scholarly journals Upper-Ocean Salinity Variability in the Tropical Pacific: Case Study for Quasi-Decadal Shift during the 2000s Using TRITON Buoys and Argo Floats

2013 ◽  
Vol 26 (20) ◽  
pp. 8126-8138 ◽  
Author(s):  
Takuya Hasegawa ◽  
Kentaro Ando ◽  
Iwao Ueki ◽  
Keisuke Mizuno ◽  
Shigeki Hosoda
Keyword(s):  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Sea Surface ◽  
Upper Ocean ◽  
Salinity Variability ◽  
Ocean Salinity ◽  
Central Equatorial Pacific ◽  
Western Equatorial Pacific ◽  
Sea Surface Temperature Anomalies ◽  
The Tropical Pacific

Abstract Upper-ocean salinity variation in the tropical Pacific is investigated during the 2000s, when Triangle Trans-Ocean Buoy Network (TRITON) buoys and Argo floats were deployed and more salinity data were observed than in previous periods. This study focuses on upper-ocean salinity variability during the warming period of El Niño–Southern Oscillation (ENSO)-like quasi-decadal (QD)-scale sea surface temperature anomalies over the central equatorial Pacific (January 2002–December 2005; hereafter “warm QD phase”). It is shown that strong negative salinity anomalies occur in the western tropical Pacific and the off-equatorial Pacific in the upper ocean at depths less than 80 m, showing a horseshoe-like pattern centered at the western tropical Pacific during the warm QD phase. TRITON mooring buoy data in the western equatorial Pacific show that low-salinity and high-temperature water could be transported eastward from the western equatorial Pacific to the central equatorial Pacific during the warm QD phase. Similar patterns, but with the opposite sign of salinity anomalies, appear in the cold QD phase during January 2007–December 2009 with negative sea surface temperature anomalies over the central equatorial Pacific. It is suggested that effects from zonal salinity advection and precipitation could contribute to the generation of the salinity variations in the western equatorial Pacific for QD phases during the 2000s. On the other hand, the contribution of meridional salinity advection is much less than that of zonal salinity advection. In addition, El Niño Modoki and La Niña events could affect salinity changes for warm and cold QD phases via interannual-scale zonal salinity advection variations in the western equatorial Pacific during the 2000s.

scholarly journals Effects of Salinity Variability on Recent El Niño Events

Atmosphere ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 475 ◽  
Author(s):  
Hai Zhi ◽  
Rong-Hua Zhang ◽  
Pengfei Lin ◽  
Shiwei Shi
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
El Niño ◽  
El Nino ◽  
Equatorial Pacific ◽  
Sea Surface ◽  
Surface Salinity ◽  
Central Pacific ◽  
Salinity Variability ◽  
Central Equatorial Pacific

Ocean salinity variability provides a new way to study the evolution of the the El Niño-Southern Oscillation (ENSO). Comparisons between the salinity variation and related processes responsible for sea surface temperature anomaly (SSTA) were extensively examined for the two strong El Niño (EN) events in 1997/1998 and 2015/2016, and a special EN event in 2014/2015. The results show that the development of EN is significantly correlated with a sea surface salinity anomaly (SSSA) in the tropical western-central Pacific. In the spring of 1997 and 2015 with strong EN events, the western-central equatorial Pacific exhibited significant negative SSSA that propagated eastward to the west of the dateline. The negative SSSA induced increased barrier layer thickness (BLT) which enhanced sea surface temperature (SST) warming in the tropical central Pacific. In contrast, although a negative SSSA occurred during April of the 2014/2015 weak EN event in the western-central equatorial Pacific, this SSSA was mainly confined to between 160° E and 180° E without significant eastward movement, resulting in a weakened BLT thickening process and a weak modulation effect on SST. We also confirm that the surface forcing associated with fresh water flux (FWF: evaporation (E) minus precipitation (P)) plays a prominent role in the surface salinity tendency in the tropical Pacific during EN events. Moreover, the negative FWF anomaly leads a strong negative SSSA by two months. Compared with the two strong ENs, the early negative FWF anomaly in the weak 2014/2015 EN did not present distinct development and eastward propagation and weakened rapidly in the summer of 2015. We demonstrate that change in salinity can modulate the ENSO, and the variation of SSSA and associated physical processes in the tropical western-central Pacific and could be used as an indicator for predicting the development of ENSO.

scholarly journals Tropical Pacific Ocean Dynamical Response to Short-Term Sulfate Aerosol Forcing

2019 ◽  
Vol 32 (23) ◽  
pp. 8205-8221
Author(s):  
Tarun Verma ◽  
R. Saravanan ◽  
P. Chang ◽  
S. Mahajan
Keyword(s):  
Pacific Ocean ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Sulfate Aerosol ◽  
Upper Ocean ◽  
Sulfate Aerosols ◽  
Tropical Pacific Ocean ◽  
Aerosol Forcing ◽  
Ocean Atmosphere ◽  
The Tropical Pacific

Abstract The large-scale and long-term climate impacts of anthropogenic sulfate aerosols consist of Northern Hemisphere cooling and a southward shift of the tropical rain belt. On interannual time scales, however, the response to aerosols is localized with a sizable imprint on local ocean–atmosphere interaction. A large concentration of anthropogenic sulfates over Asia may impact ENSO by modifying processes and interactions that generate this coupled ocean–atmosphere variability. Here, we use climate model experiments with different degrees of ocean–atmosphere coupling to study the tropical Pacific response to an abrupt increase in anthropogenic sulfates. These include an atmospheric general circulation model (GCM) coupled to either a full-ocean GCM or a slab-ocean model, or simply forced by climatology of sea surface temperature. Comparing the responses helps differentiate between the fast atmospheric and slow ocean-mediated responses, and highlights the role of ocean–atmosphere coupling in the latter. We demonstrate the link between the Walker circulation and the equatorial Pacific upper-ocean dynamics in response to increased sulfate aerosols. The local surface cooling due to sulfate aerosols emitted over the Asian continent drives atmospheric subsidence over the equatorial west Pacific. The associated anomalous circulation imparts westerly momentum to the underlying Pacific Ocean, leading to an El Niño–like upper-ocean response and a transient warming of the east equatorial Pacific Ocean. The oceanic adjustment eventually contributes to its decay, giving rise to a damped oscillation of the tropical Pacific Ocean in response to abrupt anthropogenic sulfate aerosol forcing.

Upper ocean salinity balance in the western equatorial Pacific

1998 ◽  
Vol 103 (C12) ◽  
pp. 27567-27587 ◽  
Author(s):  
Meghan F. Cronin ◽  
Michael J. McPhaden
Keyword(s):  
Equatorial Pacific ◽  
Upper Ocean ◽  
Ocean Salinity ◽  
Western Equatorial Pacific ◽  
Salinity Balance

Observed Strengthening of the Zonal Sea Surface Temperature Gradient across the Equatorial Pacific Ocean*

2009 ◽  
Vol 22 (16) ◽  
pp. 4316-4321 ◽  
Author(s):  
Kristopher B. Karnauskas ◽  
Richard Seager ◽  
Alexey Kaplan ◽  
Yochanan Kushnir ◽  
Mark A. Cane
Keyword(s):  
Pacific Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Ocean Dynamics ◽  
Sea Surface ◽  
Recent Attempt ◽  
Sst Gradient ◽  
The Tropical Pacific

Abstract Decadal variations of very small amplitude [∼0.3°C in sea surface temperature (SST)] in the tropical Pacific Ocean, the genesis region of the interannual El Niño–Southern Oscillation (ENSO) phenomenon, have been shown to have powerful impacts on global climate. Future projections from different climate models do not agree on how this critical feature will change under the influence of anthropogenic forcing. A number of attempts have been made to resolve this issue by examining observed trends from the 1880s to the present, a period of rising atmospheric concentrations of greenhouse gases. A recent attempt concluded that the three major datasets disagreed on the trend in the equatorial gradient of SST. Using a corrected version of one of these datasets, and extending the analysis to the seasonal cycle, it is shown here that all agree that the equatorial Pacific zonal SST gradient has strengthened from 1880 to 2005 during the boreal fall when this gradient is normally strongest. This result appears to favor a theory for future changes based on ocean dynamics over one based on atmospheric energy considerations. Both theories incorporate the expectation, based on ENSO theory, that the zonal sea level pressure (SLP) gradient in the tropical Pacific is coupled to SST and should therefore strengthen along with the SST gradient. While the SLP gradient has not strengthened, it is found that it appears to have weakened only during boreal spring, consistent with the SST seasonal trends. Most of the coupled models included in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report underestimate the strengthening SST gradient in boreal fall, and show almost no change in the SLP gradient in any season. The observational analyses herein suggest that both theories are at work but with relative strengths that vary seasonally, and that the two theories need not be inconsistent with each other.

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