scholarly journals Closing the Gap Between the Coral Sea and the Equator: Direct Observations of the North Australian Western Boundary Currents

2018 ◽  
Vol 123 (12) ◽  
pp. 9212-9231 ◽  
Author(s):  
Ken R. Ridgway ◽  
Jessica A. Benthuysen ◽  
Craig Steinberg
Keyword(s):  
Western Boundary ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
The North ◽  
Direct Observations ◽  
Coral Sea ◽  
Closing The Gap

Mean and eddy kinetic energy of the Gulf Stream from multiyear underwater glider surveys

2020 ◽  
Author(s):  
Robert E. Todd
Keyword(s):  
Kinetic Energy ◽  
Gulf Stream ◽  
Three Dimensional ◽  
Eddy Kinetic Energy ◽  
Cape Cod ◽  
Western Boundary ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
Global Circulation Models ◽  
The North

<p>Subtropical western boundary currents play a key role in ocean energy storage and transport and are characterized by elevated mean and eddy kinetic energy. Due to a lack of spatially broad subsurface observations of velocity, most studies of kinetic energy in western boundary currents have relied on satellite-based estimates of surface geostrophic velocity. Since 2015, Spray autonomous underwater gliders have completed more than 175 crossings of the Gulf Stream distributed over more than 1,500 km in along-stream extent between between Miami, FL (~25°N) and Cape Cod, MA (~40°N). The observations include roughly 14,000 absolute ocean velocity profiles in the upper 1000 m. Novel three-dimensional estimates of mean and eddy kinetic energy are constructed along the western margin of the North Atlantic at 10-m vertical resolution. The horizontal and vertical distributions of mean and eddy kinetic energy are analyzed in light of existing independent estimates and theoretical expectations. Observation-based estimates of mean and eddy-kinetic energy such as these serve as important metrics for validation of global circulation models that must adequately represent western boundary currents.</p>

The Various Aspects of the Large- scale Atmospheric Circulation Response to the Northern Hemispheric Ocean Western Boundary Currents

2020 ◽  
Author(s):  
Nour-Eddine Omrani ◽  
Fumiaki Ogawa ◽  
Hisashi Nakamura ◽  
Noel Keenlyside ◽  
Sandro Lubis ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
North Atlantic ◽  
Western Boundary ◽  
Significant Implication ◽  
Western Boundary Currents ◽  
Near Surface ◽  
Boundary Currents ◽  
The North ◽  
The North Atlantic ◽  
The Impact

<p>Semi-idealized Atmospheric General Circulation-Model (AGCM) experiments are used, in order to study the different aspects of the hemisphere-scale wintertime troposphere/stratosphere-coupled circulation that are maintained by the North Atlantic and Pacific Ocean Western Boundary Currents (OWBCs). Here we show that the North Atlantic and Pacific OWBCs jointly maintain and shape the wintertime hemispheric circulation and its leading mode of variability Northern Annular Mode (NAM). The OWBCs energize baroclinic waves that reinforce quasi-annular hemispheric structure in the tropospheric eddy-driven jetstreams and NAM variability. Without the OWBCs, the wintertime NAM variability is much weaker and its impact on the continental and maritime surface climate is largely insignificant. Atmospheric energy redistribution caused by the OWBCs acts to damp the near-surface atmospheric baroclinicity and compensates the associated oceanic meridional energy transport in agreement with the Bjerknes compensation. Furthermore, the OWBCs substantially weaken the wintertime stratospheric polar vortex by enhancing the upward planetary wave propagation, and thereby affecting both stratospheric and tropospheric NAM-annularity. It is shown that the impact of OWBCs on northern hemisphere circulation has significant implication for stratosphere/troposphere dynamical coupling, time-scales on the NAM, frequency of Sudden stratospheric warming and potential formation of polar stratospheric clouds.</p><p> </p><p>Reference:</p><p>Omrani et al., 2019: Key Role of the ocean Western Boundary currents in shaping the Northern Hemisphere climate, Scientific Reports, https://doi.org/10.1038/s41598-019-39392-y</p><p> </p>

scholarly journals North Atlantic Western Boundary Currents Are Intense Dissolved Organic Carbon Streams

2020 ◽  
Vol 7 ◽  
Author(s):  
Marcos Fontela ◽  
Fiz F. Pérez ◽  
Herlé Mercier ◽  
Pascale Lherminier
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
North Atlantic ◽  
Gulf Stream ◽  
Western Boundary ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
The North ◽  
The North Atlantic

In the North Atlantic, there are two main western boundary currents related to the Atlantic Meridional Overturning Circulation (AMOC): the Gulf Stream flowing northward and the Deep Western Boundary Current (DWBC) flowing southward. Here we analyze data from the OVIDE section (GO-SHIP A25 Portugal-Greenland 40–60°N) that crosses the DWBC and the northward extension of the Gulf Stream, the North Atlantic Current. We show that North Atlantic western boundary currents play a key role in the transport of dissolved organic matter, specifically dissolved organic carbon (DOC). Revisited transports and budgets of DOC with new available data identify the eastern Subpolar North Atlantic (eSPNA) as an important source of locally produced organic matter for the North Atlantic and a key region in the supply of bioavailable DOC to the deep ocean. The East Greenland Current, and its upstream source the East Reykjanes Ridge Current on the eastern flank of the mid-Atlantic ridge, are export pathways of bioavailable DOC toward subtropical latitudes. The fast overturning and subsequent remineralization of DOC produced in the autotrophic eSPNA explains up to 38% of the total oxygen consumption in the deep North Atlantic between the OVIDE section and 24°N. Carbon budgets that do not take into account this organic remineralization process overestimates the natural uptake of carbon dioxide (CO2) from the atmosphere by one third. The inclusion of DOC transports in regional carbon budgets reconciles the estimates of CO2 uptake in the North Atlantic between model and observations.

Spatial variability of phytoplankton in the Pacific western boundary currents during summer 2014

2017 ◽  
Vol 68 (10) ◽  
pp. 1887
Author(s):  
Yunyan Chen ◽  
Xiaoxia Sun ◽  
Mingliang Zhu ◽  
Shan Zheng ◽  
Yongquan Yuan ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Size Fraction ◽  
Western Boundary ◽  
Flow Cytometry Analysis ◽  
Concentration Data ◽  
Western Boundary Currents ◽  
Chl A ◽  
Boundary Currents ◽  
The North ◽  
The Pacific

The spatial distribution of phytoplankton was investigated during the summer of 2014 in two different regions of the Pacific western boundary current, namely the Warm Pool near the equator and the subtropical Kuroshio south area. Traditional approaches (size-fractionated chlorophyll-a (Chl-a) and microscopic analyses) combined with single-cell analysis (using a flow cytometer) were used to analyse the whole range of phytoplankton. Flow cytometry analysis resolved five clusters, two belonging to the pico-size fraction and three belonging to the nano-size fraction. Microscopy analysis revealed that the genera Coscinodiscus, Rhizosolenia, Chaetoceros and Ceratium were numerically dominant in the region studied. The lowest values of Chl-a, phytoplankton abundance and carbon biomass were found in the Kuroshio south area. Both Chl-a concentration data and flow cytometry analysis revealed that picophytoplankton were the predominant contributors to phytoplankton in the Pacific western boundary currents. Along the three transects during the summer cruise, Synechococcus and nanocyanobacteria-like organisms numerically dominated in surface waters with higher temperature. In contrast, eukaryotes were primarily distributed in subsurface waters with higher nutrients, especially in the eddy upwelling region mainly associated with the North Equatorial Counter Current. The vertical distribution of phytoplankton over the epipelagic layer reinforces the important role of currents in the north-western Pacific during summer.

scholarly journals Bjerknes-like Compensation in the Wintertime North Pacific

2015 ◽  
Vol 45 (5) ◽  
pp. 1339-1355 ◽  
Author(s):  
Stuart P. Bishop ◽  
Frank O. Bryan ◽  
R. Justin Small
Keyword(s):  
North Pacific ◽  
Kuroshio Extension ◽  
Western Boundary ◽  
Meridional Heat Transport ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific ◽  
Kuroshio Extension Region

AbstractObservational and model evidence has been mounting that mesoscale eddies play an important role in air–sea interaction in the vicinity of western boundary currents and can affect the jet stream storm track. What is less clear is the interplay between oceanic and atmospheric meridional heat transport in the vicinity of western boundary currents. It is first shown that variability in the North Pacific, particularly in the Kuroshio Extension region, simulated by a high-resolution fully coupled version of the Community Earth System Model matches observations with similar mechanisms and phase relationships involved in the variability. The Pacific decadal oscillation (PDO) is correlated with sea surface height anomalies generated in the central Pacific that propagate west preceding Kuroshio Extension variability with a ~3–4-yr lag. It is then shown that there is a near compensation of O(0.1) PW (PW ≡ 1015 W) between wintertime atmospheric and oceanic meridional heat transport on decadal time scales in the North Pacific. This compensation has characteristics of Bjerknes compensation and is tied to the mesoscale eddy activity in the Kuroshio Extension region.

scholarly journals Radiating Instability of a Meridional Boundary Current

2008 ◽  
Vol 38 (10) ◽  
pp. 2294-2307 ◽  
Author(s):  
Hristina G. Hristova ◽  
Joseph Pedlosky ◽  
Michael A. Spall
Keyword(s):  
Western Boundary ◽  
Far Field ◽  
Boundary Current ◽  
Important Conclusion ◽  
Western Boundary Currents ◽  
Horizontal Structure ◽  
Boundary Currents ◽  
Zonal Jets ◽  
Eastern Boundary ◽  
Eastern Boundary Current

Abstract A linear stability analysis of a meridional boundary current on the beta plane is presented. The boundary current is idealized as a constant-speed meridional jet adjacent to a semi-infinite motionless far field. The far-field region can be situated either on the eastern or the western side of the jet, representing a western or an eastern boundary current, respectively. It is found that when unstable, the meridional boundary current generates temporally growing propagating waves that transport energy away from the locally unstable region toward the neutral far field. This is the so-called radiating instability and is found in both barotropic and two-layer baroclinic configurations. A second but important conclusion concerns the differences in the stability properties of eastern and western boundary currents. An eastern boundary current supports a greater number of radiating modes over a wider range of meridional wavenumbers. It generates waves with amplitude envelopes that decay slowly with distance from the current. The radiating waves tend to have an asymmetrical horizontal structure—they are much longer in the zonal direction than in the meridional, a consequence of which is that unstable eastern boundary currents, unlike western boundary currents, have the potential to act as a source of zonal jets for the interior of the ocean.

scholarly journals From the western boundary currents to the Pacific Equatorial Undercurrent: Modeled pathways and water mass evolutions

2011 ◽  
Vol 116 (C12) ◽  
Author(s):  
Mélanie Grenier ◽  
Sophie Cravatte ◽  
Bruno Blanke ◽  
Christophe Menkes ◽  
Ariane Koch-Larrouy ◽  
...  
Keyword(s):  
Water Mass ◽  
Western Boundary ◽  
Western Boundary Currents ◽  
Equatorial Undercurrent ◽  
Boundary Currents ◽  
The Pacific
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