Sea Surface Salinity Change since 1950: Internal Variability Versus Anthropogenic Forcing

AbstractUsing an eastern tropical Pacific pacemaker experiment called the Pacific Ocean–Global Atmosphere (POGA) run, this study investigated the internal variability in sea surface salinity (SSS) and its impacts on the assessment of long-term trends. By constraining the eastern tropical Pacific sea surface temperature variability with observations, the POGA experiment successfully simulated the observed variability of SSS. The long-term trend in POGA SSS shows a general pattern of salty regions becoming saltier (e.g., the northern Atlantic) and fresh regions becoming fresher, which agrees with previous studies. The 1950-2012 long-term trend in SSS is modulated by the internal variability associated with the Interdecadal Pacific Oscillation (IPO). Due to this variability, there are some regional discrepancies in the SSS 1950–2012 long-term change between POGA and the free-running simulation forced with historical radiative forcing, especially for the western tropical Pacific and southeastern Indian Ocean. Our analysis shows that the tropical Pacific cooling and intensified Walker Circulation caused the SSS to increase in the western tropical Pacific and decrease in the southeastern Indian Ocean during the 20-year period of 1993–2012. This decadal variability has led to large uncertainties in the estimation of radiative-forced trends on a regional scale. For the 63-year period of 1950–2012, the IPO caused an offset of ∼40% in the radiative-forced SSS trend in the western tropical Pacific and ∼170% enhancement in the trend in the southeastern Indian Ocean. Understanding and quantifying the contribution of internal variability to SSS trends help improve the skill for estimates and prediction of salinity/water cycle changes.

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A coral δ18O record of ENSO driven sea surface salinity variability in Fiji (south -western tropical Pacific)

Geophysical Research Letters ◽

10.1029/2000gl011843 ◽

2000 ◽

Vol 27 (23) ◽

pp. 3897-3900 ◽

Cited By ~ 59

Author(s):

Nolwenn Le Bec ◽

Anne Julliet-Leclerc ◽

Thierry Corrège ◽

Dominique Blamart ◽

Thierry Delcroix

Keyword(s):

Tropical Pacific ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Western Tropical Pacific ◽

Salinity Variability

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Regional difference of sea surface salinity variations in the western tropical pacific

Journal of Oceanography ◽

10.1007/s10872-021-00598-2 ◽

2021 ◽

Author(s):

Yating Ouyang ◽

Yuhong Zhang ◽

Jianwei Chi ◽

Qiwei Sun ◽

Yan Du

Keyword(s):

Regional Difference ◽

Low Frequency ◽

Tropical Pacific ◽

Sea Surface ◽

Sea Surface Salinity ◽

Freshwater Flux ◽

Surface Salinity ◽

Ocean Reanalysis ◽

Western Tropical Pacific ◽

Freshwater Forcing

AbstractRegional difference of sea surface salinity (SSS) variations in the western tropical Pacific is investigated with Ocean Reanalysis System 5 datasets. Three robust zonal bands of SSS variations have been identified in the northwestern tropical Pacific (NWTP), the western equatorial tropical Pacific (WEqP), and the southwestern tropical Pacific (SWTP), respectively. SSS in the WEqP and the SWTP has a strong interannual variability that is related to ENSO. In the WEqP, SSS variations are mainly controlled by anomalous freshwater flux, while in the SWTP they are governed by both freshwater forcing and oceanic processes. In the NWTP, SSS variations present a low-frequency variability that is correlated with Interdecadal Pacific Oscillation (IPO), which is mostly dominated by the freshwater flux and strongly adjusted by the ocean advection and mixed layer changes. After removing interannual signals, the SSS in all three regions are highly related to IPO, indicating that IPO has a general influence on the western tropical Pacific.

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Towards long-term (2002-present) reconstruction of northern Indian Ocean Sea Surface Salinity based on AMSR-E and L-band Radiometer data

10.5194/egusphere-egu21-10945 ◽

2021 ◽

Author(s):

Marie Montero ◽

Nicolas Reul ◽

Clément de Boyer Montégut ◽

Jérôme Vialard ◽

Jean Tournadre

Keyword(s):

Indian Ocean ◽

North Indian Ocean ◽

Sea Surface ◽

Sea Surface Salinity ◽

Northern Indian Ocean ◽

Surface Salinity ◽

The North ◽

X Band ◽

L Band

Salinity plays an important role in the oceanic circulation, because of its impact on pressure gradients and the upper ocean stability. This is particularly the case in the North Indian Ocean where freshwater inputs from monsoonal rain and rivers into the Bay of Bengal and strong evaporation in the Arabian Sea leads to high salinity contrasts, and a strong variability tied to the large monsoonal currents seasonal cycle.In situ salinity data is however too sparse to allow a detailed study of the contrasted and variable Northern Indian Ocean Sea Surface Salinity (SSS). This situation has changed since the launch of SMOS in 2009, and the advent of L-band-based SSS remote sensing with a much higher spatio-temporal sampling. Here, we explore the capacity of C and X-band measurements, such as those of AMSR-E (May 2002-October 2011) to reconstruct Northern Indian Ocean SSS prior 2009. Previous studies have indeed demonstrated the ability of C- and X-band products to reconstruct SSS in high-contrast regions like river estuaries, especially at high Sea Surface Temperature (SST), like in the Northern Indian Ocean.&#160;We are currently focusing on the development of the algorithm to reconstruct salinity from the C- and X-band data of AMSR-E. The ESA Climate Change Initiative (CCI) SSS dataset build from a merge of SMOS, Aquarius and SMAP data, provides a reference SSS that is both used for training our algorithm and for validation, over the common AMSR-E and CCI period (January 2010 to October 2011).Our first results are encouraging: spatial contrast between the low-SSS values close to estuaries and along the coast and higher SSS in the middle of the Bay of Bengal as well as some aspects of the seasonal cycle are reproduced. However, spurious signals linked to either radio frequency interferences still need to be filtered out and signals associated with other residual geophysical contributions (e.g. wind, atmospheric vapor content) need to be better estimated. The long-term goal of this work is to merge the C-, X-, and L-band data with in-situ measurements and thus provide a long-term reconstruction of monthly SSS in the north Indian Ocean with a ~50km resolution.

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Isolation of sea surface salinity maps on various timescales in the tropical Pacific Ocean

Journal of Oceanography ◽

10.1007/s10872-012-0126-8 ◽

2012 ◽

Vol 68 (5) ◽

pp. 687-701 ◽

Cited By ~ 6

Author(s):

Jian Chen ◽

Ren Zhang ◽

Huizan Wang ◽

Yuzhu An ◽

Peng Peng ◽

...

Keyword(s):

Pacific Ocean ◽

Tropical Pacific ◽

Sea Surface ◽

Sea Surface Salinity ◽

Tropical Pacific Ocean ◽

Surface Salinity ◽

The Tropical Pacific

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Assessing Sea Surface Salinity Derived by Aquarius in the Indian Ocean

IEEE Geoscience and Remote Sensing Letters ◽

10.1109/lgrs.2013.2277391 ◽

2014 ◽

Vol 11 (4) ◽

pp. 719-722 ◽

Cited By ~ 7

Author(s):

Smitha Ratheesh ◽

Rashmi Sharma ◽

Rajesh Sikhakolli ◽

Raj Kumar ◽

Sujit Basu

Keyword(s):

Indian Ocean ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Salinity ◽

The Indian Ocean

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Influence of the Madden-Julian Oscillation on sea surface salinity in the Indian Ocean

Geophysical Research Letters ◽

10.1029/2011gl049047 ◽

2011 ◽

Vol 38 (17) ◽

pp. n/a-n/a ◽

Cited By ~ 16

Author(s):

Gary Grunseich ◽

Bulusu Subrahmanyam ◽

Anthony Arguez

Keyword(s):

Indian Ocean ◽

Sea Surface ◽

Sea Surface Salinity ◽

Madden Julian Oscillation ◽

Surface Salinity ◽

The Indian Ocean

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Meridional Distribution of Surface CO2 along 67°E of the Indian Ocean

10.5194/egusphere-egu2020-20849 ◽

2020 ◽

Author(s):

Dong-Jin Kang ◽

Sang-Hwa Choi ◽

Daeyeon Kim ◽

Gyeong-Mok Lee

Keyword(s):

Indian Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Seawater ◽

Surface Salinity ◽

The North ◽

The Indian Ocean ◽

North And South

Surface seawater carbon dioxide was observed from 3 &#176;S to 27 &#176;S along 67 &#176;E of the Indian Ocean in April 2018 and 2019. Partial pressure of CO2(pCO2) in the surface seawater and the atmosphere were observed every two minutes using an underway CO2 measurement system (General Oceanics Model 8050) installed on R/V Isabu. Surface water temperature and salinity were measured as well. The pCO2 was measured using Li-7000 NDIR. Standard gases were measured every 8 hours in five classes with concentrations of 0 &#181;atm, 202 &#181;atm, 350 &#181;atm, 447 &#181;atm, and 359.87 &#181;atm. The fCO2 of atmosphere remained nearly constant at 387 &#177; 2 &#181;atm, but the surface seawater fCO2 peaked at about 3 &#176;S and tended to decrease toward the north and south. The distribution of fCO2 in surface seawater according to latitude tends to be very similar to that of sea surface temperature. In order to investigate the factors that control the distribution of fCO2 in surface seawater, we analyzed the sea surface temperature, sea surface salinity, and other factors. The effects of salinity are insignificant, and the surface fCO2 distribution is mainly controlled by sea surface temperature and other factors that can be represented mainly by biological activity and mixing.

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