Top: Winds evaporate water from the subtropical North Atlantic Ocean, leaving behind high levels of salinity during the spring. The exported moisture makes its way to the African Sahel, where it soaks the arid land and gradually builds up soil moisture over the course of three months. The soil moisture couples with convection in the atmosphere to create a feedback loop that draws in additional moisture from the North Atlantic and Mediterranean. This increases precipitation during the summer African monsoon season. Bottom: In the western North Atlantic, higher springtime salinities are an indicator of enhanced moisture export onto the continental U.S., which converges in the South. This greatly increases soil moisture there, allowing the Sun's energy to evaporate water leading to more atmospheric convection on land. The intensified convection on land draws in more moisture from the Gulf of Mexico and leads to the enhancement of the Great Plains Low Level Jet, which carries moisture to the upper Midwest in summer. (Illustration by Eric Taylor, Woods Hole Oceanographic Institution) - 

Ray Schmitt from WHOI and his colleagues first found evidence of a clear link between higher sea surface salinity levels in the North Atlantic Ocean and increased rainfall on land in the African Sahel—the area between the Sahara Desert and the savannah across Central Africa. The results were published in the May 6, 2016 issue of Science Advances. 

Schmitt and his colleagues also found that high springtime salinity in the western North Atlantic correlates with high summer rainfall in the U.S. Midwest. Those results were published in the May 1, 2016 issue of the Journal of Climate.

- See more at: http://www.whoi.edu/news-release/salty-oceans-rainfall#sthash.UThOHm7P.dpuf

 

Reference : W15- 15 - 056

Release date : 18/09/2015

Deadline for receipt of applications: 07 november 2015

 

 

Ifremer, through its research work and expert advice, contributes to knowledge of the oceans and their resources, to monitoring of marine and coastal environments and to the sustainable development of marine activities. To these ends, Ifremer conceives and operates tools for observation, experimentation and monitoring, and manage the oceanographic databases.

Created in 1984, Ifremer is a public institute of an industrial and commercial nature (EPIC). It is supervised jointly by the Ministry of Higher Education and Research and the Ministry of Ecology, Sustainable Development and Energy. Within Ifremer, the Laboratory of Oceanography from Space (LOS) is seeking to appoint a Researcher to reinforce is major role and expertise for the production, validation and scientific exploitation of the Sea Surface Salinity (SSS) data obtained from several satellite missions such as SMOS, Aquarius, potentially SMAP and AMSR-2. LOS develops closed partnerships with the French scientific community, also collaborating with international partner organisations (ESA, CNES, NASA, EUMETSAT,..) in the frame of several national and international projects, including contractual activities.

 

The LOS includes a research and data processing team to gain a better knowledge of the ocean from various observations. This group gathers technicians, engineers and researchers to conduct analyses, algorithm development, processing and distribution of elaborated geophysical products derived from the combination of in situ and satellite observations, such as surface winds, surface waves, currents, surface temperature and salinity, sea ice characteristics, …

 

The satellite missions to estimate sea surface Salinity are rather new with the first launch end 2009 for the ESA SMOS mission. These new datasets still demand a strong expertise in both passive microwave remote sensing and ocean surface physics. A thematic exploitation platform dedicated to ocean surface salinity is currently under development to aim at fostering the scientific use of both satellite and in situ SSS observations, complemented and used synergistically with observations from numerous other Earth observation instruments (temperature, altimetry, scatterometry, optical and ocean color properties, precipitation,..).

 

The successful researcher will contribute to improve our understanding of the dynamical processes responsible for the variability of the SSS fields associated with the global water cycle. Research themes are open to different aspects on specific physical processes (vertical mixing at small scale, meso-scale horizontal transport, air-sea interactions, Evaporation minus Precipitation or river run off fluxes, mixed layer and haline stratification, etc..) or/and focus on key geographic zones (oceanic basins, marginal seas, river run off, Tropical Cyclone area, polar regions..). The researcher will develop analyses based on existing in situ and satellite data but will also consider the potential combination with new and future missions observations (Sentinel-1 and 3, SMAP launched since january 2015, CFOSAT with a foresseen launch in December 2017, or  SWOT in 2020).

As principal activities, the researcher will have to:

• Undertake studies on the signatures of the global water cycle and its variability in ocean surface salinity,

 

• Exploit the complementarities between in situ and satellite observations characterizing the upper ocean salinity,

• Participate to the definition and exploitation of future and new observations (combined exploitation, SMOS follow on, GNSS-R, ...), and of new measurement protocols,

• Identify new fields of applications involving the combined use of observations characterizing the coupled atmosphere/ocean/land/ice system.

Knowledge, Skills & Qualifications:

 

·       The position requires a Ph.D. degree in oceanography or/and meteorology, fluid mechanics, geophysical fluid dynamics, air/sea interface, ocean remote sensing, geostatistics, or a closely related discipline.

·       Specific skills are required in :

ü  English,

ü  Applied mathematics,

ü  signal processing

ü  Oceanography

ü  Meteorology

 

• The successful candidate is expected to demonstrate autonomy, collaborative team efforts and a strong interest in the scientific context and other related scientific topics studied in the Ifremer’s Département Océanographie et Dynamique des Écosystèmes (ODE): LABEX Mer, Pôle thématique Océan and oceanic small-scale studies etc.)

 

Appropriate background checks are required.

 

The post available is a permanent researcher position, with a preferred starting date of December 2015/ January 2016. Closing date for applications: 7 november 2015

 

For further information, see:

http://wwz.ifremer.fr/institut_eng/Ifremer-careers/Jobs-and-Internships/Researcher-in-Ocean-Remote-Sensing-and-Water-Cycle

 

and you can send an email for details to nreul@ifremer.fr

Towards a better estimation of surface currents using satellite Sea Surface Salinity data

 

Sea Surface Salinity from SMOS (color) in the Gulf Stream region superimposed with surface currents deduced from altimeters (Reul et al., 2014).

 

Sea surface Height (SSH)  data from altimeters are key observations to reveal the ocean variability at large spatial scales (>100-200 kms). Currently orbiting altimeters do not provide the ocean variability at the smaller so-called meso-scales (from 50 to 200 km) and sub-mesoscales  (< 20 km). Recent theoretical, numerical and experimental studies (e.g. Earth Simulator simulations at very high resolution) have however revealed  that  the ocean surface dynamic in these ranges of horizontal scales is no more characteristics of bi-dimensional turbulence, so that the dynamic at smaller scale cannot be directly inferred from the large scale ones, e.g., through direct energy cascade.

 

SSH can allow a better constraint of the estimation of the surface density field to help assess in more detail the characteristics of correlation between these fields. As proposed in several recent papers (Lapeyre and Klein, 2006; Isern-Fontanet et al., 2008; LaCasce, J. H., 2012) subsurface velocity and density fields can be extrapolated from sea surface density and SSH via the Surface Quasi-Geostrophic (SQG) formalism. Such method was shown to be particularly successful in energetic regions like the Gulf Stream extension (Wang et al., 2013).

Lacking regular sea surface salinity (SSS) field mapping capability at sufficient spatial resolution, these previous works all assumed that temperature dominates the surface density variations and generally used a constant SSS value. SQG methods implicitly assume the surface density and interior potential vorticity (PV) are correlated. In fact, the two fields are often quite different. Were they perfectly correlated (or anti-correlated), the sea surface height

would resemble the surface density. But satellite SSH and SST anomalies are found to be not always coincident (e.g. Wang, 2013). While there are regions where SST and SSH anomalies are correlated, there are others where they are not. Surface heating/cooling can thus modify the surface signature of near-surface density anomalies (their strength and lateral structures) making them different from surface pressure gradient that is reflected in SSH variability. Moreover, interior PV can be non-zero due to baroclinic instabilities that affect surface pressure without changing the surface density. Finally, in presence of strong horizontal gradients of salinity, surface density is not always dominated by temperature.

            The combination of the new SMOS and Aquarius satellite SSS with SST and SSH data provide a first opportunity to estimate the synoptic surface density fields on mesoscales and to further assess the level of correlation between the latter and the SSH fields. The post-doc candidate will analyse such correlation in several key dynamical areas of the world ocean.

 

Key words: surface currents, sea surface salinity, SMOS, density, altimetry, temperature

 

 

Ifremer offers post-doctoral positions to young French or foreign scientists who have completed their PhD. and are motivated by development and innovation in various fields of Marine Sciences : technology and ecotechnology, aquaculture, fisheries, environment, risks analysis, physics of oceans, etc.

Postdoctoral positions are contracted for a duration of 12 months, possibly renewable for a non-renewable 6-month period.

Interested applicants should send :

1. A handwritten letter including the specific skills and competence for the particular postdoctoral position you are interested in.
2. A detailed curriculum vitae.
3. A summary of work previously done, mentioning the date of submission of the thesis,
4. A list of publications and communications / symposia.
5. Two letters of recommendation.

Complementary information can be obtained through exchanges with the Scientist Contact at ifremer.

 The criteria for selecting candidates are the following :

• The Curriculum Vitae of the nominee must be consistent with the proposal regarding the post-doctoral position.
• The candidate must be under 35 years old at December 31, 2014.
• The candidate has not previously performed post-doctoral research at Ifremer.
• The candidate has spent a majority of his (her) doctoral position out of Ifremer.

The list of subjects of the call for post-doctoral candidates can be downloaded here :

Postdoctoral positions will begin from the 1st of November, 2015.

The candidate will work in the Ifremer Mediterannean Center located in La Seyne-sur-Mer