Contemporary estimates of Pan-Arctic freshwater discharge from GRACE and reanalysis

Streamflow from Arctic river basins has been increasing in recent decades in response to warming climate. In addition to being a sensitive indicator of global change, Arctic discharge is a critical component of the freshwater budget of the Arctic Ocean, where increasing freshwater flows may slow rates of North Atlantic Deep Water formation and heat transport by the thermohaline circulation. However, quantifying rates of freshwater discharge from the entire Pan-Arctic drainage has been troublesome using traditional stream gauging methods. Here we use satellite measurements of variations in continental water storage from the GRACE mission to present first estimates of monthly freshwater discharge from the entire Pan-Arctic for the period 2003-2005. Results show that rates of Pan-Arctic discharge for this time period (3588 +/- 257 km3 yr-1) are significantly larger than those suggested by gauge-based estimates (3238 km3 yr-1), and furthermore, may indicate that discharge rates are accelerating.