The specific OSNAP objectives are to:
- Quantify the subpolar AMOC and its intra-seasonal to interannual variability via overturning metrics, including associated fluxes of heat and freshwater.
- Determine the pathways of overflow waters in the NASPG to investigate the connectivity of the deep boundary current system.
- Relate AMOC variability to deep water mass variability and basin-scale wind forcing.
- Determine the nature and degree of the subpolar-subtropical AMOC connectivity.
- Determine from new OSNAP measurements the configuration of an optimally efficient long-term AMOC monitoring system in the NASPG.
The first two objectives will be met via the observing system, while the latter three goals will be achieved in coordination with ongoing and planned programs.
OSNAP will contribute to an assessment of the critical measurements needed for a multi-decadal observing system and will provide essential ground truth to AMOC model estimates. The intent is to move toward an observing system where a few critical in situ observations, coupled with satellite observations and the Argo float array, provide a reliable and sustainable measure of the AMOC for decades to come.
A key aim of this proposed work is to build a North Atlantic MOC observing system by integrating observations from the RAPID-MOCHA-WBTS 26.5°N array and from the Nordic Seas exchange across the GSR. Overflows through the Denmark Strait, across the Iceland Ridge and through Faroe Bank Channel, and the inflows west and east of Iceland and west of Scotland have been monitored for decades through research efforts in Iceland, the Faroe Islands, Norway, Denmark and Scotland. Currently, the continuance of these efforts has been assured through 2017 via the approval of NACLIM (North Atlantic CLIMate). Together, OSNAP, the GSR observations and the RAPID 26°N observational systems provide a means to evaluate inter-gyre connectivity and to establish a long-term comprehensive observing system in the North Atlantic.