Near-surface Salinity Research Articles

Summer Chukchi Sea Near-Surface Salinity Variability in Satellite Observations and Ocean Models

Summer Chukchi Sea Near-Surface Salinity Variability in Satellite Observations and Ocean Models

The coupling of winds, ocean turbulence, and High Salinity Shelf Water in the Terra Nova Bay Polynya

The Terra Nova Bay (TNB) Polynya in the Western Ross Sea of Antarctica is a major producer of High Salinity Shelf Water (HSSW), a precursor to Antarctica Bottom Water (AABW). Processes occurring in and around the polynya can therefore effect change in the lower limb of overturning circulation in this region. Here, we use data from a densely-instrumented upper-ocean mooring, deployed for 1 year in a region of active HSSW formation within TNB, to examine the coupling of surface brine rejection and vertical mixing to katabatic wind forcing. We find a high correlation between salinity and winds during the wintertime HSSW production season at the mooring site, with a lag-response of 20 h in near-surface (∼47 m) salinity to winds measured at the nearby Automatic Weather Station (AWS) Manuela. Salinity and temperature measurements show a fully destratified water column by June, with a lag-response of near-seabed (∼360 m) salinity to near-surface salinity of just 5 h. Measurements of turbulent kinetic energy (TKE) dissipation rate (ɛ) from moored pulse-coherent acoustic Doppler current profilers (ADCPs) show general agreement with classic boundary layer scaling (BLS), and calculations of a vertical mixing timescale using the Obukhov length scale average to ∼2.5 h during austral winter, consistent with the 5-h lag time observed in the salinity data. Comparisons to data from concurrent mooring deployments along the southern boundary of TNB, as well as to previously published assessments of model simulations and data from Climatic Long-term Interaction for the Mass-balance in Antarctica (CLIMA) moorings, allow us to explore spatial variability in the coupling of winds and salinity across TNB and to speculate on possible HSSW circulation pathways.

A statistical analysis of tropical salinity and its relationship to SST, highlighting two contrasting areas

Tropical air-sea interactions, near-surface salinity (Ss), and sea surface temperature (SST) fluctuations are studied via ocean reanalysis products in the period 1980–2020. The statistical work considers how the net heat and water balance affects mixed layer depth (MLD) and coupling between the upper ocean and atmosphere. Field correlations of Ss – SST exhibit significant negative values in tropical latitudes 10S-15 N, between the semi-permanent marine anticyclones and the equatorial trough. Highlighting contrasts in two areas: the tropical east Atlantic and subtropical southwest Indian Ocean, annual cycles, inter-annual fluctuations of 6 – 8 yr, and long-term downward trends of Ss emerge. The SW Indian Ocean exhibits large swings of net heat and water balance as the monsoon reverses, and steady running-correlations of Ss and SST. The E Atlantic has a subdued annual cycle, and running-correlations are weak and unsteady. In both areas the Ss lags SST by a month. A fresh minus salty composite analysis reveals that the two contrasting areas respond to opposing phases of the Southern Oscillation: E Atlantic (La Nina) and SW Indian (El Nino). Projected long-term trends for increased tropical marine rainfall could be neutralized by declining runoff from continental monsoons. Statistical outcomes infer that a 0.1 ppt reduction of near-surface salinity leads to a 5 m reduction of MLD and a 0.4 C increase of tropical SST, contributing to deeper atmospheric convection. Limitations of the study derive from inferences based on infrequent salinity measurements.

Automatic Detection of Rainfall at Hourly Time Scales from Mooring Near-Surface Salinity in the Eastern Tropical Pacific

Abstract We explore the use of ocean near-surface salinity (NSS), that is, salinity at 1-m depth, as a rainfall occurrence detector for hourly precipitation using data from the Salinity Processes in the Upper-Ocean Regional Studies–2 (SPURS-2) mooring at 10°N, 125°W. Our proposed unsupervised learning algorithm consists of two stages. First, an empirical quantile-based identification of dips in NSS enables us to capture most events with hourly averaged rainfall rate of >5 mm h−1. Overestimation of precipitation duration is then corrected locally by fitting a parametric model based on the salinity balance equation. We propose a local precipitation model composed of a small number of calibration parameters representing individual rainfall events and their location in time. We show that unsupervised rainfall detection can be formulated as a statistical problem of predicting these variables from NSS data. We present our results and provide a validation technique based on data collected at the SPURS-2 mooring. Significance Statement Continuous monitoring of precipitation in the ocean is challenging when a physical rain gauge is not available in the region of interest. Indirect detection of precipitation using available data, such as changes in ocean near-surface salinity (NSS) can be used to construct a virtual rainfall detector. We propose to combine data-based and model-based methods to detect rainfall without the use of a physical rain gauge. We use NSS and precipitation data from a mooring in the eastern tropical Pacific Ocean to develop and test the method.

Mineralogical Composition of Some Iraqi Soil Samples

Twenty five soil samples were collected from various parts of uncultivated areas in Iraq including Rabe'a, Mosul, Hatra, Beygee, Balad, Radhwnaia, Abu Graib, Wasit, Anbar and Basrah. These samples were examined by XRD to determine the mineral constituents. Clay fractions were separated for clay mineralogy.
 The results showed that the clay minerals represent about 40% of the mineral constituents of the samples, dominated by montmorillonite, illite, palygorskite and chlorite having various proportions. The non-clay minerals are represented by calcite and dolomite which present as detrital grains and representing about 32% of the mineral constituents. Quartz comes with about 22% and feldspars with about 5%. The water-soluble salts in the soil samples varied according to the sampling location and represented about 0.3% on average, increasing from north to south. 
 The study showed the relation of the soil mineralogy with source rocks, and the most of the Iraqi soils are the results of erosion, weathering and transported by rivers. The authigenic minerals are locally precipitated from near-surface saline ground waters. 

Characterizing near-surface salinity variability in the northern Bay of Bengal and its potential drivers during extreme freshening years of the 2011–2019 period

Northern Bay of Bengal (BoB) receives a significant amount of freshwater, from precipitation and river discharge, which makes it comparatively low saline, specifically during August/September. However, the factors that determine the dispersal of this freshwater within the BoB remain relatively less addressed. Analysis of the near-surface salinity data from a moored buoy located in the northern BoB during 2011–2019 supplemented with satellite and model data showed prominent interannual variability viz. time of occurrence, persistence and magnitude of freshening. The surface salinity exhibit significant lowering during 2011, 2015 and 2017 with unique prolonged freshening in 2017. The offshore advection of low salinity water is initiated with sustained low wind stress further favoured by existing surface circulation and mesoscale eddies contributing to the unique characteristics. In addition, the maximum freshening observed in 2011 coincides with positive Indian Ocean Dipole event, whereas that of the prolonged freshening in 2017 is favored with anomalously low wind stress.

Impacts of evaporation and inundation on near-surface salinity at a coastal wetland park

Salinization is one of the main causes of conversion between different ecosystems and landuse functions in coastal wetlands. In this paper, we studied the spatiotemporal dynamics of soil moisture and salinity in a reclaimed national wetland park in Guangdong Province, China. We found that diel evaporation affected soil water up to 40 cm deep. Extreme rainfall only increased topsoil moisture with limited leaching effects on soil salinity. Salt accumulation occurred between 40 and 70 cm depth in rainy season, lasting until the end of monitoring period. Whereas the topsoil was salinized between land-surface to 30 cm deep in dry season, which was recovered after rainfall. This result suggested that the force balance between capillarity and gravity created a relative stable saline layer which was not flushed out during inundation. Therefore, considering these site-specific features could lead to the improved understanding of the migration of salinity in the soil profiles.

Variability of Near-Surface Salinity in the Nordic Seas Over the Past Three Decades (1991-2019)

The Nordic Seas have been widely implicated by deep water formation as a part of Atlantic Meridional Overturning Circulation. This study explores the spatiotemporal variations in the near-surface salinity over the Nordic Seas associated with surface freshening factors by using monthly TOPAZ4 reanalysis data from 1991 to 2019. We first show that reliability of TOPAZ4 data compared to the salinity products of other reanalysis data, satellite data, and in-situ measurements in the Nordic Seas. The salinity variability was larger in the Greenland Sea (GS) than in the Norwegian Sea (NS) on both time scales of seasonal and interannual. The seasonal change of GS salinity was coincident with the seasonality of sea ice extent. The longer-time variations are decomposed by empirical orthogonal function (EOF) analysis. The GS salinity is mainly affected by current advection (29%) and sea ice extent (11%). The interannual response of salinity to the sea ice extent over the GS differs by season. NS salinity variability responds to the strength of the Subpolar Gyre associated with a large-scale atmospheric system that caused the freshening event in the mid-1990s. The propagation of the northward Atlantic Water core is observed over the period of about 3 years from the Faroe Shetland Channel to the Fram Strait at a speed of 2.6-6.5° year-1. Other freshening factors such as sea ice export from the Arctic, freshwater flux at the Fram Strait, and net precipitation are also discussed. For the past three decades, the continuous trend appeared only in the sea ice extent, which might be a signal of climate changes over high latitude. However, there was no significant trend other than the periodic change in a few years to the decadal time scale in the salinity of GS and NS. As preconditioning for deep convection, near-surface salinity within Greenland Sea Gyre was influenced by salinity fluctuation in both GS and NS.

JCOPE-FGO: an eddy-resolving quasi-global ocean reanalysis product

In the present research, we provide a brief description and assessment of the oceanic fields analyzed in the newly developed eddy-resolving quasi-global ocean reanalysis product, named the Japan Coastal Ocean Predictability Experiments-Forecasting Global Ocean (JCOPE-FGO). This product covers the quasi-global ocean with a horizontal resolution of 0.1° × 0.1°. Validations of analyzed temperature and salinity fields by JCOPE-FGO against in situ observations revealed that our product can capture various aspects of observed hydrographic structures in the world ocean, including frontal structures near the surface and thermohaline properties of water masses, as well as their spatiotemporal variability. Furthermore, we have assessed dynamical fields analyzed in JCOPE-FGO using satellite altimeters and surface drifters, and found that our product can represent the mean state and variability of the upper ocean circulation in many regions. A notable feature of JCOPE-FGO is the inclusion of an updated global river runoff, and impacts of river forcing have been assessed by an additional reanalysis experiment without river forcing. We found that the removal of continental river discharge leads to dramatic changes in the near-surface salinity and related fields around river mouths of large rivers, but large changes are mostly confined to narrow regions near the coast. As an example of the substantial impact of river runoff, we discuss the dispersion of low-salinity water from the Mississippi river to the Gulf of Mexico: a comparison between the analyzed salinity fields from both reanalysis products with those from satellite observations demonstrated that the inclusion of river runoff is essential for an accurate representation of its seasonal variability. Several key issues that warrant further improvements are discussed for future development.

Increasing stratification as observed by satellite sea surface salinity measurements

Changes in the Earth’s water cycle can be estimated by analyzing sea surface salinity. This variable reflects the balance between precipitation and evaporation over the ocean, since the upper layers of the ocean are the most sensitive to atmosphere–ocean interactions. In situ measurements lack spatial and temporal synopticity and are typically acquired at few meters below the surface. Satellite measurements, on the contrary, are synoptic, repetitive and acquired at the surface. Here we show that the satellite-derived sea surface salinity measurements evidence an intensification of the water cycle (the freshest waters become fresher and vice-versa) which is not observed at the in-situ near-surface salinity measurements. The largest positive differences between surface and near-surface salinity trends are located over regions characterized by a decrease in the mixed layer depth and the sea surface wind speed, and an increase in sea surface temperature, which is consistent with an increased stratification of the water column due to global warming. These results highlight the crucial importance of using satellites to unveil critical changes on ocean–atmosphere fluxes.

Is the Surface Salinity Difference between the Atlantic and Indo-Pacific a Signature of the Atlantic Meridional Overturning Circulation?

AbstractThe high Atlantic surface salinity has sometimes been interpreted as a signature of the Atlantic meridional overturning circulation and an associated salt advection feedback. Here, the role of oceanic and atmospheric processes for creating the surface salinity difference between the Atlantic and Indo-Pacific is examined using observations and a conceptual model. In each basin, zonally averaged data are represented in diagrams relating net evaporation and surface salinity S. The data-pair curves in the –S plane share common features in both basins. However, the slopes of the curves are generally smaller in the Atlantic than in the Indo-Pacific, indicating a weaker sensitivity of the Atlantic surface salinity to net evaporation variations. To interpret these observations, a conceptual advective–diffusive model of the upper-ocean salinity is constructed. Notably, the –S relations can be qualitatively reproduced with only meridional diffusive salt transport. In this limit, the interbasin difference in salinity is caused by the spatial structure of net evaporation, which in the Indo-Pacific oceans contains lower meridional wavenumbers that are weakly damped by the diffusive transport. The observed Atlantic –S relationship at the surface reveals no clear influence of northward advection associated with the meridional overturning circulation; however, a signature of northward advection emerges in the relationship when the salinity is vertically averaged over the upper kilometer. The results indicate that the zonal-mean near-surface salinity is shaped primarily by the spatial pattern of net evaporation and the diffusive meridional salt transport due to wind-driven gyres and mesoscale ocean eddies, rather than by salt advection within the meridional overturning circulation.

Winter surface salinity in the northeastern Gulf of Maine from five years of SMAP satellite data

Wintertime freshwater transport into the Gulf of Maine (GoM) is typically controlled by a seasonal velocity increase in the fresh upstream Nova Scotia Current (NSC). Repeat satellite observations from the Soil Moisture Active Passive mission have mapped significant GoM surface salinity anomalies in four of five recent winters. These satellite data are used in combination with Jordan basin buoy and model datasets to investigate the likelihood that variable wind-forcing of the NSC contributed to these anomalies. This stems from regional ocean circulation studies suggesting that strengthening of alongshore southwesterly winds on the Scotian shelf weakens NSC transport into the GoM, while cross-shore southeasterly winds may also contribute to NSC weakening, and vice versa. A 17-year time series analysis of GoM buoy and satellite data shows that near-surface salinity in the eastern GoM can indeed be modulated by both alongshore and cross-shore winds through their impact on the NSC. The NSC geostrophic current modulation correlates with buoy-observed surface salinity anomalies when using a one month advective lead time. For a shorter 5-year period, a SMAP-derived salinity anomaly index in the eastern GoM indicates a similar relation to NSC variation and also correlates with Scotian Shelf wind anomalies. The relationships between winter wind and NSC transport variability are confirmed using output from a 19-year high resolution global ocean simulation. Attribution of these local wind anomalies to basin-scale atmospheric patterns shows that most years with strong winter GoM freshening coincide with weakening of a North Atlantic Oscillation-like wind pattern. But its reversals do not always correspond with a saline GoM. This contrast suggests that wind forcing more directly controls fresh winter GoM anomalies but not salty. Instead, they are partly due to density-driven advection from neighboring warm and saline Atlantic slope water including episodic Gulf Stream instabilities. • SMAP detects significant eastern GoM SSSA (up to 1 psu) in four of five winters. • Jordan basin SSSA correlation with Nova Scotia Current geostrophic anomaly is ~0.7. • Only half of the above correlation is explained by wind-driven current variations. • Eastern GoM satellite SSSA index is better indicator of fresh Scotian Shelf inflows.

Elastic properties as indicators of heat flux into cold near-surface Arctic sediments

Temperatures in the terrestrial Arctic today are increasing at the highest rate on earth, and heat flux into the cold sediments may result in extensive thawing. Thawing sediments lose their mechanical strength; therefore, warming has significant geomorphic consequences. We have combined heat flux, rock physics, and seismic modeling to estimate the change in elastic properties related to various published future climate scenarios in the Arctic, and we thus investigate the feasibility of exposing thawing rates from seismic data. The heat-flux model was validated using temperature data continuously recorded at the surface and within a well in Adventdalen, Svalbard. We estimated the evolving temperatures in an upper vertical section of the well using the heat-flux model, and we compared them with actual measured well temperatures. The modeled and measured data were consistent, even though our simplified model ignores heat transport due to fluid flow and the effects of clay. The heat-flux modeling resulted in subsurface isotherms that were input to rock-physics modeling based on two-end-member mixing of fully frozen and unfrozen composites to delineate possible climate effects on the seismic properties of the sediments. The results show that the elastic and seismic properties of (partly) frozen unconsolidated near-surface saline sediments strongly depend on heat flux into the subsurface, and they vary seasonally and between different climate scenarios. Seismic data obtained by full-waveform modeling and real experiments in Adventdalen show that time-lapse analysis of Rayleigh waves may be an efficient tool for monitoring heat flux into the terrestrial Arctic.

Near-Surface Salinity Reveals the Oceanic Sources of Moisture for Australian Precipitation through Atmospheric Moisture Transport

AbstractThe long-term trend of sea surface salinity (SSS) reveals an intensification of the global hydrological cycle due to human-induced climate change. This study demonstrates that SSS variability can also be used as a measure of terrestrial precipitation on interseasonal to interannual time scales, and to locate the source of moisture. Seasonal composites during El Niño–Southern Oscillation/Indian Ocean dipole (ENSO/IOD) events are used to understand the variations of moisture transport and precipitation over Australia, and their association with SSS variability. As ENSO/IOD events evolve, patterns of positive or negative SSS anomaly emerge in the Indo-Pacific warm pool region and are accompanied by atmospheric moisture transport anomalies toward Australia. During co-occurring La Niña and negative IOD events, salty anomalies around the Maritime Continent (north of Australia) indicate freshwater export and are associated with a significant moisture transport that converges over Australia to create anomalous wet conditions. In contrast, during co-occurring El Niño and positive IOD events, a moisture transport divergence anomaly over Australia results in anomalous dry conditions. The relationship between SSS and atmospheric moisture transport also holds for pure ENSO/IOD events but varies in magnitude and spatial pattern. The significant pattern correlation between the moisture flux divergence and SSS anomaly during the ENSO/IOD events highlights the associated ocean–atmosphere coupling. A case study of the extreme hydroclimatic events of Australia (e.g., the 2010/11 Brisbane flood) demonstrates that the changes in SSS occur before the peak of ENSO/IOD events. This raises the prospect that tracking of SSS variability could aid the prediction of Australian rainfall.

The role of the Magellan Strait on the southwest South Atlantic shelf

We analyze historical hydrographic data together with recent high-resolution hydrographic and underwater glider observations collected in the Magellan Strait to determine the water mass characteristics and exchanges between the continental shelves of the southeast South Pacific and southwest South Atlantic around southern South America. The near-surface salinity distribution and water mass analyses indicate a strong interoceanic connectivity associated with diluted subantarctic waters of the Pacific Ocean through the Magellan Strait which in turn are further diluted largely by inflows from the Almirantazgo Fjord via the Whiteside Channel. The lowest salinity waters reach the Atlantic shelf via the Magellan Strait. This core of low salinity waters (S < 31.5) are observed on the northern portion of the strait's Atlantic mouth and creates a strong baroclinic signal that leads to intense eastward geostrophic velocities suggesting a net Pacific to Atlantic transport (0.038–0.074 Sv, 1 Sv = 106 m3 s−1). This flow plays a significant role on the thermohaline characteristics and extent of the subantarctic shelf waters that occupy the Atlantic shelf. The low salinity inflow from the Magellan Strait combines with saltier inflows through the Le Maire Strait and farther east that feed the Atlantic shelf.

Inter-annual variability of shelf water volume on the northeastern Canadian and United States continental shelf, 1973–2013

Understanding the variability of waters confined to the northeastern United States and Canadian continental shelf is essential in determining factors that influence hydrographic patterns and structure, changes in fisheries stocks and planktonic assemblages, and the impact of Arctic warming. Shelf waters (SHW) located between Newfoundland and Cape Hatteras are characterized by lower salinity (<34 PSU) and lower temperatures than the generally warmer and more saline slope waters located farther offshore. Significant inter-annual variability of SHW volume has been noted from previous studies within the more limited Mid Atlantic Bight sub-region. Multiple factors may impact the volume of SHW, including local and remote river runoff and precipitation, release and equator-ward transport of fresh water from the Arctic and sub-polar gyre, ice melt from Greenland, cross-shelf removal, and both vertical and horizontal mixing processes. Here, we estimate inter-annual variability of SHW volume over the large shelf domain located between Newfoundland and Cape Hatteras from 1973 through 2013. Objectively-analyzed (OA) annual mean SHW thickness and error (as a percent of data variance) is computed for each of eleven sub-regions spanning our study domain for the 41-year period. Results show significant decreasing trends in SHW volume within 5 of the 11 sub-regions (The Grand Banks through the Eastern Scotian Shelf sub-regions) in agreement with previous work which has shown a decreasing trend of northern Labrador Current transport. OA annual mean SHW volume anomalies were cross-correlated with annual mean shelf slope front (SSF) position anomalies for corresponding sub-regions, displaying a highly significant relationship for the Georges Bank, the Mid Atlantic Bight, and the DelMarVa Hatteras shelf, with higher volumes corresponding to more offshore SSF positions. Annual mean near-surface salinity anomalies, when cross-correlated with OA annual mean SHW volume anomalies, displayed significant positive correlations from the Gulf of St. Lawrence northeast to the Newfoundland shelf and displayed primarily negative correlations from the Gulf of Maine to the DelMarVa Hatteras sub-region. The North Atlantic Oscillation annual indices displayed significant cross-correlations with annual mean OA SHW volume anomalies only for the Tail of the Grand Banks and Georges Bank., There were no significant cross correlations computed between the OA annual mean SHW volume anomalies and the NAO winter index for corresponding years.

Factors underlying changes in salinity around the southeastern Antilles

Abstract A plume of fresh water, originating from the Amazon and Orinoco Rivers, infiltrates the southeastern Caribbean. Here, some of factors underlying changes of near-surface salinity are investigated using ocean and atmosphere reanalyses that include winds, currents, sea temperature, salinity, rainfall, and river basin run-off during pre-season (April–June) and in-season (July–September) periods 1980–2016. Composite results demonstrate that increased northeasterly trade winds and an accelerated North Brazil Current feed Amazon and Orinoco River water northwestward into the Caribbean, underpinning a 0.5C warming of sea temperature and an increase in the frequency and intensity of passing hurricanes. This chain of events is partially related to the Atlantic meridional mode.

Salinity Rain Impact Model (RIM) for SMAP

When oceanic rainfall occurs, it creates a vertical salinity profile that is fresher at the surface. This freshwater lens is mixed downward by turbulent diffusion, dissipating over a few hours until the upper layer (1–5 m depth) becomes well mixed. Thus, there will be a transient bias between the in situ bulk salinity and the satellite-measured sea surface salinity (SSS) (representative of the first centimeter of the ocean depth). Based on measurements of Aquarius (AQ) SSS under rainy conditions, a model called rain impact model (RIM) was developed to assess the SSS variations due to the accumulation of rainfall prior to the time of the AQ observation. RIM uses ocean surface salinities from hybrid coordinate ocean model and the NOAA global precipitation product, climate prediction center morphing, to estimate changes in the near-surface salinity profile. Also, the RIM analysis has been applied to soil moisture and ocean salinity with similar results observed. The Soil Moisture Active Passive (SMAP) satellite carries an L -band radiometer, which measures SSS over a swath of 1000 km at 40-km resolution. SMAP can extend AQ salinity data record with improved temporal/spatial sampling. This paper describes RIM that simulates the effects of rain accumulation on SMAP SSS, showing good correlation between the model and the observed SSS values. Given the better resolution of SMAP, the goal of this paper is to continue the previous analysis of AQ to better understand the effects of the instantaneous and accumulated rain on the salinity measurements.

Observations of Near-Surface Salinity and Temperature Structure with Dual-Sensor Lagrangian Drifters During SPURS-2

Observations of Near-Surface Salinity and Temperature Structure with Dual-Sensor Lagrangian Drifters During SPURS-2

Assessment of Aquarius sea surface salinity with Argo in the Bay of Bengal

ABSTRACTThis study validates three Aquarius sea surface salinity (SSS) Level 2 products against Argo salinity in the Bay of Bengal (BoB) for the period 26 August 2011 through 30 April 2015. The Aquarius SSS products used here include the standard product processed by the Aquarius Data Processing System (ADPS) and two data sets from the Jet Propulsion Laboratory (JPL): the Combined Active-Passive algorithm with and without rain correction (i.e. CAP and CAPRC). The bias and root-mean-square difference (RMSD) of the ADPS, CAP and CAPRC with respect to Argo salinity is −0.14 ± 0.60 psu, 0.03 ± 0.53 psu, and 0.07 ± 0.52 psu, respectively. A large negative bias (large RMSD) value is observed in the northern bay and along the Sumatra coast in the ADPS (all three Aquarius products) with a remarkable seasonal variation. We evaluate the errors induced by the geographic displacement and the difference in depth of the measurement and show that these errors are significant in regards to the validation of Aquarius in our study region. The strong negative bias is mainly caused by the near-surface salinity stratification. Frequent heavy precipitation events in the BoB induce a freshening bias of approximately −0.13 psu (mm h−1)−1 that lasted for less than 6 h, contributed 21% to the overall bias of the ADPS SSS and partly caused the high RMSD values observed along the Sumatra coast. The large SSS RMSD in the northern bay is largely induced by small-scale variations in SSS, and the overall RMSD is reduced by approximately 11% when the horizontal-SSS-gradient-induced RMSD is isolated. Therefore, the potential influences of the spatial representation errors associated with the spatial displacement between the satellite and in-situ measurements need to be considered when evaluating the satellite SSS values measured over marginal seas or plume regions that have rich-precipitation or strong small-scale SSS variations.