Arctic Ocean Freshwater Dynamics: Transient Response to Increasing River Runoff and Precipitation

Simulations from a coupled ice-ocean general circulation model are used to assess the effectson Arctic Ocean freshwater storage of changes in freshwater input through river runoff and precipitation.We employ the climate response function framework to examine responses of freshwater content to abruptchanges in freshwater input. To the lowest order, the response of ocean freshwater content is linear, withan adjustment time scale of approximately 10 years, indicating that anomalies in Arctic Ocean freshwaterexport are proportional to anomalies in freshwater content. However, the details of the transient responseof the ocean depend on the source of freshwater input. An increase in river runoff results in a fairly smoothresponse in freshwater storage consistent with an essentially linear relation between total freshwatercontent and discharge of excess freshwater through the main export straits. However, the response to achange in precipitation is subject to greater complexity, which can be explained by the localized formationand subsequent export of salinity anomalies which introduce additional response time scales. The resultspresented here suggest that future increases in Arctic Ocean freshwater input in the form of precipitationare more likely to be associated with variability in the storage and release of excess freshwater than areincreases in freshwater input from river runoff