![Page 1: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/1.jpg)
Ocean (surface) salinity an in situ perspective
G. ReverdinLOCEAN, UMR CNRS/UPMC/IRD, Paris, France
(indebted to numerous colleagues in France, US, Spain…)
![Page 2: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/2.jpg)
Salinity
• Water with anions and cations in fixed’ ratios (Dittmar, 40 samples from the Challenger Expedition1874-1877)
• Thus, to 0-order S=fn(C,T), and density=fn(T,S,P)(small increase 0(0.003 psu) due to increase
DIC; small overall decrease due to glacial melt/change of ocean mass)
S evolves with E-P+R, ocean circulation, mixing
![Page 3: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/3.jpg)
What do we measure
• Measured with respect to a standard water (more or less since 1900)- first by measuring Chlorinity; - more recently, conductivity
Lost in Fathom: London
![Page 4: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/4.jpg)
How do we measure it
• Discrete samples 110 y (0.1 psu)
• Thermosalinographs 40 y (ships, drifters) (0.02 psu)
• Argo floats (0.01 psu) (and other profilers)
![Page 5: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/5.jpg)
Different networks
SO SSSG. Alory, T. DelcroixSOCAT, GOSUD, SAMOS
(all require careful validation)
Surface drifters (SPURS)L. Centurioni, V. HormannJ. Font, G. Reverdin
Requires also careful validation)
![Page 6: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/6.jpg)
Mapping of climatology
Sufficient data: Last 40 yearsReverdin et al, 2007; Delcroix et al., 2005
Gordon and Giulivi, 2014
![Page 7: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/7.jpg)
Examples of variability
Subpolar gyre : TSGs (20 years)earlier sampling 100 years
NAC
LC
Binning in boxes or along tracks…
![Page 8: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/8.jpg)
Subpolar gyre
Binning data 1°x1 month :scales resolved a few degrees and a few monthsLarge spatial coherence : modulation of gyre
Larger signal : circulation
![Page 9: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/9.jpg)
West Greenland / Nfld shelves
Larger seasonal modulation on shelves; harder to interpret(for example, expectation of huge melt in 2011-2012, and no low S)Possible phase opposition West Greenland/ Newfoundland shelf
![Page 10: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/10.jpg)
Spatial mapping of individual fields (~10 years)
April-June 1997
300-500 km scales can be retrieved (away from fronts),even with the spare Argo sampling (and surface TSG sampling)ISAS (Gaillard, 2009); Reverdin et al., 2002; Reverdin et al., 2007
![Page 11: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/11.jpg)
Displacement of the fresh poolwestern equatorial Pacific
(binning Delcroix et al., 2011; scales 1000 km*100km*3 months)
Singh et al., 2012, but also Delcroix and Picaut, 1998, Maes et al, 2006
Displacements advected by zoal currents + P influence
![Page 12: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/12.jpg)
ENSO/El Niño
Singh et al., 2011Different flavors of ENSO (EP, CP)With SSS patterns that relate to currents/P
![Page 13: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/13.jpg)
Warm pool
(Cravatte et al, 2007) Trends in PDO and SSS
![Page 14: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/14.jpg)
Trends– natural variabilityA climate change perspective
Trend SSS/century in climate models(compared to obs 1970-2002)Terray et al 2012; Delcroix et al., 2011
Pacific seems to be robust, but N. Atlantic within natural variability
![Page 15: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/15.jpg)
Longer time series(feasible in NE subpolar gyre with some data adjustments over the last 120 years)
Reverdin et al., 2010
T and S correlated, but present also differencesLow-frequency S presents weak seasonal dependencyrelated to modulation of westerlies (NAO) with 0-4 years lag (0.63)Studies on the 1990s transition indicates that in winter it is related mostly to changes in ocean circulation/inputs to the gyre (and E-P)
Multi-decadal filter
Fresh
Salty
Fresh
![Page 16: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/16.jpg)
Further southThe worse sampling
Better sampling further northBut gaps remain
In all cases: issues of corrections/qualification of data(particularly in the 1920s) (requires adjustment of data)There is often a need to bin in ‘big’ boxes (and interannual smoothing+ averaging different seasons)
![Page 17: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/17.jpg)
Trends
No relation (in phase) between NATLAnd NASG (possible delayed phase)45-50°N, already signal characteristicof NASG (2 years earlier)
NA
TA
IG
![Page 18: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/18.jpg)
Meso-scales need to be resolved to study higher
frequency variability (seasonal or less)even on the large scales
Examples from SPURS (1-year survey of NA subtropical gyre)
Feature associated with transport of fresh/warm anomaly from south(Busecke et al., 2014)
R. SchmittA. Gordon
![Page 19: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/19.jpg)
The largest scales haveRms =0.14 (cor=0.5 with SMOS)
The smaller meso-scalescan have 0.2 psu signals asMuch as large scales over 1000 km…Thus possible strong fronts and vertical circulations…(but in some areas/seasons T and S Compensated, whichis scale-dependent)Kolodziejczyk et al., 2014
Meso-scaleSSS variability
100 km
20 km
![Page 20: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/20.jpg)
SPURS SSS seasonal signalinfluence of the eddy and meso-scale structures to d(V’S’)/dy
80 0.10
Gordon et al, 2014(SODA reanalysis)
![Page 21: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/21.jpg)
Local SPURS budget evaluated100 km x 100 km box
Estimates of dSSS/dt from driftersNear SPURS moring (red)Compared to Aquarius+Aviso estimateCenturioni et al., 2015
Farrar
![Page 22: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/22.jpg)
Near surface stratification
The low wind; high SW case (Asher et al., 2014)
Gradients day-time, a few percents of the surface of the oceans
![Page 23: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/23.jpg)
Rainfall-induced stratificationS(15-cm) – S(45-cm)
17 events SVP-BS / Surplas (ITCZ/SPCZ)
Individual rain events : 25% more at 15-cm, but for less than an hour(also, T decrease and stratification); wind estimated ‘SSMI’, not measured
![Page 24: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/24.jpg)
Extreme rain event!
No wind! (means no wave energy in 20 cm – 1m wave length domain)Little S gradient between 4cm and 50 cm (~1 unit) thus at least 12 cmRain in 90 minutes, but should be more as decrease below 50 cm...Strong T-gradient (implies probably ~100 W/m2 cooling); secondary drops?
1 h
![Page 25: Ocean (surface) salinity an in situ perspective G. Reverdin LOCEAN, UMR CNRS/UPMC/IRD, Paris, France (indebted to numerous colleagues in France, US, Spain…)](https://reader035.vdocument.in/reader035/viewer/2022070605/5a4d1ace7f8b9ab05997086a/html5/thumbnails/25.jpg)
Conclusions & Perspectives- In situ data can be used to have long time series, but issues on some old data remain
and cast doubts on some results
- No identification of Atlantic basin-scale SSS trends over the last 118 years
- When data density high enough, spatial patterns of low frequency modes of variability can be investigated (from 2-D to 3-D in the last 10y)
- Dedicated surveys/instrumentation to test certain balances on smaller spatial scales: example of SPURS1 (but also COARE)
V’S’ ~ 1 E-3 from SSS (smoothed 200 km/1 month) + Aviso current V’S’ ~ 3 E-3 from drifter SSS + velocitiesThus 22-30 cm of equivalent rainfall (compared to 130 cm for E-P)
- Complementarity with satellite data to be developed both in SSS and improved surface current products