Sea Surface Salinity Distribution in the Southern Ocean as Observed From Space

Since 2010, space missions dedicated to Sea Surface Salinity (SSS) have been providing observations with almost complete coverage of the global ocean and a resolution of about 45 km every 3 days. The European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) mission was the first orbiting radiometer to collect regular SSS observations from space. The Aquarius and SMAP (Soil Moisture Active-Passive) missions of the National Aeronautics and Space Administration (NASA) then reinforced the SSS observing system between mid-2011 and mid-2015 and since mid-2015, respectively.Using the most recent SSS Climate Change Initiative project dataset merging data from the 3 missions, this study investigates the SSS signal associated with mesoscale eddies in the Southern Ocean. Eddies location and characteristics are obtained from the daily v3 mesoscale eddy trajectory atlas produced by CLS. SSS anomalies along the eddies journey are computed and compared to Sea Surface Temperature (SST) anomalies (v4 Remote Sensing Systems) as well as the SubAntarctic Front (SAF) position (CTOH, LEGOS). The vertical structure of the eddies is further investigated using profiles from colocated Argo autonomous floats.&#160;This study highlights a robust signal in SSS depending on both the eddies rotation (cyclone/anticyclone) and latitudinal position with respect to the SAF. Moreover, this dependence is not found in SST. These observations reveal oceanic the interaction of eddies with the larger scale ocean water masses. SSS and SST anomalies composites indeed show different patterns either bi-poles linked with horizontal stirring of fronts, mono-poles from trapping water or vertical mixing changes, or a mix of the two.This analysis gives strong hints for the erosion of subsurface waters, such as mode waters, induced by enhanced mixing caused by the deep-reaching eddies of the southern ocean.

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Community review of Southern Ocean satellite data needs

Antarctic Science ◽

10.1017/s0954102016000390 ◽

2016 ◽

Vol 29 (2) ◽

pp. 97-138 ◽

Cited By ~ 10

Author(s):

A. Pope ◽

P. Wagner ◽

R. Johnson ◽

J.D. Shutler ◽

J. Baeseman ◽

...

Keyword(s):

Southern Ocean ◽

Satellite Data ◽

Marine Biology ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Starting Point ◽

Data Continuity ◽

Derived Data

AbstractThis review represents the Southern Ocean community’s satellite data needs for the coming decade. Developed through widespread engagement and incorporating perspectives from a range of stakeholders (both research and operational), it is designed as an important community-driven strategy paper that provides the rationale and information required for future planning and investment. The Southern Ocean is vast but globally connected, and the communities that require satellite-derived data in the region are diverse. This review includes many observable variables, including sea ice properties, sea surface temperature, sea surface height, atmospheric parameters, marine biology (both micro and macro) and related activities, terrestrial cryospheric connections, sea surface salinity, and a discussion of coincident andin situdata collection. Recommendations include commitment to data continuity, increases in particular capabilities (sensor types, spatial, temporal), improvements in dissemination of data/products/uncertainties, and innovation in calibration/validation capabilities. Full recommendations are detailed by variable as well as summarized. This review provides a starting point for scientists to understand more about Southern Ocean processes and their global roles, for funders to understand the desires of the community, for commercial operators to safely conduct their activities in the Southern Ocean, and for space agencies to gain greater impact from Southern Ocean-related acquisitions and missions.

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Modeling geologically abrupt climate changes in the Miocene

Climate of the Past Discussions ◽

10.5194/cpd-6-2687-2010 ◽

2010 ◽

Vol 6 (6) ◽

pp. 2687-2701

Author(s):

B. J. Haupt ◽

D. Seidov

Keyword(s):

Southern Ocean ◽

Climate Changes ◽

Computer Experiments ◽

Time Span ◽

Sea Surface ◽

Central American ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Salinity Changes ◽

Cooling Trend

Abstract. The gradual cooling of the Cenozoic, including the Miocene epoch, was punctuated by many geologically abrupt warming and cooling episodes – strong deviations from the cooling trend with time span of ten to hundred thousands of years. Our working hypothesis is that some of those warming episodes at least partially might have been caused by dynamics of the emerging Antarctic Ice Sheet, which, in turn, might have caused strong changes of sea surface salinity in the Miocene Southern Ocean. Feasibility of this hypothesis is explored in a series of coupled ocean-atmosphere computer experiments. The results suggest that relatively small and geologically short-lived changes in freshwater balance in the Southern Ocean could have significantly contributed to at least two prominent warming episodes in the Miocene. Importantly, the experiments also suggest that the Southern Ocean was more sensitive to the salinity changes in the Miocene than today, which can attributed to the opening of the Central American Isthmus as a major difference between the Miocene and the present-day ocean-sea geometry.

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Interrelationships of Sea Surface Salinity, Chlorophyll-α Concentration, and Sea Surface Temperature Near the Antarctic Ice Edge

Journal of Climate ◽

10.1175/jcli-d-20-0716.1 ◽

2021 ◽

pp. 1-50

Author(s):

Cynthia Garcia-Eidell ◽

Josefino C. Comiso ◽

Max Berkelhammer ◽

Larry Stock

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Ice Melt ◽

Biogeochemical Models ◽

Basin Scale

AbstractSatellite data can now provide a coherent picture of sea surface salinity (SSS), chlorophyll-α concentration (Chl?), sea surface temperature (SST), and sea ice cover across the Southern Ocean. The availability of these data at the basin scale enables novel insight into the physical and biological processes in an area that has historically been difficult to gather in situ data from. The analysis shows large regional and interannual variability of these parameters but also strong coherence across the Southern Ocean. The covariability of the parameters near the marginal ice zone shows a generally negative relationship between SSS and Chl??(r = -0.87). This may in part be attributed to the large seasonality of the variables, but analysis of data within the spring period (from November to December) shows similarly high correlation (r =-0.81). This is the first time that a large-scale robust connection between low salinity and high phytoplankton concentration during ice melt period has been quantified. Chlorophyll-α concentration is also well correlated with SST (r = 0.79) providing a potential indicator of the strength of the temperature limitation on primary productivity in the region. The observed correlation also varied regionally due to differences in ice melt patterns during spring and summer. Overall, this study provides new insights into the physical characteristics of the Southern Ocean as observed from space. In a continually warming and freshening Southern Ocean, the relationships observed here provide key data source for testing ocean biogeochemical models and assessing the effect of sea ice-ocean processes on primary production.

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Variability of Sea-Air Carbon Dioxide Flux in Autumn Across the Weddell Gyre and Offshore Dronning Maud Land in the Southern Ocean

Frontiers in Marine Science ◽

10.3389/fmars.2020.614263 ◽

2021 ◽

Vol 7 ◽

Author(s):

Margaret Ojone Ogundare ◽

Agneta Fransson ◽

Melissa Chierici ◽

Warren R. Joubert ◽

Alakendra N. Roychoudhury

Keyword(s):

Carbon Dioxide ◽

Southern Ocean ◽

Carbon Dioxide Flux ◽

Weddell Sea ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Study Region ◽

Entire Study ◽

Weddell Gyre

Sea surface fugacity of carbon dioxide (fCO2ssw) was measured across the Weddell gyre and the eastern sector in the Atlantic Southern Ocean in autumn. During the occupation between February and April 2019, the region of the study transect was a potential ocean CO2 sink. A net CO2 flux (FCO2) of −6.2 (± 8; sink) mmol m–2 d–1 was estimated for the entire study region, with the largest average CO2 sink of −10.0 (± 8) mmol m–2 d–1 in the partly ice-covered Astrid Ridge (AR) region near the coast at 68°S and −6.1 (± 8) mmol m–2d–1 was observed in the Maud Rise (MR) region. A CO2 sink was also observed south of 66°S in the Weddell Sea (WS). To assess the main drivers describing the variability of fCO2ssw, a correlation model using fCO2 and oxygen saturation was considered. Spatial distributions of the fCO2 saturation/O2 saturation correlations, described relative to the surface water properties of the controlling variables (chlorophyll a, apparent oxygen utilization (AOU), sea surface temperature, and sea surface salinity) further constrained the interplay of the processes driving the fCO2ssw distributions. Photosynthetic CO2 drawdown significantly offsets the influence of the upwelling of CO2-rich waters in the central Weddell gyre and enhanced the CO2 sink in the region. FCO2 of −6.9 mmol m–2 d–1 estimated for the Weddell gyre in this study was different from FCO2 of −2.5 mmol m–2 d–1 in autumn estimated in a previous study. Due to low CO2 data coverage during autumn, limited sea-air CO2 flux estimates from direct sea-surface CO2 observations particularly for the Weddell gyre region are available with which to compare the values estimated in this study. This highlights the importance of increasing seasonal CO2 observations especially during autumn/winter to improving the seasonal coverage of flux estimates in the seasonal sea ice-covered regions of the Southern Ocean.

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A Comparison of Satellite-Derived Sea Surface Salinity and Salt Fluxes in the Southern Ocean

Remote Sensing in Earth Systems Sciences ◽

10.1007/s41976-018-0001-5 ◽

2018 ◽

Vol 1 (1-2) ◽

pp. 1-13 ◽

Cited By ~ 2

Author(s):

Brady S. Ferster ◽

Bulusu Subrahmanyam

Keyword(s):

Southern Ocean ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Salinity

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Southern Ocean anthropogenic carbon sink constrained by sea surface salinity

Science Advances ◽

10.1126/sciadv.abd5964 ◽

2021 ◽

Vol 7 (18) ◽

pp. eabd5964

Author(s):

Jens Terhaar ◽

Thomas L. Frölicher ◽

Fortunat Joos

Keyword(s):

Southern Ocean ◽

Ocean Circulation ◽

Carbon Sink ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Anthropogenic Carbon ◽

Multimodel Ensembles ◽

Ocean Observations ◽

Emissions Scenario

The ocean attenuates global warming by taking up about one quarter of global anthropogenic carbon emissions. Around 40% of this carbon sink is located in the Southern Ocean. However, Earth system models struggle to reproduce the Southern Ocean circulation and carbon fluxes. We identify a tight relationship across two multimodel ensembles between present-day sea surface salinity in the subtropical-polar frontal zone and the anthropogenic carbon sink in the Southern Ocean. Observations and model results constrain the cumulative Southern Ocean sink over 1850-2100 to 158 ± 6 petagrams of carbon under the low-emissions scenario Shared Socioeconomic Pathway 1-2.6 (SSP1-2.6) and to 279 ± 14 petagrams of carbon under the high-emissions scenario SSP5-8.5. The constrained anthropogenic carbon sink is 14 to 18% larger and 46 to 54% less uncertain than estimated by the unconstrained estimates. The identified constraint demonstrates the importance of the freshwater cycle for the Southern Ocean circulation and carbon cycle.

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Matchup Characteristics of Sea Surface Salinity Using a High-Resolution Ocean Model

Remote Sensing ◽

10.3390/rs13152995 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2995

Author(s):

Frederick M. Bingham ◽

Severine Fournier ◽

Susannah Brodnitz ◽

Karly Ulfsax ◽

Hong Zhang

Keyword(s):

High Resolution ◽

Time Window ◽

Single Point ◽

Ocean Model ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Argo Floats ◽

Statistical Measures ◽

Salinity Difference

Sea surface salinity (SSS) satellite measurements are validated using in situ observations usually made by surfacing Argo floats. Validation statistics are computed using matched values of SSS from satellites and floats. This study explores how the matchup process is done using a high-resolution numerical ocean model, the MITgcm. One year of model output is sampled as if the Aquarius and Soil Moisture Active Passive (SMAP) satellites flew over it and Argo floats popped up into it. Statistical measures of mismatch between satellite and float are computed, RMS difference (RMSD) and bias. The bias is small, less than 0.002 in absolute value, but negative with float values being greater than satellites. RMSD is computed using an “all salinity difference” method that averages level 2 satellite observations within a given time and space window for comparison with Argo floats. RMSD values range from 0.08 to 0.18 depending on the space–time window and the satellite. This range gives an estimate of the representation error inherent in comparing single point Argo floats to area-average satellite values. The study has implications for future SSS satellite missions and the need to specify how errors are computed to gauge the total accuracy of retrieved SSS values.

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Sea Surface Salinity Response to Tropical Cyclones Based on Satellite Observations

Remote Sensing ◽

10.3390/rs13030420 ◽

2021 ◽

Vol 13 (3) ◽

pp. 420

Author(s):

Jingru Sun ◽

Gabriel Vecchi ◽

Brian Soden

Keyword(s):

Tropical Cyclones ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Translation Speed ◽

Salinity Stratification ◽

Left Hand ◽

In Situ Data ◽

Salinity Response ◽

The Right

Multi-year records of satellite remote sensing of sea surface salinity (SSS) provide an opportunity to investigate the climatological characteristics of the SSS response to tropical cyclones (TCs). In this study, the influence of TC winds, rainfall and preexisting ocean stratification on SSS evolution is examined with multiple satellite-based and in-situ data. Global storm-centered composites indicate that TCs act to initially freshen the ocean surface (due to precipitation), and subsequently salinify the surface, largely through vertical ocean processes (mixing and upwelling), although regional hydrography can lead to local departure from this behavior. On average, on the day a TC passes, a strong SSS decrease is observed. The fresh anomaly is subsequently replaced by a net surface salinification, which persists for weeks. This salinification is larger on the right (left)-hand side of the storm motion in the Northern (Southern) Hemisphere, consistent with the location of stronger turbulent mixing. The influence of TC intensity and translation speed on the ocean response is also examined. Despite having greater precipitation, stronger TCs tend to produce longer-lasting, stronger and deeper salinification especially on the right-hand side of the storm motion. Faster moving TCs are found to have slightly weaker freshening with larger area coverage during the passage, but comparable salinification after the passage. The ocean haline response in four basins with different climatological salinity stratification reveals a significant impact of vertical stratification on the salinity response during and after the passage of TCs.

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Using Saildrones to Validate Arctic Sea-Surface Salinity from the SMAP Satellite and from Ocean Models

Remote Sensing ◽

10.3390/rs13050831 ◽

2021 ◽

Vol 13 (5) ◽

pp. 831

Author(s):

Jorge Vazquez-Cuervo ◽

Chelle Gentemann ◽

Wenqing Tang ◽

Dustin Carroll ◽

Hong Zhang ◽

...

Keyword(s):

Arctic Ocean ◽

Sea Surface ◽

Sea Surface Salinity ◽

The Arctic ◽

Future Research ◽

Surface Salinity ◽

Cold Temperatures ◽

Yukon River ◽

Arctic Sea ◽

The Arctic Ocean

The Arctic Ocean is one of the most important and challenging regions to observe—it experiences the largest changes from climate warming, and at the same time is one of the most difficult to sample because of sea ice and extreme cold temperatures. Two NASA-sponsored deployments of the Saildrone vehicle provided a unique opportunity for validating sea-surface salinity (SSS) derived from three separate products that use data from the Soil Moisture Active Passive (SMAP) satellite. To examine possible issues in resolving mesoscale-to-submesoscale variability, comparisons were also made with two versions of the Estimating the Circulation and Climate of the Ocean (ECCO) model (Carroll, D; Menmenlis, D; Zhang, H.). The results indicate that the three SMAP products resolve the runoff signal associated with the Yukon River, with high correlation between SMAP products and Saildrone SSS. Spectral slopes, overall, replicate the −2.0 slopes associated with mesoscale-submesoscale variability. Statistically significant spatial coherences exist for all products, with peaks close to 100 km. Based on these encouraging results, future research should focus on improving derivations of satellite-derived SSS in the Arctic Ocean and integrating model results to complement remote sensing observations.

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