scholarly journals Along-Stream Evolution of Gulf Stream Volume Transport

2020 ◽  
Vol 50 (8) ◽  
pp. 2251-2270 ◽  
Author(s):  
Joleen Heiderich ◽  
Robert E. Todd
Keyword(s):  
Lower Bound ◽  
Gulf Stream ◽  
Sea Water ◽  
Global Climate ◽  
Volume Transport ◽  
Underwater Gliders ◽  
Cape Hatteras ◽  
Upper Bound Estimate ◽  
Stream Transport

AbstractThe Gulf Stream affects global climate by transporting water and heat poleward. The current’s volume transport increases markedly along the U.S. East Coast. An extensive observing program using autonomous underwater gliders provides finescale, subsurface observations of hydrography and velocity spanning more than 15° of latitude along the path of the Gulf Stream, thereby filling a 1500-km-long gap between long-term transport measurements in the Florida Strait and downstream of Cape Hatteras. Here, the glider-based observations are combined with shipboard measurements along Line W near 68°W to provide a detailed picture of the along-stream transport increase. To account for the influences of Gulf Stream curvature and adjacent circulation (e.g., corotating eddies) on transport estimates, upper- and lower-bound transports are constructed for each cross–Gulf Stream transect. The upper-bound estimate for time-averaged volume transport above 1000 m is 32.9 ± 1.2 Sv (1 Sv ≡ 106 m3 s−1) in the Florida Strait, 57.3 ± 1.9 Sv at Cape Hatteras, and 75.6 ± 4.7 Sv at Line W. Corresponding lower-bound estimates are 32.3 ± 1.1 Sv in the Florida Strait, 54.5 ± 1.7 Sv at Cape Hatteras, and 69.9 ± 4.2 Sv at Line W. Using the temperature and salinity observations from gliders and Line W, waters are divided into seven classes to investigate the properties of waters that are transported by and entrained into the Gulf Stream. Most of the increase in overall Gulf Stream volume transport above 1000 m stems from the entrainment of subthermocline waters, including upper Labrador Sea Water and Eighteen Degree Water.

Along-stream evolution of Gulf Stream volume transport and water properties from underwater glider observations

2020 ◽  
Author(s):  
Joleen Heiderich ◽  
Robert E. Todd
Keyword(s):  
Gulf Stream ◽  
Volume Transport ◽  
Water Masses ◽  
Labrador Sea ◽  
Western Boundary ◽  
Intermediate Water ◽  
Underwater Glider ◽  
Boundary Current ◽  
Cape Hatteras ◽  
Stream Transport

<p>The Gulf Stream is the western boundary current in the subtropical North Atlantic and a principal component of the upper limb of the Atlantic Meridional Overturning Circulation. Thus, it plays an important role in poleward heat and volume transport, as well as in the redistribution and modification of various water masses. Despite its importance in the climate system, many details of the Gulf Stream’s increase in volume along the US East Coast and the associated entrainment of various water masses are not well known due to a paucity of sustained subsurface measurements within and near the Gulf Stream. Observations from more than 30 Spray autonomous underwater glider missions comprising over 22,000 profiles and more than 180 distinct cross-Gulf Stream transects collected between 2004 and the present fill a 1,500-km-long gap in sustained subsurface measurements; they provide concurrent measurements of hydrography and velocity in and near the Gulf Stream over more than 15 degrees of latitude between Florida and New England. These observations are used to characterize the along-stream evolution of Gulf Stream volume transport including classification by water properties. Remotely formed intermediate waters (i.e., Antarctic Intermediate Water (AAIW) and upper Labrador Sea Water (uLSW)) are significant components of Gulf Stream transport. AAIW is formed at high southern latitudes and enters the Gulf Stream through the Florida Strait, while uLSW is formed through deep convection in the Labrador Sea and encounters the Gulf Stream at Cape Hatteras as the uppermost layer of the Deep Western Boundary Current. Though it is well known where AAIW and uLSW initially encounter the Gulf Stream, their distribution, advection, and modification within the Gulf Stream remain poorly resolved. The extensive glider observations are used to characterize the evolution and intermittency of AAIW and uLSW pathways within and near the Gulf Stream, including effects of near-bottom mixing and the mechanisms by which uLSW crosses isobaths to arrive over the O(1000)-m-deep Blake Plateau south of Cape Hatteras. This first look at Gulf Stream transport by water class and the three-dimensional pathways followed by intermediate water masses within the Gulf Stream provides a reference for global circulation models to replicate.</p>

Cross-Shelf Exchange Associated With the Gulf Stream in the South Atlantic Bight: Direct Observations Using an Autonomous Underwater Glider

2018 ◽  
Vol 52 (3) ◽  
pp. 19-27 ◽  
Author(s):  
Ruoying He ◽  
Austin C. Todd ◽  
Chad Lembke ◽  
Todd Kellison ◽  
Chris Taylor ◽  
...  
Keyword(s):  
Gulf Stream ◽  
Moving Boundary ◽  
South Atlantic ◽  
South Atlantic Bight ◽  
Underwater Glider ◽  
The South ◽  
Underwater Gliders ◽  
Direct Observations ◽  
Autonomous Underwater Glider

AbstractAn autonomous underwater glider was deployed in March 2014 to sample the Gulf Stream and its adjacent shelf waters in the South Atlantic Bight, providing a new look at cross-shelf exchange associated with Gulf Stream dynamics. Observations collected over 4 weeks reveal significant cross-shelf exchange (up to 0.5 Sv) at the shoreward edge of the Gulf Stream, which was 2 orders of magnitude larger than estimates from long-term mean hydrographic conditions. Gulf Stream frontal eddies may have contributed to some of the largest fluxes of heat (0.5°C Sv) and salt (0.03 Sv g/kg) onto the shelf. We estimate that the largest upwelling event during the mission could have brought nitrate concentrations over 20 μM to within 125 m of the surface. This study demonstrates clear capabilities of autonomous underwater gliders for sampling in and near fast moving boundary currents to obtain unique and critical in situ observations effectively.

scholarly journals Loop Current Variability as Trigger of Coherent Gulf Stream Transport Anomalies

2019 ◽  
Vol 49 (8) ◽  
pp. 2115-2132 ◽  
Author(s):  
Joël J.-M. Hirschi ◽  
Eleanor Frajka-Williams ◽  
Adam T. Blaker ◽  
Bablu Sinha ◽  
Andrew Coward ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Gulf Stream ◽  
Time Lag ◽  
Ocean Model ◽  
Surface Velocity ◽  
Loop Current ◽  
Intrinsic Variability ◽  
Cape Hatteras ◽  
Florida Straits ◽  
Stream Transport

AbstractSatellite observations and output from a high-resolution ocean model are used to investigate how the Loop Current in the Gulf of Mexico affects the Gulf Stream transport through the Florida Straits. We find that the expansion (contraction) of the Loop Current leads to lower (higher) transports through the Straits of Florida. The associated surface velocity anomalies are coherent from the southwestern tip of Florida to Cape Hatteras. A simple continuity-based argument can be used to explain the link between the Loop Current and the downstream Gulf Stream transport: as the Loop Current lengthens (shortens) its path in the Gulf of Mexico, the flow out of the Gulf decreases (increases). Anomalies in the surface velocity field are first seen to the southwest of Florida and within 4 weeks propagate through the Florida Straits up to Cape Hatteras and into the Gulf Stream Extension. In both the observations and the model this propagation can be seen as pulses in the surface velocities. We estimate that the Loop Current variability can be linked to a variability of several Sverdrups (1Sv = 106 m3 s−1) through the Florida Straits. The exact timing of the Loop Current variability is largely unpredictable beyond a few weeks and its variability is therefore likely a major contributor to the chaotic/intrinsic variability of the Gulf Stream. However, the time lag between the Loop Current and the flow downstream of the Gulf of Mexico means that if a lengthening/shortening of the Loop Current is observed this introduces some predictability in the downstream flow for a few weeks.

Fifty years of Marine and Freshwater Research

1999 ◽  
Keyword(s):  
Coral Reefs ◽  
Sea Level ◽  
Climate Changes ◽  
Sea Water ◽  
Global Climate ◽  
Short Term ◽  
Natural Factors ◽  
Carbon Dioxide Concentrations ◽  
Minimal Damage

Factors causing global degradation of coral reefs are examined briefly as a basis for predicting the likely consequences of increases in these factors. The earlier consensus was that widespread but localized damage from natural factors such as storms, and direct anthropogenic effects such as increased sedimentation, pollution and exploitation, posed the largest immediate threat to coral reefs. Now truly global factors associated with accelerating Global Climate Change are either damaging coral reefs or have the potential to inflict greater damage in the immediate future: e.g. increases in coral bleaching and mortality, and reductions in coral calcification due to changes in sea-water chemistry with increasing carbon dioxide concentrations. Rises in sea level will probably disrupt human communities and their cultures by making coral cays uninhabitable, whereas coral reefs will sustain minimal damage from the rise in sea level. The short-term (decades) prognosis is indeed grim, with major reductions almost certain in the extent and biodiversity of coral reefs, and severe disruptions to cultures and economies dependent on reef resources. The long-term (centuries to millennia) prognosis is more encouraging because coral reefs have remarkable resilience to severe disruption and will probably show this resilience in the future when climate changes either stabilize or reverse.

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.

Global and local threats to coral reef functioning and existence: review and predictions

1999 ◽  
Author(s):  
Clive R. Wilkinson
Keyword(s):  
Coral Reefs ◽  
Sea Level ◽  
Sea Water ◽  
Global Climate ◽  
Short Term ◽  
Natural Factors ◽  
Carbon Dioxide Concentrations ◽  
Minimal Damage ◽  
Global And Local

Factors causing global degradation of coral reefs are examined briefly as a basis for predicting the likely consequences of increases in these factors. The earlier consensus was that widespread but localized damage from natural factors such as storms, and direct anthropogenic effects such as increased sedimentation, pollution and exploitation, posed the largest immediate threat to coral reefs. Now truly global factors associated with accelerating Global Climate Change are either damaging coral reefs or have the potential to inflict greater damage in the immediate future: e.g. increases in coral bleaching and mortality, and reductions in coral calcification due to changes in sea-water chemistry with increasing carbon dioxide concentrations. Rises in sea level will probably disrupt human communities and their cultures by making coral cays uninhabitable, whereas coral reefs will sustain minimal damage from the rise in sea level. The short-term (decades) prognosis is indeed grim, with major reductions almost certain in the extent and biodiversity of coral reefs, and severe disruptions to cultures and economies dependent on reef resources. The long-term (centuries to millennia) prognosis is more encouraging because coral reefs have remarkable resilience to severe disruption and will probably show this resilience in the future when climate changes either stabilize or reverse.

scholarly journals On the long-term stability of Gulf Stream transport based on 20 years of direct measurements

2014 ◽  
Vol 41 (1) ◽  
pp. 114-120 ◽  
Author(s):  
T. Rossby ◽  
C. N. Flagg ◽  
K. Donohue ◽  
A. Sanchez-Franks ◽  
J. Lillibridge
Keyword(s):  
Gulf Stream ◽  
Term Stability ◽  
Long Term Stability ◽  
Direct Measurements ◽  
Stream Transport

Diatoms and aquatic palynomorphs in the sediments of the Eurasian Arctic seas and their significance for paleooceanological investigations in the Arctic

2019 ◽  
pp. 246-251
Author(s):  
Yelena I. Polyakova ◽  
Yekaterina I. Novichkova ◽  
Tatiana S. Klyuvitkina ◽  
Elizaveta A. Agafonova ◽  
Irina M. Kryukova
Keyword(s):  
Bering Sea ◽  
Surface Sediments ◽  
Sea Water ◽  
The Arctic ◽  
Marginal Filter ◽  
Arctic Seas ◽  
Hydrological Parameters ◽  
The Arctic Ocean ◽  
Long Term Studies

Presented the results of long-term studies of diatoms and aquatic palynomorphs in surface sediments of the Arctic seas and the possibility of their use for the reconstructions of paleocirculation water masses, advection of Atlantic and Bering sea water into the Arctic ocean, changes in the river runoff to the seas, sedimentary processes in the marginal filter of the largest rivers, seasonal sea ice cover and other hydrological parameters.

On Climate Change Risks of Long-Term Socio-Economic Development in Russia

2019 ◽  
pp. 79-95
Author(s):  
N.E. Terentiev
Keyword(s):  
Climate Change ◽  
Economic Development ◽  
Technological Innovation ◽  
Global Climate Change ◽  
Global Climate ◽  
Climate Risk ◽  
Climate Change Risks ◽  
Socio Economic Development ◽  
Management Policies

Based on the latest data, paper investigates the dynamics of global climate change and its impact on economic growth in the long-term. The notion of climate risk is considered. The main directions of climate risk management policies are analyzed aimed, first, at reducing anthropogenic greenhouse gas emissions through technological innovation and structural economic shifts; secondly, at adaptation of population, territories and economic complexes to the irreparable effects of climate change. The problem of taking into account the phenomenon of climate change in the state economic policy is put in the context of the most urgent tasks of intensification of long-term socio-economic development and parrying strategic challenges to the development of Russia.

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