scholarly journals The Origin of Along-Shelf Pressure Gradient in the Middle Atlantic Bight

2011 ◽  
Vol 41 (9) ◽  
pp. 1720-1740 ◽  
Author(s):  
F.-H. Xu ◽  
L.-Y. Oey
Keyword(s):  
Pressure Gradient ◽  
Sea Level ◽  
Gulf Stream ◽  
Process Model ◽  
Sea Water ◽  
Tide Gauge ◽  
Middle Atlantic Bight ◽  
Middle Atlantic ◽  
Sea Surface Slopes ◽  
Cape Hatteras

Abstract It is quite widely accepted that the along-shelf pressure gradient (ASPG) contributes in driving shelf currents in the Middle Atlantic Bight (MAB) off the northeastern U.S. coast; its origin, however, remains a subject for debate. Based on analyses of 16 yr (1993–2008) of satellite, tide gauge, river, and wind data and numerical experiments, the authors suggest that river and Coastal Labrador Sea Water (CLSW) transport contribute to a positive mean ASPG (tilt up northward) in the ratio of approximately 1:7 (i.e., CLSW dominates), whereas wind and the Gulf Stream tend to produce a negative mean ASPG in the ratio of approximately 1:6. Data also indicate seasonal and interannual variations of ASPG that correlate with the Gulf Stream’s shift and eddy kinetic energy north of the Gulf Stream (N-EKE) due to warm-core rings. A southward shift in the Gulf Stream produces a sea level drop north of Cape Hatteras, which is most rapid in winter. The N-EKE peaks in late spring to early summer and is larger in some years than others. A process model is used to show that ring propagation along the MAB slope and ring impingement upon the shelf break north of Cape Hatteras generate along-isobath density gradients and cross-shelfbreak transports that produce sea level change on the shelf; the dominant ageostrophic term in the depth-integrated vorticity balance is the joint effect of baroclinicity and relief (JEBAR) term. In particular, the shelf’s sea surface slopes down to the north when rings approach Cape Hatteras.

scholarly journals Global sea level reconstruction for 1900–2015 reveals regional variability in ocean dynamics and an unprecedented long weakening in the Gulf Stream flow since the 1990s

Ocean Science ◽  
2020 ◽  
Vol 16 (4) ◽  
pp. 997-1016
Author(s):  
Tal Ezer ◽  
Sönke Dangendorf
Keyword(s):  
Sea Level ◽  
Gulf Stream ◽  
Tide Gauge ◽  
Meridional Overturning Circulation ◽  
Ocean Dynamics ◽  
South Atlantic Bight ◽  
Regional Variability ◽  
Coastal Sea ◽  
Global Sea Level

Abstract. A new monthly global sea level reconstruction for 1900–2015 was analyzed and compared with various observations to examine regional variability and trends in the ocean dynamics of the western North Atlantic Ocean and the US East Coast. Proxies of the Gulf Stream (GS) strength in the Mid-Atlantic Bight (GS-MAB) and in the South Atlantic Bight (GS-SAB) were derived from sea level differences across the GS. While decadal oscillations dominate the 116-year record, the analysis showed an unprecedented long period of weakening in the GS flow since the late 1990s. The only other period of long weakening in the record was during the 1960s–1970s, and red noise experiments showed that is very unlikely that those just occurred by chance. Ensemble empirical mode decomposition (EEMD) was used to separate oscillations at different timescales, showing that the low-frequency variability of the GS is connected to the Atlantic Multi-decadal Oscillation (AMO) and the Atlantic Meridional Overturning Circulation (AMOC). The recent weakening of the reconstructed GS-MAB was mostly influenced by weakening of the upper mid-ocean transport component of AMOC as observed by the RAPID measurements for 2005–2015. Comparison between the reconstructed sea level near the coast and tide gauge data for 1927–2015 showed that the reconstruction underestimated observed coastal sea level variability for timescales less than ∼5 years, but lower-frequency variability of coastal sea level was captured very well in both amplitude and phase by the reconstruction. Comparison between the GS-SAB proxy and the observed Florida Current transport for 1982–2015 also showed significant correlations for oscillations with periods longer than ∼5 years. The study demonstrated that despite the coarse horizontal resolution of the global reconstruction (1∘ × 1∘), long-term variations in regional dynamics can be captured quite well, thus making the data useful for studies of long-term variability in other regions as well.

Sea level variabilities in the Gulf Stream between Cape Hatteras and 50°W: A Geosat study

1990 ◽  
Vol 95 (C10) ◽  
pp. 17957 ◽  
Author(s):  
Jorge Vazquez ◽  
Victor Zlotnicki ◽  
Lee-Lueng Fu
Keyword(s):  
Sea Level ◽  
Gulf Stream ◽  
Cape Hatteras

A Gulf Stream-derived pycnocline intrusion on the Middle Atlantic Bight shelf

1990 ◽  
Vol 95 (C12) ◽  
pp. 22305 ◽  
Author(s):  
Glen Gawarkiewicz ◽  
Robert K. McCarthy ◽  
Kenneth Barton ◽  
Ann K. Masse ◽  
Thomas M. Church
Keyword(s):  
Gulf Stream ◽  
Middle Atlantic Bight ◽  
Middle Atlantic

scholarly journals A Shelf Water Cascading Event near Cape Hatteras

2021 ◽  
Author(s):  
Lu Han ◽  
Harvey Seim ◽  
John Bane ◽  
Robert E. Todd ◽  
Mike Muglia
Keyword(s):  
Continental Shelf ◽  
Gulf Stream ◽  
Stream Water ◽  
Subsurface Layer ◽  
Open Ocean ◽  
South Atlantic Bight ◽  
Shelf Water ◽  
Carbon Export ◽  
Middle Atlantic ◽  
Cape Hatteras

AbstractCarbon-rich Middle Atlantic Bight (MAB) and South Atlantic Bight (SAB) shelf waters typically converge on the continental shelf near Cape Hatteras. Both are often exported to the adjacent open ocean in this region. During a survey of the region in mid-January 2018, there was no sign of shelf water export at the surface. Instead, a subsurface layer of shelf water with high chlorophyll and dissolved oxygen was observed at the edge of the Gulf Stream east of Cape Hatteras. Strong cooling over the MAB and SAB shelves in early January led to shelf waters being denser than offshore surface waters. Driven by the density gradient, the denser shelf waters cascaded beneath the Gulf Stream and were subsequently entrained into the Gulf Stream, as they were advected northeastward. Underwater glider observations 80 km downstream of the export location captured 0.44 Sv of shelf waters transported along the edge of the Gulf Stream in January 2018. In total, as much as 7×106 kg of carbon was exported from the continental shelf to a greater depth in the open ocean during this 5-day-long cascading event. Earlier observations of near-bottom temperature and salinity at a depth of 230 m captured several multiday episodes of shelf water at a location that was otherwise dominated by Gulf Stream water, indicating that the January 2018 cascading event was not unique. Cascading is an important, yet little-studied pathway of carbon export and sequestration at Cape Hatteras.

scholarly journals Satellite Altimetry and Tide Gauge Observed Teleconnections between Long-Term Sea Level Variability in the U.S. East Coast and the North Atlantic Ocean

2019 ◽  
Vol 11 (23) ◽  
pp. 2816
Author(s):  
Qing Xu ◽  
Kai Tu ◽  
Yongcun Cheng ◽  
Weiping Wang ◽  
Yongjun Jia ◽  
...  
Keyword(s):  
Sea Level ◽  
North Atlantic ◽  
Satellite Altimetry ◽  
North Atlantic Ocean ◽  
Tide Gauge ◽  
Atlantic Multidecadal Oscillation ◽  
Meridional Overturning Circulation ◽  
Sea Level Variability ◽  
Tropical North Atlantic ◽  
Cape Hatteras

Rising sea levels amplify the threat and magnitude of storm surges in coastal areas. The U.S. east coast region north of Cape Hatteras has shown a significant sea level rise acceleration and is believed to be a “hot-spot” for accelerating tidal flooding. To better understand the forcing mechanism of long-term regional sea level change, in order to more efficiently implement local sea level rise adaptation and mitigation measures, this work investigated the teleconnections between low-frequency sea level variability in the coastal region north of Cape Hatteras and the subpolar/tropical North Atlantic Ocean by using tide gauge measurements, satellite altimetry data and a sea level reconstruction dataset. The correlation analysis demonstrates that the tide-gauge measured sea level variability in the area north of Cape Hatteras is highly and positively correlated with that observed by satellite altimetry in the subpolar and tropical North Atlantic between 1993 and 2002. Over the following decade (2003–2012), the phase of the teleconnection in the subpolar region was reversed and the spatio-temporal correlation in the tropical North Atlantic was enhanced. Furthermore, the positive correlation in the region north of Cape Hatteras’s near shore area is strengthened, while the negative correlation in the Gulf Stream front region is weakened. The North Atlantic Oscillation and Atlantic Multidecadal Oscillation, which affect variations of the Atlantic Meridional Overturning Circulation and Gulf Stream, were shown to have significant impacts on the decadal changes of the teleconnections. Coherent with satellite altimetry data, the reconstructed sea level dataset in the 20th century exhibits similar spatial correlation patterns with the Atlantic Meridional Overturning Circulation, North Atlantic Oscillation and Atlantic Multidecadal Oscillation indices.

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