scholarly journals Characteristics of the seasonal cycle of surface layer salinity in the global ocean

2011 ◽  
Vol 8 (6) ◽  
pp. 2377-2415 ◽  
Author(s):  
F. M. Bingham ◽  
G. R. Foltz ◽  
M. J. McPhaden
Keyword(s):  
Surface Layer ◽  
Seasonal Variability ◽  
Seasonal Cycle ◽  
Arabian Sea ◽  
Mixed Layer Depth ◽  
Bimodal Distribution ◽  
Surface Fluxes ◽  
Global Ocean ◽  
Freshwater Flux ◽  
The North

Abstract. The seasonal variability of surface layer salinity (SLS), evaporation (E), precipitation (P) and E-P over the global ocean is examined using in situ salinity data and the National Center for Environmental Prediction's Climate System Forecast Reanalysis. Seasonal amplitudes and phases are calculated using harmonic analysis and presented in all areas of the open ocean between 60° S and 60° N. Areas with large amplitude SLS seasonal variations include: the intertropical convergence zone in the Atlantic, Pacific and Indian Oceans; western marginal seas of the Pacific; and the Arabian Sea. The median value in areas that have statistically significant seasonal cycles of SLS is 0.19. Between about 60° S and 60° N, 37 % of the ocean surface has a significant seasonal cycle of SLS and 75 % a seasonal cycle of E-P. Phases of SLS have a bimodal distribution, with most areas of the ocean peaking in SLS in either March/April or September/October. The same calculation is done with surface freshwater flux using a mixed-layer depth climatology. With the exception of an area near the western boundaries of the North Atlantic and North Pacific, seasonal variability is dominated by precipitation. Surface freshwater fluxes also have a bimodal distribution, with peaks in January and July, 1–2 months before the peaks of SLS. The amplitudes and phases of SLS and surface fluxes compare well in a qualitative sense, suggesting that much of the variability in SLS is due to E-P forcing. However, the amplitudes of SLS are somewhat larger than would be expected and the peak of SLS comes typically about one month earlier than expected. The differences of the amplitudes of the two quantities is largest in such areas as the Amazon River plume, the Arabian Sea, the ITCZ and the eastern equatorial Pacific and Atlantic, indicating that other processes such as ocean mixing and lateral transport must be important, especially in the tropics.

scholarly journals Characteristics of the seasonal cycle of surface layer salinity in the global ocean

Ocean Science ◽  
2012 ◽  
Vol 8 (5) ◽  
pp. 915-929 ◽  
Author(s):  
F. M. Bingham ◽  
G. R. Foltz ◽  
M. J. McPhaden
Keyword(s):  
Surface Layer ◽  
Mixed Layer ◽  
Seasonal Variability ◽  
Seasonal Cycle ◽  
Arabian Sea ◽  
Mixed Layer Depth ◽  
Bimodal Distribution ◽  
Global Ocean ◽  
Late Winter ◽  
Freshwater Forcing

Abstract. The seasonal variability of surface layer salinity (SLS), evaporation (E), precipitation (P), E-P, advection and vertical entrainment over the global ocean is examined using in situ salinity data, the National Centers for Environmental Prediction's Climate System Forecast Reanalysis and a number of other ancillary data. Seasonal amplitudes and phases are calculated using harmonic analysis and presented in all areas of the open ocean between 60° S and 60° N. Areas with large amplitude SLS seasonal variations include: the intertropical convergence zone (ITCZ) in the Atlantic, Pacific and Indian Oceans; western marginal seas of the Pacific; and the Arabian Sea. The median amplitude in areas that have statistically significant seasonal cycles of SLS is 0.19. Between about 60° S and 60° N, 37% of the ocean surface has a statistically significant seasonal cycle of SLS and 75% has a seasonal cycle of E-P. Phases of SLS have a bimodal distribution, with most areas in the Northern Hemisphere peaking in SLS in March/April and in the Southern Hemisphere in September/October. The seasonal cycle is also estimated for surface freshwater forcing using a mixed-layer depth climatology. With the exception of areas near the western boundaries of the North Atlantic and North Pacific, seasonal variability is dominated by precipitation. Surface freshwater forcing also has a bimodal distribution, with peaks in January and July, 1–2 months before the peaks of SLS. Seasonal amplitudes and phases calculated for horizontal advection show it to be important in the tropical oceans. Vertical entrainment, estimated from mixed-layer heaving, is largest in mid and high latitudes, with a seasonal cycle that peaks in late winter. The amplitudes and phases of SLS and surface fluxes compare well in a qualitative sense, suggesting that much of the variability in SLS is due to E-P. However, the amplitudes of SLS are somewhat different than would be expected and the peak of SLS comes typically about one month earlier than expected. The differences of the amplitudes of the two quantities is largest in such areas as the Amazon River plume, the Arabian Sea, the ITCZ and the eastern equatorial Pacific and Atlantic.

Implications of a regional-scale process (the Lakshadweep low) on the mesozooplankton community structure of the Arabian Sea

2019 ◽  
Vol 70 (3) ◽  
pp. 345 ◽  
Author(s):  
K. K. Karati ◽  
G. Vineetha ◽  
T. V. Raveendran ◽  
P. K. Dineshkumar ◽  
K. R. Muraleedharan ◽  
...  
Keyword(s):  
Physical Process ◽  
Arabian Sea ◽  
Mixed Layer Depth ◽  
Regional Scale ◽  
Zooplankton Community ◽  
Ocean Basin ◽  
Zooplankton Biomass ◽  
Global Ocean ◽  
Mesozooplankton Community ◽  
Tropical Ocean

The Arabian Sea, a major tropical ocean basin in the northern Indian Ocean, is one of the most productive regions in the global ocean. Although the classical Arabian Sea ‘paradox’ describes the geographical and seasonal invariability in zooplankton biomass in this region, the effect of the Lakshadweep low (LL), a regional-scale physical process, on the zooplankton community has not yet been evaluated. The LL, characterised by low sea surface height and originating around the vicinity of the Lakshadweep islands during the mid-summer monsoon, is unique to the Arabian Sea. The present study investigated the effect of the LL on the zooplankton community. The LL clearly had a positive effect, with enhanced biomass and abundance in the mixed-layer depth of the LL region. Copepods and chaetognaths formed the dominant taxa, exhibiting strong affinity towards the physical process. Of the 67 copepod species observed, small copepods belonging to the families Paracalanidae, Clausocalanidae, Calanidae, Oncaeidae and Corycaeidae dominated the LL region. Phytoplankton biomass (chlorophyll-a) was the primary determinant influencing the higher preponderance of the copepod community in this region.

Variability of the Oceanic Mixed Layer, 1960–2004

2008 ◽  
Vol 21 (5) ◽  
pp. 1029-1047 ◽  
Author(s):  
James A. Carton ◽  
Semyon A. Grodsky ◽  
Hailong Liu
Keyword(s):  
Mixed Layer ◽  
North Atlantic ◽  
Southern Oscillation ◽  
Mixed Layer Depth ◽  
Global Ocean ◽  
Boreal Summer ◽  
Layer Depth ◽  
The North ◽  
The North Atlantic ◽  
Mixed Layers

Abstract A new monthly uniformly gridded analysis of mixed layer properties based on the World Ocean Atlas 2005 global ocean dataset is used to examine interannual and longer changes in mixed layer properties during the 45-yr period 1960–2004. The analysis reveals substantial variability in the winter–spring depth of the mixed layer in the subtropics and midlatitudes. In the North Pacific an empirical orthogonal function analysis shows a pattern of mixed layer depth variability peaking in the central subtropics. This pattern occurs coincident with intensification of local surface winds and may be responsible for the SST changes associated with the Pacific decadal oscillation. Years with deep winter–spring mixed layers coincide with years in which winter–spring SST is low. In the North Atlantic a pattern of winter–spring mixed layer depth variability occurs that is not so obviously connected to local changes in winds or SST, suggesting that other processes such as advection are more important. Interestingly, at decadal periods the winter–spring mixed layers of both basins show trends, deepening by 10–40 m over the 45-yr period of this analysis. The long-term mixed layer deepening is even stronger (50–100 m) in the North Atlantic subpolar gyre. At tropical latitudes the boreal winter mixed layer varies in phase with the Southern Oscillation index, deepening in the eastern Pacific and shallowing in the western Pacific and eastern Indian Oceans during El Niños. In boreal summer the mixed layer in the Arabian Sea region of the western Indian Ocean varies in response to changes in the strength of the southwest monsoon.

scholarly journals The global ocean circulation on a retrograde rotating earth

2011 ◽  
Vol 7 (2) ◽  
pp. 487-499 ◽  
Author(s):  
V. Kamphuis ◽  
S. E. Huisman ◽  
H. A. Dijkstra
Keyword(s):  
Ocean Circulation ◽  
Deep Water ◽  
North Pacific ◽  
Global Ocean ◽  
Freshwater Flux ◽  
Deep Water Formation ◽  
The North ◽  
Water Formation ◽  
Global Ocean Circulation ◽  
The North Pacific

Abstract. To understand the three-dimensional ocean circulation patterns that have occurred in past continental geometries, it is crucial to study the role of the present-day continental geometry and surface (wind stress and buoyancy) forcing on the present-day global ocean circulation. This circulation, often referred to as the Conveyor state, is characterised by an Atlantic Meridional Overturning Circulation (MOC) with a deep water formation at northern latitudes and the absence of such a deep water formation in the North Pacific. This MOC asymmetry is often attributed to the difference in surface freshwater flux: the Atlantic as a whole is a basin with net evaporation, while the Pacific receives net precipitation. This issue is revisited in this paper by considering the global ocean circulation on a retrograde rotating earth, computing an equilibrium state of the coupled atmosphere-ocean-land surface-sea ice model CCSM3. The Atlantic-Pacific asymmetry in surface freshwater flux is indeed reversed, but the ocean circulation pattern is not an Inverse Conveyor state (with deep water formation in the North Pacific) as there is relatively weak but intermittently strong deep water formation in the North Atlantic. Using a fully-implicit, global ocean-only model the stability properties of the Atlantic MOC on a retrograde rotating earth are also investigated, showing a similar regime of multiple equilibria as in the present-day case. These results indicate that the present-day asymmetry in surface freshwater flux is not the most important factor setting the Atlantic-Pacific salinity difference and, thereby, the asymmetry in the global MOC.

scholarly journals Role of North Pacific Mixed Layer in the Response of SST Annual Cycle to Global Warming

2015 ◽  
Vol 28 (23) ◽  
pp. 9451-9458 ◽  
Author(s):  
Changlin Chen ◽  
Guihua Wang
Keyword(s):  
Global Warming ◽  
Mixed Layer ◽  
Annual Cycle ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Mixed Layer Depth ◽  
Ecological Impacts ◽  
Global Ocean ◽  
The North ◽  
The North Pacific

Abstract The annual cycle of sea surface temperature (SST) in the North Pacific Ocean is examined in terms of its response to global warming based on climate model simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). As the global ocean warms up, the SST in the North Pacific generally tends to increase and the warming is greater in summer than in winter, leading to a significant intensification of SST annual cycle. The mixed layer temperature equation is used to examine the mechanism of this intensification. Results show that the decrease of mixed layer depth (MLD) in summer is the main reason behind the intensification of SST annual cycle. Because the MLD in summer is much shallower than that in winter, the incoming net heat flux is trapped in a thinner surface layer in summer, causing a warmer summer SST and the amplification of SST annual cycle. The change of the SST annual cycle in the North Pacific may have profound ecological impacts.

On the Seasonal variability eastern boundary of the North Atlantic Subtropical Gyre

2021 ◽  
Author(s):  
Maria Dolores Pérez-Hernández ◽  
Pedro Vélez-Belchí ◽  
Verónica Caínzos ◽  
Daniel Santana-Toscano ◽  
Cristina Arumí-Planas ◽  
...  
Keyword(s):  
North Atlantic ◽  
Seasonal Variability ◽  
Seasonal Cycle ◽  
Subtropical Gyre ◽  
North Equatorial Current ◽  
Eastern Region ◽  
The North ◽  
Equatorial Current ◽  
The North Atlantic ◽  
Ocean Observing

<p>On the eastern region of the North Atlantic Subtropical Gyre, the Canary Current connects the Azores Current with the North Equatorial Current. Several studies link the seasonality of the AMOC (as measured by the RAPID program) to the seasonality of the main flows existing on the Canary basin. Since 2003, the RaProCan project which is the Canary Islands component of the Spanish Institute of Oceanography ocean observing system, monitors the Canary basin. In 2015, the RaProCan project joined efforts with the Seasonal Variability of the AMOC: Canary Current (SeVaCan) project of the Instituto de Oceanografía y Cambio Global (IOCAG) to increase the temporal resolution of the observations. Hence, during 2015 a hydrographic cruise took place in each season (February, April, July, and November) to complete the seasonal cycle of the basin. Here we present results from these cruises to describe the seasonal cycle of the area. A sensitive analysis is carried out to understand the representativeness of the cycle to be able to compare it with the AMOC seasonal cycle.</p>

New contribution on spatial and seasonal variability of environmental conditions of the Golfo San Jorge benthic system, Argentina

2008 ◽  
Vol 88 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Mónica Fernández ◽  
José Mora ◽  
Ana Roux ◽  
Daniel A. Cucchi Colleoni ◽  
Juan C. Gasparoni
Keyword(s):  
Organic Matter ◽  
Seasonal Variability ◽  
Seasonal Cycle ◽  
Nutritional Value ◽  
Bottom Water ◽  
Chemical Parameters ◽  
Temperate Water ◽  
The North ◽  
Physico Chemical ◽  
North And South

A new contribution on spatial and seasonal variability of physico-chemical parameters of the Golfo San Jorge benthic system from autumn 2001 through summer to 2002 is presented. Temperature, salinity, density, oxygen content and chlorophyll-a in bottom water as well as concentration of total organic matter, total organic carbon, total nitrogen, total phosphorus, chlorophyll-a and phaeopigments in sediments were analysed. The origin and nutritional value of the deposited organic matter were also assessed. The results reflect the existence of: (1) a typical temperate water seasonal cycle; (2) a bimodal cycle in the phytoplanktonic production; and (3) seasonal variations in the chemical variables and in organic matter origin in sediments.Three sectors which geographically correspond with those identified in previous studies were defined: (1) the inner area of the gulf; (2) the areas next to the north and south extremes; and (3) the coastal and south-east part.

scholarly journals Seasonal and El Niño Variability in Weekly Satellite Evaporation over the Global Ocean during 1996–98

2006 ◽  
Vol 19 (10) ◽  
pp. 2025-2035 ◽  
Author(s):  
Alberto M. Mestas-Nuñez ◽  
Abderrahim Bentamy ◽  
Kristina B. Katsaros
Keyword(s):  
Latent Heat ◽  
El Niño ◽  
Seasonal Cycle ◽  
Arabian Sea ◽  
El Nino ◽  
Phase Relationship ◽  
South Pacific ◽  
Heat Fluxes ◽  
Global Ocean ◽  
North And South

Abstract The seasonal and anomaly variability of satellite-derived weekly latent heat fluxes occurring over the global oceans during a 3-yr period (January 1996–December 1998) is investigated using EOF and harmonic analyses. The seasonal cycle of latent heat flux is estimated by least squares fitting the first three (annual, semiannual, and 4 month) harmonics to the data. The spatial patterns of amplitudes of these harmonics agree well with the corresponding patterns for wind speed. The annual harmonic captures an oscillation that reflects high evaporation in late fall/early winter and low evaporation in late spring/early summer in both hemispheres, with larger amplitudes in the Northern Hemisphere over the western side of the oceans and significant phase differences within each hemisphere. The main feature of the semiannual harmonic is its large amplitude in the Asian monsoon region (e.g., in the Arabian Sea its amplitude is about 1.5 larger than the annual) and the out-of-phase relationship of this region with the high latitudes of the North Pacific, consistent with other studies. The third harmonic shows three main regions with relatively large amplitudes, one in the Arabian Sea and two out-of-phase regions in the central midlatitude North and South Pacific. After removing this estimate of the seasonal cycle from the data, the leading EOF of the anomalies isolates the 1997–98 El Niño signal, with enhanced evaporation in the eastern tropical Pacific, around the Maritime Continent, in the midlatitude North and South Pacific, and the equatorial Indian Ocean, and reduced evaporation elsewhere around the global ocean during April 1997–April 1998. This pattern is consistent with known patterns of ENSO variability and with the “atmospheric bridge” teleconnection concept. The current study illustrates the usefulness of satellite-derived latent heat fluxes for climatic applications.

scholarly journals Destratification and Restratification of the Spring Surface Boundary Layer in a Subtropical Front

2021 ◽  
Author(s):  
Eric Kunze ◽  
John B. Mickett ◽  
James B. Girton
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Surface Fluxes ◽  
Minor Role ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Subtropical Front ◽  
The North ◽  
A Minor ◽  
The North Pacific

AbstractDestratification and restratification of a ~50-m thick surface boundary layer in the North Pacific Subtropical Front are examined during 24-31 March 2017 in the wake of a storm using a ~ 5-km array of 23 chi-augmented EM profiling floats (u, v, T, S, χT), as well as towyo and ADCP ship surveys, shipboard air-sea surface fluxes and parameterized shortwave penetrative radiation. During the first four days, nocturnal destabilizing buoyancy-fluxes mixed the surface layer over almost its full depth every night followed by restratification to N ~ 2 × 10–3 rad s–1 during daylight. Starting on 28 March, nocturnal destabilizing buoyancy-fluxes weakened because weakening winds reduced the latent heat-flux. Shallow mixing and stratified transition layers formed above ~20-m depth. The remnant layer in the lower part of the surface layer was insulated from destabilizing surface forcing. Penetrative radiation, turbulent buoyancy-fluxes and horizontal buoyancy advection all contribute to restratification of this remnant layer, closing the budget to within measurement uncertainties. Buoyancy advective restratification (slumping) plays a minor role. Before 28 March, measured advective restratification ∫(uzbx + vzby)dt is confined to daytime, is often destratifying and is much stronger than predictions of geostrophic adjustment, mixed-layer eddy instability and Ekman buoyancy-flux predictions because of storm-forced inertial shear. Starting on 28 March, the subinertial envelope of measured buoyancy advective restratification in the remnant layer resembles MLE parameterization predictions.

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