scholarly journals Observing the Galápagos–EUC Interaction: Insights and Challenges

2010 ◽  
Vol 40 (12) ◽  
pp. 2768-2777 ◽  
Author(s):  
Kristopher B. Karnauskas ◽  
Raghu Murtugudde ◽  
Antonio J. Busalacchi
Keyword(s):  
Climate Models ◽  
Current System ◽  
Critical Role ◽  
Equatorial Undercurrent ◽  
Eastern Equatorial Pacific ◽  
The Pacific ◽  
Adcp Measurements ◽  
Equatorial Current ◽  
Coupled Variability ◽  
Striking Effect

Abstract Although sustained observations yield a description of the mean equatorial current system from the western Pacific to the eastern terminus of the Tropical Atmosphere Ocean (TAO) array, a comprehensive observational dataset suitable for describing the structure and pathways of the Equatorial Undercurrent (EUC) east of 95°W does not exist and therefore climate models are unconstrained in a region that plays a critical role in ocean–atmosphere coupling. Furthermore, ocean models suggest that the interaction between the EUC and the Galápagos Islands (∼92°W) has a striking effect on the basic state and coupled variability of the tropical Pacific. To this end, the authors interpret historical measurements beginning with those made in conjunction with the discovery of the Pacific EUC in the 1950s, analyze velocity measurements from an equatorial TAO mooring at 85°W, and analyze a new dataset from archived shipboard ADCP measurements. Together, the observations yield a possible composite description of the EUC structure and pathways in the eastern equatorial Pacific that may be useful for model validation and guiding future observation.

Implications of Radiolarian Assemblages for the Late Quaternary Paleoceanography of the Eastern Equatorial Pacific

1985 ◽  
Vol 24 (2) ◽  
pp. 204-218 ◽  
Author(s):  
Cynthia T. Schramm
Keyword(s):  
Surface Water ◽  
Late Quaternary ◽  
Zonal Flow ◽  
Equatorial Pacific ◽  
Equatorial Undercurrent ◽  
Ice Volume ◽  
The Past ◽  
Eastern Equatorial Pacific ◽  
The Pacific ◽  
Radiolarian Assemblages

The distribution of radiolarian assemblages identified by Q-mode factor analysis of radiolarian microfossils in surface sediments from low latitudes in the Pacific Ocean reflects their associations with surface water masses. Downcore fluctuations of these radiolarian assemblages at two sites, RC10-65 and V19–29, indicate changes in circulation in the eastern equatorial Pacific during the past 500,000 yr. Surface-water radiolarian assemblages characteristic of zonal flow have dominated siliceous sedimentation in the eastern equatorial Pacific, except during times of intense upwelling which can occur along the coast of Peru and in the Equatorial Undercurrent. Fluctuations in the importance of this upwelling have not been consistent with glacial/interglacial changes in ice volume throughout the late Quaternary. Intensification of upwelling in the equatorial divergence, however, has consistently coincided with increases in ice volume in the past 500,000 yr. The times at which changes in the nature of the relationship between upwelling and ice volume occur (approximately 240,000 and 380,000 yr B.P.) roughly coincide with times of observed changes in other proxy indicators of oceanographic conditions in the Pacific and Indian oceans.

scholarly journals The Pacific Equatorial Undercurrent in Three Generations of Global Climate Models and Glider Observations

2020 ◽  
Vol 125 (11) ◽  
Author(s):  
Kristopher B. Karnauskas ◽  
Julie Jakoboski ◽  
T. M. Shaun Johnston ◽  
W. Brechner Owens ◽  
Daniel L. Rudnick ◽  
...  
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Equatorial Undercurrent ◽  
Three Generations ◽  
The Pacific

scholarly journals Circulation, eddies, oxygen, and nutrient changes in the eastern tropical South Pacific Ocean

Ocean Science ◽  
2015 ◽  
Vol 11 (3) ◽  
pp. 455-470 ◽  
Author(s):  
R. Czeschel ◽  
L. Stramma ◽  
R. A. Weller ◽  
T. Fischer
Keyword(s):  
Pacific Ocean ◽  
Large Scale ◽  
Current System ◽  
Oxygen Deficiency ◽  
South Pacific ◽  
Upper Ocean ◽  
Net Community Production ◽  
Equatorial Undercurrent ◽  
South Pacific Ocean ◽  
Eastern Equatorial Pacific

Abstract. A large subsurface oxygen deficiency zone is located in the eastern tropical South Pacific Ocean (ETSP). The large-scale circulation in the eastern equatorial Pacific and off the coast of Peru in November/December 2012 shows the influence of the equatorial current system, the eastern boundary currents, and the northern reaches of the subtropical gyre. In November 2012 the equatorial undercurrent (EUC) is centered at 250 m depth, deeper than in earlier observations. In December 2012, the equatorial water is transported southeastward near the shelf in the Peru–Chile undercurrent (PCUC) with a mean transport of 1.4 Sv. In the oxygen minimum zone (OMZ), the flow is overlaid with strong eddy activity on the poleward side of the OMZ. Floats with parking depth at 400 m show fast westward flow in the mid-depth equatorial channel and sluggish flow in the OMZ. Floats with oxygen sensors clearly show the passage of eddies with oxygen anomalies. The long-term float observations in the upper ocean lead to a net community production estimate at about 18° S of up to 16.7 mmol C m−3 yr−1 extrapolated to an annual rate and 7.7 mmol C m−3 yr−1 for the time period below the mixed layer. Oxygen differences between repeated ship sections are influenced by the Interdecadal Pacific Oscillation (IPO), by the phase of El Niño, by seasonal changes, and by eddies, and hence have to be interpreted with care. At and south of the Equator the decrease in oxygen in the upper ocean since 1976 is related to an increase in nitrate, phosphate, and in part silicate.

scholarly journals Circulation, eddies, oxygen and nutrient changes in the eastern tropical South Pacific Ocean

2014 ◽  
Vol 11 (5) ◽  
pp. 2205-2243
Author(s):  
R. Czeschel ◽  
L. Stramma ◽  
R. A. Weller ◽  
T. Fischer
Keyword(s):  
Pacific Ocean ◽  
Large Scale ◽  
Current System ◽  
Oxygen Deficiency ◽  
South Pacific ◽  
Upper Ocean ◽  
Net Community Production ◽  
Equatorial Undercurrent ◽  
South Pacific Ocean ◽  
Eastern Equatorial Pacific

Abstract. A large, subsurface oxygen deficiency zone is located in the eastern tropical South Pacific Ocean (ETSP). The large-scale circulation in the eastern equatorial Pacific and off Peru in November/December 2012 shows the influence of the equatorial current system, the eastern boundary currents, and the northern reaches of the subtropical gyre. In November 2012 the Equatorial Undercurrent is centered at 250 m depth, deeper than in earlier observations. In December 2012 the equatorial water is transported southeastward near the shelf in the Peru-Chile Undercurrent with a mean transport of 1.6 Sv. In the oxygen minimum zone (OMZ) the flow is overlaid with strong eddy activity on the poleward side of the OMZ. Floats with parking depth at 400 m show fast westward flow in the mid-depth equatorial channel and sluggish flow in the OMZ. Floats with oxygen sensors clearly show the passage of eddies with oxygen anomalies. The long-term float observations in the upper ocean lead to a net community production estimate at about 18° S of up to 16.7 mmol C m−3 yr1 extrapolated to an annual rate and 7.7 mmol C m−3 yr−1 for the time period below the mixed layer. Oxygen differences between repeated ship sections are influenced by the Interdecadal Pacific Oscillation, by the phase of El Niño, by seasonal changes, and by eddies and hence have to be interpreted with care. At and south of the equator the decrease in oxygen in the upper ocean since 1976 is related to an increase in nitrate, phosphate, and in part in silicate.

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