Description of task
This activity addresses the time-varying processes by which the signals ofArctic change are transferred through subarctic seas to lower latitudes, and hence directly addresses the efficiency with which the Arctic communicates with the Ocean's thermohaline 'conveyor'.
The "switchgear" problem will be addressed by maintaining and augmenting the existing freshwater flux arrays in the W. Fram Strait (NPI), midway along the E. Greenland shelf at 74N (UNIHAM), and S of Denmark Strait (UNIHAM, CEFAS) to provide the first continuing measure of gross and net freshwater flux for comparison with changes in the regional windfield and ocean circulation. The NAOSIM model will be the main interpretative tool (AWI). Model hindcasts for the last 50 years, leading up to actual conditions during the DAMOCLES period, will be analysed to determine the pathways of fresh water from the Arctic to the northern North Atlantic. Water mass formation and spreading processes will be investigated with special attention to periods of extreme anomalies in Arctic ice cover. The leakage of freshwater, Atlantic & Arctic water masses from the East Greenland Current into the Greenland and Iceland seas will also be estimated from analysis of historical data and recent hydrographical data (FIMR, met.no).
Effects on the global thermohaline circulation will be assessed by using DAMOCLES funding to set up collaboration with a UK RAPID project (U Reading) to assimilate all N Atlantic hydrographic datasets for the past 40 years into a global ocean model. By establishing a link to this ongoing project we will focus on the impact of high latitude N Atlantic data from ASOF and DAMOCLES, and assess changes in fluxes of mass, heat and freshwater at critical sites and straits between the Arctic and N Atlantic. This will improve our understanding of the space-time scale of climate anomalies associated with these strait fluxes on a larger scale than can be tackled in DAMOCLES alone. The arctic performance of the global model will be compared with the regional arctic high-level data assimilation effort in core theme 4.
The results of this "output" task on the switchgear issue and on the effects on the global circulation will contribute the overarching activity 2 (evaluation of observations and models on climate timescales).
