scholarly journals Interannual Variability of Sea Surface Temperature off Java and Sumatra in a Global GCM*

2008 ◽  
Vol 21 (11) ◽  
pp. 2451-2465 ◽  
Author(s):  
Yan Du ◽  
Tangdong Qu ◽  
Gary Meyers
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Mixed Layer ◽  
Heat Budget ◽  
Sea Surface ◽  
Surface Mixed Layer ◽  
Horizontal Advection ◽  
Cold Anomaly ◽  
Sst Anomalies

Abstract Using results from the Simple Ocean Data Assimilation (SODA), this study assesses the mixed layer heat budget to identify the mechanisms that control the interannual variation of sea surface temperature (SST) off Java and Sumatra. The analysis indicates that during the positive Indian Ocean Dipole (IOD) years, cold SST anomalies are phase locked with the season cycle. They may exceed −3°C near the coast of Sumatra and extend as far westward as 80°E along the equator. The depth of the thermocline has a prominent influence on the generation and maintenance of SST anomalies. In the normal years, cooling by upwelling–entrainment is largely counterbalanced by warming due to horizontal advection. In the cooling episode of IOD events, coastal upwelling–entrainment is enhanced, and as a result of mixed layer shoaling, the barrier layer no longer exists, so that the effect of upwelling–entrainment can easily reach the surface mixed layer. Horizontal advection spreads the cold anomaly to the interior tropical Indian Ocean. Near the coast of Java, the northern branch of an anomalous anticyclonic circulation spreads the cold anomaly to the west near the equator. Both the anomalous advection and the enhanced, wind-driven upwelling generate the cold SST anomaly of the positive IOD. At the end of the cooling episode, the enhanced surface thermal forcing overbalances the cooling effect by upwelling/entrainment, and leads to a warming in SST off Java and Sumatra.

scholarly journals Seasonality of Decadal Sea Surface Temperature Anomalies in the Northwestern Pacific

2006 ◽  
Vol 19 (12) ◽  
pp. 2953-2968 ◽  
Author(s):  
Takashi Mochizuki ◽  
Hideji Kida
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Mixed Layer ◽  
Surface Heat Flux ◽  
Heat Budget ◽  
Surface Heat ◽  
Sea Surface ◽  
Northwestern Pacific ◽  
Sst Anomaly

Abstract The seasonality of the decadal sea surface temperature (SST) anomalies and the related physical processes in the northwestern Pacific were investigated using a three-dimensional bulk mixed layer model. In the Kuroshio–Oyashio Extension (KOE) region, the strongest decadal SST anomaly was observed during December–February, while that of the central North Pacific occurred during February–April. From an examination of the seasonal heat budget of the ocean mixed layer, it was revealed that the seasonal-scale enhancement of the decadal SST anomaly in the KOE region was controlled by horizontal Ekman temperature transport in early winter and by vertical entrainment in autumn. The temperature transport by the geostrophic current made only a slight contribution to the seasonal variation of the decadal SST anomaly, despite controlling the upper-ocean thermal conditions on decadal time scales through the slow Rossby wave adjustment to the wind stress curl. When averaging over the entire KOE region, the contribution from the net sea surface heat flux was also no longer significantly detected. By examining the horizontal distributions of the local thermal damping rate, however, it was concluded that the wintertime decadal SST anomaly in the eastern KOE region was rather damped by the net sea surface heat flux. It was due to the fact that the anomalous local thermal damping of the SST anomaly resulting from the vertical entrainment in autumn was considerably strong enough to suppress the anomalous local atmospheric thermal forcing that acted to enhance the decadal SST anomaly.

scholarly journals Mechanisms of asymmetry in sea surface temperature anomalies associated with the Indian Ocean Dipole revealed by closed heat budget

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mai Nakazato ◽  
Shoichiro Kido ◽  
Tomoki Tozuka
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Indian Ocean Dipole ◽  
Heat Budget ◽  
Vertical Mixing ◽  
Sea Surface ◽  
Subsurface Temperature ◽  
Thermocline Feedback ◽  
The Indian Ocean ◽  
Sst Anomalies

AbstractThe Indian Ocean Dipole (IOD) is an interannual climate mode of the tropical Indian Ocean. Although it is known that negative sea surface temperature (SST) anomalies in the eastern pole during the positive IOD are stronger than positive SST anomalies during the negative IOD, no consensus has been reached on the relative importance of various mechanisms that contribute to this asymmetry. Based on a closed mixed layer heat budget analysis using a regional ocean model, here we show for the first time that the vertical mixing plays an important role in causing such asymmetry in SST anomalies in addition to the contributions from the nonlinear advection and the thermocline feedback proposed by previous studies. A decomposition of the vertical mixing term indicates that nonlinearity in the anomalous vertical temperature gradient associated with subsurface temperature anomalies and anomalous vertical mixing coefficients is the main driver of such asymmetry. Such variations in subsurface temperature are induced by the anomalous southeasterly trade winds along the Indonesian coast that modulate the thermocline depth through coastal upwelling/downwelling. Thus, the thermocline feedback contributes to the SST asymmetry not through the vertical advection as previously suggested, but via the vertical mixing.

scholarly journals The Obduction of Equatorial 13°C Water in the Pacific Identified by a Simulated Passive Tracer*

2010 ◽  
Vol 40 (10) ◽  
pp. 2282-2297 ◽  
Author(s):  
Tangdong Qu ◽  
Shan Gao ◽  
Ichiro Fukumori ◽  
Rana A. Fine ◽  
Eric J. Lindstrom
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Mixed Layer ◽  
Tropical Pacific ◽  
Sea Surface ◽  
Surface Mixed Layer ◽  
Passive Tracer ◽  
Eastern Tropical Pacific ◽  
Easterly Wind ◽  
The Pacific

Abstract The obduction of equatorial 13°C Water in the Pacific is investigated using a simulated passive tracer of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO). The result shows that the 13°C Water initialized in the region 8°N–8°S, 130°–90°W enters the surface mixed layer in the eastern tropical Pacific, mainly through upwelling near the equator, in the Costa Rica Dome, and along the coast of Peru. Approximately two-thirds of this obduction occurs within 10 years after the 13°C Water being initialized, with the upper portion of the water mass reaching the surface mixed layer in only about a month. The obduction of the 13°C Water helps to maintain a cool sea surface temperature year-round, equivalent to a surface heat flux of about −6.0 W m−2 averaged over the eastern tropical Pacific (15°S–15°N, 130°W–eastern boundary) for the period of integration (1993–2006). During El Niño years, when the thermocline deepens as a consequence of the easterly wind weakening, the obduction of the 13°C Water is suppressed, and the reduced vertical entrainment generates a warming anomaly of up to 10 W m−2 in the eastern tropical Pacific and in particular along the coast of Peru, providing explanations for the warming of sea surface temperature that cannot be accounted for by local winds alone. The situation is reversed during La Niña years.

scholarly journals What Controls Seasonal Evolution of Sea Surface Temperature in the Bay of Bengal? Mixed Layer Heat Budget Analysis Using Moored Buoy Observations Along 90°E

Oceanography ◽  
2016 ◽  
Vol 29 (2) ◽  
pp. 202-213 ◽  
Author(s):  
V.P. Thangaprakash ◽  
M.S. Girishkumar ◽  
K. Suprit ◽  
N. Suresh Kumar ◽  
Dipanjan Chaudhuri ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Mixed Layer ◽  
Bay Of Bengal ◽  
Heat Budget ◽  
Sea Surface ◽  
Seasonal Evolution ◽  
Budget Analysis ◽  
Mixed Layer Heat Budget ◽  
Moored Buoy

scholarly journals The Persistence of Winter Sea Surface Temperature in the North Atlantic

2003 ◽  
Vol 16 (9) ◽  
pp. 1364-1377 ◽  
Author(s):  
Gaëlle de Coëtlogon ◽  
Claude Frankignoul
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Mixed Layer ◽  
North Atlantic ◽  
Sea Surface ◽  
The North ◽  
Sst Anomaly ◽  
The North Atlantic ◽  
The Impact ◽  
Sst Anomalies

Abstract The impact of the seasonal variations of the mixed-layer depth on the persistence of sea surface temperature (SST) anomalies is studied in the North Atlantic, using observations. A significant recurrence of winter SST anomalies during the following winter occurs in most of the basin, but not in the subtropical area of strong subduction. When taking reemergence into account, the e-folding timescale of winter SST anomalies generally exceeds 1 yr, and is about 16 months for the dominant SST anomaly tripole. The influence of advection by the mean oceanic currents is investigated by allowing for a displacement of the maximum recurrent correlation and, alternatively, by considering the SST anomaly evolution along realistic mean displacement paths. Taking into account the nonlocality of the reemergence generally increases the wintertime persistence, most notably in the northern part of the domain. The passive response of the mixed layer to the atmospheric forcing thus has a red spectrum down to near-decadal frequencies.

Daily to Decadal Sea Surface Temperature Variability Driven by State-Dependent Stochastic Heat Fluxes

2006 ◽  
Vol 36 (10) ◽  
pp. 1940-1958 ◽  
Author(s):  
Philip Sura ◽  
Matthew Newman ◽  
Michael A. Alexander
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Mixed Layer ◽  
Multiplicative Noise ◽  
The State ◽  
Sea Surface ◽  
Sst Variability ◽  
State Dependent ◽  
Sst Anomalies

Abstract The classic Frankignoul–Hasselmann hypothesis for sea surface temperature (SST) variability of an oceanic mixed layer assumes that the surface heat flux can be simply parameterized as noise induced by atmospheric variability plus a linear temperature relaxation rate. It is suggested here, however, that rapid fluctuations in this rate, as might be expected, for example, from gustiness of the sea surface winds, are large enough that they cannot be ignored. Such fluctuations cannot be fully modeled by noise that is independent of the state of the SST anomaly itself. Rather, they require the inclusion of a state-dependent (i.e., multiplicative) noise term, which can be expected to affect both persistence and the relative occurrence of high-amplitude anomalies. As a test of this hypothesis, daily observations at several Ocean Weather Stations (OWSs) are examined. Significant skewness and kurtosis of the distributions of SST anomalies is found, which is shown to be consistent with a multiplicative noise model. The observed wintertime SST distribution at OWS P is reproduced using a single-column variable-depth mixed layer model; the resulting non-Gaussianity is found to be largely due to the state dependence of rapidly varying (effectively stochastic) sensible and latent heat flux anomalies. The authors’ model for the non-Gaussianity of anomalous SST variability (counterintuitively) implies that the multiplicative noise increases the persistence, predictability, and variance of midlatitude SST anomalies. The effect is strongest on annual and longer time scales and may, therefore, be important to the understanding and modeling of interannual and interdecadal SST and related climate variability.

scholarly journals Sea Surface Temperature Variability over the Tropical Indian Ocean during the ENSO and IOD Events in 2016 and 2017

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 587
Author(s):  
Sartaj Khan ◽  
Shengchun Piao ◽  
Guangxue Zheng ◽  
Imran Ullah Khan ◽  
David Bradley ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
El Nino ◽  
Indian Subcontinent ◽  
Tropical Indian Ocean ◽  
Sea Surface ◽  
La Nina ◽  
The Indian Ocean ◽  
Sst Anomalies

2016 and 2017 were marked by strong El Niño and weak La Niña events, respectively, in the tropical East Pacific Ocean. The strong El Niño and weak La Niña events in the Pacific significantly impacted the sea surface temperature (SST) in the tropical Indian Ocean (TIO) and were followed by extreme negative and weak positive Indian Ocean Dipole (IOD) phases in 2016 and 2017, which triggered floods in the Indian subcontinent and drought conditions in East Africa. The IOD is an irregular and periodic oscillation in the Indian Ocean, which has attracted much attention in the last two decades due to its impact on the climate in surrounding landmasses. Much work has been done in the past to investigate global climate change and its impact on the evolution of IOD. The dynamic behind it, however, is still not well understood. The present study, using various satellite datasets, examined and analyzed the dynamics behind these events and their impacts on SST variability in the TIO. For this study, the monthly mean SST data was provided by NOAA Optimum Interpolation Sea Surface Temperature (OISST). SST anomalies were measured on the basis of 30-year mean daily climatology (1981–2010). It was determined that the eastern and western poles of the TIO play quite different roles during the sequence of negative and positive IOD phases. The analysis of air-sea interactions and the relationship between wind and SST suggested that SST is primarily controlled by wind force in the West pole. On the other hand, the high SST that occurred during the negative IOD phase induced local convection and westerly wind anomalies via the Bjerknes feedback mechanism. The strong convection, which was confined to the (warm) eastern equatorial Indian Ocean was accompanied by east–west SST anomalies that drove a series of downwelling Kelvin waves that deepened the thermocline in the east. Another notable feature of this study was its observation of weak upwelling along the Omani–Arabian coast, which warmed the SST by 1 °C in the summer of 2017 (as compared to 2016). This warming led to increased precipitation in the Bay of Bengal (BoB) region during the summer of 2017. The results of the present work will be important for the study of monsoons and may be useful in predicting both droughts and floods in landmasses in the vicinity of the Indian Ocean, especially in the Indian subcontinent and East African regions.

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