The Northwestern North Atlantic: a Retrospective Analysis of Observations from the CV Oleander on the Shelf and Slope

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

This study examines the long-term variability in the northwestern North Atlantic over the continental shelf and slope using long-duration observations collected by a ship of opportunity and output from a regional high-resolution numerical model. This area has been highlighted as a hotspot of sea level rise and ocean warming with the trends superimposed on strong interannual to decadal variability. This study will investigate the processes driving the low-frequency variability of shelf temperature and sea level, with a focus on the physical mechanisms underlying the recent changes. The project also includes the development of observation-based coastal temperature indexes from profiles collected by the CV Oleander, a commercial vessel that operates weekly round-trip transits between New Jersey and Bermuda, and investigation of potential predictors of interannual variability of these temperature indexes relating to sea level and atmospheric pressure. The processes to be studied have important implications for both climate and commercial fisheries. Results will be presented in both climate and continental shelf workshops. The PIs will provide the data products derived from the observations to the science community via existing Oleander Program websites. The PIs will also continue public communication and outreach efforts including visits to a local 8th grade classroom, building on a long-term outreach effort with the middle school science teacher and outreach directed to commercial fishermen through the Commercial Fisheries Research Foundation in Rhode Island, which has strong links to Woods Hole Oceanographic Institution. This project will support and train a graduate student who has already published a peer-reviewed paper on this data set. The temperature sections (spanning 37 years) and velocity sections (spanning 22 years) have been collected with expendable bathythermographs (XBTs) and a shipboard acoustic Doppler current profiler (ADCP) via the CV Oleander. This data set is unique in terms of its high resolution, extended duration over multiple decades, and co-located temperature and velocity observations. Temperature data collected by the CV Oleander can resolve the interannual to decadal signals embedded in the region's annual cycle. Further, the exceptional duration of the temperature records amassed along a constant ship route, and their combination with velocity and surface salinity measurements from the ship and complementary data sets (e.g., satellite altimetry, reanalysis winds, and tide gauge data) will allow this study to characterize the variability and to explore mechanisms driving the changes such as shifts in Gulf Stream position, changes in large scale wind forcing, and changes in along-shelf advection. The study will also capitalize on existing output from a high-resolution numerical model that captures variability in the region with fidelity. This region has been identified as having a very high rate of ocean warming relative to the global mean rate. Variability in this region links open-ocean phenomena (Gulf Stream, Deep Western Boundary Current, and Atlantic Meridional Overturning Circulation, AMOC) to shelf phenomena (Middle Atlantic Bight shelf circulation, shelfbreak jet dynamics, and ecosystem dynamics).