More Like this

1. Diatom hotspots driven by western boundary current instability.

   Oliver, H. (April 2021, Geophysical research letters)

   null (Ed.)

   Climatic changes have decreased the stability of the Gulf Stream (GS), increasing the frequency at which its meanders interact with the Mid-Atlantic Bight (MAB) continental shelf and slope region. These intrusions are thought to suppress biological productivity by transporting low-nutrient water to the otherwise productive shelf edge region. Here we present evidence of widespread, anomalously intense subsurface diatom hotspots in the MAB slope sea that likely resulted from a GS intrusion in July 2019. The hotspots (at ∼50 m) were associated with water mass properties characteristic of GS water (∼100 m); it is probable that the hotspots resulted from the upwelling of GS water during its transport into the slope sea, likely by a GS meander directly intruding onto the continental slope east of where the hotspots were observed. Further work is required to unravel how increasingly frequent direct GS intrusions could influence MAB marine ecosystems. 

   more » « less
2. Increased gulf stream warm core ring formations contributes to an observed increase in salinity maximum intrusions on the Northeast Shelf

   https://doi.org/10.1038/s41598-023-34494-0  

   Silver, Adrienne; Gangopadhyay, Avijit; Gawarkiewicz, Glen; Fratantoni, Paula; Clark, Jenifer (May 2023, Scientific Reports)

   Abstract We present observational evidence of a significant increase in Salinity Maximum intrusions in the Northeast US Shelf waters in the years following 2000. This increase is subsequent to and influenced by a previously observed regime-shift in the annual formation rate for Gulf Stream Warm Core Rings, which are relatively more saline than the shelf waters. Specifically, mid-depth salinity maximum intrusions, a cross-shelf exchange process, has shown a quadrupling in frequency on the shelf after the year 2000. This increase in intrusion frequency can be linked to a similar increase in Warm Core Ring occupancy footprint along the offshore edge of the shelf-break which has greatly increased the abundance of warm salty water within the Slope Sea. The increased ring occupancy footprint along the shelf follows from the near doubling in annual Warm Core Ring formation rate from the Gulf Stream. The increased occurrence of intrusions is likely driven by a combination of a larger number of rings in the slope sea and the northward shift in the GS position which may lead to more interactions between rings and the shelf topography. These results have significant implications for interpreting temporal changes in the shelf ecosystem from the standpoint of both larval recruitment as well as habitability for various important commercial species. 

   more » « less
3. (2024) Coastal Pioneer Mid-Atlantic Bight Western Shallow Water Mooring (CP12WESW)

   https://doi.org/10.58046/ooi-cp12wesw  

   NSF_Ocean_Observatories_Initiative (January 2024, US NSF Ocean Observatories Initiative)

   The Pioneer MAB Western Shallow Water Mooring is located on the Continental Shelf, approximately 25 meters deep. The MAB continental shelf north of Cape Hatteras is characterized by a persistent equator-ward current originating from the north, a shelfbreak front separating shelf and slope waters, distributed buoyancy inputs from rivers, variable wind forcing, and intermittent offshore forcing by Gulf Stream meanders. The Pioneer MAB Array is designed to resolve transport processes and ecosystem dynamics in the vicinity of the shelfbreak front, which is a region of complex oceanographic dynamics, intermittent mesoscale variability, and enhanced biological productivity.\nLike other moorings, the Pioneer MAB Western Shallow Water Mooring is specifically designed to examine coastal-scale phenomena and withstand the challenging conditions of shallow coastal environments. The Shallow Water Mooring contains instruments attached to a Surface Buoy floating on the sea surface, the wave-powered Wire Following Profiler (Prawler), and a Multi-Function Node (MFN) located on the seafloor. The Prawler and the MFN instruments communicate with the Surface Buoy through the inductive riser wire. Additionally, the Surface Buoy contains antennas to transmit data to shore via satellite. 

   more » « less
4. (2024) Coastal Pioneer Mid-Atlantic Bight Central Shallow Water Mooring (CP12CNSW)

   https://doi.org/10.58046/ooi-cp12cnsw  

   NSF_Ocean_Observatories_Initiative (January 2024, US NSF Ocean Observatories Initiative)

   The Pioneer MAB Central Shallow Water Mooring is located on the Continental Shelf, approximately 30 meters deep. The MAB continental shelf north of Cape Hatteras is characterized by a persistent equator-ward current originating from the north, a shelfbreak front separating shelf and slope waters, distributed buoyancy inputs from rivers, variable wind forcing, and intermittent offshore forcing by Gulf Stream meanders. The Pioneer MAB Array is designed to resolve transport processes and ecosystem dynamics in the vicinity of the shelfbreak front, which is a region of complex oceanographic dynamics, intermittent mesoscale variability, and enhanced biological productivity.\nLike other moorings, the Pioneer MAB Central Shallow Water Mooring is specifically designed to examine coastal-scale phenomena and withstand the challenging conditions of shallow coastal environments. The Shallow Water Mooring contains instruments attached to a Surface Buoy floating on the sea surface, the wave-powered Wire Following Profiler (Prawler), and a Multi-Function Node (MFN) located on the seafloor. The Prawler and the MFN instruments communicate with the Surface Buoy through the inductive riser wire. Additionally, the Surface Buoy contains antennas to transmit data to shore via satellite. 

   more » « less
5. Cross-Shelf Exchange in Prograde Antarctic Troughs Driven by Offshore-Propagating Dense Water Eddies

   https://doi.org/10.1175/JPO-D-23-0088.1  

   Gaul, Alan; Zhang, Weifeng_Gordon; Cenedese, Claudia (August 2024, Journal of Physical Oceanography)

   Abstract This study examines the link between near-bottom outflows of dense water formed in Antarctic coastal polynyas and onshore intrusions of Circumpolar Deep Water (CDW) through prograde troughs cutting across the continental shelf. Numerical simulations show that the dense water outflow is primarily in the form of cyclonic eddies. The trough serves as a topographic guide that organizes the offshore-moving dense water eddies into a chain pattern. The offshore migration speed of the dense water eddies is similar to the velocity of the dense water offshore flow in the trough, which scaling analysis finds to be proportional to the reduced gravity of the dense water and the slope of the trough sidewalls and to be inversely proportional to the Coriolis parameter. Our model simulations indicate that, as these cyclonic dense water eddies move across the trough mouth into the deep ocean, they entrain CDW from offshore and carry CDW clockwise along their periphery into the trough. Subsequent cyclonic dense water eddies then entrain the intruding CDW further toward the coast along the trough. This process of recurring onshore entrainment of CDW by a topographically constrained chain of offshore-flowing dense water eddies is consistent with topographic hotspots of onshore intrusion of CDW around Antarctica identified by other studies. It can bring CDW from offshore to close to the coast and thus impact the heat flux into Antarctic coastal regions, affecting interactions among ocean, sea ice, and ice shelves. Significance StatementTroughs cutting across the Antarctic continental shelf are a major conduit for the transport of dense shelf water from coastal formation regions to the shelf break. This study describes a process in which clockwise-spinning eddies moving offshore in prograde troughs successively entrain filaments of relatively warm Circumpolar Deep Water from offshore across the entire shelf and into the coastal region. This eddy-induced transport provides a new understanding of the shelf edge exchange process identified in previous studies and a mechanism for further onshore intrusion of the warm Circumpolar Deep Water over parts of the Antarctic shelf. The resultant onshore heat flux could potentially bring a substantial amount of heat from offshore into the coastal region and thus affect ice–ocean interactions through melting sea ice and ice shelves. 

   more » « less