Testing the relationship between NAO and Atlantic Multidecadal Variability over recent centuries using paleoclimate proxy data to improve decadal-scale climate predictions for fisheries management

Competition Relevance: One objective in the Northeast Regional Action Plan of NOAA’s Fisheries Climate Science Strategy is to improve medium-term (year to decade) climate forecast products for living marine resources. A key component of medium-term climate prediction is predicting ocean circulation. Two major ocean currents are involved in the Northeast U.S. Shelf Large Marine Ecosystem fisheries management sector, the southward Labrador Current and the northward Gulf Stream. Both are connected to the complex North Atlantic circulation and Atlantic Meridional Overturning Circulation (AMOC). Decadal-scale climate predictability of the state of the North Atlantic Ocean is strongly dependent on AMOC predictability, which requires an understanding of the climate variables that influence and are influenced by AMOC. This is what our proposal is focused on.
Scientific Rational: Investigations into the forcing factors driving decadal-scale AMOC variability have been hampered by the relatively short length of direct AMOC observations, difficulties in identifying and modeling the key physical mechanisms, and the convolution of anthropogenic radiative forcing with natural variability during the era of instrumental climate records. This project aims to test a recent hypothesis about the driving mechanism of AMOC decadal variability, using high-resolution paleoclimate archives that provide long (multiple centuries) records of Earth’s climatic behavior, pre-dating significant anthropogenic forcing. The idea is to identify the natural physical relationships between North Atlantic climate variables to test if they are consistent with underlying physical theories developed from modeling studies.
Summary of Work: We will specifically gather the highest possible temporal resolution paleoclimate proxies of sea surface temperature from the North Atlantic with a recent multi-proxy reconstruction of North Atlantic Oscillation (NAO) to test if the NAO is associated with heat convergence at high latitudes and if the signal is propagated to lower latitudes. The mechanism we will be testing is laid out by Wills et al. (2018) who find evidence that AMOC and NAO are coupled on decadal to multidecadal timescales. They describe the consequences of that coupling in terms of surface warming, a quantity that can be reconstructed from the highest resolution paleoclimate proxies.
Scientific and Broader Impacts: The results of the proposed analysis will provide observational evidence of the relationship between NAO and ocean temperatures in key regions of the North Atlantic that give insight into the mechanistic connections between the atmosphere and ocean circulation in this region on interannual to decadal time scales. Using paleoclimate data, we will test the hypothesis that NAO and AMOC are linked on decadal scales through oceanic heat convergence and buoyancy fluxes based on observational evidence. If the basic hypothesis is rejected, our analysis will provide alternative relationships between NAO and temperature in particular regions that can be further explored in future modeling efforts. In effect, we will be identifying relationships between key variables in a long-term observational dataset that can be used to improve the physical representation of AMOC in climate models used for making climate projections and forecast products in support of fisheries management. Such climate intelligence contributes directly to U.S. prosperity and resilience by helping to maintain healthy fisheries and the communities of people who are dependent on those fisheries.