. Compare the derived estimates with existing alternative estimates.

As a final task, a scientific roadmap for future research activities in this domain of estimating the Freshwater budget of the Arctic Ocean will be outlined.

We anticipate that a main outcome of the Arcflux project will be improved capability to monitor and quantify the seasonal variability in these freshwater fluxes.