Sea Surface Salinity Variability in Response to the Congo River Discharge

NASA Astrophysics Data System (ADS)

Moller, D.; Chao, Y.; Farrara, J. D.; Schumann, G.; Andreadis, K.

2014-12-01

Sea surface salinity (SSS) variability associated with the Congo River discharge is examined using Aquarius satellite-retrieved SSS data and vertical profiles of salinity measured by the Argo floats. The Congo River plume can be clearly identified in the Aquarius SSS data with a westward extension of 500 to 1000 km off the coast of the Democratic Republic of Congo (DRC). The peak amplitude of the SSS variability associated with the Congo River discharge exceeds 2.0 psu. Using the first two years of Aquarius data, a well-defined seasonal cycle is described: maximum fresh-water anomalies are found in the boreal winter and spring seasons. The fresh-water anomalies during the 2012-2013 winter and spring seasons are significantly fresher than the 2011-2012 winter and spring seasons. Vertical profiles of salinity derived from the Argo floats reveal that these fresh-water anomalies can be traced to 40 meters below the sea surface. Combining the Aquarius SSS data with the Argo vertical profiles of salinity, the 3D volume of these fresh-water anomalies can be inferred and used to estimate the Congo River discharge. Reasonably good agreement is found between the Congo River discharge as observed by a stream gauge at Kinshasa and that estimated from the combined Aquarius and Argo data, indicating that Aquarius data can be used to close the fresh-water budget between the coastal ocean and the Congo River. The precipitation minus evaporation portion of the freshwater flux is found to play a secondary role in this region.

Sea Surface Salinity signatures of tropical instability waves: New evidences from SMOS

NASA Astrophysics Data System (ADS)

Yin, Xiaobin; Boutin, Jacqueline; Reverdin, Gilles; Lee, Tong; Martin, Nicolas

2014-05-01

The European Space Agency's (ESA) Soil Moisture and Ocean Salinity (SMOS) mission, launched in November 2009, has been providing global maps of sea surface salinity (SSS) since 2010. SSS measurements from the SMOS satellite during June 2010 and December 2012 provide an unprecedented space-borne observation of the salinity structure of tropical instability waves (TIWs) including strong La Niña conditions during recent years. We use SMOS level 3 SSS maps averaged over 100 x 100 km2 with a 10-day running window and sampled daily over a 0.25 x 0.25° grid generated at Laboratoire d'Océanographie et du Climat: Expérimentation et Approches Numériques (http://catds.ifremer.fr/Products/Available-products-from-CEC-OS/Locean-v2013) [Boutin et al., 2013; Yin et al., 2012]. We also analyze daily SST from the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) produced on an operational basis at the UK Met Office using optimal interpolation [Donlon et al., 2011]. From a time-longitude section in the eastern Pacific ocean, westward propagations of SSS and SST anomalies along 2° N became apparent west of 90° W during June 2010 - March 2011 and June 2011 - March 2012, coincident with negative indexes in the NINO3 and NINO3.4 regions. The 33-day SSS anomaly and SST anomaly appeared together approximately in the same time and regions. The 17-day SSS anomaly is less clear than the 17-day SST anomaly. The SSS anomaly has approximate amplitude of 0.5 practical salinity scale (pss) and the SST anomaly has approximate amplitude of 2 ° C. Then, we focus on analysis of SSS and SST anomalies during June to December 2010. During this period the tropical Pacific was characterized by a strong La Niña, providing favorable conditions for the occurrence of TIWs. The high anomalies and meridional gradients of both SSS and SST appear north of the equator west of 100° W. Near 100W, they straddle the equator where South Pacific water and eastern edge upwelling water with high

Correlations Between Sea-Surface Salinity Tendencies and Freshwater Fluxes in the Pacific Ocean

NASA Technical Reports Server (NTRS)

Li, Zhen; Adamec, David

2007-01-01

Temporal changes in sea-surface salinity (SSS) from 21 years of a high resolution model integration of the Pacific Ocean are correlated with the freshwater flux that was used to force the integration. The correlations are calculated on a 1 x10 grid, and on a monthly scale to assess the possibility of deducing evaporation minus precipitation (E-P) fields from the salinity measurements to be taken by the upcoming Aquarius/SAC-D mission. Correlations between the monthly mean E-P fields and monthly mean SSS temporal tendencies are mainly zonally-oriented, and are highest where the local precipitation is relatively high. Nonseasonal (deviations from the monthly mean) correlations are highest along mid-latitude storm tracks and are relatively small in the tropics. The response of the model's surface salinity to surface forcing is very complex, and retrievals of freshwater fluxes from SSS measurements alone will require consideration of other processes, including horizontal advection and vertical mixing, rather than a simple balance between the two.

High salinity events in the northern Arabian Sea and Sea of Oman

NASA Astrophysics Data System (ADS)

Wang, Zhankun; DiMarco, Steven F.; Jochens, Ann E.; Ingle, Stephanie

2013-04-01

Moored observations in the northern Arabian Sea (NAS) show substantial velocity, temperature and dissolved oxygen fluctuations, accompanied by episodic high salinity intrusions with maximum values≥37.3 on time scales of 2-10 days after the passage of Cyclone Gonu in 2007. These events are characterized by a rapid increase in temperature, salinity and dissolved oxygen followed by an abrupt decline. The mechanisms behind these high salinity events are investigated using a comprehensive dataset of temperature and salinity profiles from ARGO floats and sea surface height anomaly maps. The spatial and temporal distribution of the Persian/Arabian Gulf outflow to the Sea of Oman is also studied using ARGO profiles. Persian Gulf water (PGW) is mainly measured close to the Strait of Hormuz or along the Oman coast on the continental slope in the Sea of Oman. Both mooring and ARGO data show that high salinity PGW can be advected off the slope and into the interior. More high salinity water is measured in the interior of the Sea of Oman within three months after the Gonu passage in summer 2007, which is caused by the combination effect of the oceanic responses to Cyclone Gonu and a clockwise eddy circulation located at northern Ras al Hadd. At other times, the high salinity water appears more in isolated patches and rare in the interior. This study provides a first look at the high salinity events appearing after Gonu and the properties and dynamics of the PGW in the northern Arabian Sea and Sea of Oman.

Spatial and Temporal Analysis of Sea Surface Salinity Using Satellite Imagery in Gulf of Mexico

NASA Astrophysics Data System (ADS)

Rajabi, S.; Hasanlou, M.; Safari, A. R.

2017-09-01

The recent development of satellite sea surface salinity (SSS) observations has enabled us to analyse SSS variations with high spatiotemporal resolution. In this regards, The Level3-version4 data observed by Aquarius are used to examine the variability of SSS in Gulf of Mexico for the 2012-2014 time periods. The highest SSS value occurred in April 2013 with the value of 36.72 psu while the lowest value (35.91 psu) was observed in July 2014. Based on the monthly distribution maps which will be demonstrated in the literature, it was observed that east part of the region has lower salinity values than the west part for all months mainly because of the currents which originate from low saline waters of the Caribbean Sea and furthermore the eastward currents like loop current. Also the minimum amounts of salinity occur in coastal waters where the river runoffs make fresh the high saline waters. Our next goal here is to study the patterns of sea surface temperature (SST), chlorophyll-a (CHLa) and fresh water flux (FWF) and examine the contributions of them to SSS variations. So by computing correlation coefficients, the values obtained for SST, FWF and CHLa are 0.7, 0.22 and 0.01 respectively which indicated high correlation of SST on SSS variations. Also by considering the spatial distribution based on the annual means, it found that there is a relationship between the SSS, SST, CHLa and the latitude in the study region which can be interpreted by developing a mathematical model.

Is the Aquarius sea surface salinity variability representative?

NASA Astrophysics Data System (ADS)

Carton, J.; Grodsky, S.

2016-12-01

The leading mode of the Aquarius monthly anomalous sea surface salinity (SSS) is evaluated within the 50S-50N belt, where SSS retrieval accuracy is higher. This mode accounts for about 18% of the variance and resembles a pattern of the ENSO-induced anomalous rainfall. The leading mode of SSS variability deducted from a longer JAMSTEC analysis also accounts for about 17% of the variance and has very similar spatial pattern and almost a perfect correspondence of its temporal principal component to the SOI index. In that sense, the Aquarius SSS variability at low and middle latitudes is representative of SSS variability that may be obtained from longer records. This is explained by the fact that during the Aquarius period (2011-2015), the SOI index changed significantly from La Nina toward El Nino state, thus spanning a significant range of its characteristic variations. Multivariate EOF analysis of anomalous SSS and SST suggests that ENSO-induced shift in the tropical Pacific rainfall produces negatively correlated variability of temperature and salinity, which are expected if the anomalous surface flux (stronger rainfall coincident with less downward radiation) drives the system. But, anomalous SSS and SST are positively correlated in some areas including the northwestern Atlantic shelf (north of the Gulfstream) and the Pacific sector adjusting to the California peninsula. This positive correlation is indicative of an advection driven regime that is analyzed separately.

Comparison of SMOS and Aquarius Sea Surface Salinity and Analysis of Possible Causes for the Differences

NASA Technical Reports Server (NTRS)

Dinnat, E. P.; Boutin, J.; Yin, X.; Le Vine, D. M.; Waldteufel, P.; Vergely, J. -L.

2014-01-01

Two ongoing space missions share the scientific objective of mapping the global Sea Surface Salinity (SSS), yet their observations show significant discrepancies. ESA's Soil Moisture and Ocean Salinity (SMOS) and NASA's Aquarius use L-band (1.4 GHz) radiometers to measure emission from the sea surface and retrieve SSS. Significant differences in SSS retrieved by both sensors are observed, with SMOS SSS being generally lower than Aquarius SSS, except for very cold waters where SMOS SSS is the highest overall. Figure 1 is an example of the difference between the SSS retrieved by SMOS and Aquarius averaged over one month and 1 degree in longitude and latitude. Differences are mostly between -1 psu and +1 psu (psu, practical salinity unit), with a significant regional and latitudinal dependence. We investigate the impact of the vicarious calibration and some components of the retrieval algorithm used by both mission on these differences.

Estimating Sea Surface Salinity and Wind Using Combined Passive and Active L-Band Microwave Observations

NASA Technical Reports Server (NTRS)

Yueh, Simon H.; Chaubell, Mario J.

2012-01-01

Several L-band microwave radiometer and radar missions have been, or will be, operating in space for land and ocean observations. These include the NASA Aquarius mission and the Soil Moisture Active Passive (SMAP) mission, both of which use combined passive/ active L-band instruments. Aquarius s passive/active L-band microwave sensor has been designed to map the salinity field at the surface of the ocean from space. SMAP s primary objectives are for soil moisture and freeze/thaw detection, but it will operate continuously over the ocean, and hence will have significant potential for ocean surface research. In this innovation, an algorithm has been developed to retrieve simultaneously ocean surface salinity and wind from combined passive/active L-band microwave observations of sea surfaces. The algorithm takes advantage of the differing response of brightness temperatures and radar backscatter to salinity, wind speed, and direction, thus minimizing the least squares error (LSE) measure, which signifies the difference between measurements and model functions of brightness temperatures and radar backscatter. The algorithm uses the conjugate gradient method to search for the local minima of the LSE. Three LSE measures with different measurement combinations have been tested. The first LSE measure uses passive microwave data only with retrieval errors reaching 1 to 2 psu (practical salinity units) for salinity, and 1 to 2 m/s for wind speed. The second LSE measure uses both passive and active microwave data for vertical and horizontal polarizations. The addition of active microwave data significantly improves the retrieval accuracy by about a factor of five. To mitigate the impact of Faraday rotation on satellite observations, the third LSE measure uses measurement combinations invariant under the Faraday rotation. For Aquarius, the expected RMS SSS (sea surface salinity) error will be less than about 0.2 psu for low winds, and increases to 0.3 psu at 25 m/s wind speed

Assimilation of Satellite Sea Surface Salinity Fields: Validating Ocean Analyses and Identifying Errors in Surface Buoyancy Fluxes

NASA Astrophysics Data System (ADS)

Mehra, A.; Nadiga, S.; Bayler, E. J.; Behringer, D.

2014-12-01

Recently available satellite sea-surface salinity (SSS) fields provide an important new global data stream for assimilation into ocean forecast systems. In this study, we present results from assimilating satellite SSS fields from NASA's Aquarius mission into the National Oceanic and Atmospheric Administration's (NOAA) operational Modular Ocean Model version 4 (MOM4), the oceanic component of NOAA's operational seasonal-interannual Climate Forecast System (CFS). Experiments on the sensitivity of the ocean's overall state to different relaxation time periods were run to evaluate the importance of assimilating high-frequency (daily to mesoscale) and low-frequency (seasonal) SSS variability. Aquarius SSS data (Aquarius Data Processing System (ADPS) version 3.0), mapped daily fields at 1-degree spatial resolution, were used. Four model simulations were started from the same initial ocean condition and forced with NOAA's daily Climate Forecast System Reanalysis (CFSR) fluxes, using a relaxation technique to assimilate daily satellite sea surface temperature (SST) fields and selected SSS fields, where, except as noted, a 30-day relaxation period is used. The simulations are: (1) WOAMC, the reference case and similar to the operational setup, assimilating monthly climatological SSS from the 2009 NOAA World Ocean Atlas; (2) AQ_D, assimilating daily Aquarius SSS; (3) AQ_M, assimilating monthly Aquarius SSS; and (4) AQ_D10, assimilating daily Aquarius SSS, but using a 10-day relaxation period. The analysis focuses on the tropical Pacific Ocean, where the salinity dynamics are intense and dominated by El Niño interannual variability in the cold tongue region and by high-frequency precipitation events in the western Pacific warm pool region. To assess the robustness of results and conclusions, we also examine the results for the tropical Atlantic and Indian Oceans. Preliminary validation studies are conducted using observations, such as satellite sea-surface height (SSH

Satellite observations of rainfall effect on sea surface salinity in the waters adjacent to Taiwan

NASA Astrophysics Data System (ADS)

Ho, Chung-Ru; Hsu, Po-Chun; Lin, Chen-Chih; Huang, Shih-Jen

2017-10-01

Changes of oceanic salinity are highly related to the variations of evaporation and precipitation. To understand the influence of rainfall on the sea surface salinity (SSS) in the waters adjacent to Taiwan, satellite remote sensing data from the year of 2012 to 2014 are employed in this study. The daily rain rate data obtained from Special Sensor Microwave Imager (SSM/I), Tropical Rainfall Measuring Mission's Microwave Imager (TRMM/TMI), Advanced Microwave Scanning Radiometer (AMSR), and WindSat Polarimetric Radiometer. The SSS data was derived from the measurements of radiometer instruments onboard the Aquarius satellite. The results show the average values of SSS in east of Taiwan, east of Luzon and South China Sea are 33.83 psu, 34.05 psu, and 32.84 psu, respectively, in the condition of daily rain rate higher than 1 mm/hr. In contrast to the rainfall condition, the average values of SSS are 34.07 psu, 34.26 psu, and 33.09 psu in the three areas, respectively at no rain condition (rain rate less than 1 mm/hr). During the cases of heavy rainfall caused by spiral rain bands of typhoon, the SSS is diluted with an average value of -0.78 psu when the average rain rate is higher than 4 mm/hr. However, the SSS was increased after temporarily decreased during the typhoon cases. A possible reason to explain this phenomenon is that the heavy rainfall caused by the spiral rain bands of typhoon may dilute the sea surface water, but the strong winds can uplift the higher salinity of subsurface water to the sea surface.

Assessing the Potential to Derive Air-Sea Freshwater Fluxes from Aquarius-Like Observations of Surface Salinity

NASA Technical Reports Server (NTRS)

Zhen, Li; Adamec, David

2009-01-01

A state-of-the-art numerical model is used to investigate the possibility of determining freshwater flux fields from temporal changes io sea-surface salinity (SSS), a goal of the satellite salinity-measuring mission, Aquarius/SAC-D. Because the estimated advective temporal scale is usually longer than the Aquarius/SAC-D revisit time, the possibility of producing freshwater flux estimates from temporal salinity changes is first examined by using a correlation analysis. For the mean seasonal cycle, the patterns of the correlations between the freshwater fluxes and surface salinity temporal tendencies are mainly zonally oriented, and are highest where the local precipitation is also relatively high. Nonseasonal (deviations from the monthly mean) correlations are highest along mid-latitude moon tracks and are relatively small in the tropics. The complex correlation patterns presented here suggest that a global retrieval of the difference between evaporation and precipitation (E-P) from salinity changes requires more complex techniques than a simple consideration of local balance with surface forcing.

Sea Surface Scanner: An advanced catamaran to study the sea surface

NASA Astrophysics Data System (ADS)

Wurl, O.; Mustaffa, N. I. H.; Ribas Ribas, M.

2016-02-01

The Sea Surface Scanner is a remote-controlled catamaran with the capability to sample the sea-surface microlayer in high resolution. The catamaran is equipped with a suite of sensors to scan the sea surface on chemical, biological and physical parameters. Parameters include UV absorption, fluorescence spectra, chlorophyll-a, photosynthetic efficiency, chromophoric dissolved organic matter (CDOM), dissolved oxygen, pH, temperature, and salinity. A further feature is a capability to collect remotely discrete water samples for detailed lab analysis. We present the first high-resolution (< 30 sec) data on the sea surface microlayer. We discuss the variability of biochemical properties of the sea surface and its implication on air-sea interaction.

ENSO related sea surface salinity variability in the equatorial Pacific

NASA Astrophysics Data System (ADS)

Qu, T.

2016-12-01

Recently available satellite and Argo data have shown coherent, large-scale sea surface salinity (SSS) variability in the equatorial Pacific. Based on this variability, several SSS indices of El Nino have been introduced by previous studies. Combining results from an ocean general circulation model with available satellite and in-situ observations, this study investigates the SSS variability and its associated SSS indices in the equatorial Pacific. The ocean's role and in particular the vertical entrainment of subtropical waters in this variability are discussed, which suggests that the SSS variability in the equatorial Pacific may play some active role in ENSO evolution.

Comparison of seasonal variability of Aquarius sea surface salinity time series with in situ observations in the Karimata Strait, Indonesia

NASA Astrophysics Data System (ADS)

Susanto, R. D.; Setiawan, A.; Zheng, Q.; Sulistyo, B.; Adi, T. R.; Agustiadi, T.; Trenggono, M.; Triyono, T.; Kuswardani, A.

2016-12-01

The seasonal variability of a full lifetime of Aquarius sea surface salinity time series from August 25, 2011 to June 7, 2015 is compared to salinity time series obtained from in situ observations in the Karimata Strait. The Karimata Strait plays dual roles in water exchange between the Pacific and the Indian Ocean. The salinity in the Karimata Strait is strongly affected by seasonal monsoon winds. During the boreal winter monsoon, northwesterly winds draws low salinity water from the South China Sea into the Java Sea and at the same time, the Java Sea receives an influx of the Indian Ocean water via the Sunda Strait. The Java Sea water will reduce the main Indonesian throughflow in the Makassar Strait. Conditions are reversed during the summer monsoon. Low salinity water from the South China Sea also controls the vertical structure of water properties in the upper layer of the Makassar Strait and the Lombok Strait. As a part of the South China Sea and Indonesian Seas Transport/Exchange (SITE) program, trawl resistance bottom mounted CTD was deployed in the Karimata Strait in mid-2010 to mid-2016 at water depth of 40 m. CTD casts during the mooring recoveries and deployments are used to compare the bottom salinity data. This in situ salinity time series is compared with various Aquarius NASA salinity products (the level 2, level 3 ascending and descending tracks and the seven-days rolling averaged) to check the consistency, correlation and statistical analysis. The preliminary results show that the seasonal variability of Aquarius salinity time series has larger amplitude variability compared to that of in situ data.

Remote Sensing of Salinity: The Dielectric Constant of Sea Water

NASA Technical Reports Server (NTRS)

LeVine, David M.; Lang, R.; Utku, C.; Tarkocin, Y.

2011-01-01

Global monitoring of sea surface salinity from space requires an accurate model for the dielectric constant of sea water as a function of salinity and temperature to characterize the emissivity of the surface. Measurements are being made at 1.413 GHz, the center frequency of the Aquarius radiometers, using a resonant cavity and the perturbation method. The cavity is operated in a transmission mode and immersed in a liquid bath to control temperature. Multiple measurements are made at each temperature and salinity. Error budgets indicate a relative accuracy for both real and imaginary parts of the dielectric constant of about 1%.

A comparison of sea surface salinity in the equatorial Pacific Ocean during the 1997-1998, 2012-2013, and 2014-2015 ENSO events

NASA Astrophysics Data System (ADS)

Corbett, Caroline M.; Subrahmanyam, Bulusu; Giese, Benjamin S.

2017-11-01

Sea surface salinity (SSS) variability during the 1997-1998 El Niño event and the failed 2012-2013 and 2014-2015 El Niño events is explored using a combination of observations and ocean reanalyses. Previously, studies have mainly focused on the sea surface temperature (SST) and sea surface height (SSH) variability. This analysis utilizes salinity data from Argo and the Simple Ocean Data Assimilation (SODA) reanalysis to examine the SSS variability. Advective processes and evaporation minus precipitation (E-P) variability is understood to influence SSS variability. Using surface wind, surface current, evaporation, and precipitation data, we analyze the causes for the observed SSS variability during each event. Barrier layer thickness and upper level salt content are also examined in connection to subsurface salinity variability. Both advective processes and E-P variability are important during the generation and onset of a successful El Niño, while a lack of one or both of these processes leads to a failed ENSO event.

AQUARIUS: A Passive/Active Microwave Sensor to Monitor Sea Surface Salinity Globally from Space

NASA Technical Reports Server (NTRS)

LeVine, David; Lagerloef, Gary S. E.; Colomb, F. Raul; Chao, Yi

2004-01-01

Salinity is important for understanding ocean dynamics, energy exchange with the atmosphere and the global water cycle. Existing data is limited and much of the ocean has never even been sampled. Sea surface salinity can be measured remotely by satellite and a three year mission for this purpose called AquariudSAC-D has recently been selected by NASA's Earth System Science Pathfinder (ESSP) program. The objective is to map the salinity field globally with a spatial resolution of 100 km and a monthly average accuracy of 0.2 psu. The mission, scheduled for launch in 2008, is a partnership of the United States National Aeronautics and Space Agency (NASA) and the Argentine Comision National de Actividades Epaciales (CONAE).

Tropical Pacific sea surface salinity variability derived from SMOS data: Comparison with in-situ observations.

NASA Astrophysics Data System (ADS)

Ballabrera, Joaquim; Hoareau, Nina; Umbert, Marta; Martínez, Justino; Turiel, Antonio

2013-04-01

Prediction of El Niño/Southern Oscillation (ENSO), and its relation with global climate anomalies, continues to be an important research effort in short-term climate forecasting. This task has become even more challenging as researchers are becoming more and more convinced that there is not a single archetypical El Niño (or La Niña) pattern, but several. During some events (called now Standard or East Pacific), the largest temperature anomalies are located at the eastern part of the Pacific. However, during some of the most recent events, the largest anomalies are restricted to the central part of the Pacific Ocean, and are now called Central Pacific or Modoki (a Japanese word for "almost") events. Although the role of salinity in operational ENSO forecasting was initially neglected (in contrast with temperature, sea level, or surface winds), recent studies have shown that salinity does play a role in the preconditioning of ENSO. Moreover, some researchers suggest that sea surface salinity might play a role (through the modulation of the western Pacific barrier layer) to favor the Standard or the Modoki nature of each event. Sea Surface Salinity maps are being operationally generated from microwave (L-band, 1.4 Ghz) brightness temperature maps. The L-band frequency was chosen because is the optimal one for ocean salinity measurements. However, after three years of satellite data, it has been found that noise in brightness temperatures (due to natural and artificial sources) is larger than expected. Moreover, the retrieval of SSS information requires special care because of the low sensitivity of the brightness temperature to SSS: from 0.2-0.8 K per salinity unit. Despite of all these facts, current accuracy of SS maps ranges from 0.2-0.4, depending on the processing level and the region being considered. We present here our study about the salinity variability in the tropical Pacific Ocean from the 9-day, 0.25 bins salinity maps derived from the SMOS

On the role of inter-basin surface salinity contrasts in global ocean circulation

NASA Astrophysics Data System (ADS)

Seidov, D.; Haupt, B. J.

2002-08-01

The role of sea surface salinity (SSS) contrasts in maintaining vigorous global ocean thermohaline circulation (TOC) is revisited. Relative importance of different generalizations of sea surface conditions in climate studies is explored. Ocean-wide inter-basin SSS contrasts serve as the major controlling element in global TOC. These contrasts are shown to be at least as important as high-latitudinal freshwater impacts. It is also shown that intra-basin longitudinal distribution of sea surface salinity, as well as intra- and inter-basin longitudinal distribution of sea surface temperature, is not crucial to conveyor functionality if only inter-basin contrasts in sea surface salinity are retained. This is especially important for paleoclimate and future climate simulations.

Freshening of the Labrador Sea Surface Waters in the 1990s: Another Great Salinity Anomaly

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa; Koblinsky, Chester J. (Technical Monitor)

2002-01-01

Both the observed and simulated time series of the Labrador Sea surface salinities show a major freshening event since the middles. It continues the series of decoder events of the 1970s and 1980s from which the freshening in the early 1970's was named as the Great Salinity Anomaly (GSA). These events are especially distinguishable in the late summer (August and September) time series. The observed data suggests that the 1990's freshening may equal the GSA in magnitude. This recent event is associated with a large reduction in the overturning rate between the early and latter part of the 1990s. Both the observations and model results indicate that the surface salinity conditions appear to be returning towards normal daring 1999 and 2000 in the coastal area, but offshore, the model predicts the freshening to linger on after peaking 1997.

Reconstruction from EOF analysis of SMOS salinity data in Mediterranean Sea

NASA Astrophysics Data System (ADS)

Parard, Gaelle; Alvera-Azcárate, Aida; Barth, Alexander; Olmedo, Estrella; Turiel, Antonio; Becker, Jean-Marie

2017-04-01

Sea Surface Salinity (SSS) data from the Soil Moisture and Ocean Salinity (SMOS) mission is reconstructed in the North Atlantic and the Mediterranean Sea using DINEOF (Data Interpolating Empirical Orthogonal Functions). We used the satellite data Level 2 from SMOS Barcelona Expert Centre between 2011 and 2015. DINEOF is a technique that reconstructs missing data and removes noise by retaining only an optimal set of EOFs. DINEOF analysis is used to detect and remove outliers from the SMOS SSS daily field. The gain obtained with DINEOF method and L2 SMOS data give a higher spatial and temporal resolution between 2011 and 2015, allow to study the SSS variability from daily to seasonal resolution. In order to improve the SMOS salinity data reconstruction we combine with other parameters measured from satellite such chlorophyll, sea surface temperature, precipitation and CDOM variability. After a validation of the SMOS satellite data reconstruction with in situ data (CTD, Argo float salinity measurement) in the North Atlantic and Mediterranean Sea, the main SSS processes and their variability are studied. The gain obtained with the higher spatial and temporal resolution with SMOS salinity data give assess to study the characteristics of oceanic structures in North Atlantic and Mediterranean Sea.

Aquarius: A Mission to Monitor Sea Surface Salinity from Space

NASA Technical Reports Server (NTRS)

LeVine, D. M.; Lagerloef, G. S. E.; Pellerano, F.; Yueh, S.; Colomb, R.

2006-01-01

Aquarius is a combination radiometer and scatterometer (radar) operating at L-band (1.413 GHz for the radiometer and 1.26 GHz for the scatterometer). The primary instrument for measuring salinity is the radiometer. The scatterometer will provide a correction for surface roughness (waves) which is one of the largest potential sources of error in the retrieval. Unique features of the sensor are the large reflector (2.5 meter offset fed reflector with three feeds), polarimetric operation, and the tight thermal control. The three feeds produce three beams arranged to image in pushbroom fashion looking to the side of the orbit away from the sun to avoid sunglint. Polarimetric operation is included to assist in correcting for Faraday rotation which can be important at L-band. The tight thermal control is necessary to meet stability requirements (less than 0.12K drift over 7 days) which have been imposed to assist in meeting the science requirements for the retrieval of surface salinity (0.2 psu). The sensor will be in a sun-synchronous orbit at about 650 km with equatorial crossings of 6ad6pm (ascending at 6 pm). The objective is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean. To accomplish this, the measurement goals are a spatial resolution of 100 km and retrieval accuracy of 0.2 psu globally on a monthly basis. Aquarius is being developed by NASA and is a partnership between JPL and the Goddard Space Flight Center. The SAC-D mission is being developed by CONAE and will include the spacecraft and several additional instruments, including visible and infrared cameras and a microwave radiometer to monitor rain and wind velocity over the oceans, and sea ice.

Effect of Water Surface Salinity on Evaporation: The Case of a Diluted Buoyant Plume Over the Dead Sea

NASA Astrophysics Data System (ADS)

Mor, Z.; Assouline, S.; Tanny, J.; Lensky, I. M.; Lensky, N. G.

2018-03-01

Evaporation from water bodies strongly depends on surface water salinity. Spatial variation of surface salinity of saline water bodies commonly occurs across diluted buoyant plumes fed by freshwater inflows. Although mainly studied at the pan evaporation scale, the effect of surface water salinity on evaporation has not yet been investigated by means of direct measurement at the scale of natural water bodies. The Dead Sea, a large hypersaline lake, is fed by onshore freshwater springs that form local diluted buoyant plumes, offering a unique opportunity to explore this effect. Surface heat fluxes, micrometeorological variables, and water temperature and salinity profiles were measured simultaneously and directly over the salty lake and over a region of diluted buoyant plume. Relatively close meteorological conditions prevailed in the two regions; however, surface water salinity was significantly different. Evaporation rate from the diluted plume was occasionally 3 times larger than that of the main salty lake. In the open lake, where salinity was uniform with depth, increased wind speed resulted in increased evaporation rate, as expected. However, in the buoyant plume where diluted brine floats over the hypersaline brine, wind speed above a threshold value (˜4 m s-1) caused a sharp decrease in evaporation probably due to mixing of the stratified plume and a consequent increase in the surface water salinity.

Mechanisms for Seasonal and Interannual Sea Surface Salinity Variability in the Indian Ocean

NASA Astrophysics Data System (ADS)

Köhler, J.; Stammer, D.; Serra, N.; Bryan, F.

2016-12-01

Space-borne salinity data in the Indian Ocean are analyzed over the period 2000-2015 based on data from the European Space Agency's (ESA) "Soil Moisture and Ocean Salinity" (SMOS) and the National Aeronautical Space Agency's (NASA) "Aquarius/SAC-D" missions. The seasonal variability is the dominant mode of sea surface salinity (SSS) variability in the Indian Ocean, accounting for more than 50% of salinity variance. Through a combined analysis of the satellite and ARGO data, dominant forcing terms for seasonal salinity changes are identified. It is found, that E-P controls seasonal salinity tendency in the western Indian Ocean, where the ITCZ has a strong seasonal cycle. In contrast, Ekman advection is the dominant term in the northern and eastern equatorial Indian Ocean. The influence of vertical processes on the salinity tendency is enhanced in coastal upwelling regions and south of the equator due to mid-ocean upwelling. Jointly those processes can explain most of the observed seasonal cycle with a correlation of 0.85 and an RMS difference of 0.07/month. However, the detailed composition of driving terms depends on underlying data products. In general, our study confirms previous results from Lisan Yu (2011); however, in the eastern Indian Ocean contrasting results indicate the leading role of meridional Ekman advection to the seasonal salinity tendency instead of surface external forces due to precipitation. The inferred dominant salinity budget terms are confirmed by results obtained from a high resolution NCAR Core model run driven by NCEP forcing fields. From an EOF analysis of the salinity fields after substracting the annual and semiannual cycle we found that the first EOF mode explains more than 20% of salinity variance. The first principal component of SSS EOF is correlated with the Indian Ocean Dipole Mode Index. Nevertheless the EOF pattern shows a meridional tripole structure, while the IOD describes a zonal SST dipole (Saji et al, 1999).

Deglacial development of (sub) sea surface temperature and salinity in the subarctic northwest Pacific: Implications for upper-ocean stratification

NASA Astrophysics Data System (ADS)

Riethdorf, Jan-Rainer; Max, Lars; Nürnberg, Dirk; Lembke-Jene, Lester; Tiedemann, Ralf

2013-01-01

Based on models and proxy data, it has been proposed that salinity-driven stratification weakened in the subarctic North Pacific during the last deglaciation, which potentially contributed to the deglacial rise in atmospheric carbon dioxide. We present high-resolution subsurface temperature (TMg/Ca) and subsurface salinity-approximating (δ18Oivc-sw) records across the last 20,000 years from the subarctic North Pacific and its marginal seas, derived from combined stable oxygen isotopes and Mg/Ca ratios of the planktonic foraminiferal species Neogloboquadrina pachyderma (sin.). Our results indicate regionally differing changes of subsurface conditions. During the Heinrich Stadial 1 and the Younger Dryas cold phases, our sites were subject to reduced thermal stratification, brine rejection due to sea-ice formation, and increased advection of low-salinity water from the Alaskan Stream. In contrast, the Bølling-Allerød warm phase was characterized by strengthened thermal stratification, stronger sea-ice melting, and influence of surface waters that were less diluted by the Alaskan Stream. From direct comparison with alkenone-based sea surface temperature estimates (SSTUk'37), we suggest deglacial thermocline changes that were closely related to changes in seasonal contrasts and stratification of the mixed layer. The modern upper-ocean conditions seem to have developed only since the early Holocene.

Ultra Stable Microwave Radiometers for Future Sea Surface Salinity Missions

NASA Technical Reports Server (NTRS)

Wilson, William J.; Tanner, Alan B.; Pellerano, Fernando A.; Horgan, Kevin A.

2005-01-01

The NASA Earth Science System Pathfinder (ESSP) mission Aquarius will measure global sea surface salinity with 100-km spatial resolution every 8 days with an average monthly salinity accuracy of 0.2 psu (parts per thousand). This requires an L-band low-noise radiometer with the long-term calibration stability of less than 0.1 K over 8 days. This three-year research program on ultra stable radiometers has addressed the radiometer requirements and configuration necessary to achieve this objective for Aquarius and future ocean salinity missions. The system configuration and component performance have been evaluated with radiometer testbeds at both JPL and GSFC. The research has addressed several areas including component characterization as a function of temperature, a procedure for the measurement and correction for radiometer system non-linearity, noise diode calibration versus temperature, low noise amplifier performance over voltage, and temperature control requirements to achieve the required stability. A breadboard radiometer, utilizing microstrip-based technologies, has been built to demonstrate this long-term stability. This report also presents the results of the radiometer test program, a detailed radiometer noise model, and details of the operational switching sequence optimization that can be used to achieve the low noise and stability requirements. Many of the results of this research have been incorporated into the Aquarius radiometer design and will allow this instrument to achieve its goals.

Study of the Formation and Evolution of Precipitation Induced Sea Surface Salinity Minima in the Tropical Pacific Using HYCOM

NASA Astrophysics Data System (ADS)

Gallagher, R. L.

2016-02-01

During heavy rain events in the tropics, areas of relatively low salinity water collect on the ocean surface. Rainfall events increase the buoyancy of the ocean surface and impact upper ocean salinity and temperature profiles. This resists downward mixing and as a result can persist (SPURS II planning group, 2012; Oceanography 28(1) 150-159). Salinity at the surface adjusts through advective and diffusive mixing processes (Scott, J. et al, 2013; AGU Fall meeting abstracts). This project investigates the upper ocean salinity response in both advection and diffusion dominated regions. The changes in ocean surface salinity are tracked before, during, and after rainfall events. Data from a standard oceanographic model, HYCOM, are used to identify areas where each surface process is significant. Rainfall events are identified using a TRMM dataset. It provides a tropical rainfall analysis which uses amalgamated satellite data to develop detailed global precipitation grids between 50 o north and south latitude. TRMM is useful due its high temporal and spatial resolutions. The salinity response in HYCOM is tested against simple theoretical advective and diffusive mixing models. The magnitude of sea surface salinity minima, their persistence and the precision by which HYCOM can resolve these phenomena are of interest.

A Coral-based Reconstruction of Sea Surface Salinity at Sabine Bank, Vanuatu from 2007 to 1843 CE

NASA Astrophysics Data System (ADS)

Gorman, M. K.; Quinn, T. M.; Taylor, F. W.; Dunn, E. M.; Cabioch, G.; Ballu, V.; Maes, C.; Austin, J. A.; Saustrup, S.; Pelletier, B.

2011-12-01

We present a reconstruction of sea surface salinity (SSS) derived from a coral δ18O time series extending from 2007-1843 CE at Sabine Bank, Vanuatu (SBV, 166.04° E, 15.94°S). This reconstruction is significant because instrumental records of SSS are rare in time and space, yet the SSS response to the El Niño Southern Oscillation (ENSO) forcing is large in many regions of the tropical oceans. There is a strong positive relationship between sea surface temperature anomalies (SSTA) in the central Pacific (Niño 3.4 region; canonical ENSO signal) and six month lagged sea surface salinity anomalies (SSSA, data from Delcroix et al., 2011) at SBV, which establishes a dynamical link between surface ocean variability at SBV and ENSO variability. We calculate a coral δ18O anomaly time series and note that there is a strong correlation between it and instrumental SSS variations over the period 1970-2007 (r = 0.70, p < 0.01). We compute a linear transfer function that we use to predict SSS variations given observed coral δ18O variations. A calibration-verification exercise conducted over two intervals (1970-1987, 1988-2007) resulted in similar correlations between instrumental and reconstructed SSS for both time periods, which provides confidence in our SSS reconstructions in the pre-1970 interval. We further test our SBV transfer function by applying it to a previously published coral δ18O record from Malo Channel, Vanuatu (Kilbourne et al., 2004b), located 130 km to the east of Sabine Bank. The reconstructed SSS time series from the two locations over their common time interval (1991-1939 CE) are nearly always the same within error, indicating that the ENSO-influenced salinity signal is regional in extent, and can be reconstructed using coral δ18O records from Vanuatu. We observe high salinity excursions (>0.5 psu) pre-1970 corresponding to strong ENSO warm phase events recorded in the SST instrumental record and historical ENSO record (i.e. 1941-42, 1918-19, 1877

Aquarius and Remote Sensing of Sea Surface Salinity from Space

NASA Technical Reports Server (NTRS)

LeVine, David M.; Lagerloef, G. S. E.; Torrusio, S.

2012-01-01

Aquarius is an L-band radiometer and scatterometer instrument combination designed to map the salinity field at the surface of the ocean from space. The instrument is designed to provide global salinity maps on a monthly basis with a spatial resolution of 150 km and an accuracy of 0.2 psu. The science objective is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean. This data will promote understanding of ocean circulation and its role in the global water cycle and climate.

Freshwater exchanges and surface salinity in the Colombian basin, Caribbean Sea.

PubMed

Beier, Emilio; Bernal, Gladys; Ruiz-Ochoa, Mauricio; Barton, Eric Desmond

2017-01-01

Despite the heavy regional rainfall and considerable discharge of many rivers into the Colombian Basin, there have been few detailed studies about the dilution of Caribbean Surface Water and the variability of salinity in the southwestern Caribbean. An analysis of the precipitation, evaporation and runoff in relation to the climate variability demonstrates that although the salt balance in the Colombian Basin overall is in equilibrium, the area south of 12°N is an important dilution sub-basin. In the southwest of the basin, in the region of the Panama-Colombia Gyre, Caribbean Sea Water is diluted by precipitation and runoff year round, while in the northeast, off La Guajira, its salinity increases from December to May by upwelling. At the interannual scale, continental runoff is related to El Niño Southern Oscillation, and precipitation and evaporation south of 12°N are related to the Caribbean Low Level Jet. During El Niño years the maximum salinification occurs in the dry season (December-February) while in La Niña years the maximum dilution (or freshening), reaching La Guajira Coastal Zone, occurs in the wet season (September-November).

Freshwater exchanges and surface salinity in the Colombian basin, Caribbean Sea

PubMed Central

2017-01-01

Despite the heavy regional rainfall and considerable discharge of many rivers into the Colombian Basin, there have been few detailed studies about the dilution of Caribbean Surface Water and the variability of salinity in the southwestern Caribbean. An analysis of the precipitation, evaporation and runoff in relation to the climate variability demonstrates that although the salt balance in the Colombian Basin overall is in equilibrium, the area south of 12°N is an important dilution sub-basin. In the southwest of the basin, in the region of the Panama-Colombia Gyre, Caribbean Sea Water is diluted by precipitation and runoff year round, while in the northeast, off La Guajira, its salinity increases from December to May by upwelling. At the interannual scale, continental runoff is related to El Niño Southern Oscillation, and precipitation and evaporation south of 12°N are related to the Caribbean Low Level Jet. During El Niño years the maximum salinification occurs in the dry season (December-February) while in La Niña years the maximum dilution (or freshening), reaching La Guajira Coastal Zone, occurs in the wet season (September-November). PMID:28777801

Compact, Lightweight Dual-Frequency Microstrip Antenna Feed for Future Soil Moisture and Sea Surface Salinity Missions

NASA Technical Reports Server (NTRS)

Yueh, Simon; Wilson, William J.; Njoku, Eni; Dinardo, Steve; Hunter, Don; Rahmat-Samii, Yahya; Kona, Keerti S.; Manteghi, Majid

2006-01-01

The development of a compact, lightweight, dual-frequency antenna feed for future soil moisture and sea surface salinity (SSS) missions is described. The design is based on the microstrip stacked-patch array (MSPA) to be used to feed a large lightweight deployable rotating mesh antenna for spaceborne L-band (approx.1 GHz) passive and active sensing systems. The design features will also enable applications to airborne soil moisture and salinity remote sensing sensors operating on small aircrafts. This paper describes the design of stacked patch elements and 16-element array configuration. The results from the return loss, antenna pattern measurements and sky tests are also described.

Sun Glint and Sea Surface Salinity Remote Sensing

NASA Technical Reports Server (NTRS)

Dinnat, Emmanuel P.; LeVine, David M.

2007-01-01

A new mission in space, called Aquarius/SAC-D, is being built to measure the salinity of the world's oceans. Salinity is an important parameter for understanding movement of the ocean water. This circulation results in the transportation of heat and is important for understanding climate and climate change. Measuring salinity from space requires precise instruments and a careful accounting for potential sources of error. One of these sources of error is radiation from the sun that is reflected from the ocean surface to the sensor in space. This paper examines this reflected radiation and presents an advanced model for describing this effect that includes the effects of ocean waves on the reflection.

Salinity controls on Na incorporation in Red Sea planktonic foraminifera

NASA Astrophysics Data System (ADS)

Mezger, E. M.; de Nooijer, L. J.; Boer, W.; Brummer, G. J. A.; Reichart, G. J.

2016-12-01

Whereas several well-established proxies are available for reconstructing past temperatures, salinity remains challenging to assess. Reconstructions based on the combination of (in)organic temperature proxies and foraminiferal stable oxygen isotopes result in relatively large uncertainties, which may be reduced by application of a direct salinity proxy. Cultured benthic and planktonic foraminifera showed that Na incorporation in foraminiferal shell calcite provides a potential independent proxy for salinity. Here we present the first field calibration of such a potential proxy. Living planktonic foraminiferal specimens from the Red Sea surface waters were collected and analyzed for their Na/Ca content using laser ablation quadrupole inductively coupled plasma mass spectrometry. Using the Red Sea as a natural laboratory, the calibration covers a broad range of salinities over a steep gradient within the same water mass. For both Globigerinoides ruber and Globigerinoides sacculifer calcite Na/Ca increases with salinity, albeit with a relatively large intraspecimen and interspecimen variability. The field-based calibration is similar for both species from a salinity of 36.8 up to 39.6, while values for G. sacculifer deviate from this trend in the northernmost transect. It is hypothesized that the foraminifera in the northernmost part of the Red Sea are (partly) expatriated and hence should be excluded from the Na/Ca-salinity calibration. Incorporation of Na in foraminiferal calcite therefore provides a potential proxy for salinity, although species-specific calibrations are still required and more research on the effect of temperature is needed.

Detecting Global Hydrological Cycle Intensification in Sea Surface Salinity

NASA Astrophysics Data System (ADS)

Poague, J.; Stine, A.

2016-12-01

Global warming is expected to intensify the global hydrological cycle, but significant regional differences exist in the predicted response. The proposed zonal mean thermodynamic response is enhanced horizontal moisture transport associated with increased saturation vapor pressure, which in turn drives additional net precipitation in the tropics and at high latitudes and additional net evaporation in the subtropics. Sea surface salinity (SSS) anomalies are forced from above by changes in evaporation minus precipitation (E-P) and thus will respond to changes in the global hydrological cycle, opening the possibility of using historical SSS anomalies to diagnose the response of the hydrological cycle to warming. We estimate zonal mean SSS trends in the Atlantic and Pacific ocean basins from 1955-2015 to test whether historical changes in the global hydrological cycle are consistent with a primarily thermodynamic response. Motivated by this observation, we calculate the sensitivity of basin zonal-mean SSS anomalies to sea surface temperature (SST) forcing as a function of timescale to diagnose and estimate the signal-to-noise ratio of the purely thermodynamic signal as a function of timescale. High-frequency variability in SSS anomalies is likely to be influenced by variability in atmospheric circulation, complicating the attribution of the link between basin zonal-mean SSS anomalies and global SST anomalies. We therefore estimate the basin zonal mean SSS anomaly response to the major modes of large-scale dynamic variability. We find a strong correlation between detrended zonal-mean SSS anomalies and the Pacific-North American index (R=0.71,P<0.01) in the Pacific Ocean. We interpret the relationship between zonal mean SSS anomalies and temperature in terms of the relative contribution of thermodynamic and dynamic processes.

The effect of precipitation on measuring sea surface salinity from space

NASA Astrophysics Data System (ADS)

Jin, Xuchen; Pan, Delu; He, Xianqiang; Wang, Difeng; Zhu, Qiankun; Gong, Fang

2017-10-01

The sea surface salinity (SSS) can be measured from space by using L-band (1.4 GHz) microwave radiometers. The L-band has been chosen for its sensitivity of brightness temperature to the change of salinity. However, SSS remote sensing is still challenging due to the low sensitivity of brightness temperature to SSS variation: for the vertical polarization, the sensitivity is about 0.4 to 0.8 K/psu with different incident angles and sea surface temperature; for horizontal polarization, the sensitivity is about 0.2 to 0.6 K/psu. It means that we have to make radiometric measurements with accuracy better than 1K even for the best sensitivity of brightness temperature to SSS. Therefore, in order to retrieve SSS, the measured brightness temperature at the top of atmosphere (TOA) needs to be corrected for many sources of error. One main geophysical source of error comes from atmosphere. Currently, the atmospheric effect at L-band is usually corrected by absorption and emission model, which estimate the radiation absorbed and emitted by atmosphere. However, the radiation scattered by precipitation is neglected in absorption and emission models, which might be significant under heavy precipitation. In this paper, a vector radiative transfer model for coupled atmosphere and ocean systems with a rough surface is developed to simulate the brightness temperature at the TOA under different precipitations. The model is based on the adding-doubling method, which includes oceanic emission and reflection, atmospheric absorption and scattering. For the ocean system with a rough surface, an empirical emission model established by Gabarro and the isotropic Cox-Munk wave model considering shadowing effect are used to simulate the emission and reflection of sea surface. For the atmospheric attenuation, it is divided into two parts: For the rain layer, a Marshall-Palmer distribution is used and the scattering properties of the hydrometeors are calculated by Mie theory (the scattering

Impacts of sea-surface salinity in an eddy-resolving semi-global OGCM

NASA Astrophysics Data System (ADS)

Furue, Ryo; Takatama, Kohei; Sasaki, Hideharu; Schneider, Niklas; Nonaka, Masami; Taguchi, Bunmei

2018-02-01

To explore the impacts of sea-surface salinity (SSS) on the interannual variability of upper-ocean state, we compare two 10-year runs of an eddy-resolving ocean general circulation model (OGCM): in one, SSS is strongly restored toward a monthly climatology (World Ocean Atlas '98) and in the other, toward the SSS of a monthly gridded Argo product. The inclusion of the Argo SSS generally improves the interannual variability of the mixed layer depth; particularly so in the western tropical Pacific, where so-called "barrier layers" are reproduced when the Argo SSS is included. The upper-ocean subsurface salinity variability is also improved in the tropics and subtropics even below the mixed layer. To understand the reason for the latter improvement, we separate the salinity difference between the two runs into its "dynamical" and "spiciness" components. The dynamical component is dominated by small-scale noise due to the chaotic nature of mesoscale eddies. The spiciness difference indicates that as expected from the upper-ocean general circulation, SSS variability in the mixed layer is subducted into the thermocline in subtropics; this signal is generally advected downward, equatorward, and westward in the equator-side of the subtropical gyre. The SSS signal subducted in the subtropical North Pacific appears to enter the Indian Ocean through the Indonesian Throughflow, although this signal is weak and probably insignificant in our model.

The Impact of the Assimilation of Aquarius Sea Surface Salinity Data in the GEOS Ocean Data Assimilation System

NASA Technical Reports Server (NTRS)

Vernieres, Guillaume Rene Jean; Kovach, Robin M.; Keppenne, Christian L.; Akella, Santharam; Brucker, Ludovic; Dinnat, Emmanuel Phillippe

2014-01-01

Ocean salinity and temperature differences drive thermohaline circulations. These properties also play a key role in the ocean-atmosphere coupling. With the availability of L-band space-borne observations, it becomes possible to provide global scale sea surface salinity (SSS) distribution. This study analyzes globally the along-track (Level 2) Aquarius SSS retrievals obtained using both passive and active L-band observations. Aquarius alongtrack retrieved SSS are assimilated into the ocean data assimilation component of Version 5 of the Goddard Earth Observing System (GEOS-5) assimilation and forecast model. We present a methodology to correct the large biases and errors apparent in Version 2.0 of the Aquarius SSS retrieval algorithm and map the observed Aquarius SSS retrieval into the ocean models bulk salinity in the topmost layer. The impact of the assimilation of the corrected SSS on the salinity analysis is evaluated by comparisons with insitu salinity observations from Argo. The results show a significant reduction of the global biases and RMS of observations-minus-forecast differences at in-situ locations. The most striking results are found in the tropics and southern latitudes. Our results highlight the complementary role and problems that arise during the assimilation of salinity information from in-situ (Argo) and space-borne surface (SSS) observations

The role of sea surface salinity in ENSO related water cycle anomaly

NASA Astrophysics Data System (ADS)

Tang, Wenqing; Yueh, Simon

2017-04-01

This study investigates the role of sea surface salinity (SSS) in the water cycle anomaly associated with El Niño Southern Oscillation (ENSO). The 2015-16 El Niño, one of the strongest ENSO events observed in centuries, coincident with unprecedented coverage of spacebased remote sensing of SSS over global oceans. We analyze three SSS data sets: from the NASA's missions of SMAP and Aquarius, and the ESA's Soil Moisture and Ocean Salinity (SMOS). One typical characteristics of an ENSO event is the zonal displacement of the Western equatorial Pacific Fresh Pool (WPFP). The edge of the pool extends eastward during El Niño, retreats westward during La Niña. For super El Niño, the eastern edge of WPFP extends much more east across the equatorial Pacific. Indeed, SSS from SMAP reveals much stronger eastward migration of WPFP starting in April 2015. The eastern edge of WPFP reached 140°W in March 2016, about 40° more eastward extension than Aquarius observed in previous years. In the following months from March to June 2016, WPFP retreated westward, coincident with the ending of this strong El Niño event [WMO, El Nino/La Nina update, 2016]. SMOS data shows similar feature, confirming that there is no systematic biases between SMAP and Aquarius retrievals. We examine the linkage between the observed SSS variation and ENSO related water cycle anomaly by integrated analysis of SSS data sets in conjunction with other satellite and in situ measurements on rain, wind, evaporation and ocean currents. Based on the governing equation of the mixed layer salt budget, the freshwater exchange between air-sea interfaces is estimated as residual of the mixed-layer salinity (MLS) temporal change and advection (Focean), as an alternative to evaporation minus precipitation (FE-P). We analyzed the spatial and temporal variation of Focean and FE-P to explore the anomalous signature in the oceanic and atmospheric branches of the water cycle associated with 2015/16 ENSO. The maximum

Usage of satellite data SMOS in order to characterize Sea Surface Salinity in the western Mediterranean

NASA Astrophysics Data System (ADS)

Brook, Anna; Robins, Lotem; Olmedo Casal, Estrella

2017-04-01

Measuring the level of Sea Surface Salinity (SSS) is a principle component in order to understand climate processes that occur today and for better understanding of climate change in the future; Different processes create different salt concentration in different places in the oceans. This different salinity level had a role in determining the vertical and horizontal water fluxes. As the first three meters of the ocean surface contain more heat than that in the whole atmosphere, the influence of the salinity level on the layering of the different water levels and the different fluxes, thus, it is an important factor determining air sea interaction. An existing problem in predicting the oceans is the lack of salinity samples in the oceans. While Sea surface Temperature (SST) could be evaluated easier from remote sensed devices, analyzing data at the Near Infra-Red and Visual wavelength. Measuring and locating salinity spectral signature was an obstacle. This lack of data caused problems running different models that describe different parameters of the ocean, both in depth and surface. One of the main goals of a program called: Soil Moisture and Ocean Salinity (SMOS), is to deliver data on a global scale concerning the sea surface salinity (SSS). The main idea of the SMOS technology is based on the differences between the electro-magnetic properties (spectral signatures) of distilled water and salted water. High concentration of salt revealed by analyzing the energy emitted from the ocean's surface, using detectors that are sensitive for the wavelength at the range of 21 cm (L-band: 1.4 GHz). One of the main problems, measuring this wavelength, is that it requires very large antennas. In order to solve this problem, a Y shaped satellite was built, on each of its arms, 69 antennas were attached, with equal distances between each antenna. Each antenna is 165 mm on the diameter and their height is 19 mm. This antenna transmits all the information they receive to a

Groundwater-saline lakes interaction - The contribution of saline groundwater circulation to solute budget of saline lakes: a lesson from the Dead Sea

NASA Astrophysics Data System (ADS)

Kiro, Yael; Weinstein, Yishai; Starinsky, Abraham; Yechieli, Yoseph

2013-04-01

Saline lakes act as base level for both surface water and groundwater. Thus, a change in lake levels is expected to result in changes in the hydrogeological system in its vicinity, exhibited in groundwater levels, location of the fresh-saline water interface, sub-lacustrine groundwater discharge (SGD) and saline water circulation. All these processes were observed in the declining Dead Sea system, whose water level dropped by ~35 meters in the last 50 years. This work focuses mainly on the effect of circulation of Dead Sea water in the aquifer, which continues even in this very rapid base level drop. In general, seawater circulation in coastal aquifers is now recognized as a major process affecting trace element mass balances in coastal areas. Estimates of submarine groundwater discharge (SGD) vary over several orders of magnitude (1-1000000 m3/yr per meter shoreline). These estimates are sensitive to fresh-saline SGD ratios and to the temporal and spatial scales of the circulation. The Dead Sea system is an excellent natural field lab for studying seawater-groundwater interaction and large-scale circulation due to the absence of tides and to the minor role played by waves. During Dead Sea water circulation in the aquifer several geochemical reactions occur, ranging from short-term adsorption-desorption reactions and up to long-term precipitation and dissolution reactions. These processes affect the trace element distribution in the saline groundwater. Barite and celestine, which are supersaturated in the lake water, precipitate during circulation in the aquifer, reducing barium (from 5 to 1.5 mg/L), strontium (from 350 to 300 mg/L) and the long-lived 226Ra (from 145 to 60 dpm/L) in the saline groundwater. Redox-controlled reactions cause a decrease in uranium from 2.4 to 0.1 μg/L, and an increase in iron from 1 to 13 mg/L. 228Ra (t1/2=5.75 yr) activity in the Dead Sea is ~1 dpm/L and increase gradually as the saline water flows further inland until reaching

A new record of Atlantic sea surface salinity from 1896-2013 reveals the signatures of climate variability and long-term trends

NASA Astrophysics Data System (ADS)

Friedman, A. R.; Reverdin, G. P.; Khodri, M.; Gastineau, G.

2017-12-01

In the North Atlantic, sea surface salinity is both an indicator of the hydrological cycle and an active component of the ocean circulation. As an indirect "ocean rain gauge", surface salinity reflects the net surface fluxes of evaporation - precipitation + runoff, along with advection and vertical mixing. Subpolar surface salinity also may influence the strength of deep convection and the Atlantic Meridional Overturning Circulation (AMOC). However, continuous surface salinity time series beginning before the 1950s are rare, limiting our ability to resolve modes of variability and long-term trends. Here, we present a new gridded surface salinity record in the Atlantic from 1896-2013, compiled from a variety of historical sources. The compilation covers most of the Atlantic from 20°S-70°N, at 100-1000 km length scale and interannual temporal resolution, allowing us to resolve major modes of variability and linkages with large-scale Atlantic climate variations. We find that the low-latitude (tropical and subtropical) Atlantic and the subpolar Atlantic surface salinity are negatively correlated, with subpolar anomalies leading low-latitude anomalies by about a decade. Subpolar surface salinity varies in phase with the Atlantic Multidecadal Oscillation (AMO), whereas low-latitude surface salinity lags the AMO and varies in phase with the low-frequency North Atlantic Oscillation (NAO). Additionally, northern tropical surface salinity is anticorrelated with the AMO and with Sahel rainfall, suggesting that it reflects the latitude of the Intertropical Convergence Zone. The 1896-2013 long-term trend features an amplification of the mean Atlantic surface salinity gradient pattern, with freshening in the subpolar Atlantic and salinification in the tropical and subtropical Atlantic. We find that regressing out the AMO and the low-frequency NAO has little effect on the long-term residual trend. The spatial trend structure is consistent with the "rich-get-richer" hydrological

Recent trends and variations in Baltic Sea temperature, salinity, stratification and circulation

NASA Astrophysics Data System (ADS)

Elken, Jüri; Lehmann, Andreas; Myrberg, Kai

2015-04-01

The presentation highlights the results of physical oceanography from BACC II (Second BALTEX Assessment of Climate Change for the Baltic Sea basin) book based on the review of recent literature published until 2013. We include also information from some more recent publications. A recent warming trend in sea surface waters has been clearly demonstrated by all available methods: in-situ measurements, remote sensing data and modelling tools. In particular, remote sensing data for the period 1990-2008 indicate that the annual mean SST has increased even by 1°C per decade, with the greatest increase in the northern Bothnian Bay and also with large increases in the Gulf of Finland, the Gulf of Riga, and the northern Baltic Proper. Although the increase in the northern areas is affected by the recent decline in the extent and duration of sea ice, and corresponding changes in surface albedo, warming is still evident during all seasons and with the greatest increase occurring in summer. The least warming of surface waters (0.3-0.5°C per decade) occurred northeast of Bornholm Island up to and along the Swedish coast, probably owing to an increase in the frequency of coastal upwelling forced by the westerly wind events. Comparing observations with the results of centennial-scale modelling, recent changes in sea water temperature appear to be within the range of the variability observed during the past 500 years. Overall salinity pattern and stratification conditions are controlled by river runoff, wind conditions, and salt water inflows through the Danish straits. The mean top-layer salinity is mainly influenced by the accumulated river runoff, with higher salinity during dry periods and lower salinity during wet periods. Observations reveal a low-salinity period above the halocline starting in the 1980s. The strength of stratification and deep salinity are reduced when the mean zonal wind stress increases, as it occurred since 1987. Major Baltic Inflows of highly saline

Sea surface salinity of the Eocene Arctic Azolla event using innovative isotope modeling

NASA Astrophysics Data System (ADS)

Speelman, E. N.; Sewall, J. O.; Noone, D.; Huber, M.; Sinninghe Damste, J. S.; Reichart, G. J.

2009-04-01

With the realization that the Eocene Arctic Ocean was covered with enormous quantities of the free floating freshwater fern Azolla, new questions regarding Eocene conditions facilitating these blooms arose. Our present research focuses on constraining the actual salinity of, and water sources for, the Eocene Arctic basin through the application of stable water isotope tracers. Precipitation pathways potentially strongly affect the final isotopic composition of water entering the Arctic Basin. Therefore we use the Community Atmosphere Model (CAM3), developed by NCAR, combined with a recently developed integrated isotope tracer code to reconstruct the isotopic composition of global Eocene precipitation and run-off patterns. We further addressed the sensitivity of the modeled hydrological cycle to changes in boundary conditions, such as pCO2, sea surface temperatures (SSTs) and sea ice formation. In this way it is possible to assess the effect of uncertainties in proxy estimates of these parameters. Overall, results of all runs with Eocene boundary conditions, including Eocene topography, bathymetry, vegetation patterns, TEX86 derived SSTs and pCO2 estimates, show the presence of an intensified hydrological cycle with precipitation exceeding evaporation in the Arctic region. Enriched, precipitation weighted, isotopic values of around -120‰ are reported for the Arctic region. Combining new results obtained from compound specific isotope analyses (δD) on terrestrially derived n-alkanes extracted from Eocene sediments, and model outcomes make it possible to verify climate reconstructions for the middle Eocene Arctic. Furthermore, recently, characteristic long-chain mid-chain ω20 hydroxy wax constituents of Azolla were found in ACEX sediments. δD values of these C32 - C36 diols provide insight into the isotopic composition of the Eocene Arctic surface water. As the isotopic signature of the runoff entering the Arctic is modelled, and the final isotopic composition of

Sensitivity of Global Sea-Air CO2 Flux to Gas Transfer Algorithms, Climatological Wind Speeds, and Variability of Sea Surface Temperature and Salinity

NASA Technical Reports Server (NTRS)

McClain, Charles R.; Signorini, Sergio

2002-01-01

Sensitivity analyses of sea-air CO2 flux to gas transfer algorithms, climatological wind speeds, sea surface temperatures (SST) and salinity (SSS) were conducted for the global oceans and selected regional domains. Large uncertainties in the global sea-air flux estimates are identified due to different gas transfer algorithms, global climatological wind speeds, and seasonal SST and SSS data. The global sea-air flux ranges from -0.57 to -2.27 Gt/yr, depending on the combination of gas transfer algorithms and global climatological wind speeds used. Different combinations of SST and SSS global fields resulted in changes as large as 35% on the oceans global sea-air flux. An error as small as plus or minus 0.2 in SSS translates into a plus or minus 43% deviation on the mean global CO2 flux. This result emphasizes the need for highly accurate satellite SSS observations for the development of remote sensing sea-air flux algorithms.

Sea-ice transport driving Southern Ocean salinity and its recent trends.

PubMed

Haumann, F Alexander; Gruber, Nicolas; Münnich, Matthias; Frenger, Ivy; Kern, Stefan

2016-09-01

Recent salinity changes in the Southern Ocean are among the most prominent signals of climate change in the global ocean, yet their underlying causes have not been firmly established. Here we propose that trends in the northward transport of Antarctic sea ice are a major contributor to these changes. Using satellite observations supplemented by sea-ice reconstructions, we estimate that wind-driven northward freshwater transport by sea ice increased by 20 ± 10 per cent between 1982 and 2008. The strongest and most robust increase occurred in the Pacific sector, coinciding with the largest observed salinity changes. We estimate that the additional freshwater for the entire northern sea-ice edge entails a freshening rate of -0.02 ± 0.01 grams per kilogram per decade in the surface and intermediate waters of the open ocean, similar to the observed freshening. The enhanced rejection of salt near the coast of Antarctica associated with stronger sea-ice export counteracts the freshening of both continental shelf and newly formed bottom waters due to increases in glacial meltwater. Although the data sources underlying our results have substantial uncertainties, regional analyses and independent data from an atmospheric reanalysis support our conclusions. Our finding that northward sea-ice freshwater transport is also a key determinant of the mean salinity distribution in the Southern Ocean further underpins the importance of the sea-ice-induced freshwater flux. Through its influence on the density structure of the ocean, this process has critical consequences for the global climate by affecting the exchange of heat, carbon and nutrients between the deep ocean and surface waters.

Improving an Atlantic Fisheries DSS using Sea Surface Salinity Data from NASA's Aquarius Mission

NASA Technical Reports Server (NTRS)

Guest, DeNeice

2007-01-01

This report assesses the capacity of incorporating NASA#s Aquarius SSS (sea surface salinity) data into the SMAST (School of Marine Science and Technology) DSS for Fisheries Science. This data will enhance the SMAST DSS by providing SSS over a large area. Aquarius is a focused satellite mission designed to measure global SSS. SSS mapping is limited because conventional in situ SSS sampling is too sparse to give a large-scale view of the salinity variability. Aquarius will resolve missing physical processes that link the water cycle, the climate, and the ocean. The SMAST Fisheries program provides a DSS for fisheries science. It collects fisheries and environmental data, integrates them into a suite of data assimilation ocean models, and provides hindcasts, nowcasts, and forecasts for fisheries research, fisheries management, and the fishery industry. Currently, SMAST is using SSS data from the National Oceanic and Atmospheric Administration#s National Data Buoy Center. The SMAST DSS would be enhanced with SSS data from the Aquarius mission.

Ocean Surface Emissivity at L-band (1.4 GHz): The Dependence on Salinity and Roughness

NASA Technical Reports Server (NTRS)

LeVine, D. M.; Lang, R.; Wentz, F.; Messiner, T.

2012-01-01

A characterization of the emissivity of sea water at L-band is important for the remote sensing of sea surface salinity. Measurements of salinity are currently being made in the radio astronomy band at 1.413 GHz by ESA's Soil Moisture and Ocean Salinity (SMOS) mission and NASA's Aquarius instrument aboard the Aquarius/SAC-D observatory. The goal of both missions is accuracy on the order of 0.1 psu. This requires accurate knowledge of the dielectric constant of sea water as a function of salinity and temperature and also the effect of waves (roughness). The former determines the emissivity of an ideal (i.e. flat) surface and the later is the major source of error from predictions based on a flat surface. These two aspects of the problem of characterizing the emissivity are being addressed in the context of the Aquarius mission. First, laboratory measurements are being made of the dielectric constant of sea water. This is being done at the George Washington University using a resonant cavity. In this technique, sea water of known salinity and temperature is fed into the cavity along its axis through a narrow tube. The sea water changes the resonant frequency and Q of the cavity which, if the sample is small enough, can be related to the dielectric constant of the sample. An extensive set of measurements have been conducted at 1.413 GHz to develop a model for the real and imaginary part of the dielectric constant as a function of salinity and temperature. The results are compared to the predictions of models based on parameterization of the Debye resonance of the water molecule. The models and measurements are close; however, the differences are significant for remote sensing of salinity. This is especially true at low temperatures where the sensitivity to salinity is lowest.

Distribution of Surface pH and Total Alkalinity at the Sea of Okhotsk and the East Sea in October 2007

NASA Astrophysics Data System (ADS)

Shim, J.; Kang, D.; Jin, Y.; Obzhirov, A.

2008-12-01

Surface pH, total alkalinity, temperature and salinity were measured at the Sea of Okhotsk and the East Sea (along a track from Vladivostok to the northeastern slope of Sakhalin Island through Soya Strait: 42°N, 132°E - 55°N, 145°E) in October 2007. Continuous pH measurements were conducted using an underway potentiometric pH system modified from Tishchenko et al. (2002) and discrete total alkalinity measurements were made by direct titration with hydrochloric acid. Warm saline surface waters were observed in the East Sea (from Vladivostok to Soya Strait), and relatively cold less-saline waters were observed in the Sea of Okhotsk (at the eastern slopes of Sakhalin Island). In the East Sea and the Sea of Okhotsk, surface pH ranged from 8.063 to 8.158 and 8.047 to 8.226, and total alkalinity normalized to salinity 35 ranged from 2323 to 2344 μmol kg-1 and 2367 to 2422 μmol kg-1, respectively. Due to the freshwater input from rivers and geochemical activity in the water column and sediment, the Sea of Okhotsk generally showed much wider ranges of water properties and richer in carbonate parameters than those of the East Sea. Particularly, water properties changed dramatically at the eastern slopes of Sakhalin Island; surface salinity decreased southward by about 0.5-1 psu and pH and normalized total alkalinity increased southward by about 0.05-0.1 and 20-50 μmol kg-1, respectively. Thus, pCO2 concentration calculated from pH and total alkalinity, ranged from 350-375 μatm in the north to 280-300 μatm in the south of the Okhotsk Sea. The high pH and normalized total alkalinity, and low pCO2 and salinity in the south might be the result of surface water mixing with fresh water discharge from rivers and/or the results of massive primary production along the eastern coast of Sakhalin Island. In the most study area, surface pCO2 ranged from 280 to 370 μatm and was undersaturated relative to atmosphere. Therefore, the Sea of Okhotsk and the East Sea acted as

Wind-induced interannual variability of sea level slope, along-shelf flow, and surface salinity on the Northwest Atlantic shelf

NASA Astrophysics Data System (ADS)

Li, Yun; Ji, Rubao; Fratantoni, Paula S.; Chen, Changsheng; Hare, Jonathan A.; Davis, Cabell S.; Beardsley, Robert C.

2014-04-01

In this study, we examine the importance of regional wind forcing in modulating advective processes and hydrographic properties along the Northwest Atlantic shelf, with a focus on the Nova Scotian Shelf (NSS)-Gulf of Maine (GoM) region. Long-term observational data of alongshore wind stress, sea level slope, and along-shelf flow are analyzed to quantify the relationship between wind forcing and hydrodynamic responses on interannual time scales. Additionally, a simplified momentum balance model is used to examine the underlying mechanisms. Our results show significant correlation among the observed interannual variability of sea level slope, along-shelf flow, and alongshore wind stress in the NSS-GoM region. A mechanism is suggested to elucidate the role of wind in modulating the sea level slope and along-shelf flow: stronger southwesterly (northeastward) winds tend to weaken the prevailing southwestward flow over the shelf, building sea level in the upstream Newfoundland Shelf region, whereas weaker southwesterly winds allow stronger southwestward flow to develop, raising sea level in the GoM region. The wind-induced flow variability can influence the transport of low-salinity water from the Gulf of St. Lawrence to the GoM, explaining interannual variations in surface salinity distributions within the region. Hence, our results offer a viable mechanism, besides the freshening of remote upstream sources, to explain interannual patterns of freshening in the GoM.

Ocean to land moisture transport is reflected in sea surface salinity

NASA Astrophysics Data System (ADS)

Schmitt, R. W.; Schanze, J. J.; Li, L.; Ummenhofer, C.

2016-02-01

The ocean has a much larger water cycle than the land, with global ocean evaporation of 13 Sverdrups being 10 times larger than the sum of all river flows. This disparity and the different dynamics of dry surfaces, have led to an unfortunate disconnect between terrestrial hydrologists and oceanographers. Here we show that there is in fact a close coupling between the water cycles of ocean and land. In both cases there is much local recycling of moisture, since it does not travel far in the atmosphere. We argue that the most important water cycle variable is the net export (or import) of water from (to) an area. Over the open ocean this is just evaporation minus precipitation (E-P). The "P vs E" plot is a valuable tool for identifying the source and sink regions of the water cycle. The subtropical high pressure systems are the source regions of the water cycle, with a global net export of 4.5 Sv. The three sinks are the ITCZ in the tropics, the high latitude subpolar lows, and the land, all at about 1.5 Sv, though the subpolar lows do receive more water than the tropics, where high rainfall is maintained by much local recycling. Of course, the signature of E-P in the open ocean is the sea surface salinity (SSS), as only net freshwater fluxes can create salinity variations. With the land receiving 1/3 of the oceanic export, we should expect close coupling between terrestrial rainfall and the salinity of nearby oceans, and SSS variations have indeed been found to be valuable for seasonal rainfall forecasts on land. The remarkable 3-6 month lead of winter-spring SSS over summer rainfall appears to be mediated by the recycling process on land through soil moisture. When soil moisture is high, terrestrial regions can become more oceanic-like, with solar heating energizing evaporation and leading to down-stream propagation of the moisture signal (the "brown ocean" effect). The correlation of high SSS with high rainfall promises to be a very valuable seasonal prediction

Detection and variability of the Congo River plume from satellite derived sea surface temperature, salinity, ocean colour and sea level

NASA Astrophysics Data System (ADS)

Hopkins, Jo; Lucas, Marc; Dufau, Claire; Sutton, Marion; Lauret, Olivier

2013-04-01

The Congo River in Africa has the world's second highest annual mean daily freshwater discharge and is the second largest exporter of terrestrial organic carbon into the oceans. It annually discharges an average of 1,250 × 109 m3 of freshwater into the southeast Atlantic producing a vast fresh water plume, whose signature can be traced hundreds of kilometres from the river mouth. Large river plumes such as this play important roles in the ocean carbon cycle, often functioning as carbon sinks. An understanding of their extent and seasonality is therefore essential if they are to be realistically accounted for in global assessments of the carbon cycle. Despite its size, the variability and dynamics of the Congo plume are minimally documented. In this paper we analyse satellite derived sea surface temperature, salinity, ocean colour and sea level anomaly to describe and quantify the extent, strength and variability of the far-field plume and to explain its behaviour in relation to winds, ocean currents and fresh water discharge. Empirical Orthogonal Function analysis reveals strong seasonal and coastal upwelling signals, potential bimodal seasonality of the Angola Current and responses to fresh water discharge peaks in all data sets. The strongest plume-like signatures however were found in the salinity and ocean colour where the dominant sources of variability come from the Congo River itself, rather than from the wider atmosphere and ocean. These two data sets are then analysed using a statistically based water mass detection technique to isolate the behaviour of the plume. The Congo's close proximity to the equator means that the influence of the earth's rotation on the fresh water inflow is relatively small and the plume tends not to form a distinct coastal current. Instead, its behaviour is determined by wind and surface circulation patterns. The main axis of the plume between November and February, following peak river discharge, is oriented northwest, driven

Bacterial responses to fluctuations and extremes in temperature and brine salinity at the surface of Arctic winter sea ice.

PubMed

Ewert, Marcela; Deming, Jody W

2014-08-01

Wintertime measurements near Barrow, Alaska, showed that bacteria near the surface of first-year sea ice and in overlying saline snow experience more extreme temperatures and salinities, and wider fluctuations in both parameters, than bacteria deeper in the ice. To examine impacts of such conditions on bacterial survival, two Arctic isolates with different environmental tolerances were subjected to winter-freezing conditions, with and without the presence of organic solutes involved in osmoprotection: proline, choline, or glycine betaine. Obligate psychrophile Colwellia psychrerythraea strain 34H suffered cell losses under all treatments, with maximal loss after 15-day exposure to temperatures fluctuating between -7 and -25 °C. Osmoprotectants significantly reduced the losses, implying that salinity rather than temperature extremes presents the greater stress for this organism. In contrast, psychrotolerant Psychrobacter sp. strain 7E underwent miniaturization and fragmentation under both fluctuating and stable-freezing conditions, with cell numbers increasing in most cases, implying a different survival strategy that may include enhanced dispersal. Thus, the composition and abundance of the bacterial community that survives in winter sea ice may depend on the extent to which overlying snow buffers against extreme temperature and salinity conditions and on the availability of solutes that mitigate osmotic shock, especially during melting. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Aquarius: An Instrument to Monitor Sea Surface Salinity from Space

NASA Technical Reports Server (NTRS)

LeVine, D. M.; Lagerloef, G. S .E.; Colomb, R.; Yueh, S.; Pellerano, F.

2007-01-01

Aquarius is a combined passive/active L-band microwave instrument that is being developed to map the salinity field at the surface of the ocean from space. The data will support studies of the coupling between ocean circulation, global water cycle, and climate. Aquarius is part of the Aquarius/SAC-D mission, which is a partnership between the U.S. (National Aeronautics and Space Administration) and Argentina (CONAE). The primary science objective of this mission is to monitor the seasonal and interannual variation of the large-scale features of the surface salinity field in the open ocean with a spatial resolution of 150 km and a retrieval accuracy of 0.2 psu globally on a monthly basis.

Sea surface salinity fronts in the Tropical Atlantic Ocean

NASA Astrophysics Data System (ADS)

Ruiz-Etcheverry, L.; Maximenko, N. A.; Melnichenko, O.

2016-12-01

Marine fronts are narrow boundaries that separate water masses of different properties. These fronts are caused by various forcing and believed to be an important component of the coupled ocean-atmosphere system, particularly in the tropical oceans. In this study, we use sea surface salinity (SSS) observations from Aquarius satellite to investigate the spatial structure and temporal variability of SSS fronts in the tropical Atlantic. A number of frontal features have been identified. The mean magnitude of the SSS gradient is maximum near the mouth of the Congo River (0.3-0.4 psu/100km). Relative maxima are also observed in the Inter Tropical Convergence Zone (ITCZ), the Gulf of Guinea, and the mouth of the Amazon River. The pattern of the magnitude of the SSS anomaly gradient revealed that the interaction between river plumes and saltier interior water is complex and highly variable during the three-year observation period. The variability of the magnitude of the density anomaly gradient computed from Aquarius SSS and Reynolds SST is also discussed. Images of the ocean color are utilized to trace the movement of the Congo and Amazon River plumes and compare them with the magnitude of the SSS gradient. Additionally, we analyze de circulation associated with the Amazon plume with altimetry data, and the vertical structure and its changes in time through Argo profiles.

The interaction between sea ice and salinity-dominated ocean circulation: implications for halocline stability and rapid changes of sea-ice cover

NASA Astrophysics Data System (ADS)

Jensen, M. F.; Nilsson, J.; Nisancioglu, K. H.

2016-02-01

In this study, we develop a simple conceptual model to examine how interactions between sea ice and oceanic heat and freshwater transports affect the stability of an upper-ocean halocline in a semi-enclosed basin. The model represents a sea-ice covered and salinity stratified ocean, and consists of a sea-ice component and a two-layer ocean; a cold, fresh surface layer above a warmer, more saline layer. The sea-ice thickness depends on the atmospheric energy fluxes as well as the ocean heat flux. We introduce a thickness-dependent sea-ice export. Whether sea ice stabilizes or destabilizes against a freshwater perturbation is shown to depend on the representation of the vertical mixing. In a system where the vertical diffusivity is constant, the sea ice acts as a positive feedback on a freshwater perturbation. If the vertical diffusivity is derived from a constant mixing energy constraint, the sea ice acts as a negative feedback. However, both representations lead to a circulation that breaks down when the freshwater input at the surface is small. As a consequence, we get rapid changes in sea ice. In addition to low freshwater forcing, increasing deep-ocean temperatures promote instability and the disappearance of sea ice. Generally, the unstable state is reached before the vertical density difference disappears, and small changes in temperature and freshwater inputs can provoke abrupt changes in sea ice.

Stable near-surface ocean salinity stratifications due to evaporation observed during STRASSE

NASA Astrophysics Data System (ADS)

Asher, William E.; Jessup, Andrew T.; Clark, Dan

2014-05-01

Under conditions with a large solar flux and low wind speed, a stably stratified warm layer forms at the ocean surface. Evaporation can then lead to an increase in salinity in the warm layer. A large temperature gradient will decrease density enough to counter the density increase caused by the salinity increase, forming a stable positive salinity anomaly at the surface. If these positive salinity anomalies are large in terms of the change in salinity from surface to the base of the gradient, if their areal coverage is a significant fraction of the satellite footprint, and if they persist long enough to be in the satellite field of view, they could be relevant for calibration and validation of L-band microwave salinity measurements. A towed, surface-following profiler was deployed from the N/O Thalassa during the Subtropical Atlantic Surface Salinity Experiment (STRASSE). The profiler measured temperature and conductivity in the surface ocean at depths of 10, 50, and 100 cm. The measurements show that positive salinity anomalies are common at the ocean surface for wind speeds less than 4 m s-1 when the average daily insolation is >300 W m-2 and the sea-to-air latent heat flux is greater than zero. A semiempirical model predicts the observed dependence of measured anomalies on environmental conditions. However, the model results and the field data suggest that these ocean surface salinity anomalies are not large enough in terms of the salinity difference to significantly affect microwave radiometric measurements of salinity.

Microstrip Antenna for Remote Sensing of Soil Moisture and Sea Surface Salinity

NASA Technical Reports Server (NTRS)

Ramhat-Samii, Yahya; Kona, Keerti; Manteghi, Majid; Dinardo, Steven; Hunter, Don; Njoku, Eni; Wilson, Wiliam; Yueh, Simon

2009-01-01

This compact, lightweight, dual-frequency antenna feed developed for future soil moisture and sea surface salinity (SSS) missions can benefit future soil and ocean studies by lowering mass, volume, and cost of the antenna system. It also allows for airborne soil moisture and salinity remote sensors operating on small aircraft. While microstrip antenna technology has been developed for radio communications, it has yet to be applied to combined radar and radiometer for Earth remote sensing. The antenna feed provides a key instrument element enabling high-resolution radiometric observations with large, deployable antennas. The design is based on the microstrip stacked-patch array (MSPA) used to feed a large, lightweight, deployable, rotating mesh antenna for spaceborne L-band (approximately equal to 1 GHz) passive and active sensing systems. The array consists of stacked patches to provide dual-frequency capability and suitable radiation patterns. The stacked-patch microstrip element was designed to cover the required L-band center frequencies at 1.26 GHz (lower patch) and 1.413 GHz (upper patch), with dual-linear polarization capabilities. The dimension of patches produces the required frequencies. To achieve excellent polarization isolation and control of antenna sidelobes for the MSPA, the orientation of each stacked-patch element within the array is optimized to reduce the cross-polarization. A specialized feed-distribution network was designed to achieve the required excitation amplitude and phase for each stacked-patch element.

Consistency of Aquarius version-4 sea surface salinity with Argo products on various spatial and temporal scales

NASA Astrophysics Data System (ADS)

Lee, T.

2016-12-01

Understanding the accuracies of satellite-derived sea surface salinity (SSS) measurements in depicting temporal changes and the dependence of the accuracies on spatio-temporal scales are important to applications, capability assessment, and future mission design. This study quantifies the consistency between Aquarius Version-4 monthly gridded SSS (released in October 2015) with two widely used Argo monthly gridded near-surface salinity products. The analysis focused on their consistency in depicting temporal changes (including seasonal and non-seasonal) on various spatial scales: 1°x1°, 3°x3°, and 10°x10°. Globally averaged standard deviation (STD) values for Aquarius-Argo salinity differences on these three spatial scales are 0.16, 0.14, 0.09 psu, compared to those between the two Argo products of 0.10, 0.09, and 0.04 psu. Aquarius SSS compare better with Argo data on non-seasonal (e.g., interannual and intraseasonal) than for seasonal time scales. The seasonal Aquarius-Argo SSS differences are mostly concentrated at high latitudes. The Aquarius team is making active efforts to further reduce these high-latitude seasonal biases. The consistency between Aquarius and Argo salinity is similar to that between the two Argo products in the tropics and subtropics for non-seasonal signals, and in the tropics for seasonal signals. Therefore, the representativeness errors of the Argo products for various spatial scales (related to sampling and gridding) need to be taken into account when estimating the uncertainty of Aquarius SSS. The globally averaged uncertainty of large-scale (10°x10°) non-seasonal Aquarius SSS is approximately 0.04 psu. These estimates reflect the significant improvements of Aquarius Version-4 SSS over the previous versions. The estimates can be used as baseline requirements for future ocean salinity missions from space.

Magmatic pulse driven by sea-level changes associated with the Messinian salinity crisis

PubMed Central

Sternai, Pietro; Caricchi, Luca; Garcia-Castellanos, Daniel; Jolivet, Laurent; Sheldrake, Tom E.; Castelltort, Sébastien

2017-01-01

Between 5 and 6 million years ago, during the so-called Messinian salinity crisis, the Mediterranean basin became a giant salt repository. The possibility of abrupt and kilometre-scale sea-level changes during this extreme event is debated. Messinian evaporites could signify either deep- or shallow-marine deposits, and ubiquitous erosional surfaces could indicate either subaerial or submarine features. Significant and fast reductions in sea level unload the lithosphere, which can increase the production and eruption of magma. Here we calculate variations in surface load associated with the Messinian salinity crisis and compile the available time constraints for pan-Mediterranean magmatism. We show that scenarios involving a kilometre-scale drawdown of sea level imply a phase of net overall lithospheric unloading at a time that appears synchronous with a magmatic pulse from the pan-Mediterranean igneous provinces. We verify the viability of a mechanistic link between unloading and magmatism using numerical modelling of decompression partial mantle melting and dike formation in response to surface load variations. We conclude that the Mediterranean magmatic record provides an independent validation of the controversial kilometre-scale evaporative drawdown and sheds new light on the sensitivity of magmatic systems to the surface forcing. PMID:29081834

Compact, Lightweight Dual- Frequency Microstrip Antenna Feed for Future Soil Moisture and Sea Surface Salinity Missions

NASA Technical Reports Server (NTRS)

Yueh, Simon H.; Wilson, William J.; Njoku, Eni; Hunter, Don; Dinardo, Steve; Kona, Keerti S.; Manteghi, Majid; Gies, Dennis; Rahmat-Samii, Yahya

2004-01-01

The development of a compact, lightweight, dual frequency antenna feed for future soil moisture and sea surface salinity (SSS) missions is described. The design is based on the microstrip stacked-patch array (MSPA) to be used to feed a large lightweight deployable rotating mesh antenna for spaceborne L-band (approx. 1 GHz) passive and active sensing systems. The design features will also enable applications to airborne sensors operating on small aircrafts. This paper describes the design of stacked patch elements, 16-element array configuration and power-divider beam forming network The test results from the fabrication of stacked patches and power divider were also described.

The Ups and Downs of Measuring Sea Surface Salinity from Space

NASA Astrophysics Data System (ADS)

Banks, C. J.; Gommenginger, C. P.; Srokosz, M. A.; Snaith, H. M.

2012-12-01

In November 2009, the European Space Agency (ESA) launched the Soil Moisture and Ocean Salinity (SMOS) satellite and a new era of satellite oceanography began vastly improving our ability to synoptically measure sea surface salinity (SSS). SMOS was joined in June 2011 by the NASA/Argentine Aquarius/SAC-D mission designed specifically to measure SSS. Although there are significant differences in how both satellites retrieve SSS, both utilise passive systems to measure the response of the brightness temperature (Tb) at L-band (1.4 GHz). We report on-going investigations into the validation of SMOS and Aquarius 'Level 3' measurements of SSS using monthly data on a 1° by 1° global grid between 60°S and 60°N. Previous studies have indicated significant temporally varying differences between SSS from SMOS ascending passes and from SMOS descending passes: therefore, for both SMOS and Aquarius, data from ascending and descending passes will be studied separately. Both satellites have sun-synchronous orbits but the direction of travel for the two satellites are twelve hours out of phase (i.e. at approximately 6 a.m. local time SMOS is travelling south-to-north (ascending) and Aquarius is travelling north-to-south (descending) whereas at 6 p.m. the directions of travel are switched). For validation purposes two separate monthly, 1° by 1° datasets are used over the same locations as the satellite data. The first is based on averaged near-surface salinity (depth less than 10 m) as derived from the drifting Argo float programme. The second validation data source is output from the UK Met Office Forecasting Ocean Assimilation Model (FOAM) based on NEMO (Nucleus for European Modelling of the Ocean). The SMOS Level 3 products are developed from ESA Level 2 products after quality control (QC) based on flags and SSS error provided in the ESA Level 2 products. Aquarius data (QC) is based only on data flags and a simple selection of in-range SSS values ([30, 40]). The study is

Surface Salinity Variability in the North Atlantic During Recent Decades

NASA Technical Reports Server (NTRS)

Haekkinen, Sirpa

2001-01-01

The sea surface salinity (SSS) variability in the North Atlantic is investigated using numerical model simulations for the last 50 years based on atmospheric forcing variability from Comprehensive Atmosphere Ocean Data Set (COADS) and National Center for Environmental Prediction / National Center for Atmospheric Research (NCEP/NCAR) Reanalysis. The largest interannual and longer term variability occurs in two regions: the Labrador Sea and the North Equatorial Countercurrent (NECC) region. In both regions the seasonality of the surface salinity variability is prominent with the maximum standard deviation occurring in the summer/fall period. In the Labrador Sea the summer SSS anomalies far exceed those of wintertime in amplitude. The interannual SSS variability in the subpolar gyre can be attributed to two factors: excess ice melt and heat flux (i.e. deep mixing) variations. On the other hand, heat flux variability can also lead to meridional overturning changes on decadal time scales such that weak overturning is manifested in fresh surface conditions in the subpolar gyre. The overturning changes also influence the NECC region SSS variability. Moreover, the subpolar freshening events are expected to occur during the negative phase of North Atlantic Oscillation which is associated with a weak wintertime surface heat loss in the subpolar gyre. No excess sea ice melt or precipitation is necessary for the formation of the fresh anomalies, because with the lack of wide-spread deep mixing, the fresh water that would be expected based on climatology, would accumulate at the surface. Thus, the fresh water 'conveyor' in the Atlantic operates via the overturning circulation such that deep mixing inserts fresh water while removing heat from the water column.

Assessing recent air-sea freshwater flux changes using a surface temperature-salinity space framework

NASA Astrophysics Data System (ADS)

Grist, Jeremy P.; Josey, Simon A.; Zika, Jan D.; Evans, Dafydd Gwyn; Skliris, Nikolaos

2016-12-01

A novel assessment of recent changes in air-sea freshwater fluxes has been conducted using a surface temperature-salinity framework applied to four atmospheric reanalyses. Viewed in the T-S space of the ocean surface, the complex pattern of the longitude-latitude space mean global Precipitation minus Evaporation (PME) reduces to three distinct regions. The analysis is conducted for the period 1979-2007 for which there is most evidence for a broadening of the (atmospheric) tropical belt. All four of the reanalyses display an increase in strength of the water cycle. The range of increase is between 2% and 30% over the period analyzed, with an average of 14%. Considering the average across the reanalyses, the water cycle changes are dominated by changes in tropical as opposed to mid-high latitude precipitation. The increases in the water cycle strength, are consistent in sign, but larger than in a 1% greenhouse gas run of the HadGEM3 climate model. In the model a shift of the precipitation/evaporation cells to higher temperatures is more evident, due to the much stronger global warming signal. The observed changes in freshwater fluxes appear to be reflected in changes in the T-S distribution of the Global Ocean. Specifically, across the diverse range of atmospheric reanalyses considered here, there was an acceleration of the hydrological cycle during 1979-2007 which led to a broadening of the ocean's salinity distribution. Finally, although the reanalyses indicate that the warm temperature tropical precipitation dominated water cycle change, ocean observations suggest that ocean processes redistributed the freshening to lower ocean temperatures.

Satellite surface salinity maps to determine fresh water fluxes in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Gabarro, Carolina; Estrella, Olmedo; Emelianov, Mikhail; Ballabrera, Joaquim; Turiel, Antonio

2017-04-01

Salinity and temperature gradients drive the thermohaline circulation of the oceans, and play a key role in the ocean-atmosphere coupling. The strong and direct interactions between the ocean and the cryosphere (primarily through sea ice and ice shelves) are also a key ingredient of the thermohaline circulation. Recent observational studies have documented changes in upper Arctic Ocean hydrography [1, 2]. The ESA's Soil Moisture and Ocean Salinity (SMOS) mission, launched in 2009, have the objective to measure soil moisture over the continents and sea surface salinity over the oceans [3]. However, SMOS is also making inroads in Cryospheric science, as the measurements of thin ice thickness and sea ice concentration. SMOS carries an innovative L-band (1.4 GHz, or 21-cm wavelength), passive interferometric radiometer (the so-called MIRAS) that measures the electromagnetic radiation emitted by the Earth's surface, at about 50 km spatial resolution wide swath (1200-km), and with a 3-day revisit time at the equator, but more frequently at the poles. Although the SMOS radiometer operating frequency offers almost the maximum sensitivity of the brightness temperature (TB) to sea surface salinity (SSS) variations, such sensitivity is rather low, even lower at cold waters [4]: 90% of ocean SSS values span a range of brightness temperatures of just 5K. This implies that the SMOS SSS retrieval requires a high performance of the MIRAS interferometric radiometer [5]. New algorithms, recently developed at the Barcelona Expert Center (BEC) to improve the quality of SMOS measurements [6], allow for the first time to derive cold-water SSS maps from SMOS data, and to observe the variability of the SSS in the higher north Atlantic and the Arctic Ocean. In this work, we will provide an assessment of the quality of these new SSS Arctic maps, and we will illustrate their potential to monitor the impact on ocean state of the discharges from the main rivers to the Arctic Ocean. Moreover

Hourly changes in sea surface salinity in coastal waters recorded by Geostationary Ocean Color Imager

NASA Astrophysics Data System (ADS)

Liu, Rongjie; Zhang, Jie; Yao, Haiyan; Cui, Tingwei; Wang, Ning; Zhang, Yi; Wu, Lingjuan; An, Jubai

2017-09-01

In this study, we monitored hourly changes in sea surface salinity (SSS) in turbid coastal waters from geostationary satellite ocean color images for the first time, using the Bohai Sea as a case study. We developed a simple multi-linear statistical regression model to retrieve SSS data from Geostationary Ocean Color Imager (GOCI) based on an in situ satellite matched-up dataset (R2 = 0.795; N = 41; Range: 26.4 to 31.9 psμ). The model was then validated using independent continuous SSS measurements from buoys, with the average percentage difference of 0.65%. The model was applied to GOCI images from the dry season during an astronomical tide to characterize hourly changes in SSS in the Bohai Sea. We found that the model provided reasonable estimates of the hourly changes in SSS and that trends in the modeled and measured data were similar in magnitude and direction (0.43 vs 0.33 psμ, R2 = 0.51). There were clear diurnal variations in the SSS of the Bohai Sea, with a regional average of 0.455 ± 0.079 psμ (0.02-3.77 psμ). The magnitude of the diurnal variations in SSS varied spatially, with large diurnal variability in the nearshore, particularly in the estuary, and small variability in the offshore area. The model for the riverine area was based on the inverse correlation between SSS and CDOM absorption. In the offshore area, the water mass of the North Yellow Sea, characterized by high SSS and low CDOM concentrations, dominated. Analysis of the driving mechanisms showed that the tidal current was the main control on hourly changes in SSS in the Bohai Sea.

Consistency of Aquarius version-4 sea surface salinity with Argo products on various spatial and temporal scales

NASA Astrophysics Data System (ADS)

Lee, Tong

2017-04-01

Understanding the accuracies of satellite-derived sea surface salinity (SSS) measurements in depicting temporal changes and the dependence of the accuracies on spatiotemporal scales are important to capability assessment, future mission design, and applications to study oceanic phenomena of different spatiotemporal scales. This study quantifies the consistency between Aquarius Version-4 monthly gridded SSS (released in late 2015) with two widely used Argo monthly gridded near-surface salinity products. The analysis focused on their consistency in depicting temporal changes (including seasonal and non-seasonal) on various spatial scales: 1˚ x1˚ , 3˚ x3˚ , and 10˚ x10˚ . Globally averaged standard deviation (STD) values for Aquarius-Argo salinity differences on these three spatial scales are 0.16, 0.14, 0.09 psu, compared to those between the two Argo products of 0.10, 0.09, and 0.04 psu. Aquarius SSS compare better with Argo data on non-seasonal (e.g., interannual and intraseasonal) than for seasonal time scales. The seasonal Aquarius-Argo SSS differences are mostly concentrated at high latitudes. The Aquarius team is making active efforts to further reduce these high-latitude seasonal biases. The consistency between Aquarius and Argo salinity is similar to that between the two Argo products in the tropics and subtropics for non-seasonal signals, and in the tropics for seasonal signals. Therefore, the representativeness errors of the Argo products for various spatial scales (related to sampling and gridding) need to be taken into account when estimating the uncertainty of Aquarius SSS. The globally averaged uncertainty of large-scale (10˚ x10˚ ) non-seasonal Aquarius SSS is approximately 0.04 psu. These estimates reflect the significant improvements of Aquarius Version-4 SSS over the previous versions. The estimates can be used as baseline requirements for future ocean salinity missions from space. The spatial distribution of the uncertainty estimates is

δ18O and salinity variability from the Last Glacial Maximum to Recent in the Bay of Bengal and Andaman Sea

NASA Astrophysics Data System (ADS)

Sijinkumar, A. V.; Clemens, Steven; Nath, B. Nagender; Prell, Warren; Benshila, Rachid; Lengaigne, Matthieu

2016-03-01

Oxygen isotopes of surface, thermocline and bottom dwelling foraminifera were analysed from two well-dated Andaman Sea cores and combined with nine previously published records from the Bay of Bengal (BoB) and Andaman Sea to create a transect spanning 20°N to 5°N. Combined with temperature estimates and the observed seawater δ18O-salinity relationship, these data are used to estimate past changes in BoB salinity structure. Compared to modern, mid-Holocene (9-6 cal ka BP) surface waters in the northern BoB were 2.5 psμ (8%) fresher, Andaman Sea were 3.8 psμ (12%) fresher, and southern BoB were 1.2 psμ (3.5%) fresher. Conversely, during the last glacial maximum (LGM), surface waters in the northern BoB were 2.9 psμ (9%) more saline while Andaman Sea were essentially unchanged and southern BoB were 1.7 psμ (4.9%) more saline compared to modern. The relative freshness of the Andaman during the last glacial maximum is likely the result of basin morphology during sea level low stand, resulting in reduced surface water mixing with the open BoB as well as shelf emergence, causing increased proximity of the core locations to river outflow. Sensitivity experiments using a regional ocean model indicate that the increased mid-Holocene north to south (20°N to 5°N) salinity gradient can be achieved with a ∼50% increase in precipitation/runoff while the decreased glacial age gradient can be achieved with a ∼50% reduction in precipitation/runoff. During the deglaciation, both surface and thermocline-dwelling species in the Andaman and northern BoB exhibit depleted δ18O within the Younger Dryas (YD), indicating colder and/or more saline conditions. None of the records from the southern BoB site have clear YD structure, possibly due to the combined effects of bioturbation and low sedimentation rates.

Freshwater impacts recorded in tetraunsaturated alkenones and alkenone sea surface temperatures from the Okhotsk Sea across millennial-scale cycles

NASA Astrophysics Data System (ADS)

Harada, Naomi; Sato, Miyako; Sakamoto, Tatsuhiko

2008-09-01

We present records of phytoplankton-produced alkenones down a long piston core, which reveal changes of sea surface temperature (SST) and sea surface salinity (SSS) in the southwestern Okhotsk Sea over the past 120 ka. Between 20 and 60 ka B.P., alkenone-derived temperatures typically increased by 6°C-8°C from periods corresponding, within a few hundred years, to stadials to those corresponding to interstadials recorded in Greenland ice cores. The abundance of C37:4 alkenone relative to total C37 alkenones (percent C37:4), a possible proxy for salinity, indicated that during most low SSS was associated with high SST. The warm freshwater events might be related to (1) a decline in the supply of saline water entering the Okhotsk Sea through the Soya Strait; (2) strengthening of the freshwater supply from the Amur River and precipitation over the Okhotsk Sea, associated mainly with increased Asian summer monsoon activity; and (3) the effect of melting sea ice. These findings increase our understanding of the close linkage between high and low latitudes in relation to climate change and the synchronicity of climate changes within a few centuries between the Pacific and the Atlantic sides of the Northern Hemisphere.

Statistical characterization of global Sea Surface Salinity for SMOS level 3 and 4 products

NASA Astrophysics Data System (ADS)

Gourrion, J.; Aretxabaleta, A. L.; Ballabrera, J.; Mourre, B.

2009-04-01

The Soil Moisture and Ocean Salinity (SMOS) mission of the European Space Agency will soon provide sea surface salinity (SSS) estimates to the scientific community. Because of the numerous geophysical contamination sources and the instrument complexity, the salinity products will have a low signal to noise ratio at level 2 (individual estimates??) that is expected to increase up to mission requirements (0.1 psu) at level 3 (global maps with regular distribution) after spatio-temporal accumulation of the observations. Geostatistical methods such as Optimal Interpolation are being implemented at the level 3/4 production centers to operate this noise reduction step. The methodologies require auxiliary information about SSS statistics that, under Gaussian assumption, consist in the mean field and the covariance of the departures from it. The present study is a contribution to the definition of the best estimates for mean field and covariances to be used in the near-future SMOS level 3 and 4 products. We use complementary information from sparse in-situ observations and imperfect outputs from state-of-art model simulations. Various estimates of the mean field are compared. An alternative is the use of a SSS climatology such as the one provided by the World Ocean Atlas 2005. An historical SSS dataset from the World Ocean Database 2005 is reanalyzed and combined with the recent global observations obtained by the Array for Real-Time Geostrophic Oceanography (ARGO). Regional tendencies in the long-term temporal evolution of the near-surface ocean salinity are evident, suggesting that the use of a SSS climatology to describe the current mean field may introduce biases of magnitude similar to the precision goal. Consequently, a recent SSS dataset may be preferred to define the mean field needed for SMOS level 3 and 4 production. The in-situ observation network allows a global mapping of the low frequency component of the variability, i.e. decadal, interannual and seasonal

Optimizing Surface Winds using QuikSCAT Measurements in the Mediterranean Sea During 2000-2006

DTIC Science & Technology

2009-02-28

Temperature and salinity from the 1/4° Generalized Digital Envi- ronmental Model ( GDEM ) monthly climatology developed at the Naval Oceanographic...monthly GDEM climatology was also used for relaxation of the sea-surface salinity (SSS) to keep the surface salinity balance on track. The net heat...salinity from the GDEM clima- tology are used to initialize themodel. There is a relaxation tomonthly mean SSS fromGDEM. The referencemixed-layer

Impact of Sea Surface Salinity on Coupled Dynamics for the Tropical Indo Pacific

NASA Astrophysics Data System (ADS)

Busalacchi, A. J.; Hackert, E. C.

2014-12-01

In this presentation we assess the impact of in situ and satellite sea surface salinity (SSS) observations on seasonal to interannual variability of tropical Indo-Pacific Ocean dynamics as well as on dynamical ENSO forecasts using a Hybrid Coupled Model (HCM) for 1993-2007 (cf., Hackert et al., 2011) and August 2011 until February 2014 (cf., Hackert et al., 2014). The HCM is composed of a primitive equation ocean model coupled with a SVD-based statistical atmospheric model for the tropical Indo-Pacific region. An Ensemble Reduced Order Kalman Filter (EROKF) is used to assimilate observations to constrain dynamics and thermodynamics for initialization of the HCM. Including SSS generally improves NINO3 sea surface temperature anomaly validation. Assimilating SSS gives significant improvement versus just subsurface temperature for all forecast lead times after 5 months. We find that the positive impact of SSS assimilation is brought about by surface freshening in the western Pacific warm pool that leads to increased barrier layer thickness (BLT) and shallower mixed layer depths. Thus, in the west the net effect of assimilating SSS is to increase stability and reduce mixing, which concentrates the wind impact of ENSO coupling. Specifically, the main benefit of SSS assimilation for 1993-2007 comes from improvement to the Spring Predictability Barrier (SPB) period. In the east, the impact of Aquarius satellite SSS is to induce more cooling in the NINO3 region as a result of being relatively more salty than in situ SSS in the eastern Pacific leading to increased mixing and entrainment. This, in turn, sets up an enhanced west to east SST gradient and intensified Bjerknes coupling. For the 2011-2014 period, consensus coupled model forecasts compiled by the IRI tend to erroneously predict NINO3 warming; SSS assimilation corrects this defect. Finally, we plan to update our analysis and report on the dynamical impact of including Aquarius SSS for the most-recent, ongoing 2014

Evaluation of Aquarius Version-5 Sea Surface Salinity on various spatial and temporal scales

NASA Astrophysics Data System (ADS)

Lee, T.

2017-12-01

Sea surface salinity (SSS) products from Aquarius have had three public releases with progressive improvement in data quality: Versions 2, 3, and 4, with the last one being released in October 2015. A systematic assessment of the Version-4, Level-3 Aquarius SSS product was performed on various spatial and temporal scales by comparing it with gridded Argo products (Lee 2016, Geophys. Res. Lett.). The comparison showed that the consistency of Aquarius Version-4 SSS with gridded Argo products is comparable to that between two different gridded Argo products. However, significant seasonal biases remain in high-latitude oceans. Further improvements are being made by the Aquarius team. Aquarius Version 5.0 SSS is scheduled to be released in October 2017 as the final version of the Aquarius Project. This presentation provides a similar evaluation of Version-5 SSS as reported by Lee (2016) and contrast it with the current Version-4 SSS.

The Baltic Sea natural long-term variability of salinity

NASA Astrophysics Data System (ADS)

Schimanke, Semjon; Markus Meier, H. E.

2015-04-01

The Baltic Sea is one of the largest brackish sea areas of the world. The sensitive state of the Baltic Sea is sustained by a fresh-water surplus by river discharge and precipitation on one hand as well as inflows of highly saline and oxygen-rich water masses from the North Sea on the other. Major inflows which are crucial for the renewal of the deep water occur very intermittent with a mean frequency of approximately one per year. Stagnation periods (periods without major inflows) lead for instance to a reduction of oxygen concentration in the deep Baltic Sea spreading hypoxic conditions. Depending on the amount of salt water inflow and fresh-water supply the deep water salinity of the Baltic Sea varies between 11 to 14 PSU on the decadal scale. The goal of this study is to understand the contribution of different driving factors for the decadal to multi-decadal variability of salinity in the Baltic Sea. Continuous measurement series of salinity exist from the 1950 but are not sufficiently long for the investigation of long-term fluctuations. Therefore, a climate simulation of more than 800 years has been carried out with the Rossby Center Ocean model (RCO). RCO is a biogeochemical regional climate model which covers the entire Baltic Sea. It is driven with atmospheric data dynamical downscaled from a GCM mimicking natural climate variability. The analysis focus on the role of variations in river discharge and precipitation, changes in wind speed and direction, fluctuations in temperature and shifts in large scale pressure patterns (e.g. NAO). Hereby, the length of the simulation will allow to identify mechanisms working on decadal to multi-decadal time scales. Moreover, it will be discussed how likely long stagnation periods are under natural climate variability and if the observed exceptional long stagnation period between 1983-1993 might be related to beginning climate change.

Multiangular L-band Datasets for Soil Moisture and Sea Surface Salinity Retrieval Measured by Airborne HUT-2D Synthetic Aperture Radiometer

NASA Astrophysics Data System (ADS)

Kainulainen, J.; Rautiainen, K.; Seppänen, J.; Hallikainen, M.

2009-04-01

SMOS is the European Space Agency's next Earth Explorer satellite due for launch in 2009. It aims for global monitoring of soil moisture and ocean salinity utilizing a new technology concept for remote sensing: two-dimensional aperture synthesis radiometry. The payload of SMOS is Microwave Imaging Radiometer by Aperture Synthesis, or MIRAS. It is a passive instrument that uses 72 individual L-band receivers for measuring the brightness temperature of the Earth. From each acquisition, i.e. integration time or snapshot, MIRAS provides two-dimensional brightness temperature of the scene in the instrument's field of view. Thus, consecutive snapshots provide multiangular measurements of the target once the instrument passes over it. Depending on the position of the target in instrument's swath, the brightness temperature of the target at incidence angles from zero up to 50 degrees can be measured with one overpass. To support the development MIRAS instrument, its calibration, and soil moisture and sea surface salinity retrieval algorithm development, Helsinki University of Technology (TKK) has designed, manufactured and tested a radiometer which operates at L-band and utilizes the same two-dimensional methodology of interferometery and aperture synthesis as MIRAS does. This airborne instrument, called HUT-2D, was designed to be used on board the University's research aircraft. It provides multiangular measurements of the target in its field of view, which spans up to 30 degrees off the boresight of the instrument, which is pointed to the nadir. The number of independent measurements of each target point depends on the flight speed and altitude. In addition to the Spanish Airborne MIRAS demonstrator (AMIRAS), HUT-2D is the only European airborne synthetic aperture radiometer. This paper presents the datasets and measurement campaigns, which have been carried out using the HUT-2D radiometer and are available for the scientific community. In April 2007 HUT-2D participated

Latitudinal and Longitudinal Basin-scale Surface Salinity Contrasts and Freshwater Transport by Ocean Thermohaline Circulation

NASA Astrophysics Data System (ADS)

Seidov, D.; Haupt, B. J.

2003-12-01

The role of sea surface salinity (SSS) contrasts in maintaining vigorous global ocean thermohaline circulation (THC) is revisited. Relative importance of different generalizations of sea surface conditions in climate studies is explored. In numerical experiments using an ocean general circulation model, we have aggregated the observed sea surface temperature (SST) and SSS in several different ways: we used observed unchanged SST with SSS taken as constant (34.25 psu) everywhere; SST unchanged, and SSS zonally averaged globally, i.e., in the whole World Ocean; SST averaged globally, and SSS unchanged; SST zonally averaged globally and SSS zonally averaged basin-wide in individual basins, i.e., in the Atlantic, Indian, Pacific, and Southern Oceans separately; and, finally, both SST and SSS zonally averaged in individual basins. Global zonal averaging removes all longitudinal differences in sea surface climatology among ocean basins. However, latitudinal profiles of zonally averaged parameters preserve the main character of large-scale equator-to-pole sea surface variability. Basin-wide zonal averaging does an even better job of preserving latitudinal distributions within each basin. The results of the experiments could hardly be anticipated a priory. Surprisingly, SST could be used as a 2-D field, or as a zonally-averaged field without much difference in the THC dynamics. Moreover, SST could be averaged either globally, or basin-wide, and it also did not change the overall character of THC. At the same time, THC responded vigorously to how the SSS has been changed. It appeared that the THC structure with the globally averaged SST and basin-wide averaged SSS was very close to the one obtained in the control run (control run operates with 2-D observed SST and SSS). Our main conclusion is that ocean-wide inter-basin sea surface salinity contrasts serve as the major controlling element in global thermohaline circulation. Thermal inter-basin contrasts, as well as

Mediterranean sea water budget long-term trend inferred from salinity observations

NASA Astrophysics Data System (ADS)

Skliris, N.; Zika, J. D.; Herold, L.; Josey, S. A.; Marsh, R.

2018-01-01

Changes in the Mediterranean water cycle since 1950 are investigated using salinity and reanalysis based air-sea freshwater flux datasets. Salinity observations indicate a strong basin-scale multi-decadal salinification, particularly in the intermediate and deep layers. Evaporation, precipitation and river runoff variations are all shown to contribute to a very strong increase in net evaporation of order 20-30%. While large temporal uncertainties and discrepancies are found between E-P multi-decadal trend patterns in the reanalysis datasets, a more robust and spatially coherent structure of multi-decadal change is obtained for the salinity field. Salinity change implies an increase in net evaporation of 8 to 12% over 1950-2010, which is considerably lower than that suggested by air-sea freshwater flux products, but still largely exceeding estimates of global water cycle amplification. A new method based on water mass transformation theory is used to link changes in net evaporation over the Mediterranean Sea with changes in the volumetric distribution of salinity. The water mass transformation distribution in salinity coordinates suggests that the Mediterranean basin salinification is driven by changes in the regional water cycle rather than changes in salt transports at the straits.

Impact of Aquarius and SMAP Sea Surface Salinity Observations on Seasonal Predictions of the 2015 El Nino

NASA Technical Reports Server (NTRS)

Hackert, E.; Kovach, R.; Marshak, J.; Borovikov, A.; Molod, A.; Vernieres, G.

2018-01-01

We assess the impact of satellite sea surface salinity (SSS) observations on dynamical ENSO forecasts for the big 2015 El Nino event. From March to June 2015, the availability of two overlapping satellite SSS instruments, Aquarius and SMAP (Soil Moisture Active Passive Mission), allows a unique opportunity to compare and contrast forecasts generated with the benefit of these two satellite SSS observation types. Four distinct experiments are presented that include 1) freely evolving model SSS (i.e. no satellite SSS), relaxation to 2) climatological SSS (i.e. WOA13 SSS), 3) Aquarius, and 4) SMAP initialization. Coupled hindcasts are then generated from these initial conditions for March 2015. These forecasts are then validated against observations and evaluated with respect to the observed El Nino development.

SMOS: a satellite mission to measure ocean surface salinity

NASA Astrophysics Data System (ADS)

Font, Jordi; Kerr, Yann H.; Srokosz, Meric A.; Etcheto, Jacqueline; Lagerloef, Gary S.; Camps, Adriano; Waldteufel, Philippe

2001-01-01

The ESA's SMOS (Soil Moisture and Ocean Salinity) Earth Explorer Opportunity Mission will be launched by 2005. Its baseline payload is a microwave L-band (21 cm, 1.4 GHz) 2D interferometric radiometer, Y shaped, with three arms 4.5 m long. This frequency allows the measurement of brightness temperature (Tb) under the best conditions to retrieve soil moisture and sea surface salinity (SSS). Unlike other oceanographic variables, until now it has not been possible to measure salinity from space. However, large ocean areas lack significant salinity measurements. The 2D interferometer will measure Tb at large and different incidence angles, for two polarizations. It is possible to obtain SSS from L-band passive microwave measurements if the other factors influencing Tb (SST, surface roughness, foam, sun glint, rain, ionospheric effects and galactic/cosmic background radiation) can be accounted for. Since the radiometric sensitivity is low, SSS cannot be recovered to the required accuracy from a single measurement as the error is about 1-2 psu. If the errors contributing to the uncertainty in Tb are random, averaging the independent data and views along the track, and considering a 200 km square, allow the error to be reduced to 0.1-0.2 pus, assuming all ancillary errors are budgeted.

On the calculation of air-sea fluxes of CO2 in the presence of temperature and salinity gradients

NASA Astrophysics Data System (ADS)

Woolf, D. K.; Land, P. E.; Shutler, J. D.; Goddijn-Murphy, L. M.; Donlon, C. J.

2016-02-01

The presence of vertical temperature and salinity gradients in the upper ocean and the occurrence of variations in temperature and salinity on time scales from hours to many years complicate the calculation of the flux of carbon dioxide (CO2) across the sea surface. Temperature and salinity affect the interfacial concentration of aqueous CO2 primarily through their effect on solubility with lesser effects related to saturated vapor pressure and the relationship between fugacity and partial pressure. The effects of temperature and salinity profiles in the water column and changes in the aqueous concentration act primarily through the partitioning of the carbonate system. Climatological calculations of flux require attention to variability in the upper ocean and to the limited validity of assuming "constant chemistry" in transforming measurements to climatological values. Contrary to some recent analysis, it is shown that the effect on CO2 fluxes of a cool skin on the sea surface is large and ubiquitous. An opposing effect on calculated fluxes is related to the occurrence of warm layers near the surface; this effect can be locally large but will usually coincide with periods of low exchange. A salty skin and salinity anomalies in the upper ocean also affect CO2 flux calculations, though these haline effects are generally weaker than the thermal effects.

Quantitative analysis of Paratethys sea level change during the Messinian Salinity Crisis

NASA Astrophysics Data System (ADS)

de la Vara, Alba; Meijer, Paul; van Baak, Christiaan; Marzocchi, Alice; Grothe, Arjen

2016-04-01

At the time of the Messinian Salinity Crisis in the Mediterranean Sea (i.e., the Pontian stage of the Paratethys), the Paratethys sea level dropped also. Evidence found in the sedimentary record of the Black Sea and the Caspian Sea has been interpreted to indicate that a sea level fall occurred between 5.6 and 5.5 Ma. Estimates for the magnitude of the fall range between tens of meters to more than 1500 m. The purpose of this study is to provide quantitative insight into the sensitivity of the water level of the Black Sea and the Caspian Sea to the hydrologic budget, for the case that the Paratethys is disconnected from the Mediterranean. Using a Late Miocene bathymetry based on a palaeographic map by Popov et al. (2004) we quantify the fall in sea level, the mean salinity, and the time to reach equilibrium for a wide range of negative hydrologic budgets. By combining our results with (i) estimates derived from a recent global Late Miocene climate simulation and (ii) reconstructed basin salinities, we are able to rule out a drop in sea level of the order of 1000 m in the Caspian Sea during this time period. In the Black Sea, however, such a large sea level fall cannot be fully discarded.

Salinity and hypoxia in the Baltic Sea since A.D. 1500

NASA Astrophysics Data System (ADS)

Hansson, Daniel; Gustafsson, Erik

2011-03-01

Over the past century, large salinity variability and deteriorating oxygen conditions have been observed in the Baltic Sea. These long-term changes were investigated in the central Baltic Sea using an ocean climate model with meteorological forcing based on seasonal temperature and pressure reconstructions covering the period 1500-1995. The results indicate that the salinity has slowly increased by 0.5 salinity units since 1500, peaking in the middle eighteenth century. Oxygen concentration is negatively correlated with salinity in the major part of the water column, indicating improved ventilation during a fresher state of the Baltic Sea. It is suggested that anoxic conditions have occurred in the deep water several times per century since 1500. However, since the middle twentieth century, increased oxygen consumption that is most likely the effect of anthropogenic nutrient release has resulted in a persistent oxygen deficiency in the water below 125 m. Within the limitations of our model formulation we suggest that the contemporary severe oxygen conditions are unprecedented since 1500.

Rain Impact Model Assessment of Near-Surface Salinity Stratification Following Rainfall

NASA Astrophysics Data System (ADS)

Drushka, K.; Jones, L.; Jacob, M. M.; Asher, W.; Santos-Garcia, A.

2016-12-01

Rainfall over oceans produces a layer of fresher surface water, which can have a significant effect on the exchanges between the surface and the bulk mixed layer and also on satellite/in-situ comparisons. For satellite sea surface salinity (SSS) measurements, the standard is the Hybrid Coordinate Ocean Model (HYCOM), but there is a significant difference between the remote sensing sampling depth of 0.01 m and the typical range of 5-10 m of in-situ instruments. Under normal conditions the upper layer of the ocean is well mixed and there is uniform salinity; however, under rainy conditions, there is a dilution of the near-surface salinity that mixes downward by diffusion and by mechanical mixing (gravity waves/wind speed). This significantly modifies the salinity gradient in the upper 1-2 m of the ocean, but these transient salinity stratifications dissipate in a few hours, and the upper layer becomes well mixed at a slightly fresher salinity. Based upon research conducted within the NASA/CONAE Aquarius/SAC-D mission, a rain impact model (RIM) was developed to estimate the change in SSS due to rainfall near the time of the satellite observation, with the objective to identify the probability of salinity stratification. RIM uses HYCOM (which does not include the short-term rain effects) and a NOAA global rainfall product CMORPH to model changes in the near-surface salinity profile in 0.5 h increments. Based upon SPURS-2 experimental near-surface salinity measurements with rain, this paper introduces a term in the RIM model that accounts for the effect of wind speed in the mechanical mixing, which translates into a dynamic vertical diffusivity; whereby a Generalized Ocean Turbulence Model (GOTM) is used to investigate the response to rain events of the upper few meters of the ocean. The objective is to determine how rain and wind forcing control the thickness, stratification strength, and lifetime of fresh lenses and to quantify the impacts of rain-formed fresh lenses

Modeling and Analysis of Sea-level Rise Impacts on Salinity in the Lower St. Johns River

NASA Astrophysics Data System (ADS)

Bacopoulos, P.

2015-12-01

There is deliberate attention being paid to studying sea-level rise impacts on the lower St. Johns River, a drowned coastal plain-type estuary with low topographic drive, located in northeastern Florida. One area of attention is salinity in the river, which influences the entire food web, including sea and marsh grasses, juvenile crustaceans and fishes, wading birds and migratory waterfowl, marine mammals and other predator animals. It is expected that elevated ocean levels will increase the salinity of the estuarine waters, leading to deleterious effects on dependent species of the river biology. The objective of the modeling and analysis was: 1) to establish baseline conditions of salinity for the lower St. Johns River; and 2) to examine future conditions of salinity, as impacted by sea-level rise. Establishing baseline conditions entailed validation of the model for present-day salinity in the lower St. Johns River via comparison to available data. Examining future conditions entailed application of the model for sea-level rise scenarios, with comparison to the baseline conditions, for evaluation of sea-level rise impacts on salinity. While the central focus was on the physics of sea-level rise impacts on salinity, some level of salinity-biological assessment was conducted to identify sea-level rise/salinity thresholds, as related to negatively impacting different species of the river biology.

Is there a signal of sea-level rise in Chesapeake Bay salinity?

NASA Astrophysics Data System (ADS)

Hilton, T. W.; Najjar, R. G.; Zhong, L.; Li, M.

2008-09-01

We evaluate the hypothesis that sea-level rise over the second half of the 20th century has led to detectable increases in Chesapeake Bay salinity. We exploit a simple, statistical model that predicts monthly mean salinity as a function of Susquehanna River flow in 23 segments of the main stem Chesapeake Bay. The residual (observed minus modeled) salinity exhibits statistically significant linear (p < 0.05) trends between 1949 and 2006 in 13 of the 23 segments of the bay. The salinity change estimated from the trend line over this period varies from -2.0 to 2.2, with 10 of the 13 cells showing positive changes. The mean and median salinity changes over all 23 cells are 0.47 and 0.72; over the 13 cells with significant trends they are 0.71 and 1.1. We ran a hydrodynamic model of the bay under present-day and reduced sea level conditions and found a bay-average salinity increase of about 0.5, which supports the hypothesis that the salinity residual trends have a significant component due to sea-level rise. Uncertainties remain, however, due to the spatial and temporal extent of historical salinity data and the infilling of the bay due to sedimentation. The salinity residuals also exhibit interannual variability, with peaks occurring at intervals of roughly 7 to 9 years, which are partially explained by Atlantic Shelf salinity, Potomac River flow and the meridional component of wind stress.

Seasonal to Interannual Surface Ocean Salinity Trends With Aquarius Data

NASA Astrophysics Data System (ADS)

Lagerloef, G. S. E.; Kao, H. Y.; Carey, D.

2017-12-01

An important scientific goal for satellite salinity observations is to document oceanic climate trends and their link to changes in the water cycle. This study is a re-examination of seasonal to interannual sea surface salinity (SSS) variations from more recent analyses of V5.0 reprocessing of the Aquarius satellite data, Sep 2011 to May 2015. Sensor calibration over these time scales has been a concern, and the V5.0 includes improved calibration reference data compared to previous versions, which will be explained. Orthogonal mode analyses show that the annual cycle dominates the variability, and is strongest in the tropics. Interannual trends indicate the principal salinity patterns during onset of the 2015-16 El Niño. Recognizing that the Aquarius data record is now finite (Sep 2011 through May 2015) due to the mission failure in early June 2015, we will conclude with a status summary of the disposition of the Aquarius data and the prospects for continuing satellite salinity measurements.

Measuring surface salinity in the N. Atlantic subtropical gyre. The SPURS-MIDAS cruise, spring 2013

NASA Astrophysics Data System (ADS)

Font, Jordi; Ward, Brian; Emelianov, Mikhail; Morisset, Simon; Salvador, Joaquin; Busecke, Julius

2014-05-01

SPURS-MIDAS (March-April 2013) on board the Spanish R/V Sarmiento de Gamboa was a contribution to SPURS (Salinity Processes in the Upper ocean Regional Study) focused on the processes responsible for the formation and maintenance of the salinity maximum associated to the North Atlantic subtropical gyre. Scientists from Spain, Ireland, France and US sampled the mesoscale and submesoscale structures in the surface layer (fixed points and towed undulating CTD, underway near surface TSG) and deployed operational and experimental drifters and vertical profilers, plus additional ocean and atmospheric data collection. Validation of salinity maps obtained from the SMOS satellite was one of the objectives of the cruise. The cruise included a joint workplan and coordinated sampling with the US R/V Endeavor, with contribution from SPURS teams on land in real time data and analysis exchange. We present here an overview of the different kinds of measurements made during the cruise, as well as a first comparison between SMOS-derived sea surface salinity products and salinity maps obtained from near-surface sampling in the SPURS-MIDAS area and from surface drifters released during the cruise.

Rainfall Imprint on Sea Surface Salinity in the ITCZ: new satellite perspectives

NASA Astrophysics Data System (ADS)

Boutin, J.; Viltard, N.; Supply, A.; Martin, N.; Vergely, J. L.; Hénocq, C.; Reverdin, G. P.

2016-02-01

The European Soil Moisture and Ocean Salinity (SMOS) satellite mission monitors sea surface salinity (SSS) over the global ocean for more than 5 years since 2010. The MADRAS microwave radiometer carried by the French (CNES) Indian (ISRO) satellite mission Megha-Tropiques sampled the 30° N-30° S region end of 2011 and in 2012, very complementary to other Global Precipitation Measurement(GPM) missions. In tropical regions, SMOS SSS contains a large imprint of atmospheric rainfall, but is also likely affected by oceanographic processes (advection and diffusion). At local and short time scales, Boutin et al. (2013, 2014) have shown that the spatio-temporal variability of SSS is dominated by rainfall as detected by satellite microwave radiometers and have demonstrated a close to linear relationship between SMOS SSS freshening under rain cells and satellite rain rate. The order of magnitude is in remarkable agreement with the theoretical renewal model of Schlussel et al. (1997) and compatible with AQUARIUS SSS observations, as well as with in situ drifters observations although the latter are local and taken at 45cm depth while satellite L-band SSS roughly correspond to the top 1cm depth and are spatially integrated over 43-150km. It is thus expected that the combined information of satellite rain rates and satellite SSS brings new constraints on the precipitation budget. We first look at the consistency between the spatial structures of SMOS SSS decrease and of rain rates derived either from the MADRAS microwave radiometer or from the CMORPH combined products that do not use MADRAS rain rates. This provides an indirect validation of the rain rates estimates. We then investigate the impact of rain history and of wind speed on the observed SMOS freshening. Based on these results, we discuss the precision on various precipitation estimates over 2012 in the ITCZ region and the major sources of uncertainties that the SPURS2 campaign could help to resolve.

On the Impact of Snow Salinity on CryoSat-2 First-Year Sea Ice Thickness Retrievals

NASA Astrophysics Data System (ADS)

Nandan, V.; Yackel, J.; Geldsetzer, T.; Mahmud, M.

2017-12-01

European Space Agency's Ku-band altimeter CryoSat-2 (CS-2) has demonstrated its potential to provide extensive basin-scale spatial and temporal measurements of Arctic sea ice freeboard. It is assumed that CS-2 altimetric returns originate from the snow/sea ice interface (assumed to be the main scattering horizon). However, in newly formed thin ice ( 0.6 m) through to thick first-year sea ice (FYI) ( 2 m), upward wicking of brine into the snow cover from the underlying sea ice surface produces saline snow layers, especially in the bottom 6-8 cm of a snow cover. This in turn modifies the brine volume at/or near the snow/sea ice interface, altering the dielectric and scattering properties of the snow cover, leading to strong Ku-band microwave attenuation within the upper snow volume. Such significant reductions in Ku-band penetration may substantially affect CS-2 FYI freeboard retrievals. Therefore, the goal of this study is to evaluate a theoretical approach to estimate snow salinity induced uncertainty on CS-2 Arctic FYI freeboard measurements. Using the freeboard-to-thickness hydrostatic equilibrium equation, we quantify the error differences between the CS-2 FYI thickness, (assuming complete penetration of CS-2 radar signals to the snow/FYI interface), and the FYI thickness based on the modeled Ku-band main scattering horizon for different snow cover cases. We utilized naturally occurring saline and non-saline snow cover cases ranging between 6 cm to 32 cm from the Canadian Arctic, observed during late-winter from 1993 to 2017, on newly-formed ice ( 0.6 m), medium ( 1.5 m) and thick FYI ( 2 m). Our results suggest that irrespective of the thickness of the snow cover overlaying FYI, the thickness of brine-wetted snow layers and actual FYI freeboard strongly influence the amount with which CS-2 FYI freeboard estimates and thus thickness calculations are overestimated. This effect is accentuated for increasingly thicker saline snow covers overlaying newly-formed ice

Subduction of a low-salinity water mass around the Xisha Islands in the South China Sea.

PubMed

Huang, Zhida; Zhuang, Wei; Liu, Hailong; Hu, Jianyu

2018-02-15

Based on three climatologically observed temperature and salinity datasets (i.e., GDEM-V3, SCSPOD14 and WOA13), this paper reports a low-salinity (~34.32) water mass in the subsurface-to-intermediate layer around the Xisha Islands in the South China Sea. This water mass mainly subducts from the surface layer into the intermediate layer, characterized by a relatively low potential vorticity tongue extending from the bottom of mixed layer to the thermocline, and accompanied by a thermocline ventilation in spring (especially in April). The potential dynamics are the joint effects of negative wind stress curl, and an anticyclonic eddy triggered by the inherent topographic effect of the Xisha Islands, reflecting that downward vertical motion dominates the subduction. Despite lacking of the homogenous temperature and density, the low-salinity water mass is to some extent similar to the classic mode water and can be regarded as a deformed mode water in the South China Sea.

Evidence for high salinity of Early Cretaceous sea water from the Chesapeake Bay crater.

PubMed

Sanford, Ward E; Doughten, Michael W; Coplen, Tyler B; Hunt, Andrew G; Bullen, Thomas D

2013-11-14

High-salinity groundwater more than 1,000 metres deep in the Atlantic coastal plain of the USA has been documented in several locations, most recently within the 35-million-year-old Chesapeake Bay impact crater. Suggestions for the origin of increased salinity in the crater have included evaporite dissolution, osmosis and evaporation from heating associated with the bolide impact. Here we present chemical, isotopic and physical evidence that together indicate that groundwater in the Chesapeake crater is remnant Early Cretaceous North Atlantic (ECNA) sea water. We find that the sea water is probably 100-145 million years old and that it has an average salinity of about 70 per mil, which is twice that of modern sea water and consistent with the nearly closed ECNA basin. Previous evidence for temperature and salinity levels of ancient oceans have been estimated indirectly from geochemical, isotopic and palaeontological analyses of solid materials in deep sediment cores. In contrast, our study identifies ancient sea water in situ and provides a direct estimate of its age and salinity. Moreover, we suggest that it is likely that remnants of ECNA sea water persist in deep sediments at many locations along the Atlantic margin.

Influence of seasonal variations in sea level on the salinity regime of a coastal groundwater-fed wetland.

PubMed

Wood, Cameron; Harrington, Glenn A

2015-01-01

Seasonal variations in sea level are often neglected in studies of coastal aquifers; however, they may have important controls on processes such as submarine groundwater discharge, sea water intrusion, and groundwater discharge to coastal springs and wetlands. We investigated seasonal variations in salinity in a groundwater-fed coastal wetland (the RAMSAR listed Piccaninnie Ponds in South Australia) and found that salinity peaked during winter, coincident with seasonal sea level peaks. Closer examination of salinity variations revealed a relationship between changes in sea level and changes in salinity, indicating that sea level-driven movement of the fresh water-sea water interface influences the salinity of discharging groundwater in the wetland. Moreover, the seasonal control of sea level on wetland salinity seems to override the influence of seasonal recharge. A two-dimensional variable density model helped validate this conceptual model of coastal groundwater discharge by showing that fluctuations in groundwater salinity in a coastal aquifer can be driven by a seasonal coastal boundary condition in spite of seasonal recharge/discharge dynamics. Because seasonal variations in sea level and coastal wetlands are ubiquitous throughout the world, these findings have important implications for monitoring and management of coastal groundwater-dependent ecosystems. © 2014, National Ground Water Association.

On the persistence and coherence of subpolar sea surface temperature and salinity anomalies associated with the Atlantic multidecadal variability

NASA Astrophysics Data System (ADS)

Zhang, Rong

2017-08-01

This study identifies key features associated with the Atlantic multidecadal variability (AMV) in both observations and a fully coupled climate model, e.g., decadal persistence of monthly mean subpolar North Atlantic (NA) sea surface temperature (SST) and salinity (SSS) anomalies, and high coherence at low frequency among subpolar NA SST/SSS, upper ocean heat/salt content, and the Atlantic Meridional Overturning Circulation (AMOC) fingerprint. These key AMV features, which can be used to distinguish the AMV mechanism, cannot be explained by the slab ocean model results or the red noise process but are consistent with the ocean dynamics mechanism. This study also shows that at low frequency, the correlation and regression between net surface heat flux and SST anomalies are key indicators of the relative roles of oceanic versus atmospheric forcing in SST anomalies. The oceanic forcing plays a dominant role in the subpolar NA SST anomalies associated with the AMV.

Diversity of Pico- to Mesoplankton along the 2000 km Salinity Gradient of the Baltic Sea

PubMed Central

Hu, Yue O. O.; Karlson, Bengt; Charvet, Sophie; Andersson, Anders F.

2016-01-01

Microbial plankton form the productive base of both marine and freshwater ecosystems and are key drivers of global biogeochemical cycles of carbon and nutrients. Plankton diversity is immense with representations from all major phyla within the three domains of life. So far, plankton monitoring has mainly been based on microscopic identification, which has limited sensitivity and reproducibility, not least because of the numerical majority of plankton being unidentifiable under the light microscope. High-throughput sequencing of taxonomic marker genes offers a means to identify taxa inaccessible by traditional methods; thus, recent studies have unveiled an extensive previously unknown diversity of plankton. Here, we conducted ultra-deep Illumina sequencing (average 105 sequences/sample) of rRNA gene amplicons of surface water eukaryotic and bacterial plankton communities sampled in summer along a 2000 km transect following the salinity gradient of the Baltic Sea. Community composition was strongly correlated with salinity for both bacterial and eukaryotic plankton assemblages, highlighting the importance of salinity for structuring the biodiversity within this ecosystem. In contrast, no clear trends in alpha-diversity for bacterial or eukaryotic communities could be detected along the transect. The distribution of major planktonic taxa followed expected patterns as observed in monitoring programs, but groups novel to the Baltic Sea were also identified, such as relatives to the coccolithophore Emiliana huxleyi detected in the northern Baltic Sea. This study provides the first ultra-deep sequencing-based survey on eukaryotic and bacterial plankton biogeography in the Baltic Sea. PMID:27242706

Deep Coherent Vortices and Their Sea Surface Expressions

NASA Astrophysics Data System (ADS)

Ienna, Federico; Bashmachnikov, Igor; Dias, Joaquim; Peliz, Alvaro

2017-04-01

Mediterranean Water eddies, known as Meddies, are an important dynamic process occurring at depths of 1000-meters in the Northeast Atlantic Ocean. Meddies occur as a direct result of the Mediterranean Outflow exiting through the Gibraltar Strait, and represent a prevalent mechanism that can be found extensively throughout the ocean. Moreover, Meddy cores are known to produce measurable expressions at the sea surface in the form of rotating coherent vortices, not only affecting the sea surface from beneath, but also allowing for the possibility to remotely study these deep phenomena through data gathered at the sea surface. While many past studies have focused on the properties of Meddy cores, only a handful of studies focus on the physical characteristics and behavior of the surface expressions produced. Are Meddy surface expressions different from other like vortices that dominate the physical ocean surface? What are the relationships between deep and surface mechanisms, and do any feedbacks exist? To shed light on these questions, we investigate the relationship between Meddies and their sea-surface expressions through observations using in-situ float and drifter profiles and satellite altimetry. A total of 782 Meddy cores were examined in the Northeast Atlantic using temperature and salinity data obtained by CTD and Argo during the Mecanismos de transporte e de dispersão da Água Mediterrânica no Atlântico Nordeste (MEDTRANS) project, and their corresponding sea-level expressions were geo-temporally matched in satellite altimetry data. We report several statistical properties of the sea-surface expressions of Meddies, including their mean diameter and vertical magnitude, and compare the properties of their surface features to the underlying Meddy cores. We investigate how the deep core affects the surface, and whether surface expressions may in return yield information about the underlying cores. Additionally, we examine the variability of the surface

Bay of Bengal Surface and Thermocline and the Arabian Sea

DTIC Science & Technology

2015-09-30

oceanographic processes that exchange low salinity surface and upper thermocline water of the Bay of Bengal with the salty Arabian Sea and tropical Indian Ocean ...two northern embayments of the Indian Ocean . OBJECTIVES Two northern Indian Ocean embayments, the Arabian Sea and the Bay of Bengal, are so close...e.g. where do the eddies come from? 2. Investigating advective pathways, and the role of isopycnal mixing, exchanging upper ocean water between the

SMAP Salinity Artifacts Associated With Presence of Rain

NASA Astrophysics Data System (ADS)

Jacob, M. M.; Santos-Garcia, A.; Jones, L.

2016-02-01

The Soil Moisture Active Passive (SMAP) satellite carries an L-band radiometer, which measures sea surface salinity (SSS) over a swath of 1000 km @ 40 km resolution. SMAP can extend the Aquarius (AQ) salinity data record with improved temporal/spatial sampling. Previous studies [see references] have demonstrated significant differences between satellite and in-situ salinity measurements during rain. In the presence of precipitation, salinity stratification exists near the sea surface, which nullifies the presumption of a well-mixed salinity. In general, these salinity gradients last only a few hours and the upper layer becomes slightly fresher in salinity. This paper describes the Rain Impact Model (RIM) that simulates the effects of rain accumulation on the SSS [Santos-Garcia et al., 2014] applied to SMAP. This model incorporates rainfall information for the previous 24 hours to the measurement sample (in this case SMAP) and uses as initialization the Hybrid Coordinate Ocean Model (HYCOM) data. Given the better resolution of SMAP, the goal of this paper is to continue the analysis previously done with AQ to better understand the effects of the instantaneous and accumulated rain on the salinity measurements. Boutin, J., N. Martin, G. Reverdin, X. Yin, and F. Gaillard (2013), Sea surface freshening inferred from SMOS and ARGO salinity: Impact of rain, Ocean Sci., 9(1), 183-192, doi:10.5194/os-9-183-2013. Santos-Garcia, A., M. Jacob, L. Jones, W. Asher, Y. Hejazin, H. Ebrahimi, and M. Rabolli (2014), Investigation of rain effects on Aquarius Sea Surface Salinity measurements, J. Geophys. Res. Oceans, 119, 7605-7624, doi:10.1002/2014JC010137. Tang, W., S.H Yueh, A. Hayashi, A.G. Fore, W.L. Jones, A. Santos-Garcia, and M.M. Jacob, (2015), Rain-Induced Near Surface Salinity Stratification and Rain Roughness Correction for Aquarius SSS Retrieval, in Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of, 8(99), 1-11, doi: 10.1109/JSTARS.2015.2463768.

Effects of the Antenna Aperture on Remote Sensing of Sea Surface Salinity at L-Band

NASA Technical Reports Server (NTRS)

Dinnat, Emmanuel P.; LeVine, David M.

2006-01-01

Remote sensing of sea surface salinity with sufficient accuracy to meet the needs of global oceanography is a challenging task. The global variability of the salinity signal in the open ocean is only a few Kelvin even at L-band and an accuracy on the order of 0.1K is desired to study the influence of salinity on ocean circulation and energy exchange with the atmosphere. On the other hand, resolution is not an issue for understanding the dynamics of the open ocean where scales of hundreds of km are not uncommon. This permits remote sensing with large antenna footprints and spatial averaging to reduce noise. However, antennas with large footprints introduce other problems. For example, the angle of incidence and hence the brightness temperature varies over the footprint. Similarly, the polarization of brightness temperature relative to the antenna ports changes. Studies have been conducted using antenna patterns representative of the antenna that will be flown on the Aquarius mission to examine these effects. Aquarius is a pushbroom style radiometer with three beams looking across track away from the sun. The beams are at incidences angles (at the spacecraft) of about 26.5, 34 and 40 degrees each with a half-power beam width of about 5.8 degrees. It is shown that the measured brightness temperature is biased relative to the value at boresight because of changes across the field of view. The bias can be as much as 4K and positive or negative depending on polarization. Polarization mixing because of the variations of the local plane of incidence across the footprint also occur and can result in biased polarimetric measurements. A bias in the third Stokes parameter of as much as 0.4K is possible. Such effects may affect algorithms that use the third Stokes parameter to correct for Faraday rotation. Another issue associated with the antenna is sun glint. This is an issue determined by surface roughness and antenna sidelobes. Examples will be given for the random

Effects of oceanic salinity on body condition in sea snakes.

PubMed

Brischoux, François; Rolland, Virginie; Bonnet, Xavier; Caillaud, Matthieu; Shine, Richard

2012-08-01

Since the transition from terrestrial to marine environments poses strong osmoregulatory and energetic challenges, temporal and spatial fluctuations in oceanic salinity might influence salt and water balance (and hence, body condition) in marine tetrapods. We assessed the effects of salinity on three species of sea snakes studied by mark-recapture in coral-reef habitats in the Neo-Caledonian Lagoon. These three species include one fully aquatic hydrophiine (Emydocephalus annulatus), one primarily aquatic laticaudine (Laticauda laticaudata), and one frequently terrestrial laticaudine (Laticauda saintgironsi). We explored how oceanic salinity affected the snakes' body condition across various temporal and spatial scales relevant to each species' ecology, using linear mixed models and multimodel inference. Mean annual salinity exerted a consistent and negative effect on the body condition of all three snake species. The most terrestrial taxon (L. saintgironsi) was sensitive to salinity over a short temporal scale, corresponding to the duration of a typical marine foraging trip for this species. In contrast, links between oceanic salinity and body condition in the fully aquatic E. annulatus and the highly aquatic L. laticaudata were strongest at a long-term (annual) scale. The sophisticated salt-excreting systems of sea snakes allow them to exploit marine environments, but do not completely overcome the osmoregulatory challenges posed by oceanic conditions. Future studies could usefully explore such effects in other secondarily marine taxa such as seabirds, turtles, and marine mammals.

Launch and on-orbit checkout of Aquarius/SAC-D Observatory: an international remote sensing satellite mission measuring sea surface salinity

NASA Astrophysics Data System (ADS)

Sen, Amit; Caruso, Daniel; Durham, David; Falcon, Carlos

2011-11-01

The Aquarius/SAC-D observatory was launch in June 2011 from Vandenberg Air Force Base (VAFB), in California, USA. This mission is the fourth joint earth-observation endeavor between NASA and CONAE. The primary objective of the Aquarius/SAC-D mission is to investigate the links between global water cycle, ocean circulation and climate by measuring Sea Surface Salinity (SSS). Over the last year, the observatory successfully completed system level environmental and functional testing at INPE, Brazil and was transported to VAFB for launch operations. This paper will present the challenges of this mission, the system, the preparation of the spacecraft, instruments, testing, launch, inorbit checkout and commissioning of this Observatory in space.

Decadal trends in deep ocean salinity and regional effects on steric sea level

NASA Astrophysics Data System (ADS)

Purkey, S. G.; Llovel, W.

2017-12-01

We present deep (below 2000 m) and abyssal (below 4000 m) global ocean salinity trends from the 1990s through the 2010s and assess the role of deep salinity in local and global sea level budgets. Deep salinity trends are assessed using all deep basins with available full-depth, high-quality hydrographic section data that have been occupied two or more times since the 1980s through either the World Ocean Circulation Experiment (WOCE) Hydrographic Program or the Global Ship-Based Hydrographic Investigations Program (GO-SHIP). All salinity data is calibrated to standard seawater and any intercruise offsets applied. While the global mean deep halosteric contribution to sea level rise is close to zero (-0.017 +/- 0.023 mm/yr below 4000 m), there is a large regional variability with the southern deep basins becoming fresher and northern deep basins becoming more saline. This meridional gradient in the deep salinity trend reflects different mechanisms driving the deep salinity variability. The deep Southern Ocean is freshening owing to a recent increased flux of freshwater to the deep ocean. Outside of the Southern Ocean, the deep salinity and temperature changes are tied to isopycnal heave associated with a falling of deep isopycnals in recent decades. Therefore, regions of the ocean with a deep salinity minimum are experiencing both a halosteric contraction with a thermosteric expansion. While the thermosteric expansion is larger in most cases, in some regions the halosteric compensates for as much as 50% of the deep thermal expansion, making a significant contribution to local sea level rise budgets.

Long Term Surface Salinity Measurements

NASA Technical Reports Server (NTRS)

Schmitt, Raymond W.; Brown, Neil L.

2005-01-01

Our long-term goal is to establish a reliable system for monitoring surface salinity around the global ocean. Salinity is a strong indicator of the freshwater cycle and has a great influence on upper ocean stratification. Global salinity measurements have potential to improve climate forecasts if an observation system can be developed. This project is developing a new internal field conductivity cell that can be protected from biological fouling for two years. Combined with a temperature sensor, this foul-proof cell can be deployed widely on surface drifters. A reliable in-situ network of surface salinity sensors will be an important adjunct to the salinity sensing satellite AQUARIUS to be deployed by NASA in 2009. A new internal-field conductivity cell has been developed by N Brown, along with new electronics. This sensor system has been combined with a temperature sensor to make a conductivity - temperature (UT) sensor suitable for deployment on drifters. The basic sensor concepts have been proven on a high resolution CTD. A simpler (lower cost) circuit has been built for this application. A protection mechanism for the conductivity cell that includes antifouling protection has also been designed and built. Mr. A.Walsh of our commercial partner E-Paint has designed and delivered time-release formulations of antifoulants for our application. Mr. G. Williams of partner Clearwater Instrumentation advised on power and communication issues and supplied surface drifters for testing.

Evolution of anomalies of salinity of surface waters of Arctic Ocean and their possible influence on climate changes

NASA Astrophysics Data System (ADS)

Popov, A.; Rubchenia, A.

2009-04-01

Numerous of model simulations of ice extent in Arctic Ocean predict almost full disappearance of sea ice in Arctic regions by 2050. However, the nature, as against models, does not suffer the unidirectional processes. By means of various feedback responses system aspires to come in an equilibrium condition. In Arctic regions one of the most powerful generators of a negative feedback is the fresh-water stream to Greenland Sea and Northern Atlantic. Increasing or decreasing of a fresh-water volume from the Arctic basin to Greenland Sea and Northern Atlantic results in significant changes in climatic system. At the Oceanology department of Arctic and Antarctic Research Institute (AARI) (St-Petersburg, Russia) in 2007, on the basis of the incorporated Russian-American database of the oceanographic data, reconstruction of long-term time series of average salinity of ocean surface was executed. The received time series describes the period from 1950 to 1993. For allocation of the processes determining formation of changes of average salinity of surface waters in Arctic basin the correlation analysis of interrelation of the received time series and several physical parameters which could affect formation of changes of salinity was executed. We found counter-intuitive result: formation of long-term changes of average salinity of surface waters of Arctic basin in the winter period does not depend on changes of a Siberian rivers runoff. Factors of correlation do not exceed -0,31. At the same time, clear inverse relationship of salinity of surface waters from volumes of the ice formed in flaw lead polynyas of the Siberian shelf seas is revealed. In this case factors of correlation change from -0,56 to -0,7. The maximum factor of correlation is -0,7. It characterizes interrelation of total volume of the ice formed in flaw lead polynyas of all seas of the Siberian shelf and average salinity of surface waters of Arctic basin. Thus, at increase of volumes of the ice formed in

Bay of Bengal Surface and Thermocline and the Arabian Sea

DTIC Science & Technology

2014-09-30

to the atmosphere. How low the SSS gets in the Bay of Bengal or how high in the Arabian Sea, depends on the oceanic exchanges between them via a...potential impact on the SST. 3 Figure 1a: Sea surface temperature (SST) and salinity ( SSS ) relationship during ASIRI 2013 cruises. The left panel...shows the hull ADCP vector, color-coded for SSS . The SST/ SSS scatter falls along a line from the warm/salty southern regions to the cool/fresher

LLWBCS changes through surface mesoscale activity and baroclinic tides in the Solomon Sea

NASA Astrophysics Data System (ADS)

Gourdeau, L.; Djath, B.; Ganachaud, A. S.; Tchilibou, M. L.; Verron, J. A.; Jouanno, J.

2016-02-01

In the south west Pacific, the Solomon Sea is on the pathway of the Low Latitudes Western Boundary Currents that connect the subtropics to the equator. Changes in their strengths, or in their water mass properties may have implication for ENSO and its low frequency modulation. During their transit in the Solomon Sea, the salinity maximum at thermocline level, characteristic of the South Pacific Tropical Waters (SPTW), is largely eroded. Different mechanisms could explain such salt erosion whose current/bathymetry interaction, internal tides, eddy activity. The Solomon Sea is an area of high level of eddy kinetic energy (EKE), especially in the surface layers, and its complex bathymetry is favourable for generation and dissipation of internal tides. Based on high resolution modelling, glider, and altimetric data mesoscale eddies observed at the surface are analysed in their 4D aspects. Their role on water mass transformation is explored. These eddies may affect the surface layers (σ<23.3) and the upper thermocline waters (23.3< σ <24.3), but they cannot explained the erosion of the salinity maximum below. Simulations with and without explicit tides provide a description of baroclinic tides in the Solomon Sea. Their role on water mixing is evaluated, especially for the SPTW.

Relationship between the Bering Strait Throughflow and Salinity in the Bering Sea in an Atmosphere-Ocean-Ice Coupled Model

NASA Astrophysics Data System (ADS)

Kawai, Y.; Osafune, S.; Masuda, S.; Komuro, Y.

2016-12-01

The relationship between the volumetric transport of the Bering Strait throughflow (BTF) and sea surface salinity (SSS) in the Bering Sea was investigated using an atmosphere-ocean-ice coupled model, MIROC4h, which includes an eddy-permitting ocean model. The MIROC4h simulated well the seasonal cycle of BTF transport, although it overestimated the transport compared with previous studies. The interannual variations of SSS in the Bering Sea were correlated with those of BTF transport: SSS in the northwestern Bering Sea was high when BTF transport was large. The SSS anomaly associated with the BTF anomaly became evident from late autumn to spring, and SSS lagged behind the BTF by a few months. The BTF transport was strongly correlated with the SSH in the eastern Bering Sea, the southwestern Chukchi Sea, and the East Siberian Sea. The low SSH along the Russian coast in the Arctic Ocean was uncorrelated with the high SSH in the Bering Sea. The Arctic SSH affected BTF transport and the SSS in the northwestern Bering Sea independently of the SSH in the Bering Sea. We evaluated the salt budget in the northwestern Bering Sea, including Anadyr Bay. When the BTF transport in October-March was large, the horizontal convergence of salt increased and sea-ice melting decreased; both changes contributed to the increase of salinity. In contrast, evaporation-minus-precipitation and the residual component had the opposite effect. The sea-ice retreat was closely related to meridional wind anomalies that also raised the SSH in the eastern Bering Sea. Changes in upper-layer currents caused by the southerly wind anomalies in the Bering Sea contributed to the increase of the horizontal convergence of salt. In addition, the SSH anomalies in the Arctic Ocean independently affected the currents in the Bering Strait and the northwestern Bering Sea, perhaps through the propagation of shelf waves, which also led to salinization.

Overview of the Nordic Seas CARINA data and salinity measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olsen, Are; Key, Robert; Jeansson, Emil

2009-01-01

Water column data of carbon and carbon relevant hydrographic and hydrochemical parameters from 188 previously non-publicly available cruises in the Arctic, Atlantic, and Southern Ocean have been retrieved and merged into a new database: CARINA (CARbon IN the Atlantic). The data have been subject to rigorous quality control (QC) in order to ensure highest possible quality and consistency. The data for most of the parameters included were examined in order to quantify systematic biases in the reported values, i.e. secondary quality control. Significant biases have been corrected for in the data products, i.e. the three merged files with measured, calculatedmore » and interpolated values for each of the three CARINA regions; the Arctic Mediterranean Seas (AMS), the Atlantic (ATL) and the Southern Ocean (SO).With the adjustments the CARINA database is consistent both internally as well as with GLODAP (Key et al., 2004) and is suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation. The Arctic Mediterranean Seas include the Arctic Ocean and the Nordic Seas, and the quality control was carried out separately in these two areas. This contribution provides an overview of the CARINA data from the Nordic Seas and summaries the findings of the QC of the salinity data. One cruise had salinity data that were of questionable quality, and these have been removed from the data product. An evaluation of the consistency of the quality controlled salinity data suggests that they are consistent to at least 0.005.« less

Local adaptation and oceanographic connectivity patterns explain genetic differentiation of a marine diatom across the North Sea–Baltic Sea salinity gradient

PubMed Central

Sjöqvist, C; Godhe, A; Jonsson, P R; Sundqvist, L; Kremp, A

2015-01-01

Drivers of population genetic structure are still poorly understood in marine micro-organisms. We exploited the North Sea–Baltic Sea transition for investigating the seascape genetics of a marine diatom, Skeletonema marinoi. Eight polymorphic microsatellite loci were analysed in 354 individuals from ten locations to analyse population structure of the species along a 1500-km-long salinity gradient ranging from 3 to 30 psu. To test for salinity adaptation, salinity reaction norms were determined for sets of strains originating from three different salinity regimes of the gradient. Modelled oceanographic connectivity was compared to directional relative migration by correlation analyses to examine oceanographic drivers. Population genetic analyses showed distinct genetic divergence of a low-salinity Baltic Sea population and a high-salinity North Sea population, coinciding with the most evident physical dispersal barrier in the area, the Danish Straits. Baltic Sea populations displayed reduced genetic diversity compared to North Sea populations. Growth optima of low salinity isolates were significantly lower than those of strains from higher native salinities, indicating local salinity adaptation. Although the North Sea–Baltic Sea transition was identified as a barrier to gene flow, migration between Baltic Sea and North Sea populations occurred. However, the presence of differentiated neutral markers on each side of the transition zone suggests that migrants are maladapted. It is concluded that local salinity adaptation, supported by oceanographic connectivity patterns creating an asymmetric migration pattern between the Baltic Sea and the North Sea, determines genetic differentiation patterns in the transition zone. PMID:25892181

Flux of low salinity water from Aniva Bay (Sakhalin Island) to the southern Okhotsk Sea

NASA Astrophysics Data System (ADS)

Oguma, Sachiko; Ono, Tsuneo; Watanabe, Yutaka W.; Kasai, Hiromi; Watanabe, Shuichi; Nomura, Daiki; Mitsudera, Humio

2011-01-01

In this study, we examined the relationship between the low salinity water in the shelf region of the southern Okhotsk Sea which was seasonally sampled (0-200 m), and fluxes of low salinity water from Aniva Bay. To express the source of freshwater mixing in the surface layer, we applied normalized total alkalinity (NTA) and stable isotopes of seawater as chemical tracers. NTA-S diagrams indicate that NTA of low salinity water in the upper 30 m layer just off the Soya Warm Current is clearly higher than in the far offshore region in summer and autumn. Using NTA-S regression lines, we could deduce that the low salinity and high NTA water in the upper layer originates from Aniva Bay. For convenience, we defined this water as the Aniva Surface Water (ASW) with values S < 32, NTA > 2450 μmol kg -1. Formation and transport processes of ASW are discussed using historical data. The interaction between the maximum core of high NTA water on the bottom slope of eastern Aniva Bay and an anticyclonic eddy at the mouth of Aniva Bay are concluded to control ASW formation. Upwelling of the Cold Water Belt water at the tip of Cape Krillion is considered to cause ASW outflow from Aniva Bay.

The Aquarius Salinity Retrieval Algorithm

NASA Technical Reports Server (NTRS)

Meissner, Thomas; Wentz, Frank; Hilburn, Kyle; Lagerloef, Gary; Le Vine, David

2012-01-01

The first part of this presentation gives an overview over the Aquarius salinity retrieval algorithm. The instrument calibration [2] converts Aquarius radiometer counts into antenna temperatures (TA). The salinity retrieval algorithm converts those TA into brightness temperatures (TB) at a flat ocean surface. As a first step, contributions arising from the intrusion of solar, lunar and galactic radiation are subtracted. The antenna pattern correction (APC) removes the effects of cross-polarization contamination and spillover. The Aquarius radiometer measures the 3rd Stokes parameter in addition to vertical (v) and horizontal (h) polarizations, which allows for an easy removal of ionospheric Faraday rotation. The atmospheric absorption at L-band is almost entirely due to molecular oxygen, which can be calculated based on auxiliary input fields from numerical weather prediction models and then successively removed from the TB. The final step in the TA to TB conversion is the correction for the roughness of the sea surface due to wind, which is addressed in more detail in section 3. The TB of the flat ocean surface can now be matched to a salinity value using a surface emission model that is based on a model for the dielectric constant of sea water [3], [4] and an auxiliary field for the sea surface temperature. In the current processing only v-pol TB are used for this last step.

Improved measurements of mean sea surface velocity in the Nordic Seas from synthetic aperture radar

NASA Astrophysics Data System (ADS)

Wergeland Hansen, Morten; Johnsen, Harald; Engen, Geir; Øie Nilsen, Jan Even

2017-04-01

The warm and saline surface Atlantic Water (AW) flowing into the Nordic Seas across the Greenland-Scotland ridge transports heat into the Arctic, maintaining the ice-free oceans and regulating sea-ice extent. The AW influences the region's relatively mild climate and is the northern branch of the global thermohaline overturning circulation. Heat loss in the Norwegian Sea is key for both heat transport and deep water formation. In general, the ocean currents in the Nordic Seas and the North Atlantic Ocean is a complex system of topographically steered barotropic and baroclinic currents of which the wind stress and its variability is a driver of major importance. The synthetic aperture radar (SAR) Doppler centroid shift has been demonstrated to contain geophysical information about sea surface wind, waves and current at an accuracy of 5 Hz and pixel spacing of 3.5 - 9 × 8 km2. This corresponds to a horizontal surface velocity of about 20 cm/s at 35° incidence angle. The ESA Prodex ISAR project aims to implement new and improved SAR Doppler shift processing routines to enable reprocessing of the wide swath acquisitions available from the Envisat ASAR archive (2002-2012) at higher resolution and better accuracy than previously obtained, allowing combined use with Sentinel-1 and Radarsat-2 retrievals to build timeseries of the sea surface velocity in the Nordic Seas. Estimation of the geophysical Doppler shift from new SAR Doppler centroid shift retrievals will be demonstrated, addressing key issues relating to geometric (satellite orbit and attitude) and electronic (antenna mis-pointing) contributions and corrections. Geophysical Doppler shift retrievals from one month of data in January 2010 and the inverted surface velocity in the Nordic Seas are then addressed and compared to other direct and indirect estimates of the upper ocean current, in particular those obtained in the ESA GlobCurrent project.

Remote sensing of salinity

NASA Technical Reports Server (NTRS)

Thomann, G. C.

1975-01-01

The complex dielectric constant of sea water is a function of salinity at 21 cm wavelength, and sea water salinity can be determined by a measurement of emissivity at 21 cm along with a measurement of thermodynamic temperature. Three aircraft and one helicopter experiments using two different 21 cm radiometers were conducted under different salinity and temperature conditions. Single or multiple ground truth measurements were used to calibrate the data in each experiment. It is inferred from these experiments that accuracies of 1 to 2%/OO are possible with a single surface calibration point necessary only every two hours if the following conditions are met--water temperatures above 20 C, salinities above 10%/OO, and level plane flight. More frequent calibration, constraint of the aircraft's orientation to the same as it was during calibration, and two point calibration (at a high and low salinity level) rather than single point calibration may give even better accuracies in some instances.

Estimation of the barrier layer thickness in the Indian Ocean using Aquarius Salinity

NASA Astrophysics Data System (ADS)

Felton, Clifford S.; Subrahmanyam, Bulusu; Murty, V. S. N.; Shriver, Jay F.

2014-07-01

Monthly barrier layer thickness (BLT) estimates are derived from satellite measurements using a multilinear regression model (MRM) within the Indian Ocean. Sea surface salinity (SSS) from the recently launched Soil Moisture and Ocean Salinity (SMOS) and Aquarius SAC-D salinity missions are utilized to estimate the BLT. The MRM relates BLT to sea surface salinity (SSS), sea surface temperature (SST), and sea surface height anomalies (SSHA). Three regions where the BLT variability is most rigorous are selected to evaluate the performance of the MRM for 2012; the Southeast Arabian Sea (SEAS), Bay of Bengal (BoB), and Eastern Equatorial Indian Ocean (EEIO). The MRM derived BLT estimates are compared to gridded Argo and Hybrid Coordinate Ocean Model (HYCOM) BLTs. It is shown that different mechanisms are important for sustaining the BLT variability in each of the selected regions. Sensitivity tests show that SSS is the primary driver of the BLT within the MRM. Results suggest that salinity measurements obtained from Aquarius and SMOS can be useful for tracking and predicting the BLT in the Indian Ocean. Largest MRM errors occur along coastlines and near islands where land contamination skews the satellite SSS retrievals. The BLT evolution during 2012, as well as the advantages and disadvantages of the current model are discussed. BLT estimations using HYCOM simulations display large errors that are related to model layer structure and the selected BLT methodology.

Responses of Baltic Sea Ice and Open-Water Natural Bacterial Communities to Salinity Change

PubMed Central

Kaartokallio, Hermanni; Laamanen, Maria; Sivonen, Kaarina

2005-01-01

To investigate the responses of Baltic Sea wintertime bacterial communities to changing salinity (5 to 26 practical salinity units), an experimental study was conducted. Bacterial communities of Baltic seawater and sea ice from a coastal site in southwest Finland were used in two batch culture experiments run for 17 or 18 days at 0°C. Bacterial abundance, cell volume, and leucine and thymidine incorporation were measured during the experiments. The bacterial community structure was assessed using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified partial 16S rRNA genes with sequencing of DGGE bands from initial communities and communities of day 10 or 13 of the experiment. The sea ice-derived bacterial community was metabolically more active than the open-water community at the start of the experiment. Ice-derived bacterial communities were able to adapt to salinity change with smaller effects on physiology and community structure, whereas in the open-water bacterial communities, the bacterial cell volume evolution, bacterial abundance, and community structure responses indicated the presence of salinity stress. The closest relatives for all eight partial 16S rRNA gene sequences obtained were either organisms found in polar sea ice and other cold habitats or those found in summertime Baltic seawater. All sequences except one were associated with the α- and γ-proteobacteria or the Cytophaga-Flavobacterium-Bacteroides group. The overall physiological and community structure responses were parallel in ice-derived and open-water bacterial assemblages, which points to a linkage between community structure and physiology. These results support previous assumptions of the role of salinity fluctuation as a major selective factor shaping the sea ice bacterial community structure. PMID:16085826

Near-surface temperature and salinity stratification as observed with dual-sensor Lagrangian drifters deployed during SPURS-2 field campaign

NASA Astrophysics Data System (ADS)

Volkov, Denis; Dong, Shenfu; Goni, Gustavo; Lumpkin, Rick; Foltz, Greg

2017-04-01

Despite the importance of sea surface salinity (SSS) as an indicator of the hydrological cycle, many details of air-sea interaction responsible for freshwater fluxes and processes determining the near-surface salinity stratification and its variability are still poorly understood. This is primarily due to the lack of dedicated observations. The advent of satellites capable of monitoring SSS, such as the Soil Moisture and Ocean Salinity (SMOS), Aquarius, and Soil Moisture Active-Passive (SMAP) missions, has greatly advanced our knowledge of SSS distribution and variability. However, the spatial resolution of satellite retrievals is too coarse to study the upper-ocean salinity changes due to patchy and transient rain events. Furthermore, the satellites measure salinity within the upper 1 cm skin layer, which can significantly differ from in situ SSS measured at 5 m depth by most Argo floats. Differences between the Aquarius and Argo SSS can be as large as ±0.5 psu. In order to study the near-surface salinity structure in great detail and to link the satellite observations of SSS with all the oceanic and atmospheric processes that control its variability, the National Aeronautics and Space Administration has initiated two field campaigns within the framework of Salinity Processes in the Upper-Ocean Regional Study (SPURS) project (http://spurs.jpl.nasa.gov/). The first campaign, SPURS-1, took place in the evaporation-dominated subtropical North Atlantic Ocean in 2012-2013. The second campaign, SPURS-2, focused on a 3×3° domain in the Inter-Tropical Convergence Zone (ITCZ) in the eastern equatorial Pacific (123.5-126.5°W and 8.5-11.5°N), where the near-surface salinity is strongly dominated by precipitation. The first SPURS-2 cruise took place in Aug-Sep 2016 on board the R/V Roger Revelle, during which a complex multi-instrument oceanographic survey was conducted. As part of this field campaign, we deployed 6 dual-sensor Lagrangian drifters, specifically designed

Quantifying the impact of the major driving mechanisms of inter-annual variability of salinity in the North Sea

NASA Astrophysics Data System (ADS)

Núñez-Riboni, Ismael; Akimova, Anna

2017-05-01

New 67-year long (1948-2014) gridded time series of salinity in the North Sea at all depths allowed to quantify, spatially resolved, the amount of inter-annual salinity variability explained by each of its driving mechanisms: sea level pressure (SLP), precipitation, river run-off, zonal and meridional winds and currents over the eastern North Atlantic. For the current data, not only annual averages but also their deviations, as measure of turbulence, were considered. Our results summarize and expand the knowledge gathered in the last 50 years about the mechanisms driving inter-annual variability of salinity in the North Sea. Three mechanisms, uncorrelated with each other and acting over separate regions of the North Sea, arise as most important: (1) River run-off from continental Europe explains 50-80% of inter-annual salinity variations at lag 0 in the Southern and German Bights and the Norwegian Trench up to the connection with the North Atlantic, down to the seabed near the coasts and to the deep Norwegian Trench (100 m); (2) Remote variations of salinity in the Rockall Trough explain 70% of salinity variations of the tongue of high salinity in the northwestern North Sea with a lag of one year and down the water column; (3) The Neva discharge explains 60% of salinity changes in Skagerrak and southern Norwegian trench at lag 0. An explanation for this correlation might be the Baltic freshwater outflow being modulated by the Neva discharge through intensification of the estuarine gravitational circulation. We confirmed known relations between river run-off, precipitation over continental Europe, SLP over northern Europe and zonal wind over western Europe. Linked to these changes, we found also changes of meridional wind north of Scotland favoring eastward Ekman transport of salty North Atlantic waters into the North Sea off the Norwegian coast. Excluding this only case, we found no significant correlation between wind-driven currents and North Sea salinity changes

Sea level change since 2005: importance of salinity

NASA Astrophysics Data System (ADS)

Llovel, W.; Purkey, S.; Meyssignac, B.; Kolodziejczyk, N.; Blazquez, A.; Bamber, J. L.

2017-12-01

Sea level rise is one of the most important consequences of the actual global warming. Global mean sea level has been rising at a faster rate since 1993 (over the satellite altimetry era) than previous decades. This rise is expected to accelerate over the coming decades and century. At global scale, sea level rise is caused by a combination of freshwater increase from land ice melting and land water changes (mass component) and ocean warming (thermal expansion). Estimating the causes is of great interest not only to understand the past sea level changes but also to validate projections based on climate models. In this study, we investigate the global mass contribution to recent sea level changes with an alternative approach by estimating the global ocean freshening. For that purpose, we consider the unprecedented amount of salinity measurements from Argo floats for the past decade (2005-2015). We compare our results to the ocean mass inferred by GRACE data and based on a sea level budget approach. Our results bring new constrains on the global water cycle (ocean freshening) and energy budget (ocean warming) as well as on the global ocean mass directly inferred from GRACE data.

Seasonal variability of the Red Sea, from GRACE time-variable gravity and altimeter sea surface height measurements

NASA Astrophysics Data System (ADS)

Wahr, John; Smeed, David; Leuliette, Eric; Swenson, Sean

2014-05-01

Seasonal variability of sea surface height and mass within the Red Sea, occurs mostly through the exchange of heat with the atmosphere and wind-driven inflow and outflow of water through the strait of Bab el Mandab that opens into the Gulf of Aden to the south. The seasonal effects of precipitation and evaporation, of water exchange through the Suez Canal to the north, and of runoff from the adjacent land, are all small. The flow through the Bab el Mandab involves a net mass transfer into the Red Sea during the winter and a net transfer out during the summer. But that flow has a multi-layer pattern, so that in the summer there is actually an influx of cool water at intermediate (~100 m) depths. Thus, summer water in the southern Red Sea is warmer near the surface due to higher air temperatures, but cooler at intermediate depths (especially in the far south). Summer water in the northern Red Sea experiences warming by air-sea exchange only. The temperature profile affects the water density, which impacts the sea surface height but has no effect on vertically integrated mass. Here, we study this seasonal cycle by combining GRACE time-variable mass estimates, altimeter (Jason-1, Jason-2, and Envisat) measurements of sea surface height, and steric sea surface height contributions derived from depth-dependent, climatological values of temperature and salinity obtained from the World Ocean Atlas. We find good consistency, particularly in the northern Red Sea, between these three data types. Among the general characteristics of our results are: (1) the mass contributions to seasonal SSHT variations are much larger than the steric contributions; (2) the mass signal is largest in winter, consistent with winds pushing water into the Red Sea through the Strait of Bab el Mandab in winter, and out during the summer; and (3) the steric signal is largest in summer, consistent with summer sea surface warming.

Impacts of Low Salinity on Growth and Calcification in Baltic Sea Mytilus edulis x trossulus

NASA Astrophysics Data System (ADS)

Sanders, T.; Melzner, F.

2016-02-01

The Baltic Sea is characterized by a steep salinity gradient (25 psu - <5 psu) which is predicted to increase in the future due to increased precipitation. This provides an excellent biological system to study the effects of salinity and inorganic carbon supply on animal physiology. Mytilus edulis x trossulus is adapted to the low saline Baltic Sea, at the cost of slow body growth and reduced shell thickness. The explanation for the small size of Baltic mytilids has been attributed to tradeoffs in energy partitioning due to high energetic costs associated with osmoregulation. However, salinity may effect calcification mechanisms and reduce calcification and thus, body size and growth. To understand the mechanistic effects salinity has on calcification, energy budgets were quantified in larvae, juveniles and adults from 3 populations of Baltic Sea Mytilus spp. at different salinities (6, 11 and 16 psu). Net CaCO3 production at varying salinities and bicarbonate concentrations was also measured. Larvae from low salinity adapted populations (6 psu) had a 3-fold higher respiration rate compared to higher salinity populations. This was also accompanied by a delay of 48 hours in early shell formation. Reductions in growth and increases in metabolism were largest between 11 psu and 6 psu indicating that the predicted desalination of the Baltic will go along with huge energetic costs for mussel populations, potentially leading to loss of reefs in the Eastern Baltic. To investigate the mechanisms behind increased metabolic cost and decreased allocation to growth, energy budgets are presently being constrained in our three populations using modulations in food supply and temperature.

RNA-Seq analysis of salinity stress-responsive transcriptome in the liver of spotted sea bass (Lateolabrax maculatus).

PubMed

Zhang, Xiaoyan; Wen, Haishen; Wang, Hailiang; Ren, Yuanyuan; Zhao, Ji; Li, Yun

2017-01-01

Salinity is one of the most prominent abiotic factors, which greatly influence reproduction, development, growth, physiological and metabolic activities of fishes. Spotted sea bass (Lateolabrax maculatus), as a euryhaline marine teleost, has extraordinary ability to deal with a wide range of salinity changes. However, this species is devoid of genomic resources, and no study has been conducted at the transcriptomic level to determine genes responsible for salinity regulation, which impedes the understanding of the fundamental mechanism conferring tolerance to salinity fluctuations. Liver, as the major metabolic organ, is the key source supplying energy for iono- and osmoregulation in fish, however, little attention has been paid to its salinity-related functions but which should not be ignored. In this study, we perform RNA-Seq analysis to identify genes involved in salinity adaptation and osmoregulation in liver of spotted sea bass, generating from the fishes exposed to low and high salinity water (5 vs 30ppt). After de novo assembly, annotation and differential gene expression analysis, a total of 455 genes were differentially expressed, including 184 up-regulated and 271 down-regulated transcripts in low salinity-acclimated fish group compared with that in high salinity-acclimated group. A number of genes with a potential role in salinity adaptation for spotted sea bass were classified into five functional categories based on the gene ontology (GO) and enrichment analysis, which include genes involved in metabolites and ion transporters, energy metabolism, signal transduction, immune response and structure reorganization. The candidate genes identified in L. maculates liver provide valuable information to explore new pathways related to fish salinity and osmotic regulation. Besides, the transcriptomic sequencing data supplies significant resources for identification of novel genes and further studying biological questions in spotted sea bass.

RNA-Seq analysis of salinity stress–responsive transcriptome in the liver of spotted sea bass (Lateolabrax maculatus)

PubMed Central

Zhang, Xiaoyan; Wen, Haishen; Wang, Hailiang; Ren, Yuanyuan; Zhao, Ji; Li, Yun

2017-01-01

Salinity is one of the most prominent abiotic factors, which greatly influence reproduction, development, growth, physiological and metabolic activities of fishes. Spotted sea bass (Lateolabrax maculatus), as a euryhaline marine teleost, has extraordinary ability to deal with a wide range of salinity changes. However, this species is devoid of genomic resources, and no study has been conducted at the transcriptomic level to determine genes responsible for salinity regulation, which impedes the understanding of the fundamental mechanism conferring tolerance to salinity fluctuations. Liver, as the major metabolic organ, is the key source supplying energy for iono- and osmoregulation in fish, however, little attention has been paid to its salinity-related functions but which should not be ignored. In this study, we perform RNA-Seq analysis to identify genes involved in salinity adaptation and osmoregulation in liver of spotted sea bass, generating from the fishes exposed to low and high salinity water (5 vs 30ppt). After de novo assembly, annotation and differential gene expression analysis, a total of 455 genes were differentially expressed, including 184 up-regulated and 271 down-regulated transcripts in low salinity-acclimated fish group compared with that in high salinity-acclimated group. A number of genes with a potential role in salinity adaptation for spotted sea bass were classified into five functional categories based on the gene ontology (GO) and enrichment analysis, which include genes involved in metabolites and ion transporters, energy metabolism, signal transduction, immune response and structure reorganization. The candidate genes identified in L. maculates liver provide valuable information to explore new pathways related to fish salinity and osmotic regulation. Besides, the transcriptomic sequencing data supplies significant resources for identification of novel genes and further studying biological questions in spotted sea bass. PMID:28253338

The interaction between sea ice and salinity-dominated ocean circulation: implications for halocline stability and rapid changes of sea ice cover

NASA Astrophysics Data System (ADS)

Jensen, Mari F.; Nilsson, Johan; Nisancioglu, Kerim H.

2016-11-01

Changes in the sea ice cover of the Nordic Seas have been proposed to play a key role for the dramatic temperature excursions associated with the Dansgaard-Oeschger events during the last glacial. In this study, we develop a simple conceptual model to examine how interactions between sea ice and oceanic heat and freshwater transports affect the stability of an upper-ocean halocline in a semi-enclosed basin. The model represents a sea ice covered and salinity stratified Nordic Seas, and consists of a sea ice component and a two-layer ocean. The sea ice thickness depends on the atmospheric energy fluxes as well as the ocean heat flux. We introduce a thickness-dependent sea ice export. Whether sea ice stabilizes or destabilizes against a freshwater perturbation is shown to depend on the representation of the diapycnal flow. In a system where the diapycnal flow increases with density differences, the sea ice acts as a positive feedback on a freshwater perturbation. If the diapycnal flow decreases with density differences, the sea ice acts as a negative feedback. However, both representations lead to a circulation that breaks down when the freshwater input at the surface is small. As a consequence, we get rapid changes in sea ice. In addition to low freshwater forcing, increasing deep-ocean temperatures promote instability and the disappearance of sea ice. Generally, the unstable state is reached before the vertical density difference disappears, and the temperature of the deep ocean do not need to increase as much as previously thought to provoke abrupt changes in sea ice.

The French contribution to the voluntary observing ships network of sea surface salinity

NASA Astrophysics Data System (ADS)

Alory, G.; Delcroix, T.; Téchiné, P.; Diverrès, D.; Varillon, D.; Cravatte, S.; Gouriou, Y.; Grelet, J.; Jacquin, S.; Kestenare, E.; Maes, C.; Morrow, R.; Perrier, J.; Reverdin, G.; Roubaud, F.

2015-11-01

Sea Surface Salinity (SSS) is an essential climate variable that requires long term in situ observation. The French SSS Observation Service (SSS-OS) manages a network of Voluntary Observing Ships equipped with thermosalinographs (TSG). The network is global though more concentrated in the tropical Pacific and North Atlantic oceanic basins. The acquisition system is autonomous with real time transmission and is regularly serviced at harbor calls. There are distinct real time and delayed time processing chains. Real time processing includes automatic alerts to detect potential instrument problems, in case raw data are outside of climatic limits, and graphical monitoring tools. Delayed time processing relies on a dedicated software for attribution of data quality flags by visual inspection, and correction of TSG time series by comparison with daily water samples and collocated Argo data. A method for optimizing the automatic attribution of quality flags in real time, based on testing different thresholds for data deviation from climatology and retroactively comparing the resulting flags to delayed time flags, is presented. The SSS-OS real time data feed the Coriolis operational oceanography database, while the research-quality delayed time data can be extracted for selected time and geographical ranges through a graphical web interface. Delayed time data have been also combined with other SSS data sources to produce gridded files for the Pacific and Atlantic oceans. A short review of the research activities conducted with such data is given. It includes observation-based process-oriented and climate studies from regional to global scale as well as studies where in situ SSS is used for calibration/validation of models, coral proxies or satellite data.

The French Contribution to the Voluntary Observing Ships Network of Sea Surface Salinity

NASA Astrophysics Data System (ADS)

Delcroix, T. C.; Alory, G.; Téchiné, P.; Diverrès, D.; Varillon, D.; Cravatte, S. E.; Gouriou, Y.; Grelet, J.; Jacquin, S.; Kestenare, E.; Maes, C.; Morrow, R.; Perrier, J.; Reverdin, G. P.; Roubaud, F.

2016-02-01

Sea Surface Salinity (SSS) is an essential climate variable that requires long term in situ observation. The French SSS Observation Service (SSS-OS) manages a network of Voluntary Observing Ships equipped with thermosalinographs (TSG). The network is global though more concentrated in the tropical Pacific and North Atlantic oceanic basins. The acquisition system is autonomous with real time transmission and is regularly serviced at harbor calls. There are distinct real time and delayed time processing chains. Real time processing includes automatic alerts to detect potential instrument problems, in case raw data are outside of climatic limits, and graphical monitoring tools. Delayed time processing relies on a dedicated software for attribution of data quality flags by visual inspection, and correction of TSG time series by comparison with daily water samples and collocated Argo data. A method for optimizing the automatic attribution of quality flags in real time, based on testing different thresholds for data deviation from climatology and retroactively comparing the resulting flags to delayed time flags, is presented. The SSS-OS real time data feed the Coriolis operational oceanography database, while the research-quality delayed time data can be extracted for selected time and geographical ranges through a graphical web interface. Delayed time data have been also combined with other SSS data sources to produce gridded files for the Pacific and Atlantic oceans. A short review of the research activities conducted with such data is given. It includes observation-based process-oriented and climate studies from regional to global scale as well as studies where in situ SSS is used for calibration/validation of models, coral proxies or satellite data.

Laser measure of sea salinity, temperature and turbidity in depth

NASA Technical Reports Server (NTRS)

Hirschberg, J. G.; Wouters, A. W.; Byrne, J. D.

1974-01-01

A method is described in which a pulsed laser is used to probe the sea. Backscattered light is analyzed in time, intensity and wavelength. Tyndall, Raman and Brillouin scattering are used to obtain the backscatter turbidity, sound velocity, salinity, and the temperature as a function of depth.

Detecting the influence of ocean process on the moisture supply for India summer monsoon from Satellite Sea Surface Salinity

NASA Astrophysics Data System (ADS)

Tang, W.; Yueh, S. H.; Liu, W. T.; Fore, A.; Hayashi, A.

2016-02-01

A strong contrast in the onset of Indian summer monsoon was observed by independent satellites: average rain rate over India subcontinent (IS) in June was more than doubled in 2013 than 2012 (TRMM); also observed are larger area of wet soil (Aquarius) and high water storage (GRACE). The difference in IS rainfall was contributed to the moisture inputs through west coast of India, estimated from ocean wind (OSCAT2) and water vapor (TMI). This is an interesting testbed for studying the role of ocean on terrestrial water cycle, in particular the Indian monsoon, which has tremendous social-economical impact. What is the source of extra moisture in 2013 or deficit in 2012 for the monsoon onset? Is it possible to quantify the contribution of ocean process that maybe responsible for redistributing the freshwater in favor of the summer monsoon moisture supply? This study aims to identify the influence of ocean processes on the freshwater exchange between air-sea interfaces, using Aquarius sea surface salinity (SSS). We found two areas in Indian Ocean with high correlation between IS rain rate and Aquarius SSS: one area is in the Arabian Sea adjacent to IS, another area is a horizontal patch from 60°E to 100°E centered around 10°S. On the other hand, E-P (OAflux, TRMM) shows no similar correlation patterns with IS rain. Based on the governing equation of the salt budget in the upper ocean, we define the freshwater flux, F, from the oceanic branch of the water cycle, including contributions from salinity tendency, advection, and subsurface process. The tendency and advection terms are estimated using Aquarius SSS and OSCAR ocean current. We will present results of analyzing the spatial and temporal variability of F and evidence of and hypothesis on how the oceanic processes may enhance the moisture supply for summer Indian monsoon onset in 2013 comparing with 2012. The NASA Soil Moisture Active Passive (SMAP) has been producing the global soil moisture (SM) every 2-3 days

Salinity Trends within the Upper Layers of the Subpolar North Atlantic

NASA Astrophysics Data System (ADS)

Tesdal, J. E.; Abernathey, R.; Goes, J. I.; Gordon, A. L.; Haine, T. W. N.

2017-12-01

Examination of a range of salinity products collectively suggest widespread freshening of the North Atlantic from the mid-2000 to the present. Monthly salinity fields reveal negative trends that differ in magnitude and significance between western and eastern regions of the North Atlantic. These differences can be attributed to the large negative interannual excursions in salinity in the western subpolar gyre and the Labrador Sea, which are not apparent in the central or eastern subpolar gyre. This study demonstrates that temporal trends in salinity in the northwest (including the Labrador Sea) are subject to mechanisms that are distinct from those responsible for the salinity trends in central and eastern North Atlantic. In the western subpolar gyre a negative correlation between near surface salinity and the circulation strength of the subpolar gyre suggests that negative salinity anomalies are connected to an intensification of the subpolar gyre, which is causing increased flux of freshwater from the East Greenland Current and subsequent transport into the Labrador Sea during the melting season. Analyses of sea surface wind fields suggest that the strength of the subpolar gyre is linked to the North Atlantic Oscillation and Arctic Oscillation-driven changes in wind stress curl in the eastern subpolar gyre. If this trend of decreasing salinity continues, it has the potential to enhance water column stratification, reduce vertical fluxes of nutrients and cause a decline in biological production and carbon export in the North Atlantic Ocean.

Salinity Gradient of the Baltic Sea Limits the Reproduction and Population Expansion of the Newly Invaded Comb Jelly Mnemiopsis leidyi

PubMed Central

Jaspers, Cornelia; Møller, Lene Friis; Kiørboe, Thomas

2011-01-01

The recent invasion of the comb jelly Mnemiopsis leidyi into northern European waters is of major public and scientific concern. One of the key features making M. leidyi a successful invader is its high fecundity combined with fast growth rates. However, little is known about physiological limitations to its reproduction and consequent possible abiotic restrictions to its dispersal. To evaluate the invasion potential of M. leidyi into the brackish Baltic Sea we studied in situ egg production rates in different regions and at different salinities in the laboratory, representing the salinity gradient of the Baltic Sea. During October 2009 M. leidyi actively reproduced over large areas of the Baltic Sea. Egg production rates scaled with animal size but decreased significantly with decreasing salinity, both in the field (7–29) and in laboratory experiments (6–33). Temperature and zooplankton, i.e. food abundance, could not explain the observed differences. Reproduction rates at conditions representing the Kattegat, south western and central Baltic Sea, respectively, were 2.8 fold higher at the highest salinities (33 and 25) than at intermediate salinities (10 and 15) and 21 times higher compared from intermediate to the lowest salinity tested (6). Higher salinity areas such as the Kattegat, and to a lower extent the south western Baltic, seem to act as source regions for the M. leidyi population in the central Baltic Sea where a self-sustaining population, due to the low salinity, cannot be maintained. PMID:21887373

Warming and Inhibition of Salinization at the Ocean's Surface by Cyanobacteria

NASA Astrophysics Data System (ADS)

Wurl, O.; Bird, K.; Cunliffe, M.; Landing, W. M.; Miller, U.; Mustaffa, N. I. H.; Ribas-Ribas, M.; Witte, C.; Zappa, C. J.

2018-05-01

This paper describes high-resolution in situ observations of temperature and, for the first time, of salinity in the uppermost skin layer of the ocean, including the influence of large surface blooms of cyanobacteria on those skin properties. In the presence of the blooms, large anomalies of skin temperature and salinity of 0.95°C and -0.49 practical salinity unit were found, but a substantially cooler (-0.22°C) and saltier skin layer (0.19 practical salinity unit) was found in the absence of surface blooms. The results suggest that biologically controlled warming and inhibition of salinization of the ocean's surface occur. Less saline skin layers form during precipitation, but our observations also show that surface blooms of Trichodesmium sp. inhibit evaporation decreasing the salinity at the ocean's surface. This study has important implications in the assessment of precipitation over the ocean using remotely sensed salinity, but also for a better understanding of heat exchange and the hydrologic cycle on a regional scale.

Sea surface cooling in the Northern South China Sea observed using Chinese sea-wing underwater glider measurements

NASA Astrophysics Data System (ADS)

Qiu, Chunhua; Mao, Huabin; Yu, Jiancheng; Xie, Qiang; Wu, Jiaxue; Lian, Shumin; Liu, Qinyan

2015-11-01

Based on 26 days of Chinese Sea-wing underwater glider measurements and satellite microwave data, we documented cooling of the upper mixed layer of the ocean in response to changes in the wind in the Northern South China Sea (NSCS) from September 19, 2014, to October 15, 2014. The Sea-wing underwater glider measured 177 profiles of temperature, salinity, and pressure within a 55 km×55 km area, and reached a depth of 1000 m at a temporal resolution of ∼4 h. The study area experienced two cooling events, Cooling I and Cooling II, according to their timing. During Cooling I, water temperature at 1-m depth (T1) decreased by ∼1.0 °C, and the corresponding satellite-derived surface winds increased locally by 4.2 m/s. During Cooling II, T1 decreased sharply by 1.7 °C within a period of 4 days; sea surface winds increased by 7 m/s and covered the entire NSCS. The corresponding mixed layer depth (MLD) deepened sharply from 30 m to 60 m during Cooling II, and remained steady during Cooling I. We estimated temperature tendencies using a ML model. High resolution Sea-wing underwater glider measurements provided an estimation of MLD migration, allowing us to obtain the temporal entrainment rate of cool sub-thermocline water. Quantitative analysis confirmed that the entrainment rate and latent heat flux were the two major components that regulated cooling of the ML, and that the Ekman advection and sensible heat flux were small.

Submesoscale-selective compensation of fronts in a salinity-stratified ocean.

PubMed

Spiro Jaeger, Gualtiero; Mahadevan, Amala

2018-02-01

Salinity, rather than temperature, is the leading influence on density in some regions of the world's upper oceans. In the Bay of Bengal, heavy monsoonal rains and runoff generate strong salinity gradients that define density fronts and stratification in the upper ~50 m. Ship-based observations made in winter reveal that fronts exist over a wide range of length scales, but at O(1)-km scales, horizontal salinity gradients are compensated by temperature to alleviate about half the cross-front density gradient. Using a process study ocean model, we show that scale-selective compensation occurs because of surface cooling. Submesoscale instabilities cause density fronts to slump, enhancing stratification along-front. Specifically for salinity fronts, the surface mixed layer (SML) shoals on the less saline side, correlating sea surface salinity (SSS) with SML depth at O(1)-km scales. When losing heat to the atmosphere, the shallower and less saline SML experiences a larger drop in temperature compared to the adjacent deeper SML on the salty side of the front, thus correlating sea surface temperature (SST) with SSS at the submesoscale. This compensation of submesoscale fronts can diminish their strength and thwart the forward cascade of energy to smaller scales. During winter, salinity fronts that are dynamically submesoscale experience larger temperature drops, appearing in satellite-derived SST as cold filaments. In freshwater-influenced regions, cold filaments can mark surface-trapped layers insulated from deeper nutrient-rich waters, unlike in other regions, where they indicate upwelling of nutrient-rich water and enhanced surface biological productivity.

Submesoscale-selective compensation of fronts in a salinity-stratified ocean

PubMed Central

Spiro Jaeger, Gualtiero; Mahadevan, Amala

2018-01-01

Salinity, rather than temperature, is the leading influence on density in some regions of the world’s upper oceans. In the Bay of Bengal, heavy monsoonal rains and runoff generate strong salinity gradients that define density fronts and stratification in the upper ~50 m. Ship-based observations made in winter reveal that fronts exist over a wide range of length scales, but at O(1)-km scales, horizontal salinity gradients are compensated by temperature to alleviate about half the cross-front density gradient. Using a process study ocean model, we show that scale-selective compensation occurs because of surface cooling. Submesoscale instabilities cause density fronts to slump, enhancing stratification along-front. Specifically for salinity fronts, the surface mixed layer (SML) shoals on the less saline side, correlating sea surface salinity (SSS) with SML depth at O(1)-km scales. When losing heat to the atmosphere, the shallower and less saline SML experiences a larger drop in temperature compared to the adjacent deeper SML on the salty side of the front, thus correlating sea surface temperature (SST) with SSS at the submesoscale. This compensation of submesoscale fronts can diminish their strength and thwart the forward cascade of energy to smaller scales. During winter, salinity fronts that are dynamically submesoscale experience larger temperature drops, appearing in satellite-derived SST as cold filaments. In freshwater-influenced regions, cold filaments can mark surface-trapped layers insulated from deeper nutrient-rich waters, unlike in other regions, where they indicate upwelling of nutrient-rich water and enhanced surface biological productivity. PMID:29507874

Simulated changes in salinity in the York and Chickahominy Rivers from projected sea-level rise in Chesapeake Bay

USGS Publications Warehouse

Rice, Karen C.; Bennett, Mark; Shen, Jian

2011-01-01

As a result of climate change and variability, sea level is rising throughout the world, but the rate along the east coast of the United States is higher than the global mean rate. The U.S. Geological Survey, in cooperation with the City of Newport News, Virginia, conducted a study to evaluate the effects of possible future sea-level rise on the salinity front in two tributaries to Chesapeake Bay, the York River, and the Chickahominy/James River estuaries. Numerical modeling was used to represent sea-level rise and the resulting hydrologic effects. Estuarine models for the two tributaries were developed and model simulations were made by use of the Three-Dimensional Hydrodynamic-Eutrophication Model (HEM-3D), developed by the Virginia Institute of Marine Science. HEM-3D was used to simulate tides, tidal currents, and salinity for Chesapeake Bay, the York River and the Chickahominy/James River. The three sea-level rise scenarios that were evaluated showed an increase of 30, 50, and 100 centimeters (cm). Model results for both estuaries indicated that high freshwater river flow was effective in pushing the salinity back toward Chesapeake Bay. Model results indicated that increases in mean salinity will greatly alter the existing water-quality gradients between brackish water and freshwater. This will be particularly important for the freshwater part of the Chickahominy River, where a drinking-water-supply intake for the City of Newport News is located. Significant changes in the salinity gradients for the York River and Chickahominy/James River estuaries were predicted for the three sea-level rise scenarios. When a 50-cm sea-level rise scenario on the York River during a typical year (2005) was used, the model simulation showed a salinity of 15 parts per thousand (ppt) at river kilometer (km) 39. During a dry year (2002), the same salinity (15 ppt) was simulated at river km 45, which means that saltwater was shown to migrate 6 km farther upstream during a dry year

Tropical North Atlantic Coral-Based Sea Surface Temperature and Salinity Reconstructions From the Little Ice Age and Early Holocene

NASA Astrophysics Data System (ADS)

Saenger, C.; Cohen, A.; Oppo, D.; Hubbard, D.

2006-12-01

Understanding the magnitude and spatial extent of tropical sea surface temperature (SST) cooling during the Little Ice Age (~1400-1850 A.D.; LIA) is important for elucidating low-latitude paleoclimate, but present estimates are poorly constrained. We used Sr/Ca and δ18O variability within the aragonitic skeleton of the coral genus Montastrea to reconstruct SST and sea surface salinity (SSS) during the LIA and early Holocene (EH) in the tropical Atlantic. Four seasonally-resolved coral Sr/Ca records from St. Croix, U.S. Virgin Islands, and Bermuda indicate SST is highly correlated (r2 = 0.94) with modern Montastrea Sr/Ca and mean annual coral extension. A Sr/Ca -SST calibration that combines temperature and growth rate effects on coral Sr/Ca was applied to fossil St. Croix corals to reconstruct Caribbean climate during 5-10 year intervals of the LIA (440 ± 30 yBP) and EH (7200 ± 30; EH). Contrary to previous coral-based LIA proxy reconstructions, we find mean SST during the LIA was similar to today, but approximately 1.2°C cooler during the EH. Both periods exhibited higher amplitude seasonal variability indicating other SST estimates may be seasonally biased. Based on residual coral δ18O, we find the LIA and EH were saltier, which suggests previous cooling estimates of 1-3°C relative to today may be exaggerated by changes in seawater δ18O. Our results are consistent with a southerly migration of the Intertropical Convergence Zone (ITCZ) during the LIA, but their corroboration requires longer, high-resolution proxy reconstructions that place our two brief multi-annual coral records from the LIA and EH, respectively, within the context of multi-decadal variability.

[Distribution of dimethylsulfoxide (DMSO) in the surface water of the Yellow Sea and the Bohai Sea].

PubMed

Wang, Min; Zhang, Hong-Hai; Yang, Gui-Peng

2013-01-01

The horizontal distributions and diurnal variations of particulate and dissolved dimethylsulfoxide (DMSOp, DMSOd) were studied in the surface water of the Yellow Sea and the Bohai Sea in June, 2011. The determination of DMSO was based on the DMS produced by NaBH4 reduction, which was analyzed using the purge-and-trap technique coupled with gas chromatographic separation and flame photometric detection. The concentrations of DMSOp and DMSOd ranged from 5.43 to 18.35 nmol x L(-1) and from 4.75 to 43.80 nmol x L(-1), respectively, with average values of (11.47 +/- 0.25) nmol x L(-1) and (13.42 +/- 0.58) nmol x L(-1). The results showed that no relationship was found between DMSOp and environmental factors such as chlorophyll a (Chl-a), temperature and salinity, whereas a positive correlation was observed between DMSOp/Chl-a and salinity, indicating that intracellular DMSO could act as a cryo-osmoregulator. A significant relationship was also found between DMSOd and dimethylsulfide (DMS), whereas there was no relationship between DMSOd and DMSOp or DMSOd and bacteria, implying that DMSOd in the surface water was produced mainly through the photochemical oxidation of DMS. In addition, both the DMSOp and DMSOd concentrations exhibited obvious diurnal variations with the higher values in the day time.

Simulating the role of surface forcing on observed multidecadal upper-ocean salinity changes

DOE PAGES

Lago, Veronique; Wijffels, Susan E.; Durack, Paul J.; ...

2016-07-18

The ocean’s surface salinity field has changed over the observed record, driven by an intensification of the water cycle in response to global warming. However, the origin and causes of the coincident subsurface salinity changes are not fully understood. The relationship between imposed surface salinity and temperature changes and their corresponding subsurface changes is investigated using idealized ocean model experiments. The ocean’s surface has warmed by about 0.5°C (50 yr) –1 while the surface salinity pattern has amplified by about 8% per 50 years. The idealized experiments are constructed for a 50-yr period, allowing a qualitative comparison to the observedmore » salinity and temperature changes previously reported. The comparison suggests that changes in both modeled surface salinity and temperature are required to replicate the three-dimensional pattern of observed salinity change. The results also show that the effects of surface changes in temperature and salinity act linearly on the changes in subsurface salinity. In addition, surface salinity pattern amplification appears to be the leading driver of subsurface salinity change on depth surfaces; however, surface warming is also required to replicate the observed patterns of change on density surfaces. This is the result of isopycnal migration modified by the ocean surface warming, which produces significant salinity changes on density surfaces.« less

Simulating the role of surface forcing on observed multidecadal upper-ocean salinity changes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lago, Veronique; Wijffels, Susan E.; Durack, Paul J.

The ocean’s surface salinity field has changed over the observed record, driven by an intensification of the water cycle in response to global warming. However, the origin and causes of the coincident subsurface salinity changes are not fully understood. The relationship between imposed surface salinity and temperature changes and their corresponding subsurface changes is investigated using idealized ocean model experiments. The ocean’s surface has warmed by about 0.5°C (50 yr) –1 while the surface salinity pattern has amplified by about 8% per 50 years. The idealized experiments are constructed for a 50-yr period, allowing a qualitative comparison to the observedmore » salinity and temperature changes previously reported. The comparison suggests that changes in both modeled surface salinity and temperature are required to replicate the three-dimensional pattern of observed salinity change. The results also show that the effects of surface changes in temperature and salinity act linearly on the changes in subsurface salinity. In addition, surface salinity pattern amplification appears to be the leading driver of subsurface salinity change on depth surfaces; however, surface warming is also required to replicate the observed patterns of change on density surfaces. This is the result of isopycnal migration modified by the ocean surface warming, which produces significant salinity changes on density surfaces.« less

Validation of Aquarius sea surface salinity with in situ measurements from Argo floats and moored buoys

NASA Astrophysics Data System (ADS)

Tang, Wenqing; Yueh, Simon H.; Fore, Alexander G.; Hayashi, Akiko

2014-09-01

We validate sea surface salinity (SSS) retrieved from Aquarius instrument on SAC-D satellite with in situ measurements by Argo floats and moored buoy arrays. We assess the error structure of three Aquarius SSS products: the standard product processed by Aquarius Data Processing System (ADPS) and two data sets produced at the Jet Propulsion Laboratory (JPL): the Combined Active-Passive algorithm with and without rain correction, CAP and CAP_RC, respectively. We examine the effect of various filters to prevent unreliable point retrievals from entering Level 3 averaging, such as land or ice contamination, radio frequency interference (RFI), and cold water. Our analyses show that Aquarius SSS agrees well with Argo in a monthly average sense between 40°S and 40°N except in the Eastern Pacific Fresh Pool and Amazon River outflow. Buoy data within these regions show excellent agreement with Aquarius but have discrepancies with the Argo gridded products. Possible reasons include strong near-surface stratification and sampling problems in Argo in regions with significant western boundary currents. We observe large root-mean-square (RMS) difference and systematic negative bias between ADPS and Argo in the tropical Indian Ocean and along the Southern Pacific Convergence Zone. Excluding these regions removes the suspicious seasonal peak in the monthly RMS difference between the Aquarius SSS products and Argo. Between 40°S and 40°N, the RMS difference for CAP is less than 0.22 PSU for all 28 months, CAP_RC has essentially met the monthly 0.2 PSU accuracy requirement, while that for ADPS fluctuates between 0.22 and 0.3 PSU.

22-year surface salinity changes in the Seasonal Ice Zone near 140°E off Antarctica

NASA Astrophysics Data System (ADS)

Morrow, Rosemary; Kestenare, Elodie

2017-11-01

Seasonal and interannual variations in sea surface salinity (SSS) are analyzed in the Sea Ice Zone south of 60°S, from a 22-year time series of observations near 140°E. In the northern sea-ice zone during the warming, melting cycle from October to March, waters warm by an average of 3.5 °C and become fresher by 0.1 to 0.25. In the southern sea-ice zone, the surface temperatures vary from - 1 to 1 °C over summer, and the maximal SSS range occurs in December, with a minimum SSS of 33.65 near the Southern Boundary of the ACC, reaching 34.4 in the shelf waters close to the coast. The main fronts, normally defined at subsurface, are shown to have more distinct seasonal characteristics in SSS than in SST. The interannual variations in SSS are more closely linked to variations in upstream sea-ice cover than surface forcing. SSS and sea-ice variations show distinct phases, with large biannual variations in the early 1990s, weaker variations in the 2000s and larger variations again from 2009 onwards. The calving of the Mertz Glacier Tongue in February 2010 leads to increased sea-ice cover and widespread freshening of the surface layers from 2011 onwards. Summer freshening in the northern sea-ice zone is 0.05-0.07 per decade, increasing to 0.08 per decade in the southern sea-ice zone, largely influenced by the Mertz Glacier calving event at the end of our time series. The summer time series of SSS on the shelf at 140°E is in phase but less variable than the SSS observed upstream in the Adélie Depression, and thus represents a spatially integrated index of the wider SSS variations.

Bacterial Communities of Surface Mixed Layer in the Pacific Sector of the Western Arctic Ocean during Sea-Ice Melting

PubMed Central

Ha, Ho Kyung; Kim, Hyun Cheol; Kim, Ok-Sun; Lee, Bang Yong; Cho, Jang-Cheon; Hur, Hor-Gil; Lee, Yoo Kyung

2014-01-01

From July to August 2010, the IBRV ARAON journeyed to the Pacific sector of the Arctic Ocean to monitor bacterial variation in Arctic summer surface-waters, and temperature, salinity, fluorescence, and nutrient concentrations were determined during the ice-melting season. Among the measured physicochemical parameters, we observed a strong negative correlation between temperature and salinity, and consequently hypothesized that the melting ice decreased water salinity. The bacterial community compositions of 15 samples, includicng seawater, sea-ice, and melting pond water, were determined using a pyrosequencing approach and were categorized into three habitats: (1) surface seawater, (2) ice core, and (3) melting pond. Analysis of these samples indicated the presence of local bacterial communities; a deduction that was further corroborated by the discovery of seawater- and ice-specific bacterial phylotypes. In all samples, the Alphaproteobacteria, Flavobacteria, and Gammaproteobacteria taxa composed the majority of the bacterial communities. Among these, Alphaproteobacteria was the most abundant and present in all samples, and its variation differed among the habitats studied. Linear regression analysis suggested that changes in salinity could affect the relative proportion of Alphaproteobacteria in the surface water. In addition, the species-sorting model was applied to evaluate the population dynamics and environmental heterogeneity in the bacterial communities of surface mixed layer in the Arctic Ocean during sea-ice melting. PMID:24497990

Bacterial communities of surface mixed layer in the Pacific sector of the western Arctic Ocean during sea-ice melting.

PubMed

Han, Dukki; Kang, Ilnam; Ha, Ho Kyung; Kim, Hyun Cheol; Kim, Ok-Sun; Lee, Bang Yong; Cho, Jang-Cheon; Hur, Hor-Gil; Lee, Yoo Kyung

2014-01-01

From July to August 2010, the IBRV ARAON journeyed to the Pacific sector of the Arctic Ocean to monitor bacterial variation in Arctic summer surface-waters, and temperature, salinity, fluorescence, and nutrient concentrations were determined during the ice-melting season. Among the measured physicochemical parameters, we observed a strong negative correlation between temperature and salinity, and consequently hypothesized that the melting ice decreased water salinity. The bacterial community compositions of 15 samples, includicng seawater, sea-ice, and melting pond water, were determined using a pyrosequencing approach and were categorized into three habitats: (1) surface seawater, (2) ice core, and (3) melting pond. Analysis of these samples indicated the presence of local bacterial communities; a deduction that was further corroborated by the discovery of seawater- and ice-specific bacterial phylotypes. In all samples, the Alphaproteobacteria, Flavobacteria, and Gammaproteobacteria taxa composed the majority of the bacterial communities. Among these, Alphaproteobacteria was the most abundant and present in all samples, and its variation differed among the habitats studied. Linear regression analysis suggested that changes in salinity could affect the relative proportion of Alphaproteobacteria in the surface water. In addition, the species-sorting model was applied to evaluate the population dynamics and environmental heterogeneity in the bacterial communities of surface mixed layer in the Arctic Ocean during sea-ice melting.

Impact of surface roughness on L-band emissivity of the sea ice

NASA Astrophysics Data System (ADS)

Miernecki, M.; Kaleschke, L.; Hendricks, S.; Søbjærg, S. S.

2015-12-01

In March 2014 a joint experiment IRO2/SMOSice was carried out in the Barents Sea. R/V Lance equipped with meteorological instruments, electromagnetic sea ice thickness probe and engine monitoring instruments, was performing a series of tests in different ice conditions in order to validate the ice route optimization (IRO) system, advising on his route through pack ice. In parallel cal/val activities for sea ice thickness product obtained from SMOS (Soil Moisture and Ocean Salinity mission) L-band radiometer were carried out. Apart from helicopter towing the EMbird thickness probe, Polar 5 aircraft was serving the area during the experiment with L-band radiometer EMIRAD2 and Airborne Laser Scanner (ALS) as primary instruments. Sea ice Thickness algorithm using SMOS brightness temperature developed at University of Hamburg, provides daily maps of thin sea ice (up to 0.5-1 m) in polar regions with resolution of 35-50 km. So far the retrieval method was not taking into account surface roughness, assuming that sea ice is a specular surface. Roughness is a stochastic process that can be characterized by standard deviation of surface height σ and by shape of the autocorrelation function R to estimate it's vertical and horizontal scales respectively. Interactions of electromagnetic radiation with the surface of the medium are dependent on R and σ and they scales with respect to the incident wavelength. During SMOSice the radiometer was observing sea ice surface at two incidence angles 0 and 40 degrees and simultaneously the surface elevation was scanned with ALS with ground resolution of ~ 0.25 m. This configuration allowed us to calculate σ and R from power spectral densities of surface elevation profiles and quantify the effect of surface roughness on the emissivity of the sea ice. First results indicate that Gaussian autocorrelation function is suitable for deformed ice, for other ice types exponential function is the best fit.

Soil Porewater Salinity Response to Sea-level Rise in Tidal Freshwater Forested Wetlands: A Modeling Study

NASA Astrophysics Data System (ADS)

Stagg, C. L.; Wang, H.; Krauss, K.; Conrads, P. A.; Swarzenski, C.; Duberstein, J. A.; DeAngelis, D.

2017-12-01

There is a growing concern about the adverse effects of salt water intrusion via tidal rivers and creeks into tidal freshwater forested wetlands (TFFWs) due to rising sea levels and reduction of freshwater flow. The distribution and composition of plant species, vegetation productivity, and biogeochemical functions including carbon sequestration capacity and flux rates in TFFWs have been found to be affected by increasing river and soil porewater salinities, with significant shifts occurring at a porewater salinity threshold of 3 PSU. However, the drivers of soil porewater salinity, which impact the health and ecological functions of TFFWs remains unclear, limiting our capability of predicting the future impacts of saltwater intrusion on ecosystem services provided by TFFWs. In this study, we developed a soil porewater salinity model for TFFWs based on an existing salt and water balance model with modifications to several key features such as the feedback mechanisms of soil salinity on evapotranspiration reduction and hydraulic conductivity. We selected sites along the floodplains of two rivers, the Waccamaw River (SC, USA) and the Savannah River (GA and SC, USA) that represent landscape salinity gradients of both surface water and soil porewater from tidal influence of the Atlantic Ocean. These sites represent healthy, moderately and highly salt-impacted forests, and oligohaline marshes. The soil porewater salinity model was calibrated and validated using field data collected at these sites throughout 2008-2016. The model results agreed well with field measurements. Analyses of the preliminary simulation results indicate that the magnitude, seasonal and annual variability, and duration of threshold salinities (e.g., 3 PSU) tend to vary significantly with vegetation status and type (i.e., healthy, degraded forests, and oligohaline marshes), especially during drought conditions. The soil porewater salinity model could be coupled with a wetland soil biogeochemistry

An overview of new insights from satellite salinity missions on oceanography

NASA Astrophysics Data System (ADS)

Reul, Nicolas

2015-04-01

The Soil Moisture and Ocean Salinity (SMOS) mission, launched on 2 November 2009, is the European Space Agency's (ESA) second Earth Explorer Opportunity mission. The scientific objectives of the SMOS mission directly respond to the need for global observations of soil moisture and ocean salinity, two key variables describing the Earth's water cycle and having been identified as Essential Climate Variables (ECVs) by the Global Climate Observing System (GCOS). After five years of satellite Sea Surface Salinity (SSS) monitoring from SMOS data, we will present an overview of the scientific highlights these data have brougtht to the oceanographic communities. In particular, we shall review the impact of SMOS SSS and brightness tempeaerture data for the monitoring of: -Mesoscale variability of SSS (and density) in frontal structures, eddies, -Ocean propagative SSS signals (e.g. TIW, planetary waves), -Freshwater flux Monitoring (Evaportaion minus precipitation, river run off), -Large scale SSS anomalies related to climate fluctuations (e.g. ENSO, IOD), -Air-Sea interactions (equatorial upwellings, Tropical cyclone wakes) -Temperature-Salinity dependencies, -Sea Ice thickness, -Tropical Storm and high wind monitoring, -Ocean surface bio-geo chemistry.

Ionoregulatory changes during metamorphosis and salinity exposure of juvenile sea lamprey (Petromyzon marinus L.)

USGS Publications Warehouse

Reis-Santos, P.; McCormick, S.D.; Wilson, J.M.

2008-01-01

Ammocoetes of the anadromous sea lamprey Petromyzon marinus L. spend many years in freshwater before metamorphosing and migrating to sea. Metamorphosis involves the radical transformation from a substrate-dwelling, filter feeder into a free-swimming, parasitic feeder. In the present work we examined osmoregulatory differences between ammocoetes and transformers (metamorphic juveniles), and the effects of salinity acclimation. We measured the expression of key ion-transporting proteins [Na+/K+-ATPase, vacuolar (V)-type H+-ATPase and carbonic anhydrase (CA)] as well as a number of relevant blood parameters (hematocrit, [Na+] and [Cl -]). In addition, immunofluorescence microscopy was used to identify and characterize the distributions of Na+/K+-ATPase, V-type H+-ATPase and CA immunoreactive cells in the gill. Ammocoetes did not survive in the experiments with salinities greater than 10???, whereas survival in high salinity (???25-35???) increased with increased degree of metamorphosis in transformers. Plasma [Na+] and [Cl -] of ammocoetes in freshwater was lower than transformers and increased markedly at 10???. In transformers, plasma ions increased only at high salinity (>25???). Branchial Na+/K+-ATPase levels were ??? tenfold higher in transformers compared to ammocoetes and salinity did not affect expression in either group. However, branchial H +-ATPase expression showed a negative correlation with salinity in both groups. Na+/K+-ATPase immunoreactivity was strongest in transformers and associated with clusters of cells in the interlamellar spaces. H+-ATPase (B subunit) immunoreactivity was localized to epithelial cells not expressing high Na+/K+-ATPase immunoreactivity and having a similar tissue distribution as carbonic anhydrase. The results indicate that branchial Na+/K+-ATPase and salinity tolerance increase in metamorphosing lampreys, and that branchial H+-ATPase is downregulated by salinity.

The salinity effect in a mixed layer ocean model

NASA Technical Reports Server (NTRS)

Miller, J. R.

1976-01-01

A model of the thermally mixed layer in the upper ocean as developed by Kraus and Turner and extended by Denman is further extended to investigate the effects of salinity. In the tropical and subtropical Atlantic Ocean rapid increases in salinity occur at the bottom of a uniformly mixed surface layer. The most significant effects produced by the inclusion of salinity are the reduction of the deepening rate and the corresponding change in the heating characteristics of the mixed layer. If the net surface heating is positive, but small, salinity effects must be included to determine whether the mixed layer temperature will increase or decrease. Precipitation over tropical oceans leads to the development of a shallow stable layer accompanied by a decrease in the temperature and salinity at the sea surface.

The Atlantic Multidecadal Variability in surface and deep ocean temperature and salinity fields from unperturbed climate simulations

NASA Astrophysics Data System (ADS)

Zanchettin, D.; Jungclaus, J. H.

2013-12-01

Large multidecadal fluctuations in basin-average sea-surface temperature (SST) are a known feature of observed, reconstructed and simulated variability in the North Atlantic Ocean. This phenomenon is often referred to as Multidecadal Atlantic Variability or AMV. Historical AMV fluctuations are associated with analog basin-scale changes in sea-surface salinity, so that warming corresponds to salinification and cooling to freshening [Polyakov et al., 2005]. The surface imprint of the AMV further corresponds to same-sign fluctuations in the shallow ocean and with opposite-sign fluctuations in the deep ocean for both temperature and salinity [Polyakov et al., 2005]. This out-of-phase behavior reflects the thermohaline overturning circulation shaping North Atlantic's low-frequency variability. Several processes contribute to the AMV, involving both ocean-atmosphere coupled processes and deep ocean circulation [e.g., Grossmann and Klotzbach, 2009]. In particular, recirculation in the North Atlantic subpolar gyre region of salinity anomalies from Arctic freshwater export may trigger multidecadal variability in the Atlantic meridional overturning circulation, and therefore may be part of the AMV [Jungclaus et al., 2005; Dima and Lohmann, 2007]. With this contribution, we aim to improve the physical interpretation of the AMV by investigating spatial and temporal patterns of temperature and salinity fields in the shallow and deep ocean. We focus on two unperturbed millennial-scale simulations performed with the Max Planck Institute Earth system model in its paleo (MPI-ESM-P) and low-resolution (MPI-ESM-LR) configurations, which provide reference control climates for assessments of pre-industrial and historical climate simulations. The two model configurations only differ for the presence, in MPI-ESM-LR, of an active module for dynamical vegetation. We use spatial-average indices and empirical orthogonal functions/principal components to track the horizontal and vertical

Three modes of interdecadal trends in sea surface temperature and sea surface height

NASA Astrophysics Data System (ADS)

Gnanadesikan, A.; Pradal, M.

2013-12-01

It might be thought that sea surface height and sea surface temperature would be tightly related. We show that this is not necessarily the case on a global scale. We analysed this relationship in a suite of coupled climate models run under 1860 forcing conditions. The models are low-resolution variants of the GFDL Earth System Model, reported in Galbraith et al. (J. Clim. 2011). 1. Correlated changes in global sea surface height and global sea surface temperature. This mode corresponds to opening and closing of convective chimneys in the Southern Ocean. As the Southern Ocean destratifies, sea ice formation is suppressed during the winter and more heat is taken up during the summer. This mode of variability is highly correlated with changes in the top of the atmosphere radiative budget and weakly correlated with changes in the deep ocean circulation. 2. Uncorrelated changes in global sea surface height and global sea surface temperature. This mode of variability is associated with interdecadal variabliity in tropical winds. Changes in the advective flux of heat to the surface ocean play a critical role in driving these changes, which also result in significant local changes in sea level. Changes sea ice over the Southern Ocean still result in changes in solar absorption, but these are now largely cancelled by changes in outgoing longwave radiation. 3. Anticorrelated changes in global sea surface height and global sea surface temperatures. By varying the lateral diffusion coefficient in the ocean model, we are able to enhance and suppress convection in the Southern and Northern Pacific Oceans. Increasing the lateral diffusion coefficients shifts the balance sources of deep water away from the warm salty deep water of the North Atlantic and towards cold fresh deep water from the other two regions. As a result, even though the planet as a whole warms, the deep ocean cools and sea level falls, with changes of order 30 cm over 500 years. The increase in solar absorption

Climatic Influences on Southern Makassar Strait Salinity Over the Past Century

NASA Astrophysics Data System (ADS)

Murty, S. A.; Goodkin, N. F.; Halide, H.; Natawidjaja, D.; Suwargadi, B.; Suprihanto, I.; Prayudi, D.; Switzer, A. D.; Gordon, A. L.

2017-12-01

The Indonesian Throughflow (ITF) is a globally important ocean current that fuels heat and buoyancy fluxes throughout the Indo-Pacific and is known to covary in strength with the El Niño Southern Oscillation at interannual time scales. A climate system with a less well-quantified impact on the ITF is the East Asian Winter Monsoon (EAWM), which drives less saline surface waters from the South China Sea (SCS) into the Makassar Strait, obstructing surface ITF flow. We present a subannually resolved record of sea surface salinity (SSS) from 1927 to 2011 based on coral δ18O from the Makassar Strait that reveals variability in the relative contributions of different source waters to the surface waters of the Makassar Strait during the boreal winter monsoon. We find that the EAWM (January-March) strongly influences interannual SSS variability during boreal winter over the twentieth century (r = 0.54, p << 0.0001), impacting surface water circulation in the SCS and Indonesian Seas.

Modelling the salinization of a coastal lagoon-aquifer system

NASA Astrophysics Data System (ADS)

Colombani, N.; Mastrocicco, M.

2017-08-01

In this study, a coastal area constituted by alternations of saline-brackish lagoons and freshwater bodies was studied and modelled to understand the hydrological processes occurring between the lagoons, the groundwater system of the Po River Delta (Italy) and the Adriatic Sea. The contribution of both evaporation and anthropogenic factors on groundwater salinization was assessed by means of soil, groundwater and surface water monitoring. Highresolution multi-level samplers were used to capture salinity gradients within the aquifer and surface water bodies. Data were employed to calibrate a density-dependent numerical transport model implemented with SEAWAT code along a transect perpendicular to the coast line. The results show that the lagoon is hydraulically well connected with the aquifer, which provides the major source of salinity because of the upcoming of paleo-seawater from the aquitard laying at the base of the unconfined aquifer. On the contrary, the seawater (diluted by the freshwater river outflow) creates only a limited saltwater wedge. The increase in groundwater salinity could be of serious concern, especially for the pinewood located in the dune near the coast, sensitive to salinity increases. This case study represents an interesting paradigm for other similar environmental setting, where the assumption of classical aquifer salinization from a saltwater wedge intruding from the sea is often not representative of the actual aquifer’s salinization mechanisms.

Solar forcing of Florida Straits surface salinity during the early Holocene

NASA Astrophysics Data System (ADS)

Schmidt, Matthew W.; Weinlein, William A.; Marcantonio, Franco; Lynch-Stieglitz, Jean

2012-09-01

Previous studies showed that sea surface salinity (SSS) in the Florida Straits as well as Florida Current transport covaried with changes in North Atlantic climate over the past two millennia. However, little is known about earlier Holocene hydrographic variability in the Florida Straits. Here, we combine Mg/Ca-paleothermometry and stable oxygen isotope measurements on the planktonic foraminifera Globigerinoides ruber (white variety) from Florida Straits sediment core KNR166-2 JPC 51 (24° 24.70' N, 83° 13.14' W, 198 m deep) to reconstruct a high-resolution (˜25 yr/sample) early to mid Holocene record of sea surface temperature and δ18OSW (a proxy for SSS) variability. After removing the influence of global δ18OSW change due to continental ice volume variability, we find that early Holocene SSS enrichments are associated with increased evaporation/precipitation ratios in the Florida Straits during periods of reduced solar forcing, increased ice rafted debris in the North Atlantic and the development of more permanent El Niño-like conditions in the eastern equatorial Pacific. When considered with previous high-resolution reconstructions of Holocene tropical atmospheric circulation changes, our results provide evidence that variations in solar forcing over the early Holocene had a significant impact on the global tropical hydrologic cycle.

An Investigation of the Radiative Effects and Climate Feedbacks of Sea Ice Sources of Sea Salt Aerosol

NASA Astrophysics Data System (ADS)

Horowitz, H. M.; Alexander, B.; Bitz, C. M.; Jaegle, L.; Burrows, S. M.

2017-12-01

In polar regions, sea ice is a major source of sea salt aerosol through lofting of saline frost flowers or blowing saline snow from the sea ice surface. Under continued climate warming, an ice-free Arctic in summer with only first-year, more saline sea ice in winter is likely. Previous work has focused on climate impacts in summer from increasing open ocean sea salt aerosol emissions following complete sea ice loss in the Arctic, with conflicting results suggesting no net radiative effect or a negative climate feedback resulting from a strong first aerosol indirect effect. However, the radiative forcing from changes to the sea ice sources of sea salt aerosol in a future, warmer climate has not previously been explored. Understanding how sea ice loss affects the Arctic climate system requires investigating both open-ocean and sea ice sources of sea-salt aerosol and their potential interactions. Here, we implement a blowing snow source of sea salt aerosol into the Community Earth System Model (CESM) dynamically coupled to the latest version of the Los Alamos sea ice model (CICE5). Snow salinity is a key parameter affecting blowing snow sea salt emissions and previous work has assumed constant regional snow salinity over sea ice. We develop a parameterization for dynamic snow salinity in the sea ice model and examine how its spatial and temporal variability impacts the production of sea salt from blowing snow. We evaluate and constrain the snow salinity parameterization using available observations. Present-day coupled CESM-CICE5 simulations of sea salt aerosol concentrations including sea ice sources are evaluated against in situ and satellite (CALIOP) observations in polar regions. We then quantify the present-day radiative forcing from the addition of blowing snow sea salt aerosol with respect to aerosol-radiation and aerosol-cloud interactions. The relative contributions of sea ice vs. open ocean sources of sea salt aerosol to radiative forcing in polar regions is

Organic carbon source and salinity shape sediment bacterial composition in two China marginal seas and their major tributaries.

PubMed

Wang, Kai; Zou, Li; Lu, Xinxin; Mou, Xiaozhen

2018-08-15

Marginal sea sediments receive organic substrates of different origins, but whether and to what extent sediment microbial communities are reflective of the different sources of organic substrates remain unclear. To address these questions, sediment samples were collected in two connected China marginal seas, i.e., Bohai Sea and Yellow Sea, and their two major tributaries (Yellow River and Liao River). Sediment bacterial community composition (BCC) was examined using 16S rRNA gene pyrosequencing. In addition, physicochemical variables that describe environmental conditions and sediment features were measured. Our results revealed that BCCs changed with salinity and organic carbon (OC) content. Members of Gaiellaceae and Comamonadaceae showed a rapid decrease as salinity and phytoplankton-derived OC increased, while Piscirickettsiaceae and Desulfobulbaceae exhibited an opposite distribution pattern. Differences of riverine vs. marginal sea sediment BCCs could be mostly explained by salinity. However, within the marginal seas, sediment BCC variations were mainly explained by OC-related variables, including terrestrial-derived fatty acids (Terr_FA), phytoplankton-derived polyunsaturated fatty acids (Phyto_PUFA), stable carbon isotopes (δ 13 C), and carbon to nitrogen ratio (C/N). In addition to environmental variables, network analysis suggested that interactions among individual bacterial taxa might be important in shaping sediment BCCs in the studied areas. Copyright © 2018 Elsevier B.V. All rights reserved.

Assessing the Contribution of Sea Surface Temperature and Salinity to Coral δ18O using a Weighted Forward Model

NASA Astrophysics Data System (ADS)

Horlick, K. A.; Thompson, D. M.; Anderson, D. M.

2015-12-01

The isotopic ratio of 16O/18O (δ18O) in coral carbonate skeletons is a robust, high-resolution proxy for sea surface temperature (SST) and sea surface salinity (SSS) variability predating the instrumental record. Although SST and δ18O-water (correlated to SSS) variability both contribute to the δ18O signal in the coral carbonate archive, the paucity and limited temporal span of SST and SSS instrumental observations limit the ability to differentiate respective SST and SSS contribution to each δ18O record. From instrumental datasets such as HadISST v.3, ERSST, SODA, and Delcroix (2011), we forward model the δ18O ("pseudoproxy") signal using the linear bivariate forward model from Thompson 2011 ("pseudoproxy"= a1(SST)+a2(SSS)). By iteratively weighting (between 0 and 1 by 0.005) the relative contribution of SST and SSS terms to the δ18O "pseudoproxy" following Gorman et al. 2012 method, we derive the percent contributions of SST and SSS to δ18O at each site based on the weights that produce the optimal correlation to the observed coral δ18O signal. A Monte Carlo analysis of error propagation in the weighted and unweighted pseudoproxy time series was used to determine how well the weighted and unweighted forward models captured observed δ18O variance. Across the south-western Pacific (40 sites) we found that SST contributes from less than 8 to more than 78% of the variance. This work builds upon this simple forward model of coral δ18O and improves our understanding of potential sources of differences in the observed and forward modeled δ18O variability. These results may also improve SST and SSS reconstructions from corals by highlighting the reef areas whose coral δ18O signal is most heavily influenced by SST and SSS respectively. Using an inverse approach, creating a transfer function, local SST and SSS could also be reconstructed based on the site-specific weights and observed coral δ18O time series.

Interannual and Decadal Changes in Salinity in the Oceanic Subtropical Gyres

NASA Astrophysics Data System (ADS)

Bulusu, Subrahmanyam

2017-04-01

There is evidence that the global water cycle has been undergoing an intensification over several decades as a response to increasing atmospheric temperatures, particularly in regions with skewed evaporation - precipitation (E-P) patterns such as the oceanic subtropical gyres. Moreover, observational data (rain gauges, etc.) are quite sparse over such areas due to the inaccessibility of open ocean regions. In this work, a comparison of observational and model simulations are conducted to highlight the potential applications of satellite derived salinity from NASA Aquarius Salinity mission, NASA Soil Moisture and Ocean Salinity (SMOS), and ESA's Soil Moisture Active Passive (SMAP). We explored spatial and temporal salinity changes (and trends) in surface and subsurface in the oceanic subtropical gyres using Argo floats salinity data, Simple Ocean Data Assimilation (SODA) reanalysis, Estimating the Circulations & Climate of the Ocean GECCO (German ECCO) model simulations, and Hybrid Coordinate Ocean Model (HYCOM). Our results based on SODA reanalysis reveals that a positive rising trend in sea surface salinity in the subtropical gyres emphasizing evidence for decadal intensification in the surface forcing in these regions. Zonal drift in the location of the salinity maximum of the south Pacific, north Atlantic, and south Indian regions implies a change in the mean near-surface currents responsible for advecting high salinity waters into the region. Also we found out that an overall salinity increase within the mixed layer, and a subsurface salinity decrease at depths greater than 200m in the global subtropical gyres over 61 years. We determine that freshwater fluxes at the air-sea interface are the primary drivers of the sea surface salinity (SSS) signature over these open ocean regions by quantifying the advective contribution within the surface layer. This was demonstrated through a mixed layer salinity budget in each subtropical gyre based on the vertically

Messinian Salinity Crisis and Course of Messinian Valleys in the Southern Shelf of the Sea of Marmara

NASA Astrophysics Data System (ADS)

Çifçi, Günay; Barın, Burcu; Okay, Seda; Dondurur, Derman; Sorlien, Christopher; Suc, Jean-Pierre; Lericolais, Gilles

2015-04-01

The Messinian Salinity Crisis widely accepted as one of the most interesting events concerning the Mediterranean marine environment in the earth's geological history. Late Miocene tectonic changes in Mediterranean-Atlantic connectivity caused this huge event. The Sea of Marmara region has been improperly considered as a gateway between the Paratethys and Mediterranean since the Middle Miocene. However, it is a very important location for paleoclimatic research including the sea level change associated with the Messinian Salinity Crisis. Although considerable work has been carried out on the Messinian Salinity Crisis, very little has been reported on the status of the Marmara Sea during the Messinian. The case study includes the southern shelf and North İmrali Basin of the Marmara Sea, which is in the region located from the Çanakkale Strait (Dardanelles) to İmralı Island. The structural and stratigraphic interpretation were carried out using high resolution multi-channel seismic reflection (MCS) data which were collected with the facilities of Seismic Laboratory (SeisLab) in the Institute of Marine Sciences and Technology and R/V K. Piri Reis belonging to Dokuz Eylül University under the frame of several projects including TUBİTAK-NSF. Seismic profiles acquired in southern shelf of the Marmara Sea suggest that Messinian fluvial erosion has occurred at the base of all the main sub-basins. The southern shoreline has provided well-preserved evidence of Messinian fluvial erosion followed by the post-crisis marine reflooding. Interpretation is focused on the nature of erosion related to this acoustic basement and to a major angular unconformity that may merge with it. The basement and erosionalsurface are interpreted in the Çanakkale outletandon the southern shelf of the Sea of Marmara. A buried East-West to NW-SE channel cut into acoustic basement that may belong to the Messinian period was interpreted on the MCS data. For instance, based on interpretation of

Assessment of salinity intrusion in the James and Chickahominy Rivers as a result of simulated sea-level rise in Chesapeake Bay, East Coast, USA.

PubMed

Rice, Karen C; Hong, Bo; Shen, Jian

2012-11-30

Global sea level is rising, and the relative rate in the Chesapeake Bay region of the East Coast of the United States is greater than the worldwide rate. Sea-level rise can cause saline water to migrate upstream in estuaries and rivers, threatening freshwater habitat and drinking-water supplies. The effects of future sea-level rise on two tributaries of Chesapeake Bay, the James and Chickahominy (CHK) Rivers, were evaluated in order to quantify the salinity change with respect to the magnitude of sea-level rise. Such changes are critical to: 1) local floral and faunal habitats that have limited tolerance ranges to salinity; and 2) a drinking-water supply for the City of Newport News, Virginia. By using the three-dimensional Hydrodynamic-Eutrophication Model (HEM-3D), sea-level rise scenarios of 30, 50, and 100 cm, based on the U.S. Climate Change Science Program for the mid-Atlantic region for the 21st century, were evaluated. The model results indicate that salinity increases in the entire river as sea level rises and that the salinity increase in a dry year is greater than that in a typical year. In the James River, the salinity increase in the middle-to-upper river (from 25 to 50 km upstream of the mouth) is larger than that in the lower and upper parts of the river. The maximum mean salinity increase would be 2 and 4 ppt for a sea-level rise of 50 and 100 cm, respectively. The upstream movement of the 10 ppt isohaline is much larger than the 5 and 20 ppt isohalines. The volume of water with salinity between 10 and 20 ppt would increase greatly if sea level rises 100 cm. In the CHK River, with a sea-level rise of 100 cm, the mean salinity at the drinking-water intake 34 km upstream of the mouth would be about 3 ppt in a typical year and greater than 5 ppt in a dry year, both far in excess of the U.S. Environmental Protection Agency's secondary standard for total dissolved solids for drinking water. At the drinking-water intake, the number of days of salinity

Scenario simulations of future salinity and ecological consequences in the Baltic Sea and adjacent North Sea areas–implications for environmental monitoring

PubMed Central

Vuorinen, Ilppo; Hänninen, Jari; Rajasilta, Marjut; Laine, Päivi; Eklund, Jan; Montesino-Pouzols, Federico; Corona, Francesco; Junker, Karin; Meier, H.E.Markus; Dippner, Joachim W.

2015-01-01

Substantial ecological changes occurred in the 1970s in the Northern Baltic during a temporary period of low salinity (S). This period was preceded by an episodic increase in the rainfall over the Baltic Sea watershed area. Several climate models, both global and regional, project an increase in the runoff of the Northern latitudes due to proceeding climate change. The aim of this study is to model, firstly, the effects on Baltic Sea salinity of increased runoff due to projected global change and, secondly, the effects of salinity change on the distribution of marine species. The results suggest a critical shift in the S range 5–7, which is a threshold for both freshwater and marine species distributions and diversity. We discuss several topics emphasizing future monitoring, modelling, and fisheries research. Environmental monitoring and modelling are investigated because the developing alternative ecosystems do not necessarily show the same relations to environment quality factors as the retiring ones. An important corollary is that the observed and modelled S changes considered together with species’ ranges indicate what may appear under a future climate. Consequences could include a shift in distribution areas of marine benthic foundation species and some 40–50 other species, affiliated to these. This change would extend over hundreds of kilometres, in the Baltic Sea and the adjacent North Sea areas. Potential cascading effects, in coastal ecology, fish ecology and fisheries would be extensive, and point out the necessity to develop further the “ecosystem approach in the environmental monitoring”. PMID:25737660

Mathematical modelling of surface water-groundwater flow and salinity interactions in the coastal zone

NASA Astrophysics Data System (ADS)

Spanoudaki, Katerina; Kampanis, Nikolaos A.

2014-05-01

Coastal areas are the most densely-populated areas in the world. Consequently water demand is high, posing great pressure on fresh water resources. Climatic change and its direct impacts on meteorological variables (e.g. precipitation) and indirect impact on sea level rise, as well as anthropogenic pressures (e.g. groundwater abstraction), are strong drivers causing groundwater salinisation and subsequently affecting coastal wetlands salinity with adverse effects on the corresponding ecosystems. Coastal zones are a difficult hydrologic environment to represent with a mathematical model due to the large number of contributing hydrologic processes and variable-density flow conditions. Simulation of sea level rise and tidal effects on aquifer salinisation and accurate prediction of interactions between coastal waters, groundwater and neighbouring wetlands requires the use of integrated surface water-groundwater models. In the past few decades several computer codes have been developed to simulate coupled surface and groundwater flow. In these numerical models surface water flow is usually described by the 1-D Saint Venant equations (e.g. Swain and Wexler, 1996) or the 2D shallow water equations (e.g. Liang et al., 2007). Further simplified equations, such as the diffusion and kinematic wave approximations to the Saint Venant equations, are also employed for the description of 2D overland flow and 1D stream flow (e.g. Gunduz and Aral, 2005). However, for coastal bays, estuaries and wetlands it is often desirable to solve the 3D shallow water equations to simulate surface water flow. This is the case e.g. for wind-driven flows or density-stratified flows. Furthermore, most integrated models are based on the assumption of constant fluid density and therefore their applicability to coastal regions is questionable. Thus, most of the existing codes are not well-suited to represent surface water-groundwater interactions in coastal areas. To this end, the 3D integrated

Distribution of Glass Eel by the Water Surface Salinity Using Landsat TM at Pelabuhan Ratu Bay, West Java

NASA Astrophysics Data System (ADS)

Irianto, D. S.; Supriatna; Pin, TjiongGiok

2016-11-01

Eel (Anguilla spp.) is consumed fish that has an important economic value, either for local or international market. Pelabuhanratu Bay is an area with big potential for supplying eel seed. One of important factor, which affect an eel existence, is salinity, because eel migrate from fresh water, brackish, and sea naturally although the otherwise so that need ways to describe the distribution of glass eel by the salinity. To find out the percentage of salinity, it obtained from Landsat 8 Imagery in year 2015 using salinity prediction of Algorithm Cimandiri. The research has been conducted at Cimandiri Estuary, Citepus Estuary, and Cimaja Estuary based on wet and dry months. The existence of glass eel which is obtained from the catch was occurs on dry month when the most catch was occurs at the edge of estuary. The catch is reduced if it's farther from the edge of estuary, at the beach towards the sea and the inside of the river mouth with the percentage of salinity towards the sea is increase while the percentage of salinity towards the river is decrease.

Black Sea thermohaline properties: Long‐term trends and variations

PubMed Central

Stips, A.; Garcia‐Gorriz, E.; Macias Moy, D.

2017-01-01

Abstract The current knowledge about spatial and temporal dynamics of the Black Sea's thermohaline structure is incomplete because of missing data and sparse distribution of existing measurements in space and time. This study presents 56 year continuous simulations of the Black Sea's hydrodynamics using the 3D General Estuarine Transport Model (GETM), without incorporating any relaxation toward climatological or observational data fields. This property of the model allows us to estimate independent temporal trends, in addition to resolving the spatial structure. The simulations suggest that the intermediate layer temperature is characterized by a weak positive trend (warming), whereas the surface temperature does not show a clear linear trend. Different salinity trends have been established at the surface (negative), upper (weaker negative) and main halocline (positive). Three distinct dynamic periods are identified (1960–1970, 1970–1995, 1995–2015), which exhibit pronounced changes in the Black Sea's thermohaline properties and basin circulation. Strengthening of the main cyclonic circulation, accompanied by intensification of the mesoscale anticyclonic eddy formation is found. Both events strongly affect the sea surface salinity but contribute in opposing directions. Specifically, strong composite large‐scale circulation leads to an increase in sea surface salinity, while enhanced formation of mesoscale anticyclones decreases it. Salinity evolution with time is thus the result of the competition of these two opposing yet interdependent processes. PMID:28989833

El Niño-Southern Oscillation-time scale covariation of sea surface salinity and freshwater flux in the western tropical and northern subtropical Pacific

NASA Astrophysics Data System (ADS)

Nagano, Akira; Hasegawa, Takuya; Ueki, Iwao; Ando, Kentaro

2017-07-01

We examined the covariation of sea surface salinity (SSS) and freshwater flux in the western tropical and northern subtropical Pacific on the El Niño-Southern Oscillation time scale, using a canonical correlation analysis of monthly data between 2001 and 2013. The dominant covariation, i.e., the first canonical mode, has large positive and negative amplitudes in regions east of the Philippines and New Guinea, respectively, and reaches peaks in autumn to winter of El Niño years. The positive SSS anomaly east of the Philippines is advected to the Kuroshio Extension region. We found that the second canonical mode is another coupled variation with localized amplitudes of SSS under the atmospheric convergence zones in winter to spring of La Niña years. However, the negative SSS anomaly is annihilated possibly by the evaporation in the subtropical region.

Aquarius Salinity Retrieval Algorithm: Final Pre-Launch Version

NASA Technical Reports Server (NTRS)

Wentz, Frank J.; Le Vine, David M.

2011-01-01

This document provides the theoretical basis for the Aquarius salinity retrieval algorithm. The inputs to the algorithm are the Aquarius antenna temperature (T(sub A)) measurements along with a number of NCEP operational products and pre-computed tables of space radiation coming from the galaxy and sun. The output is sea-surface salinity and many intermediate variables required for the salinity calculation. This revision of the Algorithm Theoretical Basis Document (ATBD) is intended to be the final pre-launch version.

Salinity tolerances and use of saline environments by freshwater turtles: implications of sea level rise.

PubMed

Agha, Mickey; Ennen, Joshua R; Bower, Deborah S; Nowakowski, A Justin; Sweat, Sarah C; Todd, Brian D

2018-03-25

The projected rise in global mean sea levels places many freshwater turtle species at risk of saltwater intrusion into freshwater habitats. Freshwater turtles are disproportionately more threatened than other taxa; thus, understanding the role of salinity in determining their contemporary distribution and evolution should be a research priority. Freshwater turtles are a slowly evolving lineage; however, they can adapt physiologically or behaviourally to various levels of salinity and, therefore, temporarily occur in marine or brackish environments. Here, we provide the first comprehensive global review on freshwater turtle use and tolerance of brackish water ecosystems. We link together current knowledge of geographic occurrence, salinity tolerance, phylogenetic relationships, and physiological and behavioural mechanisms to generate a baseline understanding of the response of freshwater turtles to changing saline environments. We also review the potential origins of salinity tolerance in freshwater turtles. Finally, we integrate 2100 sea level rise (SLR) projections, species distribution maps, literature gathered on brackish water use, and a phylogeny to predict the exposure of freshwater turtles to projected SLR globally. From our synthesis of published literature and available data, we build a framework for spatial and phylogenetic conservation prioritization of coastal freshwater turtles. Based on our literature review, 70 species (∼30% of coastal freshwater turtle species) from 10 of the 11 freshwater turtle families have been reported in brackish water ecosystems. Most anecdotal records, observations, and descriptions do not imply long-term salinity tolerance among freshwater turtles. Rather, experiments show that some species exhibit potential for adaptation and plasticity in physiological, behavioural, and life-history traits that enable them to endure varying periods (e.g. days or months) and levels of saltwater exposure. Species that specialize on

Lowered salinity tolerance in sea skaters Halobates micans, Halobates sericeus, and Halobates sp. (Heteroptera: Gerridae).

PubMed

Sekimoto, Takero; Iyota, Koki; Osumi, Yuki; Shiraki, Takashi; Harada, Tetsuo

2013-06-01

Adult specimens of three species of oceanic sea skater, Halobates sericeus Eschscholtz, Halobates micans Eschscholtz, and Halobates sp. were placed in one of four solutions of different salinity (sea water [35-36‰], sea water : fresh water = 2:1 [23-24‰], sea water : fresh water = 1:2 [11-13‰], and fresh water [0‰]) after collection from the temperate and subtropical Pacific Ocean, tropical Indian Ocean, and Tomini Gulf in Indonesia, and observed in 2-h intervals until they died. H. micans collected from the tropical Indian Ocean survived twice a long (80-100 h) on average as H. sericeus collected from the temperate and subtropical Pacific Ocean (35-45 h) under salinities of 12-36‰. Paralysis from freshwater treatment occurred within 2-9 h in all specimens of both species of H. sericeus from the Pacific Ocean and H. micans from the Indian Ocean, and all insects died within 2 hr of starting the paralysis. In fresh water, oceanic sea skaters of H. sp. collected from the inner water of Tomini Gulf survived for ≍24 h on average, significantly longer than those collected from the open ocean. Significantly longer length of survival was shown by the three species on one-thirds, two-thirds brackish, and 100‰ sea water than on fresh water. The long length of survival shown by oceanic sea skaters even in brackish water may be an adaptation to the occasional rain fall on the sea water film.

Results from a lab study of melting sea ice

NASA Astrophysics Data System (ADS)

Wiese, M.; Griewank, P.; Notz, D.

2012-04-01

Sea-ice melting is a complex process which is not fully understood yet. In order to study sea-ice melt in detail we perform lab experiments in an approximately 2x0.7x1.2 m large tank in a cold room. We grow sea ice with different salinities at least 10 cm thick. Then we let the ice melt at different air temperatures and oceanic heat fluxes. During the melt period, we measure the evolution of ice thickness, internal temperature, salinity and surface temperature. We will present results from roughly five months of experiments. Topics will include the influence of bulk salinity on melt rates and the surface temperature. The effects of flushing on the salinity evolution and detailed thermal profiles will also be included. To investigate these processes we focus on the energy budget and the salinity evolution. These topics are linked since the thermodynamic properties of sea ice (heat capacity, heat conductivity and latent heat of fusion) are very sensitive to salinity variations. For example the heat capacity of sea ice increases greatly as the temperature approaches the melting point. This increase results in non-linear temperature profiles and enhances heat conduction into the ice. The salinity evolution during the growth phase has been investigated and measured in multiple studies over the last decades. In contrast there are no detailed lab measurements of melting ice available to quantify the effects of flushing melt water and ponding. This is partially due to the fact that the heterogeneity of melting sea ice makes it much more difficult to measure representative values.

Massive infestation by Amyloodinium ocellatum (Dinoflagellida) of fish in a highly saline lake, Salton Sea, California, USA.

PubMed

Kuperman, B I; Matey, V E

1999-12-22

Persistent fish infestation by the parasitic dinoflagellate Amyloodinium ocellatum was found at a highly saline lake, Salton Sea, California, USA. The seasonal dynamics of the infestation of young tilapia was traced in 1997-1998. First appearing in May, it became maximal in June-August, decreased in October and was not detectable in November. Outbreak of the infestation and subsequent mortality of young fish was registered at the Sea at a water temperature and salinity of 40 degrees C and 46 ppt, respectively. Some aspects of the ultrastructure of parasitic trophonts of A. ocellatum and their location on the fish from different size groups are considered. The interactions of parasitological and environmental factors and their combined effect upon fish from the Salton Sea are discussed.

Microwave emission characteristics of sea ice

NASA Technical Reports Server (NTRS)

Edgerton, A. T.; Poe, G.

1972-01-01

A general classification is presented for sea ice brightness temperatures with categories of high and low emission, corresponding to young and weathered sea ice, respectively. A sea ice emission model was developed which allows variations of ice salinity and temperature in directions perpendicular to the ice surface.

Assessment of salinity intrusion in the James and Chickahominy Rivers as a result of simulated sea-level rise in Chesapeake Bay, East Coast, USA

USGS Publications Warehouse

Rice, Karen; Bo Hong,; Jian Shen,

2012-01-01

Global sea level is rising, and the relative rate in the Chesapeake Bay region of the East Coast of the United States is greater than the worldwide rate. Sea-level rise can cause saline water to migrate upstream in estuaries and rivers, threatening freshwater habitat and drinking-water supplies. The effects of future sea-level rise on two tributaries of Chesapeake Bay, the James and Chickahominy (CHK) Rivers, were evaluated in order to quantify the salinity change with respect to the magnitude of sea-level rise. Such changes are critical to: 1) local floral and faunal habitats that have limited tolerance ranges to salinity; and 2) a drinking-water supply for the City of Newport News, Virginia. By using the three-dimensional Hydrodynamic-Eutrophication Model (HEM-3D), sea-level rise scenarios of 30, 50, and 100 cm, based on the U.S. Climate Change Science Program for the mid-Atlantic region for the 21st century, were evaluated. The model results indicate that salinity increases in the entire river as sea level rises and that the salinity increase in a dry year is greater than that in a typical year. In the James River, the salinity increase in the middle-to-upper river (from 25 to 50 km upstream of the mouth) is larger than that in the lower and upper parts of the river. The maximum mean salinity increase would be 2 and 4 ppt for a sea-level rise of 50 and 100 cm, respectively. The upstream movement of the 10 ppt isohaline is much larger than the 5 and 20 ppt isohalines. The volume of water with salinity between 10 and 20 ppt would increase greatly if sea level rises 100 cm. In the CHK River, with a sea-level rise of 100 cm, the mean salinity at the drinking-water intake 34 km upstream of the mouth would be about 3 ppt in a typical year and greater than 5 ppt in a dry year, both far in excess of the U.S. Environmental Protection Agency's secondary standard for total dissolved solids for drinking water. At the drinking-water intake, the number of days of

Linking water and carbon cycles through salinity observed from space

NASA Astrophysics Data System (ADS)

Xie, X.; Liu, W. T.

2017-12-01

The association of ocean surface salinity in global hydrological cycle and climate change has been traditionally studied through the examination of its tendency and advection as manifestation of ocean's heat and water fluxes with the atmosphere. The variability of surface heat and water fluxes are linked to top of atmosphere radiation, whose imbalance is the main cause of global warming. Besides the link of salinity to greenhouse warming through water balance, this study will focus on the effect of changing salinity on carbon dioxide flux between the ocean and the atmosphere. We have built statistical models to estimate the partial pressure of carbon dioxide (pCO2) and ocean acidification (in terms of total alkalinity and pH) using spacebased data. PCO2 is a critical parameter governing ocean as source and sink of the accumulated greenhouse gas in the atmosphere. The exchange also causes ocean acidification, which is detrimental to marine lives and ecology. Before we had sufficient spacebased salinity measurements coincident with in situ pCO2 measurement, we trained our statistical models to use satellite sea surface temperature and chlorophyll, with one model using salinity climatology and the other without. We found significant differences between the two models in regions of strong water input through river discharge and surface water flux. The pCO2 output follows the seasonal salinity advection of the Amazon outflow. The seasonal salinity advection between Bay of Bengal and Arabian Sea are followed by change of pCO2 and total alkalinity. At shorter time scales, the signatures of rain associated with intraseasonal organized convection of summer monsoon can be detected. We have observed distribution agreement of among pCO2, surface salinity, and surface water flux for variation from a few days to a few years under the Pacific ITCZ; the agreement varies slightly with season and longitudes and the reason is under study.

Coincident Retrieval of Ocean Surface Roughness and Salinity Using Airborne and Satellite Microwave Radiometry and Reflectometry Measurements during the Carolina Offshore (Caro) Experiment.

NASA Astrophysics Data System (ADS)

Burrage, D. M.; Wesson, J. C.; Wang, D. W.; Garrison, J. L.; Zhang, H.

2017-12-01

The launch of the Cyclone Global Navigation Satellite System (CYGNSS) constellation of 8 microsats carrying GPS L-band reflectometers on 15 Dec., 2016, and continued operation of the L-band radiometer on the European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) satellite, allow these complementary technologies to coincidentally retrieve Ocean surface roughness (Mean Square Slope, MSS), Surface Wind speed (WSP), and Sea Surface Salinity (SSS). The Carolina Offshore (Caro) airborne experiment was conducted jointly by NRL SSC and Purdue University from 7-11 May, 2017 with the goal of under-flying CYGNSS and SMOS and overflying NOAA buoys, to obtain high-resolution reflectometer and radiometer data for combined retrieval of MSS, SSS and WSP on the continental shelf. Airborne instruments included NRL's Salinity Temperature and Roughness Remote Scanner (STARRS) L-, C- and IR-band radiometer system, and a 4-channel dual-pol L-band (GPS) and S-band (XM radio) reflectometer, built by Purdue University. Flights either crossed NOAA buoys on various headings, or intersected with specular point ground tracks at predicted CYGNSS overpass times. Prevailing winds during Caro were light to moderate (1-8 m/s), so specular returns dominated the reflectometer Delay Doppler Maps (DDMs), and MSS was generally low. In contrast, stronger winds (1-12 m/s) and rougher seas (wave heights 1-5 m) were experienced during the preceding Maine Offshore (Maineo) experiment in March, 2016. Several DDM observables were used to retrieve MSS and WSP, and radiometer brightness temperatures produced Sea Surface Temperature (SST), SSS and also WSP estimates. The complementary relationship of Kirchoff's formula e+r=1, between radiometric emissivity, e, and reflectivity, r, was exploited to seek consistent estimates of MSS, and use it to correct the SSS retrievals for sea surface roughness effects. The relative performance and utility of the various airborne and satellite retrieval algorithms

Aquarius reveals salinity structure of tropical instability waves

NASA Astrophysics Data System (ADS)

Lee, Tong; Lagerloef, Gary; Gierach, Michelle M.; Kao, Hsun-Ying; Yueh, Simon; Dohan, Kathleen

2012-06-01

Sea surface salinity (SSS) measurements from the Aquarius/SAC-D satellite during September-December 2011 provide the first satellite observations of the salinity structure of tropical instability waves (TIWs) in the Pacific. The related SSS anomaly has a magnitude of approximately ±0.5 PSU. Different from sea surface temperature (SST) and sea surface height anomaly (SSHA) where TIW-related propagating signals are stronger a few degrees away from the equator, the SSS signature of TIWs is largest near the equator in the eastern equatorial Pacific where salty South Pacific water meets the fresher Inter-tropical Convergence Zone water. The dominant westward propagation speed of SSS near the equator is approximately 1 m/s. This is twice as fast as the 0.5 m/s TIW speed widely reported in the literature, typically from SST and SSHA away from the equator. This difference is attributed to the more dominant 17-day TIWs near the equator that have a 1 m/s dominant phase speed and the stronger 33-day TIWs away from the equator that have a 0.5 m/s dominant phase speed. The results demonstrate the important value of Aquarius in studying TIWs.

The Global Drifter Program Currents, Sea Surface Temperature, Atmospheric Pressure and Waves in the World's OceanThe Global Drifter Program Currents, Sea Surface Temperature, Atmospheric Pressure and Waves in the World's Ocean

NASA Astrophysics Data System (ADS)

Centurioni, Luca

2017-04-01

The Global Drifter Program is the principal component of the Global Surface Drifting Buoy Array, a branch of NOAA's Global Ocean Observing System and a scientific project of the Data Buoy Cooperation Panel (DBCP). The DBCP is an international program coordinating the use of autonomous data buoys to observe atmospheric and oceanographic conditions over ocean areas where few other measurements are taken. The Global Drifter Program maintains an array of over 1,250 Lagrangian drifters, reporting in near real-time and designed measure 15 m depth Lagrangian currents, sea surface temperature (SST) and sea level atmospheric pressure (SLP), among others, to fulfill the needs to observe the air-sea interface at temporal and spatial scales adequate to support short to medium-range weather forecasting, ocean state estimates and climate science. This overview talk will discuss the main achievements of the program, the main impacts for satellite SST calibration and validation, for numerical weather prediction, and it will review the main scientific findings based on the use of Lagrangian currents. Finally, we will present new developments in Lagrangian drifter technology, which include special drifters designed to measure sea surface salinity, wind and directional wave spectra. New opportunities for expanding the scope of the Global Drifter Program will be discussed.

Spatial patterns of littoral zooplankton assemblages along a salinity gradient in a brackish sea: A functional diversity perspective

NASA Astrophysics Data System (ADS)

Helenius, Laura K.; Leskinen, Elina; Lehtonen, Hannu; Nurminen, Leena

2017-11-01

The distribution patterns and diversity of littoral zooplankton are both key baseline information for understanding the functioning of coastal ecosystems, and for identifying the mechanisms by which the impacts of recently increased eutrophication are transferred through littoral food webs. In this study, zooplankton community structure and diversity along a shallow coastal area of the northern Baltic Sea were determined in terms of horizontal environmental gradients. Spatial heterogeneity of the zooplankton community was examined along the gradient. Altogether 31 sites in shallow sandy bays on the coast of southwest Finland were sampled in the summer periods of 2009 and 2010 for zooplankton and environmental variables (surface water temperature, salinity, turbidity, wave exposure, macrophyte coverage, chlorophyll a and nutrients). Zooplankton diversity was measured as both taxonomic as well as functional diversity, using trait-based classification of planktonic crustaceans. Salinity, and to a lesser extent turbidity and temperature, were found to be the main predictors of the spatial patterns and functional diversity of the zooplankton community. Occurrence of cyclopoid copepods, as well as abundances of the calanoid copepod genus Acartia and the rotifer genus Keratella were found to be key factors in differentiating sites along the gradient. As far as we know, this is the first extensive study of functional diversity in Baltic Sea coastal zooplankton communities.

Dynamic ikaite production and dissolution in sea ice - control by temperature, salinity and pCO2 conditions

NASA Astrophysics Data System (ADS)

Rysgaard, S.; Wang, F.; Galley, R. J.; Grimm, R.; Lemes, M.; Geilfus, N.-X.; Chaulk, A.; Hare, A. A.; Crabeck, O.; Else, B. G. T.; Campbell, K.; Papakyriakou, T.; Sørensen, L. L.; Sievers, J.; Notz, D.

2013-12-01

Ikaite is a hydrous calcium carbonate mineral (CaCO3 · 6H2O). It is only found in a metastable state, and decomposes rapidly once removed from near-freezing water. Recently, ikaite crystals have been found in sea ice and it has been suggested that their precipitation may play an important role in air-sea CO2 exchange in ice-covered seas. Little is known, however, of the spatial and temporal dynamics of ikaite in sea ice. Here we present evidence for highly dynamic ikaite precipitation and dissolution in sea ice grown at an out-door pool of the Sea-ice Environmental Research Facility (SERF). During the experiment, ikaite precipitated in sea ice with temperatures below -3 °C, creating three distinct zones of ikaite concentrations: (1) a mm to cm thin surface layer containing frost flowers and brine skim with bulk concentrations of > 2000 μmol kg-1, (2) an internal layer with concentrations of 200-400 μmol kg-1 and (3) a~bottom layer with concentrations of < 100 μmol kg-1. Snowfall events caused the sea ice to warm, dissolving ikaite crystals under acidic conditions. Manual removal of the snow cover allowed the sea ice to cool and brine salinities to increase, resulting in rapid ikaite precipitation. The modeled (FREZCHEM) ikaite concentrations were in the same order of magnitude as observations and suggest that ikaite concentration in sea ice increase with decreasing temperatures. Thus, varying snow conditions may play a key role in ikaite precipitation and dissolution in sea ice. This will have implications for CO2 exchange with the atmosphere and ocean.

Salinization and arsenic contamination of surface water in southwest Bangladesh.

PubMed

Ayers, John C; George, Gregory; Fry, David; Benneyworth, Laura; Wilson, Carol; Auerbach, Leslie; Roy, Kushal; Karim, Md Rezaul; Akter, Farjana; Goodbred, Steven

2017-09-11

To identify the causes of salinization and arsenic contamination of surface water on an embanked island (i.e., polder) in the tidal delta plain of SW Bangladesh we collected and analyzed water samples in the dry (May) and wet (October) seasons in 2012-2013. Samples were collected from rice paddies (wet season), saltwater ponds used for brine shrimp aquaculture (dry season), freshwater ponds and tidal channels (both wet and dry season), and rainwater collectors. Continuous measurements of salinity from March 2012 to February 2013 show that tidal channel water increases from ~0.15 ppt in the wet season up to ~20 ppt in the dry season. On the polder, surface water exceeds the World Health Organization drinking water guideline of 10 μg As/L in 78% of shrimp ponds and 27% of rice paddies, raising concerns that produced shrimp and rice could have unsafe levels of As. Drinking water sources also often have unsafe As levels, with 83% of tubewell and 43% of freshwater pond samples having >10 μg As/L. Water compositions and field observations are consistent with shrimp pond water being sourced from tidal channels during the dry season, rather than the locally saline groundwater from tubewells. Irrigation water for rice paddies is also obtained from the tidal channels, but during the wet season when surface waters are fresh. Salts become concentrated in irrigation water through evaporation, with average salinity increasing from 0.43 ppt in the tidal channel source to 0.91 ppt in the rice paddies. Our observations suggest that the practice of seasonally alternating rice and shrimp farming in a field has a negligible effect on rice paddy water salinity. Also, shrimp ponds do not significantly affect the salinity of adjacent surface water bodies or subjacent groundwater because impermeable shallow surface deposits of silt and clay mostly isolate surface water bodies from each other and from the shallow groundwater aquifer. Bivariate plots of conservative element

Measurement of ocean temperature and salinity via microwave radiometry

NASA Technical Reports Server (NTRS)

Blume, H.-J. C.; Kendall, B. M.; Fedors, J. C.

1978-01-01

Sea-surface temperature with an accuracy of 1 C and salinity with an accuracy of 1% were measured with a 1.43 and 2.65 GHz radiometer system after correcting for the influence of cosmic radiation, intervening atmosphere, sea-surface roughness, and antenna beamwidth. The radiometers are a third-generation system using null-balancing and feedback noise injection. Flight measurements from aircraft over bay regions and coastal areas of the Atlantic resulted in contour maps with spatial resolution of 0.5 km.

Metagenomic sequencing of two salton sea microbiomes.

PubMed

Hawley, Erik R; Schackwitz, Wendy; Hess, Matthias

2014-01-23

The Salton Sea is the largest inland body of water in California, with salinities ranging from brackish freshwater to hypersaline. The lake experiences high nutrient input, and its surface water is exposed to temperatures up to 40°C. Here, we report the community profiles associated with surface water from the Salton Sea.

The Aquarius Salinity Retrieval Algorithm: Early Results

NASA Technical Reports Server (NTRS)

Meissner, Thomas; Wentz, Frank J.; Lagerloef, Gary; LeVine, David

2012-01-01

The Aquarius L-band radiometer/scatterometer system is designed to provide monthly salinity maps at 150 km spatial scale to a 0.2 psu accuracy. The sensor was launched on June 10, 2011, aboard the Argentine CONAE SAC-D spacecraft. The L-band radiometers and the scatterometer have been taking science data observations since August 25, 2011. The first part of this presentation gives an overview over the Aquarius salinity retrieval algorithm. The instrument calibration converts Aquarius radiometer counts into antenna temperatures (TA). The salinity retrieval algorithm converts those TA into brightness temperatures (TB) at a flat ocean surface. As a first step, contributions arising from the intrusion of solar, lunar and galactic radiation are subtracted. The antenna pattern correction (APC) removes the effects of cross-polarization contamination and spillover. The Aquarius radiometer measures the 3rd Stokes parameter in addition to vertical (v) and horizontal (h) polarizations, which allows for an easy removal of ionospheric Faraday rotation. The atmospheric absorption at L-band is almost entirely due to O2, which can be calculated based on auxiliary input fields from numerical weather prediction models and then successively removed from the TB. The final step in the TA to TB conversion is the correction for the roughness of the sea surface due to wind. This is based on the radar backscatter measurements by the scatterometer. The TB of the flat ocean surface can now be matched to a salinity value using a surface emission model that is based on a model for the dielectric constant of sea water and an auxiliary field for the sea surface temperature. In the current processing (as of writing this abstract) only v-pol TB are used for this last process and NCEP winds are used for the roughness correction. Before the salinity algorithm can be operationally implemented and its accuracy assessed by comparing versus in situ measurements, an extensive calibration and validation

Surface water mass composition changes captured by cores of Arctic land-fast sea ice

NASA Astrophysics Data System (ADS)

Smith, I. J.; Eicken, H.; Mahoney, A. R.; Van Hale, R.; Gough, A. J.; Fukamachi, Y.; Jones, J.

2016-04-01

In the Arctic, land-fast sea ice growth can be influenced by fresher water from rivers and residual summer melt. This paper examines a method to reconstruct changes in water masses using oxygen isotope measurements of sea ice cores. To determine changes in sea water isotope composition over the course of the ice growth period, the output of a sea ice thermodynamic model (driven with reanalysis data, observations of snow depth, and freeze-up dates) is used along with sea ice oxygen isotope measurements and an isotopic fractionation model. Direct measurements of sea ice growth rates are used to validate the output of the sea ice growth model. It is shown that for sea ice formed during the 2011/2012 ice growth season at Barrow, Alaska, large changes in isotopic composition of the ocean waters were captured by the sea ice isotopic composition. Salinity anomalies in the ocean were also tracked by moored instruments. These data indicate episodic advection of meteoric water, having both lower salinity and lower oxygen isotopic composition, during the winter sea ice growth season. Such advection of meteoric water during winter is surprising, as no surface meltwater and no local river discharge should be occurring at this time of year in that area. How accurately changes in water masses as indicated by oxygen isotope composition can be reconstructed using oxygen isotope analysis of sea ice cores is addressed, along with methods/strategies that could be used to further optimize the results. The method described will be useful for winter detection of meteoric water presence in Arctic fast ice regions, which is important for climate studies in a rapidly changing Arctic. Land-fast sea ice effective fractionation coefficients were derived, with a range of +1.82‰ to +2.52‰. Those derived effective fractionation coefficients will be useful for future water mass component proportion calculations. In particular, the equations given can be used to inform choices made when

Teasing Apart Regional Climate and Meltwater Influences on Florida Straits Sea Surface Temperature and Salinity over the past 40 kyr

NASA Astrophysics Data System (ADS)

Schmidt, M. W.; Lynch-Stieglitz, J.

2008-12-01

Recent reconstructions of North Atlantic salinity variability over the last glacial cycle show that abrupt climate events are linked to major reorganizations in the low-latitude hydrologic cycle, affecting large-scale changes in evaporation minus precipitation (E-P) patterns. Although there is general agreement that the Intertropical Convergence Zone (ITCZ) migrates southward during cold stadials, it remains unclear how this shift affects the net E-P budget in the North Atlantic. In order to reconstruct a high resolution record of past sea surface temperature (SST) and salinity (SSS) in the Florida Straits across abrupt climate events of the last 40 kyr, we combine Mg/Ca paleothermometry and δ18O measurements in shells from the surface-dwelling foraminifera Globigerinoides ruber in cores KNR166-2-JPC29 (24°17'N, 83°16'W; 648 m depth; 8-20 cm/kyr sed. rate) and JPC26 (24°19.61'N, 83°15.14'W; 546 m depth; 18-240 cm/kyr sed. rate) and calculate δ18OSEAWATER (δ18OSW) variability. Removal of the δ18OSW signal due to continental ice volume variation results in the ice volume-free (IVF) δ18OSW record (a proxy for SSS variability). Although most waters flowing through the Florida Straits today originate in the tropical western Atlantic, major meltwater discharges from the Mississippi River across the last deglacial period also influenced SST and SSS in the Florida Straits. To constrain periods of increased meltwater discharge, we measured Ba/Ca ratios in G. ruber from select intervals. Because riverine waters have a much higher dissolved Ba+2 concentration relative to seawater, foraminifera Ba/Ca ratios can be used as an additional proxy to constrain periods of increase riverine discharge. Initial results suggest the hydrographic history of the Florida Straits is influenced by both meltwater discharge and regional climate variability linked to the high-latitude North Atlantic. Both the IVF- δ18OSW and Ba/Ca records reveal a prolonged period from 16.0-13.0 kyr

Comparison of coral δ18O with pseudocorals derived from in situ sea surface salinity and temperature measurements

NASA Astrophysics Data System (ADS)

DeLong, K. L.; Chaichi, N.; Maupin, C. R.; Richey, J. N.; Quinn, T. M.; Poore, R. Z.

2015-12-01

Paleoclimatologists use pseudocorals and forward modeling of coral oxygen isotopes (δ18O) to assess δ18O variations for comparison with climate model output in order to understand past tropical oceanic-atmospheric variability. Oxygen isotopic (δ18Ocoral) variability in shallow water coral skeletons is dependent on sea surface temperature (SST) and δ18O of seawater (δ18Osw), which varies with sea surface salinity (SSS). However, measurements of δ18Osw and SSS are sparse; therefore, simulated SSS (e.g., SODA) is typically used in pseudocoral investigations. Our study site is the Dry Tortugas National Park (DRTO; 24º42'N, 82º48'W) in the southeastern Gulf of Mexico (GOM) where hourly SST and SSS measurements are available from NOAA buoys (1992-2002) and the Florida Keys National Marine Sanctuary (FKNMS; 2011-2014). Here we use bivariate forward modeling of monthly average buoy SSS and SST to develop a time series of pseudocoral δ18O (δ18Op = -0.22(‰/ºC)SST + 0.11(‰/psu)SSS) for DRTO that are compared with δ18Ocoral variations from three Siderastrea siderea coral colonies growing in close proximity within the park. We use the relationship for δ18Osw and SSS determined for Flower Garden Banks coral reef in the northern GOM (27º52'N, 93º49'W) since no measurements of δ18Osw are currently available for DRTO. δ18Op co-varies with δ18Ocoral (r2 = 0.59) with a root mean square error (RMSE = 0.32‰) greater than the intercolony δ18Ocoral variability (r2 = 0.80; RSME = 0.07‰). Discrepancies between δ18Op and δ18Ocoral may be related to the lack of a local SSS-δ18Osw relationship for DRTO or uncertainties in subannual time assignment for δ18Ocoral. A new source of SSS is the NASA satellite Aquarius (2012-2014), which may be useful in future pseudocoral studies, that is evaluated along with high resolution simulated SSS (Global Ocean Physics Reanalysis GLORYS2V3; 1993-2012). We find similar correlation between Aquarius-derived SSS and FKNMS SSS (r2

An Experimental Real-Time Ocean Nowcast/Forecast System for Intra America Seas

NASA Astrophysics Data System (ADS)

Ko, D. S.; Preller, R. H.; Martin, P. J.

2003-04-01

An experimental real-time Ocean Nowcast/Forecast System has been developed for the Intra America Seas (IASNFS). The area of coverage includes the Caribbean Sea, the Gulf of Mexico and the Straits of Florida. The system produces nowcast and up to 72 hours forecast the sea level variation, 3D ocean current, temperature and salinity fields. IASNFS consists an 1/24 degree (~5 km), 41-level sigma-z data-assimilating ocean model based on NCOM. For daily nowcast/forecast the model is restarted from previous nowcast. Once model is restarted it continuously assimilates the synthetic temperature/salinity profiles generated by a data analysis model called MODAS to produce nowcast. Real-time data come from satellite altimeter (GFO, TOPEX/Poseidon, ERS-2) sea surface height anomaly and AVHRR sea surface temperature. Three hourly surface heat fluxes, including solar radiation, wind stresses and sea level air pressure from NOGAPS/FNMOC are applied for surface forcing. Forecasts are produced with available NOGAPS forecasts. Once the nowcast/forecast are produced they are distributed through the Internet via the updated web pages. The open boundary conditions including sea surface elevation, transport, temperature, salinity and currents are provided by the NRL 1/8 degree Global NCOM which is operated daily. An one way coupling scheme is used to ingest those boundary conditions into the IAS model. There are 41 rivers with monthly discharges included in the IASNFS.

Sea Surface Temperature and Ocean Color Variability in the South China Sea

NASA Astrophysics Data System (ADS)

Conaty, A. P.

2001-12-01

The South China Sea is a marginal sea in the Southeast Asian region whose surface circulation is driven by monsoons and whose surface currents have complex seasonal patterns. Its rich natural resources and strategic location have made its small islands areas of political dispute among the neighboring nations. This study aims to show the seasonal and interannual variability of sea surface temperature and ocean color in South China Sea. It makes use of NOAA's Advanced Very High Resolution Radiometer (AVHRR) satellite data sets on sea surface temperature for the period 1981-2000 and NASA's Nimbus-7 Coastal Zone Color Scanner (CZCS) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite data sets on pigment concentration (ocean color) for the period 1981-1996 and 1997-2000, respectively. Transect lines were drawn along several potential hotspot areas to show the variability in sea surface temperature and pigment concentration through time. In-situ data on sea surface temperature along South China Sea were likewise plotted to see the variability with time. Higher seasonal variability in sea surface temperature was seen at higher latitudes. Interannual variability was within 1-3 Kelvin. In most areas, pigment concentration was higher during northern hemisphere winter and autumn, after the monsoon rains, with a maximum of 30 milligrams per cubic meter.

[Adenosine triphosphatase activity in the organs of the crab Hemigrapsus sanguineus, acclimated to sea water of different salinity].

PubMed

Busev, V M

1977-01-01

In crabs acclimated to low salinity, the activity of Na, K-ATPase from the gills increases; the activity also increases in the antennal glands after acclimation of the animals to high salinity. The activity of Na, K-ATPase in the abdominal ganglion and in the heart does not depend on the salinity to which crabs had been acclimated. Changes in the activity of Mg-ATPase in the gills and antennal glands associated with acclimation of crabs to sea water with different salinity correspond to those in the activity of Na, K-ATPase.

Assessment of Simulated and Aquarius-Observed Sea Surface Salinity Using Salinity Measurements in Dry Tortugas National Park, Florida, U.S.A.: Application for Pseudocoral δ18O

NASA Astrophysics Data System (ADS)

Chaichitehrani, N.; DeLong, K. L.

2016-02-01

Salinity plays a critical role in ocean physics thus is a target for paleoclimatologic and paleoceanographic reconstruction. Here we assess the quality of space-borne sea surface salinity (SSS) determinations and simulated SSS versus SSS measurements from an open ocean coral reef site, Dry Tortugas National Park (DTNP). The oxygen isotopic composition of seawater (δ18Osw) is related to SSS, thus SSS can be used to understand δ18Osw variability when measurements of δ18Osw are sparse. In marine carbonates such as corals, δ18Ocoral varies with temperature and δ18Osw creating a bivariate system, which is difficult to calibrate with two variables. Accurate determinations of SSS from satellites and simulations can be substituted for local SSS, converted to δ18Osw, in bivariate forward models to estimate δ18Ocoral or pseudocoral thus improving calibrations of δ18Ocoral for locations and time intervals without in situ observations. Monthly and daily Aquarius-retrieved SSS data Level-3 (Official Version 3.0) with spatial resolution are compared with local SSS in DTNP obtained from Water Quality Monitoring Project for the Florida Keys National Marine Sanctuary and southwest Florida shelf, which includes DTNP, for the concurrent interval from 2011-2014. Our statistical analysis shows a satisfactory agreement between daily Aquarius SSS and local SSS (r2=0.68; RMSE=0.24 psu). Additional SSS data are obtained from the National Data Buoy Center DRYF1 station in DTNP. Monthly-simulated SSS (Global Ocean Physics Reanalysis GLORYS2V3) obtained from the MyOcean WebPortal compares relatively well with DRYF1 monthly SSS data (r2=0.68; RMSE=0.35 psu) for the earlier interval from 1998-2002. Our analysis indicates that Aquarius-retrieved and simulated SSS can be utilized as a substitute for local SSS in bivariate forward models to calculate pseudocoral δ18Ocoral as well as forward models other marine carbonates for locations without SSS observations.

The vertical dependence in the horizontal variability of salinity and temperature at the ocean surface

NASA Astrophysics Data System (ADS)

Asher, W.; Drushka, K.; Jessup, A. T.; Clark, D.

2016-02-01

Satellite-mounted microwave radiometers measure sea surface salinity (SSS) as an area-averaged quantity in the top centimeter of the ocean over the footprint of the instrument. If the horizontal variability in SSS is large inside this footprint, sub-grid-scale variability in SSS can affect comparison of the satellite-retrieved SSS with in situ measurements. Understanding the magnitude of horizontal variability in SSS over spatial scales that are relevant to the satellite measurements is therefore important. Horizontal variability of SSS at the ocean surface can be studied in situ using data recorded by thermosalinographs (TSGs) that sample water from a depth of a few meters. However, it is possible measurements made at this depth might underestimate the horizontal variability at the surface because salinity and temperature can become vertically stratified in a very near surface layer due to the effects of rain, solar heating, and evaporation. This vertical stratification could prevent horizontal gradients from propagating to the sampling depths of ship-mounted TSGs. This presentation will discuss measurements made using an underway salinity profiling system installed on the R/V Thomas Thompson that made continuous measurements of SSS and SST in the Pacific Ocean. The system samples at nominal depths of 2-m, 3-m, and 5-m, allowing the depth dependence of the horizontal variability in SSS and SST to be measured. Horizontal variability in SST is largest at low wind speeds during daytime, when a diurnal warm layer forms. In contrast, the diurnal signal in the variability of SSS was smaller with variability being slightly larger at night. When studied as a function of depth, the results show that over 100-km scales, the horizontal variability in both SSS and SST at a depth of 2 m is approximately a factor of 4 higher than the variability at 5 m.

Arctic Sea Salt Aerosol from Blowing Snow and Sea Ice Surfaces - a Missing Natural Source in Winter

NASA Astrophysics Data System (ADS)

Frey, M. M.; Norris, S. J.; Brooks, I. M.; Nishimura, K.; Jones, A. E.

2015-12-01

Atmospheric particles in the polar regions consist mostly of sea salt aerosol (SSA). SSA plays an important role in regional climate change through influencing the surface energy balance either directly or indirectly via cloud formation. SSA irradiated by sunlight also releases very reactive halogen radicals, which control concentrations of ozone, a pollutant and greenhouse gas. However, models under-predict SSA concentrations in the Arctic during winter pointing to a missing source. It has been recently suggested that salty blowing snow above sea ice, which is evaporating, to be that source as it may produce more SSA than equivalent areas of open ocean. Participation in the 'Norwegian Young Sea Ice Cruise (N-ICE 2015)' on board the research vessel `Lance' allowed to test this hypothesis in the Arctic sea ice zone during winter. Measurements were carried out from the ship frozen into the pack ice North of 80º N during February to March 2015. Observations at ground level (0.1-2 m) and from the ship's crows nest (30 m) included number concentrations and size spectra of SSA (diameter range 0.3-10 μm) as well as snow particles (diameter range 50-500 μm). During and after blowing snow events significant SSA production was observed. In the aerosol and snow phase sulfate is fractionated with respect to sea water, which confirms sea ice surfaces and salty snow, and not the open ocean, to be the dominant source of airborne SSA. Aerosol shows depletion in bromide with respect to sea water, especially after sunrise, indicating photochemically driven release of bromine. We discuss the SSA source strength from blowing snow in light of environmental conditions (wind speed, atmospheric turbulence, temperature and snow salinity) and recommend improved model parameterisations to estimate regional aerosol production. N-ICE 2015 results are then compared to a similar study carried out previously in the Weddell Sea during the Antarctic winter.

Land to sea record of the mega-eustatic cycle including the Messinian Salinity Crisis in the Mediterranean Andalusia

NASA Astrophysics Data System (ADS)

Jouannic, Gwénaël.; Gorini, Christian; Jolivet, Laurent; Clauzon, Georges; Suc, Jean-Pierre; Gargani, Julien; Melinte-Dobrinescu, Mihaela Carmen; Meyer, Bertrand

2010-05-01

The outstanding event of the Messinian Salinity Crisis is very well documented in the onshore Sorbas and Vera Andalusian basins where its process and chronology are now well-known (Gautier et al., 1994, Krijgsman et al., 1999; Clauzon et al., 2009). The detailed study of these basins was at the origin of the two-step scenario of the Messinian salinity crisis (Clauzon et al., 1996) which clarified several aspects of the "deep desiccated basin" model of Hsü et al. (1973). The scenario in two steps (first step: evaporite deposition in Mediterranean marginal basins between 5.96 and 5.60 Ma; second step: evaporites deposition between 5.60 and 5.46 Ma in the almost dried up Mediterranean central basins, and subaerial erosion and deep canyons formation on the margins; Clauzon et al., 1996, 2005, 2008) has now the broadest consensus within the scientific community (CIESM, 2008). The Sorbas and Vera basins present all the markers in terms of sequence stratigraphy whatever these events were caused by moderate or excessive sea-level changes: 1, coral reefs, showing the relative sea level before the crisis; 2, gypsum (120 m in thickness) deposited during the first sea level drop (about 150 m) between 5.96 and 5.60 Ma; 3, the widespread erosion surface during the maximum sea level fall(ca. -1500 m); 4, the re-flooding at 5.46 Ma These onshore markers have also been recorded in offshore seismic profiles, allowing a continuous mapping of the Messinian canyons from land to sea. These onshore and offshore areas (Mauffret et al., 2007; Ammar et al., 2008) have also undergone a tectonics according to their proximity to the Betic cordillera (the south of the Sorbas Basin was more affected for example). Stratigraphic markers of the messinian crisis are powerful tools to reconstruct the tectonic events since 5 Ma. This work has made possible the calibration of tectonic deformations on south Andalusia present-day onshore and offshore domains. Ammar, A., Mauffret, A., Gorini, C., Jabour

Salinity of the Delaware Estuary

USGS Publications Warehouse

Cohen, Bernard; McCarthy, Leo T.

1962-01-01

The purpose of this investigation was to obtain data on and study the factors affecting the salinity of the Delaware River from Philadelphia, Pa., to the Appoquinimink River, Del. The general chemical quality of water in the estuary is described, including changes in salinity in the river cross section and profile, diurnal and seasonal changes, and the effects of rainfall, sea level, and winds on salinity. Relationships are established of the concentrations of chloride and dissolved solids to specific conductance. In addition to chloride profiles and isochlor plots, time series are plotted for salinity or some quantity representing salinity, fresh-water discharge, mean river level, and mean sea level. The two major variables which appear to have the greatest effect on the salinity of the estuary are the fresh-water flow of the river and sea level. The most favorable combination of these variables for salt-water encroachment occurs from August to early October and the least favorable combination occurs between December and May.

Differential gene expression in the intestine of sea cucumber (Apostichopus japonicus) under low and high salinity conditions.

PubMed

Zhang, Libin; Feng, Qiming; Sun, Lina; Ding, Kui; Huo, Da; Fang, Yan; Zhang, Tao; Yang, Hongsheng

2018-03-01

Sea cucumber, Apostichopus japonicus is an important species for aquaculture, and its behavior and physiology can change in response to changing salinity conditions. For this reason, it is important to understand the molecular responses of A. japonicus when exposed to ambient changes in salinity. In this study, RNA-Seq provided a general overview of the gene expression profiles in the intestine of A. japonicus exposed to high salinity (SD40), normal salinity (SD30) and low salinity (SD20) environments. Screening for differentially expressed genes (DEGs) using the NOISeq method identified 109, 100, and 89 DEGs based on a fold change of ≥2 and divergence probability ≥0.8 according to the comparisons of SD20 vs. SD30, SD20 vs.SD40, and SD30 vs. SD40, respectively. Gene ontology analysis showed that the terms "metabolic process" and "catalytic activity" comprised the most enriched DEGs. These fell into the categories of "biological process" and "molecular function". While "cell" and "cell part" had the most enriched DEGs in the category of "cellular component". With these DEGs mapping to 2119, 159, and 160 pathways in the Kyoto Encyclopedia of Genes and Genomes database. Of these 51, 2, and 57 pathways were significantly enriched, respectively. The osmosis-specific DEGs identified in this study of A. japonicus will be important targets for further studies to understand the biochemical mechanisms involved with the adaption of sea cucumbers to changes in salinity. Copyright © 2017. Published by Elsevier Inc.

Thermal evolutions of two kinds of melt pond with different salinity

NASA Astrophysics Data System (ADS)

Kim, Joo-Hong; Wilkinson, Jeremy; Moon, Woosok; Hwang, Byongjun; Granskog, Mats

2016-04-01

Melt ponds are water pools on sea ice. Their formation reduces ice surface albedo and alter surface energy balance, by which the ice melting and freezing processes are regulated. Thus, better understanding of their radiative characteristics has been vital to improve the simulation of melting/freezing of sea ice in numerical models. A melt pond would preserve nearly fresh water if it formed on multi-year ice and no flooding of sea water occurred, whereas a melt pond would contain more salty water if it formed on thinner and porous first-year ice, if there were an inflow of sea water by streams or cracks. One would expect that the fluid dynamic/thermodynamic properties (e.g., turbulence, stability, etc.) of pond water are influenced by the salinity, so that the response of pond water to any heat input (e.g., shortwave radiation) would be different. Therefore, better understanding of the salinity-dependent thermal evolution also has significant potential to improve the numerical simulation of the sea ice melting/freezing response to radiative thermal forcing. To observe and understand the salinity-dependent thermal evolution, two ice mass balance buoys (IMBs) were deployed in two kinds (fresh and salty) of melt pond on a same ice floe on 13 August 2015 during Araon Arctic cruise. The thermistor chain, extending from the air through the pond and ice into the sea water, was deployed through a drilled borehole inside the pond. Besides, the IMBs were also accompanied with three broadband solar radiation sensors (two (up and down) in the air over melt pond and one upward-looking under sea ice) to measure the net shortwave radiation at the pond surface and the penetrating solar radiation through ice. Also, the web camera was installed to observe any updates in the conditions of equipment and surrounding environment (e.g., weather, surface state, etc.). On the date of deployment, the fresh pond had salinity of 2.3 psu, light blue color, lots of slush ice particles which

Applying machine learning to global surface ocean and seabed data to reveal the controls on the distribution of deep-sea sediments

NASA Astrophysics Data System (ADS)

Dutkiewicz, Adriana; Müller, Dietmar; O'Callaghan, Simon

2017-04-01

World's ocean basins contain a rich and nearly continuous record of environmental fluctuations preserved as different types of deep-sea sediments. The sediments represent the largest carbon sink on Earth and its largest geological deposit. Knowing the controls on the distribution of these sediments is essential for understanding the history of ocean-climate dynamics, including changes in sea-level and ocean circulation, as well as biological perturbations. Indeed, the bulk of deep-sea sediments comprises the remains of planktonic organisms that originate in the photic zone of the global ocean implying a strong connection between the seafloor and the sea surface. Machine-learning techniques are perfectly suited to unravelling these controls as they are able to handle large sets of spatial data and they often outperform traditional spatial analysis approaches. Using a support vector machine algorithm we recently created the first digital map of seafloor lithologies (Dutkiewicz et al., 2015) based on 14,400 surface samples. This map reveals significant deviations in distribution of deep-sea lithologies from hitherto hand-drawn maps based on far fewer data points. It also allows us to explore quantitatively, for the first time, the relationship between oceanographic parameters at the sea surface and lithologies on the seafloor. We subsequently coupled this global point sample dataset of 14,400 seafloor lithologies to bathymetry and oceanographic grids (sea-surface temperature, salinity, dissolved oxygen and dissolved inorganic nutrients) and applied a probabilistic Gaussian process classifier in an exhaustive combinatorial fashion (Dutkiewicz et al., 2016). We focused on five major lithologies (calcareous sediment, diatom ooze, radiolarian ooze, clay and lithogenous sediment) and used a computationally intensive five-fold cross-validation, withholding 20% of the data at each iteration, to assess the predictive performance of the machine learning method. We find that

Benthic foraminifera cultured over a large salinity gradient: first results and comparison with field data from the Baltic Sea.

NASA Astrophysics Data System (ADS)

Groeneveld, Jeroen; Filipsson, Helena L.; Austin, William E. N.; Darling, Kate; Quintana Krupinski, Nadine B.

2015-04-01

Some of the most significant challenges in paleoclimate research arise from the need to both understand and reduce the uncertainty associated with proxy methods for climate reconstructions. This is especially important for shelf and coastal environments where increasing numbers of high-resolution paleorecords are being generated. These challenges are further highlighted in connection with ECORD/IODP Expedition 347: Baltic Sea Paleoenvironments. This large-scale drilling operation took place in the Baltic Sea region during the autumn of 2013. At this time, there is a pressing need for proxy calibrations directly targeted at the brackish Baltic environment. Within the CONTEMPORARY project we are investigating different temperature and salinity proxy variables through a combination of field- and culture-based benthic foraminiferal samples, together with genetic characterization (genotyping) of the morphospecies. We have completed two field campaigns where we collected (living) foraminifera and water samples at several sites, ranging from fully marine to low salinity conditions. The core-top foraminifera have been analysed for trace metal/Ca, stable oxygen and carbon isotopes, and faunal composition. Living foraminifera collected from the sediment-water interface were cultured in sea water in two long-term experiments at different temperatures (5°C and 10°C) and at three different salinities (15, 25, and 35). The first experiment yielded a large number of reproduced and experimentally-grown Elphidium specimens. The second experiment resulted in growth but no reproduction. We will provide a summary of the experimentally grown material and discuss the challenges of generating new proxy calibrations for foraminiferal shell geochemistry in the Baltic Sea. Furthermore, specimens of Elphidium and Ammonia, found at two sampling sites (Anholt, Kattegat and Hanöbay) with differing salinities, were genotyped and the results indicate that the same genotype of Elphidium is

Sea surface cooling in the Northern South China Sea observed using Chinese Sea-wing Underwater Glider measurements

NASA Astrophysics Data System (ADS)

Qiu, C.; Mao, H.; Wu, J.

2016-02-01

Based on 26 days of Chinese Seawing underwater Glider measurements and satellite microwave data, we documented cooling of the upper mixed layer of the ocean in response to changes in the wind in the Northern South China Sea (NSCS) from September 19, 2014, to October 15, 2014. The Seawing underwater glider measured 177 profiles of temperature, salinity, and pressure within a 55 km נ55 km area, and reached a depth of 1000 m at a temporal resolution of 4 h. The study area experienced two cooling events, Cooling I and Cooling II, according to their timing. During Cooling I, water temperature at 1m depth (T1) decreased by 1.0°C, and the corresponding satellitederived surface winds increased locally by 4.2 m/s. During Cooling II, T1 decreased sharply by 1.7°C within a period of 4 days; sea surface winds increased by 7 m/s and covered the entire NSCS. The corresponding mixed layer depth (MLD) deepened sharply from 30 m to 60 m during Cooling II, and remained steady during Cooling I. We estimated temperature tendencies using a ML model. High resolution Seawing underwater glider measurements provided an estimation of MLD migration, allowing us to obtain the temporal entrainment rate of cool sub thermocline water. Quantitative analysis confirmed that the entrainment rate and latent heat flux were the two major components that regulated cooling of the ML, and that the Ekman advection and sensible heat flux were small.

Passive Microwave Measurements of Salinity: The Gulf Stream Experiment

NASA Technical Reports Server (NTRS)

LeVine, D. M.; Koblinsky, C.; Haken, M.; Howden, S.; Bingham, F.; Hildebrand, Peter H. (Technical Monitor)

2001-01-01

Passive microwave sensors at L-band (1.4 GHz) operating from aircraft have demonstrated that salinity can be measured with sufficient accuracy (I psu) to be scientifically meaningful in coastal waters. However, measuring salinity in the open ocean presents unresolved issues largely because of the much greater accuracy (approximately 0.2 psu) required of global maps to be scientifically viable. The development of a satellite microwave instrument to make global measurements of SSS (Sea Surface Salinity) is the focus of a joint JPL/GSFC/NASA ocean research program called Aquarius. In the summer of 1999 a series of measurements called, The Gulf Stream Experiment, were conducted as part of research at the Goddard Space Flight Center to test the potential for passive microwave remote sensing of salinity in the open ocean. The measurements consisted of airborne microwave instruments together with ships and drifters for surface truth. The study area was a 200 km by 100 km rectangle about 250 km east of Delaware Bay between the continental shelf waters and north wall of the Gulf Stream. The primary passive instruments were the ESTAR radiometer (L-band, H-pol) and the SLFMR radiometer (L-band, V-pol). In addition, the instruments on the aircraft included a C-band radiometer (ACMR), an ocean wave scatterometer (ROWS) and an infrared radiometer (for surface temperature). These instruments were mounted on the NASA P-3 Orion aircraft. Sea surface measurements consisted of thermosalinograph data provided by the R/V Cape Henlopen and the MN Oleander, and data from salinity and temperature sensors on three surface drifters deployed from the R/V Cape Henlopen. The primary experiment period was August 26-September 2, 1999. During this period the salinity field within the study area consisted of a gradient on the order of 2-3 psu in the vicinity of the shelf break and a warm core ring with a gradient of 1-2 psu. Detailed maps were made with the airborne sensors on August 28 and 29 and

Florida Current surface temperature and salinity variability during the last millennium

NASA Astrophysics Data System (ADS)

Lund, David C.; Curry, William

2006-06-01

The salinity and temperature of the Florida Current are key parameters affecting the transport of heat into the North Atlantic, yet little is known about their variability on centennial timescales. Here we report replicated, high-resolution foraminiferal records of Florida Current surface hydrography for the last millennium from two coring sites, Dry Tortugas and the Great Bahama Bank. The oxygen isotopic composition of Florida Current surface water (δ18Ow) near Dry Tortugas increased 0.4‰ during the course of the Little Ice Age (LIA) (˜1200-1850 A.D.), equivalent to a salinity increase of 0.8-1.5. On the Great Bahama Bank, where surface waters are influenced by the North Atlantic subtropical gyre, δ18Ow increased by 0.3‰ during the last 200 years. Although a portion (˜0.1‰) of this shift may be an artifact of anthropogenically driven changes in surface water ΣCO2, the remaining δ18Ow signal implies a 0.4-1 increase in salinity after 200 years B.P. The simplest explanation of the δ18Ow data is southward migration of the Atlantic Hadley circulation during the LIA. Scaling of the δ18Ow records to salinity using the modern low-latitude δ18Ow-S slope produces an unrealistic reversal in the salinity gradient between the two sites. Only if δ18Ow is scaled to salinity using a high-latitude δ18Ow-S slope can the records be reconciled. Variable atmospheric 14C paralleled Dry Tortugas δ18Ow, suggesting that solar irradiance paced centennial-scale migration of the Inter-Tropical Convergence Zone and changes in Florida Current salinity during the last millennium.

Remote measurement of salinity: Repeated measurements over a single flight line near the Mississippi Sound

NASA Technical Reports Server (NTRS)

Thomann, G. C.

1973-01-01

Experiments to remotely determine sea water salinity from measurements of the sea surface radiometric temperature over the Mississippi Sound were conducted. The line was flown six times at an altitude of 244 meters. The radiometric temperature of the sea surface was measured in two spectral intervals. The specifications of the equipment and the conditions under which the tests were conducted are described. Results of the tests are presented in the form of graphs.

Oceanographic influences on the sea ice cover in the Sea of Okhotsk

NASA Technical Reports Server (NTRS)

Gratz, A. J.; Parkinson, C. L.

1981-01-01

Sea ice conditions in the Sea of Okhotsk, as determined by satellite images from the electrically scanning microwave radiometer on board Nimbus 5, were analyzed in conjunction with the known oceanography. In particular, the sea ice coverage was compared with the bottom bathymetry and the surface currents, water temperatures, and salinity. It is found that ice forms first in cold, shallow, low salinity waters. Once formed, the ice seems to drift in a direction approximating the Okhotsk-Kuril current system. Two basic patterns of ice edge positioning which persist for significant periods were identified as a rectangular structure and a wedge structure. Each of these is strongly correlated with the bathymetry of the region and with the known current system, suggesting that convective depth and ocean currents play an important role in determining ice patterns.

Sensitivity of Offshore Surface Fluxes and Sea Breezes to the Spatial Distribution of Sea-Surface Temperature

NASA Astrophysics Data System (ADS)

Lombardo, Kelly; Sinsky, Eric; Edson, James; Whitney, Michael M.; Jia, Yan

2018-03-01

A series of numerical sensitivity experiments is performed to quantify the impact of sea-surface temperature (SST) distribution on offshore surface fluxes and simulated sea-breeze dynamics. The SST simulations of two mid-latitude sea-breeze events over coastal New England are performed using a spatially-uniform SST, as well as spatially-varying SST datasets of 32- and 1-km horizontal resolutions. Offshore surface heat and buoyancy fluxes vary in response to the SST distribution. Local sea-breeze circulations are relatively insensitive, with minimal differences in vertical structure and propagation speed among the experiments. The largest thermal perturbations are confined to the lowest 10% of the sea-breeze column due to the relatively high stability of the mid-Atlantic marine atmospheric boundary layer (ABL) suppressing vertical mixing, resulting in the depth of the marine layer remaining unchanged. Minimal impacts on the column-averaged virtual potential temperature and sea-breeze depth translates to small changes in sea-breeze propagation speed. This indicates that the use of datasets with a fine-scale SST may not produce more accurate sea-breeze simulations in highly stable marine ABL regimes, though may prove more beneficial in less stable sub-tropical environments.

SPURS-2: Multi-month and multi-scale observations of upper ocean salinity in a rain-dominated salinity minimum region.

NASA Astrophysics Data System (ADS)

Rainville, L.; Farrar, J. T.; Shcherbina, A.; Centurioni, L. R.

2017-12-01

The Salinity Processes in the Upper-ocean Regional Study (SPURS) is a program aimed at understanding the patterns and variability of sea surface salinity. Following the first SPURS program in an evaporation-dominated region (2012-2013), the SPURS-2 program targeted wide range of spatial and temporal scales associated with processes controlling salinity in the rain-dominated Eastern Pacific Fresh Pool. Autonomous instruments were delivered in August and September 2016 using research vessels conducted observations over one complete annual cycle. The SPURS-2 field program used coordinated observations from many different autonomous platforms, and a mix of Lagrangian and Eulerian approaches. Here we discuss the motivation, implementation, and the early of SPURS-2.

Sea surface salinity and temperature-based predictive modeling of southwestern US winter precipitation: improvements, errors, and potential mechanisms

NASA Astrophysics Data System (ADS)

Liu, T.; Schmitt, R. W.; Li, L.

2017-12-01

Using 69 years of historical data from 1948-2017, we developed a method to globally search for sea surface salinity (SSS) and temperature (SST) predictors of regional terrestrial precipitation. We then applied this method to build an autumn (SON) SSS and SST-based 3-month lead predictive model of winter (DJF) precipitation in southwestern United States. We also find that SSS-only models perform better than SST-only models. We previously used an arbitrary correlation coefficient (r) threshold, |r| > 0.25, to define SSS and SST predictor polygons for best subset regression of southwestern US winter precipitation; from preliminary sensitivity tests, we find that |r| > 0.18 yields the best models. The observed below-average precipitation (0.69 mm/day) in winter 2015-2016 falls within the 95% confidence interval of the prediction model. However, the model underestimates the anomalous high precipitation (1.78 mm/day) in winter 2016-2017 by more than three-fold. Moisture transport mainly attributed to "pineapple express" atmospheric rivers (ARs) in winter 2016-2017 suggests that the model falls short on a sub-seasonal scale, in which case storms from ARs contribute a significant portion of seasonal terrestrial precipitation. Further, we identify a potential mechanism for long-range SSS and precipitation teleconnections: standing Rossby waves. The heat applied to the atmosphere from anomalous tropical rainfall can generate standing Rossby waves that propagate to higher latitudes. SSS anomalies may be indicative of anomalous tropical rainfall, and by extension, standing Rossby waves that provide the long-range teleconnections.

Seismic atlas of the "Messinian Salinity Crisis" markers in the Mediterranean and Black seas - Volume 2

NASA Astrophysics Data System (ADS)

Lofi, Johanna

2014-05-01

The Seismic atlas of the "Messinian Salinity Crisis" markers in the Mediterranean and Black seas - Volume 2 is a publication project in the framework of the study of the Messinian Salinity Crisis. It follows the publication of a first volume in 2011 (see Editors' websites: http://ccgm.free.fr & http://sgfr.free.fr) and aims to illustrate the seismic characteristics of the MSC markers over news study areas. The Messinian Salinity Crisis is a huge outstanding succession of events that deeply modified the Mediterranean area within a short time span at the geological scale. In 2011, a seismic atlas of the Messinian markers in the Mediterranean and Black seas has been published [1]. This collective work summarizes, in one publication with a common format, the most relevant seismic features related to this exceptional event in the offshore domain. It also proposes a new global and consistent terminology for the MSC markers in the entire offshore Mediterranean area in order to avoid nomenclatural problems. Throughout 13 study areas, the seismic facies, geometry and extend of the Messinian markers (bounding surfaces and depositional units) are described. The Atlas however does not provide a complete description of all what that is known about the MSC and about the geology of each study area. Accordingly, illustrations in the Atlas should be used for a global description of the offshore imprints of the MSC at a broad scale, or for local information or site-specific general interpretations. Interpreted seismic data were carefully selected according to their quality, position and significance. Raw and interpreted seismic profiles are available on CD-Rom. Volume 2 is currently under preparation with the objectives : (1) to image the Messinian seismic marker from margins and basins that have not been illustrated in the first volume and (2) to complete the extension map of the MSC markers in the offshore and onshore domains at the Mediterranean scale. As the first volume, Volume

Carbonate saturation state of surface waters in the Ross Sea and Southern Ocean: controls and implications for the onset of aragonite undersaturation

NASA Astrophysics Data System (ADS)

DeJong, H. B.; Dunbar, R. B.; Mucciarone, D. A.; Koweek, D.

2016-02-01

Predicting when surface waters of the Ross Sea and Southern Ocean will become undersaturated with respect to biogenic carbonate minerals is challenging in part due to the lack of baseline high resolution carbon system data. Here we present 1700 surface total alkalinity measurements from the Ross Sea and along a transect between the Ross Sea and southern Chile from the austral autumn (February-March 2013). We calculate the saturation state of aragonite (ΩAr) and calcite (ΩCa) using measured total alkalinity and pCO2. In the Ross Sea and south of the Polar Front, variability in carbonate saturation state (Ω) is mainly driven by algal photosynthesis. Freshwater dilution and calcification have minimal influence on Ω variability. We estimate an early spring surface water ΩAr value of 1.2 for the Ross Sea using a total alkalinity-salinity relationship and historical pCO2 measurements. Our results suggest that the Ross Sea is not likely to become undersaturated with respect to aragonite until the year 2070.

An overview of new insights from 6 years of salinity data from SMOS mission

NASA Astrophysics Data System (ADS)

Nicolas, R.

2015-12-01

Measurements of salt held in surface seawater are becoming ever-more important for oceanographers and climatologists to gain a deeper understanding of ocean circulation and Earth's water cycle. ESA's SMOS mission is proving essential for this aim. Launched in 2009, SMOS has provided the longest continuous record (now ~6 years) of sea-surface salinity measurements from space. The salinity of surface seawater is controlled largely by the balance between evaporation and precipitation, but freshwater from rivers and the freezing and melting of ice also cause changes in concentrations. Along with temperature, salinity drives ocean circulation - the thermohaline circulation - which, in turn, plays a key role in the global climate. With a wealth of salinity data from SMOS now in hand complemented by measurements from the NASA-CONAE Aquarius satellite, which uses a different measuring technique. In this talk we shall provide an overview of how the SMOS mission - now celebrating 6 years in orbit - is providing detailed global measurements of SSS. An ensemble of key ocean processes for climate and biochemistry can now be determined and monitored for the first time from space : the detailed salinity structure of tropical instability waves along the equator and the salt exchanged across major oceanic current fronts, the occurrences of large-scale salinity anomalies in the Pacific and Indian oceans related to important climate indexes are also well-evidenced in the six year-long data. In addition, the dispersal of freshwater into the ocean from the major large tropical rivers (Amazon, Orinoco and Congo), their impact on tropical cyclone (TC) intensification and the oceanic imprints of the intense rainfall in the ITCZ and under TC can now be regularly monitored to better understand the variability of the oceanic part of the global water cycle. We will present how SMOS data, along with concurrent in situ Argo ocean-profile data, other satellite observations of sea-surface

A Compact L-band Radiometer for High Resolution sUAS-based Imaging of Soil Moisture and Surface Salinity Variations

NASA Astrophysics Data System (ADS)

Gasiewski, A. J.; Stachura, M.; Dai, E.; Elston, J.; McIntyre, E.; Leuski, V.

2014-12-01

Due to the long electrical wavelengths required along with practical aperture size limitations the scaling of passive microwave remote sensing of soil moisture and salinity from spaceborne low-resolution (~10-100 km) applications to high resolution (~10-1000 m) applications requires use of low flying aerial vehicles. This presentation summarizes the status of a project to develop a commercial small Unmanned Aerial System (sUAS) hosting a microwave radiometer for mapping of soil moisture in precision agriculture and sea surface salinity studies. The project is based on the Tempest electric-powered UAS and a compact L-band (1400-1427 MHz) radiometer developed specifically for extremely small and lightweight aerial platforms or man-portable, tractor, or tower-based applications. Notable in this combination are a highly integrated sUAS/radiometer antenna design and use of both the upwelling emitted signal from the surface and downwelling cold space signal for precise calibration using a unique lobe-differencing correlating radiometer architecture. The system achieves a spatial resolution comparable to the altitude of the UAS above the surface while referencing upwelling measurements to the constant and well-known background temperature of cold space. The radiometer has been tested using analog correlation detection, although future builds will include infrared, near-infrared, and visible (red) sensors for surface temperature and vegetation biomass correction and digital sampling for radio frequency interference mitigation. This NASA-sponsored project is being developed for commercial application in cropland water management (for example, high-value shallow root-zone crops), landslide risk assessment, NASA SMAP satellite validation, and NASA Aquarius salinity stratification studies. The system will ultimately be capable of observing salinity events caused by coastal glacier and estuary fresh water outflow plumes and open ocean rainfall events.

Plant growth under salinity and inundation stress: implications for sea-level rise on tidal wetland function

EPA Science Inventory

Climate change and sea-level rise (SLR) may increase salinity or inundation duration for tidal wetland organisms. To test the effects of these stressors on wetland productivity, we transplanted seedlings of seven common plant species to polyhaline, mesohaline and oligohaline tida...

A new perspective on origin of the East Sea Intermediate Water: Observations of Argo floats

NASA Astrophysics Data System (ADS)

Park, JongJin; Lim, Byunghwan

2018-01-01

The East Sea Intermediate Water (ESIW), defined as the salinity minimum in the East Sea (hereafter ES) (Sea of Japan), is examined with respect to its overall characteristics and its low salinity origin using historical Argo float data from 1999 to 2015. Our findings suggest that the ESIW is formed in the western Japan Basin (40-42°N, 130-133°E), especially west of the North Korean front in North Korean waters, where strong negative surface wind stress curl resides in wintertime. The core ESIW near the formation site has temperatures of 3-4 °C and less than 33.98 psu salinity, warmer and fresher than that in the southern part of the ES. In order to trace the origin of the warmer and fresher water at the sea surface in winter, we analyzed the data in three different ways: (1) spatial distribution of surface water properties using monthly climatology from the Argo float data, (2) seasonal variation of heat and salt contents at the formation site, and (3) backtracking of surface drifter trajectories. Based on these analyses, it is likely that the warmer and fresher surface water properties found in the ESIW formation site are attributed to the low-salinity surface water advected from the southern part of the ES in autumn.

Ecophysiological response of native and exotic salt marsh vegetation to waterlogging and salinity: Implications for the effects of sea-level rise.

PubMed

Li, Shi-Hua; Ge, Zhen-Ming; Xie, Li-Na; Chen, Wei; Yuan, Lin; Wang, Dong-Qi; Li, Xiu-Zhen; Zhang, Li-Quan

2018-02-05

The ecophysiological characteristics of native Phragmites australis and exotic Spartina alterniflora grown under waterlogging and salinity were investigated to explore their adaptation potential to sea level rise. The seasonal course of phenotypic traits, photosynthetic activity and chlorophyll fluorescence parameters of P. australis did not change remarkably under shallow flooding, whereas these variables were sensitive to increasing salinity. Waterlogging exacerbated the negative effects of salinity on shoot growth and photosynthetic activity of P. australis, and the combined stresses led to an absence of tassel and reproductive organs. By contrast, S. alterniflora performed well under both stresses and showed an obvious adaptation of salt secretion with increasing salinity. Light salinity was the optimal condition for S. alterniflora, and the tassel growth, chlorophyll content and fluorescence characters under moderate stresses did not differ notably. The Na + and Cl - concentrations in leaves of both species increased, and the K + content decreased in response to salinity. Under moderate and high saline levels, the ion concentrations in S. alterniflora were maintained at relatively consistent levels with increased salt secretion. We expect the degradation of P. australis and further colonization of S. alterniflora under prolonged flooding and saltwater intrusion from sea level rise on the coastline of China.

The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Satellite observations.

PubMed

Guerrero, Raul A; Piola, Alberto R; Fenco, Harold; Matano, Ricardo P; Combes, Vincent; Chao, Yi; James, Corinne; Palma, Elbio D; Saraceno, Martin; Strub, P Ted

2014-11-01

Satellite-derived sea surface salinity (SSS) data from Aquarius and SMOS are used to study the shelf-open ocean exchanges in the western South Atlantic near 35°S. Away from the tropics, these exchanges cause the largest SSS variability throughout the South Atlantic. The data reveal a well-defined seasonal pattern of SSS during the analyzed period and of the location of the export of low-salinity shelf waters. In spring and summer, low-salinity waters over the shelf expand offshore and are transferred to the open ocean primarily southeast of the river mouth (from 36°S to 37°30'S). In contrast, in fall and winter, low-salinity waters extend along a coastal plume and the export path to the open ocean distributes along the offshore edge of the plume. The strong seasonal SSS pattern is modulated by the seasonality of the along-shelf component of the wind stress over the shelf. However, the combined analysis of SSS, satellite-derived sea surface elevation and surface velocity data suggest that the precise location of the export of shelf waters depends on offshore circulation patterns, such as the location of the Brazil Malvinas Confluence and mesoscale eddies and meanders of the Brazil Current. The satellite data indicate that in summer, mixtures of low-salinity shelf waters are swiftly driven toward the ocean interior along the axis of the Brazil/Malvinas Confluence. In winter, episodic wind reversals force the low-salinity coastal plume offshore where they mix with tropical waters within the Brazil Current and create a warmer variety of low-salinity waters in the open ocean. Satellite salinity sensors capture low-salinity detrainment events from shelves SW Atlantic low-salinity detrainments cause highest basin-scale variability In summer low-salinity detrainments cause extended low-salinity anomalies.

The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Satellite observations

PubMed Central

Guerrero, Raul A; Piola, Alberto R; Fenco, Harold; Matano, Ricardo P; Combes, Vincent; Chao, Yi; James, Corinne; Palma, Elbio D; Saraceno, Martin; Strub, P Ted

2014-01-01

Satellite-derived sea surface salinity (SSS) data from Aquarius and SMOS are used to study the shelf-open ocean exchanges in the western South Atlantic near 35°S. Away from the tropics, these exchanges cause the largest SSS variability throughout the South Atlantic. The data reveal a well-defined seasonal pattern of SSS during the analyzed period and of the location of the export of low-salinity shelf waters. In spring and summer, low-salinity waters over the shelf expand offshore and are transferred to the open ocean primarily southeast of the river mouth (from 36°S to 37°30′S). In contrast, in fall and winter, low-salinity waters extend along a coastal plume and the export path to the open ocean distributes along the offshore edge of the plume. The strong seasonal SSS pattern is modulated by the seasonality of the along-shelf component of the wind stress over the shelf. However, the combined analysis of SSS, satellite-derived sea surface elevation and surface velocity data suggest that the precise location of the export of shelf waters depends on offshore circulation patterns, such as the location of the Brazil Malvinas Confluence and mesoscale eddies and meanders of the Brazil Current. The satellite data indicate that in summer, mixtures of low-salinity shelf waters are swiftly driven toward the ocean interior along the axis of the Brazil/Malvinas Confluence. In winter, episodic wind reversals force the low-salinity coastal plume offshore where they mix with tropical waters within the Brazil Current and create a warmer variety of low-salinity waters in the open ocean. Key Points Satellite salinity sensors capture low-salinity detrainment events from shelves SW Atlantic low-salinity detrainments cause highest basin-scale variability In summer low-salinity detrainments cause extended low-salinity anomalies PMID:26213672

The Bay of Bengal : an ideal laboratory for studying salinity

NASA Astrophysics Data System (ADS)

Vialard, jerome; Lengaigne, Matthieu; Akhil, Valiya; Chaitanya, Akurathi; Krishna-Mohan, Krishna; D'Ovidio, Francesco; Keerthi, Madhavan; Benshila, Rachid; Durand, Fabien; Papa, Fabrice; Suresh, Iyappan; Neetu, Singh

2017-04-01

The Bay of Bengal combines several unique features that make it an excellent laboratory to study the variability of salinity and its potential effects on the oceanic circulation and climate. This basin receives very large quantities of freshwater in association to the southwest monsoon, either directly from rain or indirectly through the runoffs of the Ganges-Brahmaputra and Irrawaddy. This large quantity of freshwater in a small, semi enclosed basin results in some of the lowest sea surface salinities (SSS) and strongest near-surface haline stratification in the tropical band. The strong monsoon winds also drive an energetic circulation, which exports the excess water received during the monsoon and results in strong horizontal salinity gradients. In this talk, I will summarize several studies of the Bay of Bengal salinity variability and its impacts undertaken in the context of an Indo-French collaboration. In situ data collected along the coast by fishermen and model results show that the intense, coastally-trapped East India Coastal Current (EICC) transports the very fresh water near the Ganges-Brahmaputra river mouth along the eastern Bay of Bengal rim to create a narrow, very fresh "river in the sea" after the southwest monsoon. The salinity-induced pressure gradient contributes to almost 50% of the EICC intensity and sustains mesoscale eddy generation through its effect on horizontal current shears and baroclinic gradients. Oceanic eddies play a strong role in exporting this fresh water from the coast to the basin interior. This "river in the sea" has a strong interannual variability related to the EICC remote modulation by the Indian Ocean Dipole (a regional climate mode). I will also discuss the potential effect of haline stratification on the regional climate through its influence on the upper ocean budget. Finally, I will briefly discuss the performance of remote-sensing for observing SSS in the Bay of Bengal.

Hydrogen sulfide production and volatilization in a polymictic eutrophic saline lake, Salton Sea, California.

PubMed

Reese, Brandi Kiel; Anderson, Michael A; Amrhein, Christopher

2008-11-15

The Salton Sea is a large shallow saline lake located in southern California that is noted for high sulfate concentrations, substantial algal productivity, and very warm water column temperatures. These conditions are well-suited for sulfide production, and sulfide has been implicated in summer fish kills, although no studies have been conducted to specifically understand hydrogen sulfide production and volatilization there. Despite polymictic mixing patterns and relatively short accumulation periods, the amount of sulfide produced is comparable to meromictic lakes. Sulfide levels in the Salton Sea reached concentrations of 1.2 mmol L(-1) of total free sulfide in the hypolimnion and 5.6 mmol L(-1) in the sediment pore water. Strong winds in late July mixed H2S into the surface water, where it depleted the entire water column of dissolved oxygen and reached a concentration of 0.1 mmol L(-1). Sulfide concentrations exceeded the toxicity threshold of tilapia (Oreochromis mossambicus) and combined with strong anoxia throughout the water column, resulted in a massive fish kill. The mixing of sulfide into the surface waters also increased atmospheric H2S concentrations, reaching 1.0 micromol m(-3). The flux of sulfide from the sediment into the water column was estimated to range from 2-3 mmol m(-2) day(-1) during the winter and up to 8 mmol m(-2) day(-1) during the summer. Application of the two-layer model for volatilization indicates that up to 19 mmol m(-2) day(-1) volatilized from the surface during the mixing event. We estimate that as much as 3400 Mg year(-1) or approximately 26% of sulfide that diffused into the water column from the deepest sediments may have been volatilized to the atmosphere.

Reconstructing Holocene temperature and salinity variations in the western Baltic Sea region: a multi-proxy comparison from the Little Belt (IODP Expedition 347, Site M0059)

NASA Astrophysics Data System (ADS)

Kotthoff, Ulrich; Groeneveld, Jeroen; Ash, Jeanine L.; Fanget, Anne-Sophie; Quintana Krupinski, Nadine; Peyron, Odile; Stepanova, Anna; Warnock, Jonathan; Van Helmond, Niels A. G. M.; Passey, Benjamin H.; Rønø Clausen, Ole; Bennike, Ole; Andrén, Elinor; Granoszewski, Wojciech; Andrén, Thomas; Filipsson, Helena L.; Seidenkrantz, Marit-Solveig; Slomp, Caroline P.; Bauersachs, Thorsten

2017-12-01

Sediment records recovered from the Baltic Sea during Integrated Ocean Drilling Program Expedition 347 provide a unique opportunity to study paleoenvironmental and climate change in central and northern Europe. Such studies contribute to a better understanding of how environmental parameters change in continental shelf seas and enclosed basins. Here we present a multi-proxy-based reconstruction of paleotemperature (both marine and terrestrial), paleosalinity, and paleoecosystem changes from the Little Belt (Site M0059) over the past ˜ 8000 years and evaluate the applicability of inorganic- and organic-based proxies in this particular setting. All salinity proxies (diatoms, aquatic palynomorphs, ostracods, diol index) show that lacustrine conditions occurred in the Little Belt until ˜ 7400 cal yr BP. A connection to the Kattegat at this time can thus be excluded, but a direct connection to the Baltic Proper may have existed. The transition to the brackish-marine conditions of the Littorina Sea stage (more saline and warmer) occurred within ˜ 200 years when the connection to the Kattegat became established after ˜ 7400 cal yr BP. The different salinity proxies used here generally show similar trends in relative changes in salinity, but often do not allow quantitative estimates of salinity. The reconstruction of water temperatures is associated with particularly large uncertainties and variations in absolute values by up to 8 °C for bottom waters and up to 16 °C for surface waters. Concerning the reconstruction of temperature using foraminiferal Mg  /  Ca ratios, contamination by authigenic coatings in the deeper intervals may have led to an overestimation of temperatures. Differences in results based on the lipid paleothermometers (long chain diol index and TEXL86) can partly be explained by the application of modern-day proxy calibrations to intervals that experienced significant changes in depositional settings: in the case of our study, the

Erosion of continental margins in the Western Mediterranean due to sea-level stagnancy during the Messinian Salinity Crisis

NASA Astrophysics Data System (ADS)

Just, Janna; Hübscher, Christian; Betzler, Christian; Lüdmann, Thomas; Reicherter, Klaus

2011-02-01

High-resolution multi-channel seismic data from continental slopes with minor sediment input off southwest Mallorca Island, the Bay of Oran (Algeria) and the Alboran Ridge reveal evidence that the Messinian erosional surface is terraced at an almost constant depth interval between 320 and 380 m below present-day sea level. It is proposed that these several hundred- to 2,000-m-wide terraces were eroded contemporaneously and essentially at the same depth. Present-day differences in these depths result from subsidence or uplift in the individual realms. The terraces are thought to have evolved during one or multiple periods of sea-level stagnancy in the Western Mediterranean Basin. According to several published scenarios, a single or multiple periods of relative sea-level stillstand occurred during the Messinian desiccation event, generally known as the Messinian Salinity Crisis. Some authors suggest that the stagnancy started during the refilling phase of the Mediterranean basins. When the rising sea level reached the height of the Sicily Sill, the water spilled over this swell into the eastern basin. The stagnancy persisted until sea level in the eastern basin caught up with the western Mediterranean water level. Other authors assigned periods of sea-level stagnancy to drawdown phases, when inflowing waters from the Atlantic kept the western sea level constant at the depth of the Sicily Sill. Our findings corroborate all those Messinian sea-level reconstructions, forwarding that a single or multiple sea-level stagnancies at the depth of the Sicily Sill lasted long enough to significantly erode the upper slope. Our data also have implications for the ongoing debate of the palaeo-depth of the Sicily Sill. Since the Mallorcan plateau experienced the least vertical movement, the observed terrace depth of 380 m there is inferred to be close to the Messinian depth of this swell.

Features of Red Sea Water Masses

NASA Astrophysics Data System (ADS)

Kartadikaria, Aditya; Hoteit, Ibrahim

2015-04-01

Features of Red Sea water mass can be divided into three types but best to be grouped into two different classes that are split at the potential density line σθ=27.4. The surface water (0-50 m) and the intermediate water (50-200 m) have nearly identical types of water mass. They appear as a maxima salinity layer for the water mass that has σθ > 26.0, and as a minimum salinity layer for water mass that has σθ < 26.0. These types of water masses are strongly affected by mixing that is controlled by seasonal variability, fresh water intrusion of the Gulf of Aden Intermediate Water (GAIW), and eddies variability. Two types of mixing; isopycnal and diapycnal mixing are part of important physical phenomena that explain the change of water mass in the Red Sea. The isopycnal mixing occurs at the neutral potential density line, connecting the Red Sea with its adjacent channel, the Gulf of Aden. Diapycnal mixing is found as a dominant mixing mode in the surface of the Red Sea Water and mainly due to energetic eddy activity. Density gradients, across which diapycnal mixing occurs, in the Red Sea are mainly due to large variations in salinity. The isolation of an extreme haline water mass below the thermocline contributes to the generation of the latitudinal shift and low diapycnal mixing. This finding further explains the difference of spatial kinetic mixing between the RSW and the Indian Ocean basin.

The Impact of Salinity on the Seasonal and Interannual Variability of the Upper Ocean Structure and Air/Sea Interaction in the South Eastern Tropical Indian Ocean

NASA Astrophysics Data System (ADS)

Soares, S. M.; Richards, K. J.; Annamalai, H.; Natarov, A.

2016-02-01

The Seychelles-Chagos thermocline ridge (SCRT) in the south-eastern tropical Indian Ocean is believed to play an important role on air/sea interactions at monsoonal and intraseasonal timescales. Large gains in predictability of monsoon and intraseasonal variability may result from studying the mechanisms of ocean feedback to the atmosphere in the SCRT region. ARGO data from 2005-2014 show a marked salinity and temperature annual cycle, where mixed layer waters are freshest and warmest around February-March and saltiest and coldest around July-August in the eastern side of the SCRT. An analysis of the mixed-layer salt budget using a mix of observational gridded products and a coupled model shows that: i) surface freshwater fluxes do not play a significant role on the SCRT salinity annual cycle, ii) the freshening during austral Spring is primarily driven by zonal advection of the large pool of less saline waters off the coast of southeast Asia and bay of Bengal, while meridional advection accounts for a large fraction of the salting during Fall. The largest interannual anomalies in the ARGO salinity record occur in the aftermath of the negative Indian Ocean Dipole events of 2005 and 2010, when February mixed layer freshening was much reduced. The appearance of the fresher waters were evident in the DYNAMO/CINDY data collected in the area during Spring 2011 following the passage of a downwelling Rossby wave. Lagrangian parcel tracking indicates a variety of sources for these fresher waters, but generally agrees with the ARGO results above. The fresh surface layer had a significant impact on the measured turbulence and mixing and may have impacted the development of Madden-Julien Oscillation events observed during DYNAMO/CINDY. Given these findings, we examine in detail the suite of DYNAMO observations, combining them with numerical modeling experiments to determine the role of eddy fluxes and vertical processes on the formation of these freshwater layers, as well as

Adaptation to different salinities exposes functional specialization in the intestine of the sea bream (Sparus aurata L.).

PubMed

Gregório, Sílvia F; Carvalho, Edison S M; Encarnação, Sandra; Wilson, Jonathan M; Power, Deborah M; Canário, Adelino V M; Fuentes, Juan

2013-02-01

The processing of intestinal fluid, in addition to a high drinking rate, is essential for osmoregulation in marine fish. This study analyzed the long-term response of the sea bream (Sparus aurata L.) to relevant changes of external salinity (12, 35 and 55 p.p.t.), focusing on the anterior intestine and in the less-often studied rectum. Intestinal water absorption, epithelial HCO(3)(-) secretion and gene expression of the main molecular mechanisms (SLC26a6, SLC26a3, SLC4a4, atp6v1b, CFTR, NKCC1 and NKCC2) involved in Cl(-) and HCO(3)(-) movements were examined. The anion transporters SLC26a6 and SLC26a3 are expressed severalfold higher in the anterior intestine, while the expression of Atp6v1b (V-type H(+)-ATPase β-subunit) is severalfold higher in the rectum. Prolonged exposure to altered external salinity was without effect on water absorption but was associated with concomitant changes in intestinal fluid content, epithelial HCO(3)(-) secretion and salinity-dependent expression of SLC26a6, SLC26a3 and SLC4a4 in the anterior intestine. However, the most striking response to external salinity was obtained in the rectum, where a 4- to 5-fold increase in water absorption was paralleled by a 2- to 3-fold increase in HCO(3)(-) secretion in response to a salinity of 55 p.p.t. In addition, the rectum of high salinity-acclimated fish shows a sustained (and enhanced) secretory current (I(sc)), identified in vitro in Ussing chambers and confirmed by the higher expression of CFTR and NKCC1 and by immunohistochemical protein localization. Taken together, the present results suggest a functional anterior-posterior specialization with regard to intestinal fluid processing and subsequently to salinity adaptation of the sea bream. The rectum becomes more active at higher salinities and functions as the final controller of intestinal function in osmoregulation.

Effects of Sea-Surface Waves and Ocean Spray on Air-Sea Momentum Fluxes

NASA Astrophysics Data System (ADS)

Zhang, Ting; Song, Jinbao

2018-04-01

The effects of sea-surface waves and ocean spray on the marine atmospheric boundary layer (MABL) at different wind speeds and wave ages were investigated. An MABL model was developed that introduces a wave-induced component and spray force to the total surface stress. The theoretical model solution was determined assuming the eddy viscosity coefficient varied linearly with height above the sea surface. The wave-induced component was evaluated using a directional wave spectrum and growth rate. Spray force was described using interactions between ocean-spray droplets and wind-velocity shear. Wind profiles and sea-surface drag coefficients were calculated for low to high wind speeds for wind-generated sea at different wave ages to examine surface-wave and ocean-spray effects on MABL momentum distribution. The theoretical solutions were compared with model solutions neglecting wave-induced stress and/or spray stress. Surface waves strongly affected near-surface wind profiles and sea-surface drag coefficients at low to moderate wind speeds. Drag coefficients and near-surface wind speeds were lower for young than for old waves. At high wind speeds, ocean-spray droplets produced by wind-tearing breaking-wave crests affected the MABL strongly in comparison with surface waves, implying that wave age affects the MABL only negligibly. Low drag coefficients at high wind caused by ocean-spray production increased turbulent stress in the sea-spray generation layer, accelerating near-sea-surface wind. Comparing the analytical drag coefficient values with laboratory measurements and field observations indicated that surface waves and ocean spray significantly affect the MABL at different wind speeds and wave ages.

Remote Sensing of Salinity and Overview of Results from Aquarius

NASA Technical Reports Server (NTRS)

Le Vine, D. M.; Dinnat, E. P.; Meissner, T.; Wentz, F.; Yueh, S. H.; Lagerloef, G. S. E.

2015-01-01

Aquarius is a combined active/passive microwave (L-band) instrument designed to map the salinity of global oceans from space. The specific goal of Aquarius is to monitor the seasonal and interannual variation of the large scale features of the sea surface salinity (SSS) field of the open ocean (i.e. away from land). The instrumentation has been designed to provide monthly maps with a spatial resolution of 150 km and an accuracy of 0.2 psu

A 20-year collection of sub-surface salinity and temperature observations for the Australian shelf seas

NASA Astrophysics Data System (ADS)

Proctor, R.; Mancini, S.; Hoenner, X.; Tattersall, K.; Pasquer, B.; Galibert, G.; Moltmann, T.

2016-02-01

Salinity and temperature measurements from different sources have been assembled into a common data structure in a relational database. Quality Control flags have been mapped to a common scheme and associated to each measurement. For datasets like gliders, moorings or ship underway which are sampled at high temporal resolution (e.g. data every second) a binning and sub-sampling approach has been applied to some datasets in order to reduce the number of measurements to hourly sampling. After averaging approximately 25 Million measurements are available in this dataset collection. A national shelf and coastal data atlas has been created using all the temperature and salinity measurements that pass various quality control checks. These observations have been binned spatially on a horizontal grid of ¼ degree with standard vertical levels (every 10 meters from the surface to 500m depth) and temporally on a monthly time range over the period January 1995 to December 2014. The number of observations in each bin has been determined and additional statistics, the mean, the standard deviation, minimum and maximum values, have been calculated, enabling a degree of uncertainty to be associated with any measurement. The data atlas is available as a Web Feature Service.

Effects of temperature and salinity on the growth of Alexandrium (Dinophyceae) isolates from the Salish Sea

PubMed Central

Bill, Brian D.; Moore, Stephanie K.; Hay, Levi R.; Anderson, Donald M.; Trainer, Vera L.

2016-01-01

Toxin-producing blooms of dinoflagellates in the genus Alexandrium have plagued the inhabitants of the Salish Sea for centuries. Yet the environmental conditions that promote accelerated growth of this organism, a producer of paralytic shellfish toxins, is lacking. This study quantitatively determined the growth response of two Alexandrium isolates to a range of temperatures and salinities, factors that will strongly respond to future climate change scenarios. An empirical equation, derived from observed growth rates describing the temperature and salinity dependence of growth, was used to hindcast bloom risk. Hindcasting was achieved by comparing predicted growth rates, calculated from in situ temperature and salinity data from Quartermaster Harbor, with corresponding Alexandrium cell counts and shellfish toxin data. The greatest bloom risk, defined at μ>0.25 d−1, generally occurred from April through November annually; however, growth rates rarely fell below 0.10 d−1. Except for a few occasions, Alexandrium cells were only observed during the periods of highest bloom risk and paralytic shellfish toxins above the regulatory limit always fell within the periods of predicted bloom occurrence. While acknowledging that Alexandrium growth rates are affected by other abiotic and biotic factors, such as grazing pressure and nutrient availability, the use of this empirical growth function to predict higher risk time frames for blooms and toxic shellfish within the Salish Sea provides the groundwork for a more comprehensive biological model of Alexandrium bloom dynamics in the region and will enhance our ability to forecast blooms in the Salish Sea under future climate change scenarios. PMID:27037588

Describing River Plume Interactions in the Northern Adriatic Sea Using High Resolution Satellite Turbidity And Sea Surface Temperature Observations

NASA Astrophysics Data System (ADS)

Brando, V. E.; Braga, F.; Zaggia, L.; Carniel, S.

2016-02-01

Sea surface temperature (SST) and turbidity (T) derived from Landsat-8 (L8) imagery were used to characterize river plumes in the Northern Adriatic Sea (NAS). Sea surface salinity (SSS) from an operational coupled ocean-wave model supported the interpretation of the plumes interaction with the receiving waters and among them. In this study we used L8 OLI and TIRS imagery of 19 November 2014 capturing a significant freshwater inflow into the NAS for mapping both T and SST at 30 meters resolution. Sharp fronts in T and SST delimited each single river plume. The isotherms and turbidity isolines coupling varied among the plumes due to differences in particle loads and surface temperatures in the discharged waters. Overall, there was a good agreement of the SSS, T, and SST fields at the mesoscale delineation of the major river plumes. Landsat-8 30m resolution enabled the identification of smaller plume structures and the description at small scale and sub-mesoscale of the plume dynamical regions for all plume structures, as well as their interactions in the NAS. Although this study presents data captured with a sensor having a revisiting time of 16 days, we expect that with the recent launch of ESA's Sentinel 2A and the forthcoming launch of Sentinel 2B the temporal resolution will increase reaching almost the 1-3 days revisit time normally associated with Ocean Colour Radiometry (OCR). Combined with their radiometric resolution similar to OCR missions, these developments will thus offer an opportunity to also describe the temporal evolution of plume structures at the sub-mesoscale.

Holocene oscillations in temperature and salinity of the surface subpolar North Atlantic.

PubMed

Thornalley, David J R; Elderfield, Harry; McCave, I Nick

2009-02-05

The Atlantic meridional overturning circulation (AMOC) transports warm salty surface waters to high latitudes, where they cool, sink and return southwards at depth. Through its attendant meridional heat transport, the AMOC helps maintain a warm northwestern European climate, and acts as a control on the global climate. Past climate fluctuations during the Holocene epoch ( approximately 11,700 years ago to the present) have been linked with changes in North Atlantic Ocean circulation. The behaviour of the surface flowing salty water that helped drive overturning during past climatic changes is, however, not well known. Here we investigate the temperature and salinity changes of a substantial surface inflow to a region of deep-water formation throughout the Holocene. We find that the inflow has undergone millennial-scale variations in temperature and salinity ( approximately 3.5 degrees C and approximately 1.5 practical salinity units, respectively) most probably controlled by subpolar gyre dynamics. The temperature and salinity variations correlate with previously reported periods of rapid climate change. The inflow becomes more saline during enhanced freshwater flux to the subpolar North Atlantic. Model studies predict a weakening of AMOC in response to enhanced Arctic freshwater fluxes, although the inflow can compensate on decadal timescales by becoming more saline. Our data suggest that such a negative feedback mechanism may have operated during past intervals of climate change.

Sea surface temperature measurements with AIRS

NASA Technical Reports Server (NTRS)

Aumann, H.

2003-01-01

The comparison of global sea surface skin temperature derived from cloud-free AIRS super window channel at 2616 cm-1 (sst2616) with the Real-Time Global Sea Surface Temperature for September 2002 shows surprisingly small standard deviation of 0.44K.

Quantitative determination of the salinity of seawater droplet in 10-6 to 10-10 gram

NASA Astrophysics Data System (ADS)

Qian, Zhengxu; Peng, Fangying

1990-09-01

The rate of evaporation of seawater droplets in the air-sea boundary layer can be estimated by its salinity change compared to the sea surface salinity. A micro-chemical method based on Farlow (1954) is developed for quantitative determination of the salinity of an individual droplet without the error due to further evaporation after sampling. A halide ion-sensitive sampling surface is prepared by colloidally dispersing brown silver dichromate into the gelatin layer of a commercially available film. The reaction of soluble chlorides with the silver salt leaves a clear white halo with diameter a on the brown film to reveal the volume of the droplet. After the film is developed in a water vapor saturated atmosphere, the halo grows to diameter d with the original as the embryo to indicate the quantity of chloride ion involved in the action. The ratio of d/(a1.5) is a function of the salinity of the droplet. The method can be used to determine the salinity of seawater droplet of 10-6 to 10-10 gram. Details of the principle and preparation, and calibration of the reagent film, are presented.

The salinity, temperature, and delta18O of the glacial deep ocean.

PubMed

Adkins, Jess F; McIntyre, Katherine; Schrag, Daniel P

2002-11-29

We use pore fluid measurements of the chloride concentration and the oxygen isotopic composition from Ocean Drilling Program cores to reconstruct salinity and temperature of the deep ocean during the Last Glacial Maximum (LGM). Our data show that the temperatures of the deep Pacific, Southern, and Atlantic oceans during the LGM were relatively homogeneous and within error of the freezing point of seawater at the ocean's surface. Our chloride data show that the glacial stratification was dominated by salinity variations, in contrast with the modern ocean, for which temperature plays a primary role. During the LGM the Southern Ocean contained the saltiest water in the deep ocean. This reversal of the modern salinity contrast between the North and South Atlantic implies that the freshwater budget at the poles must have been quite different. A strict conversion of mean salinity at the LGM to equivalent sea-level change yields a value in excess of 140 meters. However, the storage of fresh water in ice shelves and/or groundwater reserves implies that glacial salinity is a poor predictor of mean sea level.

The Impact of Sea Surface Temperature Front on Stratus-Sea Fog over the Yellow and East China Seas

NASA Astrophysics Data System (ADS)

Zhang, S.; Li, M.; Liu, F.

2013-12-01

A stratus-sea fog event occurred on 3 June 2011 over the Yellow and East China Seas (as shown in figure) is investigated observationally and numerically. Emphasis is put on the influences of the sea surface temperature front (SSTF) and of the synoptic circulations on the transition of stratus to sea fog. The southerly winds from a synoptic high pressure transport water vapor from the East China Sea to the Yellow Sea, while the subsidence induced by the high contributes to the formation of the temperature inversion on the top of the stratus or stratocumulus that appears mainly over the warm flank of a sea surface temperature front in the East China Sea. Forced by the SSTF, there is a secondary cell within the atmospheric boundary layer (ABL), with a sinking branch on the cold flank and a rising one on the warm flank of the SSTF. This sinking branch, in phase with the synoptic subsidence, forces the stratus or stratocumulus to lower in the elevation getting close to the sea surface as these clouds move northward driven by the southerly winds. The cloud droplets can either reach to the sea surface directly or evaporate into water vapor that may condense again when coming close to the cold sea surface to form fog. In this later case, the stratus and fog may separate. The cooling effect of cold sea surface counteracts the adiabatic heating induced by the subsidence and thus helps the transition of stratus to sea fog in the southern Yellow Sea. By smoothing the SSTF in the numerical experiment, the secondary cell weakens and the sea fog patches shrink obviously over the cold flank of the SSTF though the synoptic subsidence and moist advection still exist. A conceptual model is suggested for the transition of stratus to sea fog in the Yellow and East China Seas, which is helpful for the forecast of sea fog over these areas. The satellite visible image of the stratus-fog event. The fog appears in the Yellow Sea and the stratocumulus in the East China Sea.

Sea Ice Formation Rate and Temporal Variation of Temperature and Salinity at the Vicinity of Wilkins Ice Shelf from Data Collected by Southern Elephant Seals in 2008

NASA Astrophysics Data System (ADS)

Santini, M. F.; Souza, R.; Wainer, I.; Muelbert, M.; Hindell, M.

2013-05-01

The use of marine mammals as autonomous platforms for collecting oceanographic data has revolutionized the understanding of physical properties of low or non-sampled regions of the polar oceans. The use of these animals became possible due to advancements in the development of electronic devices, sensors and batteries carried by them. Oceanographic data collected by two southern elephant seals (Mirounga leonina) during the Fall of 2008 were used to infer the sea-ice formation rate in the region adjacent to the Wilkins Ice Shelf, west of the Antarctic Peninsula at that period. The sea-ice formation rate was estimated from the salt balance equation for the upper (100 m) ocean at a daily frequency for the period between 13 February and 20 June 2008. The oceanographic data collected by the animals were also used to present the temporal variation of the water temperature and salinity from surface to 300 m depth in the study area. Sea ice formation rate ranged between 0,087 m/day in early April and 0,008 m/day in late June. Temperature and salinity ranged from -1.84°C to 1.60°C and 32.85 to 34.85, respectively, for the upper 300 m of the water column in the analyzed period. The sea-ice formation rate estimations do not consider water advection, only temporal changes of the vertical profile of salinity. This may cause underestimates of the real sea-ice formation rate. The intense reduction of sea ice rate formation from April to June 2008 may be related to the intrusion of the Circumpolar Depth Water (CDW) into the study region. As a consequence of that we believe that this process can be partly responsible for the disintegration of the Wilkins Ice Shelf during the winter of 2008. The data presented here are considered a new frontier in physical and biological oceanography, providing a new approach for monitoring sea ice changes and oceanographic conditions in polar oceans. This is especially valid for regions covered by sea ice where traditional instruments deployed by

Responses to salinity in invasive cordgrass hybrids and their parental species (Spartina) in a scenario of sea level rise and climate change

USDA-ARS?s Scientific Manuscript database

Background/Question/Methods: Salinity is one of the main abiotic factors in salt marshes. Studies rooted to analyzed salinity tolerance of halophytes may help to relate their physiological tolerances with distribution limits in the field. Climate change-induced sea level rise and higher temperatures...

Wind-sea surface temperature-sea ice relationship in the Chukchi-Beaufort Seas during autumn

NASA Astrophysics Data System (ADS)

Zhang, Jing; Stegall, Steve T.; Zhang, Xiangdong

2018-03-01

Dramatic climate changes, especially the largest sea ice retreat during September and October, in the Chukchi-Beaufort Seas could be a consequence of, and further enhance, complex air-ice-sea interactions. To detect these interaction signals, statistical relationships between surface wind speed, sea surface temperature (SST), and sea ice concentration (SIC) were analyzed. The results show a negative correlation between wind speed and SIC. The relationships between wind speed and SST are complicated by the presence of sea ice, with a negative correlation over open water but a positive correlation in sea ice dominated areas. The examination of spatial structures indicates that wind speed tends to increase when approaching the ice edge from open water and the area fully covered by sea ice. The anomalous downward radiation and thermal advection, as well as their regional distribution, play important roles in shaping these relationships, though wind-driven sub-grid scale boundary layer processes may also have contributions. Considering the feedback loop involved in the wind-SST-SIC relationships, climate model experiments would be required to further untangle the underlying complex physical processes.

The relationship among sea surface roughness variations, oceanographic analyses, and airborne remote sensing analyses

NASA Technical Reports Server (NTRS)

Oertel, G. F.; Wade, T. L.

1981-01-01

The synthetic aperture radar (SAR) was studied to determine whether it could image large scale estuaries and oceanic features such as fronts and to explain the electromagnetic interaction between SAR and the individual surface front features. Fronts were observed to occur at the entrance to the Chesapeake Bay. The airborne measurements consisted of data collection by SAR onboard an F-4 aircraft and real aperture side looking radar (SLAR) in Mohawk aircraft. A total of 89 transects were flown. Surface roughness and color as well as temperature and salinity were evaluated. Cross-frontal surveys were made. Frontal shear and convergence flow were obtained. Surface active organic materials, it was indicated, are present at the air-sea interface. In all, 2000 analyses were conducted to characterize the spatial and temporal variabilities associated with water mass boundaries.

Coupled sea surface temperature-seawater δ18O reconstructions in the Arabian Sea at the millennial scale for the last 35 ka

NASA Astrophysics Data System (ADS)

Anand, Pallavi; Kroon, Dick; Singh, Arun Deo; Ganeshram, Raja S.; Ganssen, Gerald; Elderfield, Henry

2008-12-01

Two sediment cores from the western (905; 10.46°9'N, 51.56°4'E, water depth 1586 m) and eastern (SK17; 15°15'N, 72°58'E, water depth 840 m) Arabian Sea were used to study past sea surface temperatures (SST) and seawater δ18O (δ18Ow) variations for the past 35 ka. We used coupled Mg/Ca-δ18O calcite variability in two planktonic foraminiferal species: Globigerinoides ruber, which thrives throughout the year, and Globigerina bulloides, which occurs mainly when surface waters contain high nutrients during upwelling or convective mixing. SSTs in both areas based on Mg/Ca in G. ruber were ˜3 to 4°C lower during the Last Glacial Maximum (LGM; ˜21 ka) than today and the Holocene period. The SST records based on G. bulloides also indicate general cooling, down to 18°C in both areas. SSTs in the western Arabian Sea based on G. bulloides were always lower than those based on G. ruber, indicating the presence of strong seasonal temperature contrast during the Holocene and LGM. We interpret the consistent presence of this seasonal temperature contrast to reflect a combination of seasonal summer upwelling (SW monsoon) and winter convective mixing (NE monsoon) in the western Arabian Sea. In the eastern Arabian Sea, G. bulloides-based SSTs were slightly lower (about 1°C) than G. ruber-based SSTs during the Holocene, indicating the almost absence of a seasonal temperature gradient, similar to today. However, a large seasonal temperature contrast occurred during the LGM which favors the assumption that strong NE monsoon winds forced winter upwelling or convective mixing offshore Goa. SST and δ18Ow reconstructions reveal evidence of millennial-scale cycles, particularly in the eastern Arabian Sea. Here, the stadial periods (Northern Hemisphere cold periods such as Younger Dryas and Heinrich events) are marked by increasing SSTs and salty sea surface conditions relative to those during the interstadial periods. Indeed, the δ18Ow record shows evidence of low-saline

Near-surface Salinity and Temperature structure Observed with Dual-Sensor Drifters in the Subtropical South Pacific

NASA Astrophysics Data System (ADS)

Dong, S.; Volkov, D.; Goni, G. J.; Lumpkin, R.; Foltz, G. R.

2017-12-01

Three surface drifters equipped with temperature and salinity sensors at 0.2 m and 5 m depths were deployed in April/May 2015 in the subtropical South Pacific with the objective of measuring near-surface salinity differences seen by satellite and in situ sensors and examining the causes of these differences. Measurements from these drifters indicate that water at a depth of 0.2 m is about 0.013 psu fresher than at 5 m and about 0.024°C warmer. Events with large temperature and salinity differences between the two depths are caused by anomalies in surface freshwater and heat fluxes, modulated by wind. While surface freshening and cooling occurs during rainfall events, surface salinification is generally observed under weak wind conditions (≤4 m/s). Further examination of the drifter measurements demonstrates that (i) the amount of surface freshening and strength of the vertical salinity gradient heavily depend on wind speed during rain events, (ii) salinity differences between 0.2 m and 5 m are positively correlated with the corresponding temperature differences for cases with surface salinification, and (iii) temperature exhibits a diurnal cycle at both depths, whereas the diurnal cycle of salinity is observed only at 0.2 m when the wind speed is less than 6 m/s. The amplitudes of the diurnal cycles of temperature at both depths decrease with increasing wind speed. The mean diurnal cycle of surface salinity is dominated by events with winds less than 2 m/s.

Near-surface salinity and temperature structure observed with dual-sensor drifters in the subtropical South Pacific

NASA Astrophysics Data System (ADS)

Dong, Shenfu; Volkov, Denis; Goni, Gustavo; Lumpkin, Rick; Foltz, Gregory R.

2017-07-01

Three surface drifters equipped with temperature and salinity sensors at 0.2 and 5 m depths were deployed in April/May 2015 in the subtropical South Pacific with the objective of measuring near-surface salinity differences seen by satellite and in situ sensors and examining the causes of these differences. Measurements from these drifters indicate that water at a depth of 0.2 m is about 0.013 psu fresher than at 5 m and about 0.024°C warmer. Events with large temperature and salinity differences between the two depths are caused by anomalies in surface freshwater and heat fluxes, modulated by wind. While surface freshening and cooling occurs during rainfall events, surface salinification is generally observed under weak wind conditions (≤4 m/s). Further examination of the drifter measurements demonstrates that (i) the amount of surface freshening and strength of the vertical salinity gradient heavily depend on wind speed during rain events, (ii) salinity differences between 0.2 and 5 m are positively correlated with the corresponding temperature differences for cases with surface salinification, and (iii) temperature exhibits a diurnal cycle at both depths, whereas the diurnal cycle of salinity is observed only at 0.2 m when the wind speed is less than 6 m/s. The amplitudes of the diurnal cycles of temperature at both depths decrease with increasing wind speed. The mean diurnal cycle of surface salinity is dominated by events with winds less than 2 m/s.

Drivers of Antarctic sea-ice expansion and Southern Ocean surface cooling over the past four decades

NASA Astrophysics Data System (ADS)

Purich, Ariaan; England, Matthew

2017-04-01

Despite global warming, total Antarctic sea-ice coverage has increased overall during the past four decades. In contrast, the majority of CMIP5 models simulate a decline. In addition, Southern Ocean surface waters have largely cooled, in stark contrast to almost all historical CMIP5 simulations. Subantarctic Surface Waters have cooled and freshened while waters to the north of the Antarctic Circumpolar Current have warmed and increased in salinity. It remains unclear as to what extent the cooling and Antarctic sea-ice expansion is due to natural variability versus anthropogenic forcing; due for example to changes in the Southern Annular Mode (SAM). It is also unclear what the respective role of surface buoyancy fluxes is compared to internal ocean circulation changes, and what the implications are for longer-term climate change in the region. In this presentation we will outline three distinct drivers of recent Southern Ocean surface trends that have each made a significant contribution to regional cooling: (1) wind-driven surface cooling and sea-ice expansion due to shifted westerly winds, (2) teleconnections of decadal variability from the tropical Pacific, and (3) surface cooling and ice expansion due to large-scale Southern Ocean freshening, most likely driven by SAM-related precipitation trends over the open ocean. We will also outline the main reasons why climate models for the most part miss these Southern Ocean cooling trends, despite capturing overall trends in the SAM.

Modeling sea-surface temperature and its variability

NASA Technical Reports Server (NTRS)

Sarachik, E. S.

1985-01-01

A brief review is presented of the temporal scales of sea surface temperature variability. Progress in modeling sea surface temperature, and remaining obstacles to the understanding of the variability is discussed.

South Asian summer monsoon variability during the last ˜54 kyrs inferred from surface water salinity and river runoff proxies

NASA Astrophysics Data System (ADS)

Gebregiorgis, D.; Hathorne, E. C.; Sijinkumar, A. V.; Nath, B. Nagender; Nürnberg, D.; Frank, M.

2016-04-01

The past variability of the South Asian Monsoon is mostly known from records of wind strength over the Arabian Sea while high-resolution paleorecords from regions of strong monsoon precipitation are still lacking. Here, we present records of past monsoon variability obtained from sediment core SK 168/GC-1, which was collected at the Alcock Seamount complex in the Andaman Sea. We utilize the ecological habitats of different planktic foraminiferal species to reconstruct freshwater-induced stratification based on paired Mg/Ca and δ18O analyses and to estimate seawater δ18O (δ18Osw). The difference between surface and thermocline temperatures (ΔT) and δ18Osw (Δδ18Osw) is used to investigate changes in upper ocean stratification. Additionally, Ba/Ca in G. sacculifer tests is used as a direct proxy for riverine runoff and sea surface salinity (SSS) changes related to monsoon precipitation on land. Our Δδ18Osw time series reveals that upper ocean salinity stratification did not change significantly throughout the last glacial suggesting little influence of NH insolation changes. The strongest increase in temperature gradients between the mixed layer and the thermocline is recorded for the mid-Holocene and indicate the presence of a significantly shallower thermocline. In line with previous work, the δ18Osw and Ba/Ca records demonstrate that monsoon climate during the LGM was characterized by a significantly weaker southwest monsoon circulation and strongly reduced runoff. Based on our data the South Asian Summer Monsoon (SAM) over the Irrawaddyy strengthened gradually after the LGM beginning at ∼18 ka. This is some 3 kyrs before an increase of the Ba/Ca record from the Arabian Sea and indicates that South Asian Monsoon climate dynamics are more complex than the simple N-S displacement of the ITCZ as generally described for other regions. Minimum δ18Osw values recorded during the mid-Holocene are in phase with Ba/Ca marking a stronger monsoon precipitation

Wind-driven Sea-Ice Changes Intensify Subsurface Warm Water Intrusion into the West Antarctic Land Ice Front

NASA Astrophysics Data System (ADS)

Li, X.; Gille, S. T.; shang-Ping, X.; Xie, S. P.; Holland, D. M.; Holland, M. M.

2016-12-01

The climate change observed around Antarctica in recent decades is characterized by distinct zonally asymmetric patterns, with the strongest changes over West Antarctica. These changes are marked by strong land ice melting and sea ice redistribution around West Antarctica. This is associated with temperature and circulation anomalies in the ocean and atmosphere around the same area. In this study, we comprehensively examine the coherency between these changes using a combination of observations and numerical simulations. Results show that the atmospheric circulation changes distinctly drive the changes in ocean circulation and sea ice distribution. In addition, the atmospheric circulation induced sea ice changes play an important role in lifting the subsurface ocean temperature and salinity around the West Antarctica. During recent decades, the Amundsen Sea Low (ASL) has deepened, especially in austral autumn and winter. This deepened ASL has intensified the offshore wind near the coastal regions of the Ross Sea. Driven by these atmospheric changes, more sea ice has formed near West Antarctica in winter. In contrast, more sea ice melts during the summer. This strengthened sea ice seasonality has been observed and successfully reproduced in the model simulation. The wind-driven sea ice changes causes a surface freshening over the Ross and Amundsen Seas, with a subsurface salinity increase over the Ross Sea. The additional fresh/salt water fluxes thus further change the vertical distribution of salinity and strengthen the stratification in the Ross and Amundsen Seas. As a result of the above ice-ocean process, the mixed-layer depth around the Ross and Amundsen Seas shallows. By weakening the vertical heat transport near the surface layer, and inducing an upward movement of the circumpolar deep water (CDW), this process freshened and cooled the surface layer, while the salinity and temperature in the sub-surface ocean are increased, extending from 150 meters to >700

Optimisation of sea surface current retrieval using a maximum cross correlation technique on modelled sea surface temperature

NASA Astrophysics Data System (ADS)

Heuzé, Céline; Eriksson, Leif; Carvajal, Gisela

2017-04-01

Using sea surface temperature from satellite images to retrieve sea surface currents is not a new idea, but so far its operational near-real time implementation has not been possible. Validation studies are too region-specific or uncertain, due to the errors induced by the images themselves. Moreover, the sensitivity of the most common retrieval method, the maximum cross correlation, to the three parameters that have to be set is unknown. Using model outputs instead of satellite images, biases induced by this method are assessed here, for four different seas of Western Europe, and the best of nine settings and eight temporal resolutions are determined. For all regions, tracking a small 5 km pattern from the first image over a large 30 km region around its original location on a second image, separated from the first image by 6 to 9 hours returned the most accurate results. Moreover, for all regions, the problem is not inaccurate results but missing results, where the velocity is too low to be picked by the retrieval. The results are consistent both with limitations caused by ocean surface current dynamics and with the available satellite technology, indicating that automated sea surface current retrieval from sea surface temperature images is feasible now, for search and rescue operations, pollution confinement or even for more energy efficient and comfortable ship navigation.

Effects of salinity on upstream-migrating, spawning sea lamprey, Petromyzon marinus

PubMed Central

Ferreira-Martins, D.; Coimbra, J.; Antunes, C.; Wilson, J. M.

2016-01-01

The sea lamprey, Petromyzon marinus, is an anadromous, semelparous species that is vulnerable to endangered in parts of its native range due in part to loss of spawning habitat because of man-made barriers. The ability of lampreys to return to the ocean or estuary and search out alternative spawning river systems would be limited by their osmoregulatory ability in seawater. A reduction in tolerance to salinity has been documented in migrants, although the underlying mechanisms have not been characterized. We examined the capacity for marine osmoregulation in upstream spawning migrants by characterizing the physiological effects of salinity challenge from a molecular perspective. Estuarine-captured migrants held in freshwater (FW) for ∼1 week (short-term acclimation) or 2 months (long-term acclimation) underwent an incremental salinity challenge until loss of equilibrium occurred and upper thresholds of 25 and 17.5, respectively, occurred. Regardless of salinity tolerance, all lamprey downregulated FW ion-uptake mechanisms [gill transcripts of Na+:Cl− cotransporter (NCC/slc12a3) and epithelial Na+ channel (ENaC/scnn1) and kidney Na+/K+-ATPase (NKA) protein and activity but not transcript]. At their respective salinity limits, lamprey displayed a clear osmoregulatory failure and were unable to regulate [Na+] and [Cl−] in plasma and intestinal fluid within physiological limits, becoming osmocompromised. A >90% drop in haematocrit indicated haemolysis, and higher plasma concentrations of the cytosolic enzymes alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase indicated damage to other tissues, including liver. However, >80% of short-term FW-acclimated fish were able to osmoregulate efficiently, with less haemolysis and tissue damage. This osmoregulatory ability was correlated with significant upregulation of the secretory form of Na+:K+:2Cl− cotransporter (NKCC1/slc12a2) transcript levels and the re-emergence of seawater

Cultivation of activated sludge using sea mud as seed to treat industrial phenolic wastewater with high salinity.

PubMed

Tan, Songwen; Cui, Chunzhi; Hou, Yang; Chen, Xuncai; Xu, Aiqin; Li, Weiguo; You, Hong

2017-01-30

A technique is proposed to treat saline hazardous wastewater by using marine activated sludge, cultivated with sea mud as seed. Since the developed marine activated sludge had phenol-tolerant microorganisms (MAS-1, MAS-2 and MAS-3) which originated from the ocean, it was envisaged that these bacteria could survive and breakdown phenol in saline environments. In this work, typical phenol-tolerant microorganisms were isolated from the marine activated sludge and identified. After a hierarchical acclimation process, the marine activated sludge was used to treat the industrial phenolic wastewater with high salinity. The marine activated sludge was able to break down phenol and other organic components effectively and efficiently in treating the wastewater with salinity of 5.7% w/v. The results showed a high removal of phenol (99%), COD (80%) and NH 3 -N (68%). Copyright © 2016 Elsevier Ltd. All rights reserved.

Simulation of laser beam reflection at the sea surface

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric; Repasi, Endre

2011-05-01

A 3D simulation of the reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation is suitable for both the calculation of images of SWIR (short wave infrared) imaging sensor and for determination of total detected power of reflected laser light for a bistatic configuration of laser source and receiver at different atmospheric conditions. Our computer simulation comprises the 3D simulation of a maritime scene (open sea/clear sky) and the simulation of laser light reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. The propagation model for water waves is applied for sea surface animation. To predict the view of a camera in the spectral band SWIR the sea surface radiance must be calculated. This is done by considering the emitted sea surface radiance and the reflected sky radiance, calculated by MODTRAN. Additionally, the radiances of laser light specularly reflected at the wind-roughened sea surface are modeled in the SWIR band considering an analytical statistical sea surface BRDF (bidirectional reflectance distribution function). This BRDF model considers the statistical slope statistics of waves and accounts for slope-shadowing of waves that especially occurs at flat incident angles of the laser beam and near horizontal detection angles of reflected irradiance at rough seas. Simulation results are presented showing the variation of the detected laser power dependent on the geometric configuration of laser, sensor and wind characteristics.

Seasonal surface circulation, temperature, and salinity in Prince William Sound, Alaska

NASA Astrophysics Data System (ADS)

Musgrave, David L.; Halverson, Mark J.; Scott Pegau, W.

2013-02-01

Salinity, temperature, and depth profiles from 1973 to 2010 were used to construct a seasonal climatology of surface temperature, surface salinity, mixed layer depth (MLD), potential energy of mixing, and surface geostrophic circulation in Prince William Sound (PWS) and the adjacent Gulf of Alaska. Surface salinity is greatest in winter and least in summer due to the influence of increased freshwater runoff in summer. It is generally lowest in the northwest and highest in the Gulf of Alaska. The surface temperature is lowest in the winter and highest in the summer when surface heating is greatest, with little spatial variability across the Sound. The MLD is deepest in winter (9-27 m) and shallowest in summer (4-5 m). The work by winds was estimated from meteorological buoy data in central PWS and compared to the potential energy of mixing of the upper water column. The potential depth to which winds mix the upper water column was generally consistent with the MLD. The surface geostrophic circulation in the central Sound has: a southerly flow in the western central Sound in the winter; a closed, weak anticyclonic cell in spring; a closed, cyclonic cell in the summer; an open, cyclonic circulation in the fall. In the western passages, a southerly flow occurs in spring, summer, and fall. These results have important implications for oil spill response in PWS, the use of oil dispersants, and for comparison to numerical studies.

SeaRover: An Emerging Technology for Sea Surface Sensor Networks

NASA Astrophysics Data System (ADS)

Fong, T.; Kudela, R.; Curcio, J.; Davidson, K.; Darling, D.; Kirkwood, B.

2005-12-01

Introduction - SeaRover is envisioned as an autonomous surface vehicle (ASV) for coastal operations. It is intended to lower the cost of existing marine survey applications while enabling new science missions. The current conceptual design is a small vehicle with hull and propulsion system optimized to eliminate cavitation and EM noise. SeaRover will make significant advances over existing platforms by providing longer duration science missions, better positioning and mission control, larger power budgets for instrumentation and significantly lower operational costs than existing vehicles. Science Enabled by SeaRover - SeaRover's unique design and autonomous capability provides several advantages compared to traditional autonomous underwater vehicles (AUV's) and crewed surface vessels: (1) Near surface sampling: SeaRover can sample within the top 1-2 meters. This is difficult to do with crewed vessels because of draft and perturbations from the hull. (2) Adaptive monitoring of dynamic events: SeaRover will be capable of intelligent decision making, as well as real-time remote control. This will enable highly-responsive autonomous tracking of moving phenomena (e.g., algal bloom). (3) Long term monitoring: SeaRover can be deployed for extended periods of time, allowing it to be used for longitudinal baseline studies. SeaRover will represent an advance over existing platforms in terms of: (1) Mobility: operational range from 10-1000 km, GPS accuracy, trajectory control with meter precision, and launch in hours. (2) Duration: from days up to months. (3) Payload and Power: accommodate approximately 100 kg for a 6m hull. Its surface design will allow access to wind and sun energy. (4) Communication: radio, wireless, satellite, direct data return. (5) Operational Cost: target costs are $2K/day (24 hour operation), with no onboard operator. (6) Recovery/Reusability: autonomous return to safe harbor provides sample return and on-base maintenance. Large science and power

Messinian Salinity Crisis - DREAM (Deep-sea Record of Mediterranean Messinian events) drilling projects

NASA Astrophysics Data System (ADS)

Lofi, Johanna; Camerlenghi, Angelo

2014-05-01

About 6 My ago the Mediterranean Sea was transformed into a giant saline basin. This event, commonly referred to as the Messinian salinity crisis (MSC), changed the chemistry of the global ocean and had a permanent impact on both the terrestrial and marine ecosystems of a huge area surrounding the Mediterranean area. The first fascinating MSC scenario was proposed following DSDP Leg XIII in 1970 and envisaged an almost desiccated deep Mediterranean basin with a dramatic ~1,500 m drop of sea level, the incision of deep canyons by rivers on the continental margins, and a final catastrophic flooding event when the connections between the Mediterranean Sea and the Atlantic were re-established ~5.33 My ago. In spite of 40 years of multi-disciplinary research conducted on the MSC, modalities, timing, causes, chronology and consequence at local and planetary scale are still not yet fully understood, and the MSC event remains one of the longest-living controversies in Earth Science. Key factor for the controversy is the lack of a complete record of the MSC preserved in the deepest Mediterranean basins. Anywhere else, the MSC mostly generated a sedimentary/time lag corresponding to a widespread erosion surface. Correlations with the offshore depositional units are thus complex, preventing the construction of a coherent scenario linking the outcropping MSC evaporites, the erosion on the margins, and the deposition of clastics and evaporites in the abyssal plains. Recent activity by various research groups in order to identify locations for multiple-site drilling (including riser-drilling) in the Mediterranean Sea that would contribute to solve the open questions still existing about the MSC has culminated in two DREAM Magellan+ Workshops held in 2013 and 2014. A strategy and work plan have been established in order to submit an IODP Multi-phase Drilling Project("Uncovering A Salt Giant")including several site-specific drilling proposals addressing different scientific

Halophytes can salinize soil when competing with glycophytes, intensifying effects of sea level rise in coastal communities.

PubMed

Wendelberger, Kristie S; Richards, Jennifer H

2017-07-01

Sea level rise (SLR) and land-use change are working together to change coastal communities around the world. Along Florida's coast, SLR and large-scale drying are increasing groundwater salinity, resulting in halophytic (salt-tolerant) species colonizing glycophytic (salt-intolerant) communities. We hypothesized that halophytes can contribute to increased soil salinity as they move into glycophyte communities, making soils more saline than SLR or drying alone. We tested our hypothesis with a replacement-series greenhouse experiment with halophyte/glycophyte ratios of 0:4, 1:3, 2:2, 3:1, 4:0, mimicking halophyte movement into glycophyte communities. We subjected replicates to 0, 26, and 38‰ salinity for one, one, and three months, respectively, taking soil salinity and stomatal conductance measurements at the end of each treatment period. Our results showed that soil salinity increased as halophyte/glycophyte ratio increased. Either osmotic or ionic stress caused decreases in glycophyte biomass, resulting in less per-plant transpiration as compared to halophytes. At 38‰ groundwater, soil salinity increased as halophyte density increased, making conditions more conducive to further halophyte establishment. This study suggests that coastal plant community turnover may occur faster than would be predicted from SLR and anthropogenic disturbance alone.

Influence of temperature, oxygen and salinity on the metabolism of the European sea bass

NASA Astrophysics Data System (ADS)

Claireaux, G.; Lagardère, J.-P.

1999-09-01

Standard (SMR) and routine (RMR) metabolic rates of groups (4 to 5 individuals) of European sea bass ( Dicentrarchus labrax) were measured at combinations of the following factors: temperature (10, 15, 20 and 25°C), oxygenation level (air saturation to 1.5 mg dm -3) and salinity (30, 20, 10 and 5‰). The influence of these environmental conditions on fish metabolic demand was then analysed through ANOVA. At 10, 15, 20 and 25°C, standard metabolic rates were 36, 65, 89, and 91 mg O 2 kg -1 h -1, respectively, while routine oxygen consumptions covered most of the metabolic range accessible. Osmoregulatory costs are linked to metabolic activity through ventilation. This relationship was highlighted by the observed interaction between environmental salinity and temperature. We were, however, unable to detect interactions between salinity and routine metabolic rate, or between salinity and oxygenation level. In order to delineate more precisely the restrictions imposed by water oxygenation on fish metabolic performance we determined the limiting oxygen concentration curves at each experimental temperature. We followed up by modelling the bass active metabolic rate (AMR) and metabolic scope (MS) as functions of both ambient temperature and oxygenation. These mathematical models allowed the characterisation of the controlling and limiting effects of water temperature and oxygen content on the metabolic capacity of the species. Thus, AMR at 10, 15 and 20°C were estimated at 65, 160 and 360 mg O 2 kg -1 h -1, respectively. However, at higher temperature (25°C) AMR dropped slightly (to 340 mg O 2 kg -1 h -1). Bass MS increased by a factor of 9 between 10 and 20°C, but diminished at higher temperatures. The present study contributes to our current understanding of the influences of environmental factors on the metabolism of sea bass and provides a bioenergetic basis for a study of how environmental constraints govern the spatial and temporal distribution pattern of this

A global algorithm for estimating Absolute Salinity

NASA Astrophysics Data System (ADS)

McDougall, T. J.; Jackett, D. R.; Millero, F. J.; Pawlowicz, R.; Barker, P. M.

2012-12-01

The International Thermodynamic Equation of Seawater - 2010 has defined the thermodynamic properties of seawater in terms of a new salinity variable, Absolute Salinity, which takes into account the spatial variation of the composition of seawater. Absolute Salinity more accurately reflects the effects of the dissolved material in seawater on the thermodynamic properties (particularly density) than does Practical Salinity. When a seawater sample has standard composition (i.e. the ratios of the constituents of sea salt are the same as those of surface water of the North Atlantic), Practical Salinity can be used to accurately evaluate the thermodynamic properties of seawater. When seawater is not of standard composition, Practical Salinity alone is not sufficient and the Absolute Salinity Anomaly needs to be estimated; this anomaly is as large as 0.025 g kg-1 in the northernmost North Pacific. Here we provide an algorithm for estimating Absolute Salinity Anomaly for any location (x, y, p) in the world ocean. To develop this algorithm, we used the Absolute Salinity Anomaly that is found by comparing the density calculated from Practical Salinity to the density measured in the laboratory. These estimates of Absolute Salinity Anomaly however are limited to the number of available observations (namely 811). In order to provide a practical method that can be used at any location in the world ocean, we take advantage of approximate relationships between Absolute Salinity Anomaly and silicate concentrations (which are available globally).

Hydrochemical water evolution in the Aral Sea Basin. Part I: Unconfined groundwater of the Amu Darya Delta - Interactions with surface waters

NASA Astrophysics Data System (ADS)

Schettler, Georg; Oberhänsli, Hedi; Stulina, Galina; Mavlonov, Aslon A.; Naumann, Rudolf

2013-07-01

The Aral Sea, which has been affected by lake level lowering of approximately 25 m and a salinity increase from 10 to >100 g/l since 1963, represents, along with the Amu Dary Delta a dynamic hydrological system under an arid climate regime. The system receives river water inflow at high seasonal and inter-annual variability from remote alpine source areas. In the Amu Darya Delta, there is a distinct salinity contrast between the low-salinity river water (∼1 g/l) and the salinity of the unconfined GW (GWunconf: 10-95 g/l). The GWunconf levels are predominantly controlled by the seepage of the river water inflow and GW discharge into the shrinking Aral Sea. In June 2009 and August 2009, we sampled water from various sources including surface waters, GWunconf, lake water and soil leachates for chemical analyses. Evaporative enrichment, precipitation/dissolution of gypsum and precipitation of calcite drive the GWunconf to an NaCl(SO4) water type presenting a positive correlation between Na and SO4. We model the hydrochemical evolution of the GWunconf in a box model which considers the capillary rise of near-surface GW, the precipitation of minerals in the unsaturated horizon and the seasonal re-flushing of adhesive residual brines and soluble salts. The model documents a rapid increase in salinity over a few annual cycles. Furthermore, the model simulations demonstrate the importance of the aeolian redistribution of soluble salts on the hydrochemical GW evolution. In a lab experiment, halite, hexahydrite and starkeyite are precipitated during the late stages of evaporative enrichment from a representative local brine. Processes specific to different water compartments plausibly explain the variations of selected element ratios. For example, the precipitation of low-Sr calcite in irrigation canals and natural river branches of the delta lowers Ca/Sr. The dissolution of gypsum in soils (Ca/Sr mole ratio ∼ 150) and the possible precipitation of SrSO4 associated with

Solutions Network Formulation Report. Integrating Salinity Measurements from Aquarius into the Harmful Algal Blooms Observing System

NASA Technical Reports Server (NTRS)

Anderson, Daniel; Lewis, David; Hilbert, Kent

2007-01-01

This Candidate Solution suggests the use of Aquarius sea surface salinity measurements to improve the NOAA/NCDDC (National Oceanic and Atmospheric Administration s National Coastal Data Development Center) HABSOS (Harmful Algal Blooms Observing System) DST (decision support tool) by enhancing development and movement forecasts of HAB events as well as potential species identification. In the proposed configuration, recurring salinity measurements from the Aquarius mission would augment HABSOS sea surface temperature and in situ ocean current measurements. Thermohaline circulation observations combined with in situ measurements increase the precision of HAB event movement forecasting. These forecasts allow coastal managers and public health officials to make more accurate and timely warnings to the public and to better direct science teams to event sites for collection and further measurements.

Tidal Marshes across a Chesapeake Bay Subestuary Are Not Keeping up with Sea-Level Rise

PubMed Central

Beckett, Leah H.; Baldwin, Andrew H.; Kearney, Michael S.

2016-01-01

Sea-level rise is a major factor in wetland loss worldwide, and in much of Chesapeake Bay (USA) the rate of sea-level rise is higher than the current global rate of 3.2 mm yr-1 due to regional subsidence. Marshes along estuarine salinity gradients differ in vegetation composition, productivity, decomposition pathways, and sediment dynamics, and may exhibit different responses to sea-level rise. Coastal marshes persist by building vertically at rates at or exceeding regional sea-level rise. In one of the first studies to examine elevation dynamics across an estuarine salinity gradient, we installed 15 surface elevation tables (SET) and accretion marker-horizon plots (MH) in tidal freshwater, oligohaline, and brackish marshes across a Chesapeake Bay subestuary. Over the course of four years, wetlands across the subestuary decreased 1.8 ± 2.7 mm yr-1 in elevation on average, at least 5 mm yr-1 below that needed to keep pace with global sea-level rise. Elevation change rates did not significantly differ among the marshes studied, and ranged from -9.8 ± 6.9 to 4.5 ± 4.3 mm yr-1. Surface accretion of deposited mineral and organic matter was uniformly high across the estuary (~9–15 mm yr-1), indicating that elevation loss was not due to lack of accretionary input. Position in the estuary and associated salinity regime were not related to elevation change or surface matter accretion. Previous studies have focused on surface elevation change in marshes of uniform salinity (e.g., salt marshes); however, our findings highlight the need for elevation studies in marshes of all salinity regimes and different geomorphic positions, and warn that brackish, oligohaline, and freshwater tidal wetlands may be at similarly high risk of submergence in some estuaries. PMID:27467784

Highly variable Pliocene sea surface conditions in the Norwegian Sea

NASA Astrophysics Data System (ADS)

Bachem, Paul E.; Risebrobakken, Bjørg; De Schepper, Stijn; McClymont, Erin L.

2017-09-01

The Pliocene was a time of global warmth with small sporadic glaciations, which transitioned towards the larger-scale Pleistocene glacial-interglacial variability. Here, we present high-resolution records of sea surface temperature (SST) and ice-rafted debris (IRD) in the Norwegian Sea from 5.32 to 3.14 Ma, providing evidence that the Pliocene surface conditions of the Norwegian Sea underwent a series of transitions in response to orbital forcing and gateway changes. Average SSTs are 2 °C above the regional Holocene mean, with notable variability on millennial to orbital timescales. Both gradual changes and threshold effects are proposed for the progression of regional climate towards the Late Pliocene intensification of Northern Hemisphere glaciation. Cooling from 4.5 to 4.3 Ma may be linked to the onset of poleward flow through the Bering Strait. This cooling was further intensified by a period of cool summers due to weak obliquity forcing. A 7 °C warming of the Norwegian Sea at 4.0 Ma suggests a major increase in northward heat transport from the North Atlantic, leading to an enhanced zonal SST gradient in the Nordic Seas, which may be linked to the expansion of sea ice in the Arctic and Nordic Seas. A warm Norwegian Sea and enhanced zonal temperature gradient between 4.0 and 3.6 Ma may have been a priming factor for increased glaciation around the Nordic Seas due to enhanced evaporation and precipitation at high northern latitudes.

Potential role of salinity in ENSO and MJO predictions

NASA Astrophysics Data System (ADS)

Zhu, J.; Kumar, A.; Murtugudde, R. G.; Xie, P.

2017-12-01

Studies have suggested that ocean salinity can vary in response to ENSO and MJO. For example, during an El Niño event, sea surface salinity decreases in the western and central equatorial Pacific, as a result of zonal advection of low salinity water by anomalous eastward surface currents, and to a lesser extent as a result of a rainfall excess associated with atmospheric convection and warm water displacements. However, the effect of salinity on ENSO and MJO evolutions and their forecasts has been less explored. In this analysis, we explored the potential role of salinity in ENSO and MJO predictions by conducting sensitivity experiments with NCEP CFSv2. Firstly, two forecasts experiments are conducted to explore its effect on ENSO predictions, in which the interannual variability of salinity in the ocean initial states is either included or excluded. Comparisons suggested that the salinity variability is essential to correctly forecast the 2007/08 La Niña starting from April 2007. With realistic salinity initial states, the tendency to decay of the subsurface cold condition during the spring and early summer 2007 was interrupted by positive salinity anomalies in the upper central Pacific, which working together with the Bjerknes positive feedback, contributed to the development of the La Niña event. Our study suggests that ENSO forecasts will benefit from more accurate sustained salinity observations having large-scale spatial coverage. We also assessed the potential role of salinity in MJO by evaluating a long coupled free run that has a relatively realistic MJO simulation and a set of predictability experiment, both based on CFSv2. Diagnostics of the free run suggest that, while the intraseasonal SST variations lead convections by a quarter cycle, they are almost in phase only with changes in barrier layer thickness, thereby suggesting an active role of salinity on SST. Its effect on MJO predictions is further explored by controlling the surface salinity

Impact of Seawater Nonlinearities on Nordic Seas Circulation

NASA Astrophysics Data System (ADS)

Helber, R. W.; Wallcraft, A. J.; Shriver, J. F.

2017-12-01

The Nordic Seas (Greenland, Iceland, and Norwegian Seas) form an ocean basin important for Arctic-mid-latitude climate linkages. Cold fresh water from the Arctic Ocean and warm salty water from the North Atlantic Ocean meet in the Nordic Seas, where a delicate balance between temperature and salinity variability results in deep water formation. Seawater non-linearities are stronger at low temperatures and salinities making high-latitude oceans highly subject to thermbaricity and cabbeling. This presentation highlights and quantifies the impact of seawater non-linearities on the Nordic Seas circulation. We use two layered ocean circulation models, the Hybrid Coordinate Ocean Model (HYOCM) and the Modular Ocean Model version 6 (MOM6), that enable accurate representation of processes along and across density or neutral density surfaces. Different equations-of-state and vertical coordinates are evaluated to clarify the impact of seawater non-linearities. Present Navy systems, however, do not capture some features in the Nrodic Seas vertical structure. For example, observations from the Greenland Sea reveal a subsurface temperature maximum that deepens from approximately 1500 m during 1998 to 1800 m during 2005. We demonstrate that in terms of density, salinity is the largest source of error in Nordic Seas Navy forecasts, regional scale models can represent mesoscale features driven by thermobaricity, vertical coordinates are a critical issue in Nordic Sea circulation modeling.

Applying downscaled global climate model data to a hydrodynamic surface-water and groundwater model

USGS Publications Warehouse

Swain, Eric; Stefanova, Lydia; Smith, Thomas

2014-01-01

Precipitation data from Global Climate Models have been downscaled to smaller regions. Adapting this downscaled precipitation data to a coupled hydrodynamic surface-water/groundwater model of southern Florida allows an examination of future conditions and their effect on groundwater levels, inundation patterns, surface-water stage and flows, and salinity. The downscaled rainfall data include the 1996-2001 time series from the European Center for Medium-Range Weather Forecasting ERA-40 simulation and both the 1996-1999 and 2038-2057 time series from two global climate models: the Community Climate System Model (CCSM) and the Geophysical Fluid Dynamic Laboratory (GFDL). Synthesized surface-water inflow datasets were developed for the 2038-2057 simulations. The resulting hydrologic simulations, with and without a 30-cm sea-level rise, were compared with each other and field data to analyze a range of projected conditions. Simulations predicted generally higher future stage and groundwater levels and surface-water flows, with sea-level rise inducing higher coastal salinities. A coincident rise in sea level, precipitation and surface-water flows resulted in a narrower inland saline/fresh transition zone. The inland areas were affected more by the rainfall difference than the sea-level rise, and the rainfall differences make little difference in coastal inundation, but a larger difference in coastal salinities.

The Effect of a Receding Saline Lake (The Salton Sea) on Airborne Particulate Matter Composition.

PubMed

Frie, Alexander L; Dingle, Justin H; Ying, Samantha C; Bahreini, Roya

2017-08-01

The composition of ambient particulate matter (PM) and its sources were investigated at the Salton Sea, a shrinking saline lake in California. To investigate the influence of playa exposure on PM composition, PM samples were collected during two seasons and at two sites around the Salton Sea. To characterize source composition, soil samples were collected from local playa and desert surfaces. PM and soil samples were analyzed for 15 elements using mass spectrometry and X-ray diffraction. The contribution of sources to PM mass and composition was investigated using Al-referenced enrichment factors (EFs) and source factors resolved from positive matrix factorization (PMF). Playa soils were found to be significantly enriched in Ca, Na, and Se relative to desert soils. PMF analysis resolved the PM 10 data with four source factors, identified as Playa-like, Desert-like, Ca-rich, and Se. Playa-like and desert-like sources were estimated to contribute to a daily average of 8.9% and 45% of PM 10 mass, respectively. Additionally, playa sources were estimated to contribute to 38-68% of PM 10 Na. PM 10 Se concentrations showed strong seasonal variations, suggesting a seasonal cycle of Se volatilization and recondensation. These results support the importance of playas as a source of PM mass and a controlling factor of PM composition.

Response of Antarctic sea surface temperature and sea ice to ozone depletion

NASA Astrophysics Data System (ADS)

Ferreira, D.; Gnanadesikan, A.; Kostov, Y.; Marshall, J.; Seviour, W.; Waugh, D.

2017-12-01

The influence of the Antarctic ozone hole extends all the way from the stratosphere through the troposphere down to the surface, with clear signatures on surface winds, and SST during summer. In this talk we discuss the impact of these changes on the ocean circulation and sea ice state. We are notably motivated by the observed cooling of the surface Southern Ocean and associated increase in Antarctic sea ice extent since the 1970s. These trends are not reproduced by CMIP5 climate models, and the underlying mechanism at work in nature and the models remain unexplained. Did the ozone hole contribute to the observed trends?Here, we review recent advances toward answering these issues using "abrupt ozone depletion" experiments. The ocean and sea ice response is rather complex, comprising two timescales: a fast ( 1-2y) cooling of the surface ocean and sea ice cover increase, followed by a slower warming trend, which, depending on models, flip the sign of the SST and sea ice responses on decadal timescale. Although the basic mechanism seems robust, comparison across climate models reveal large uncertainties in the timescales and amplitude of the response to the extent that even the sign of the ocean and sea ice response to ozone hole and recovery remains unconstrained. After briefly describing the dynamics and thermodynamics behind the two-timescale response, we will discuss the main sources of uncertainties in the modeled response, namely cloud effects and air-sea heat exchanges, surface wind stress response and ocean eddy transports. Finally, we will consider the implications of our results on the ability of coupled climate models to reproduce observed Southern Ocean changes.

Eddy-induced salinity pattern in the North Pacific

NASA Astrophysics Data System (ADS)

Abe, H.; Ebuchi, N.; Ueno, H.; Ishiyama, H.; Matsumura, Y.

2017-12-01

This research examines spatio-temporal behavior of sea surface salinity (SSS) after intense rainfall events using observed data from Aquarius. Aquarius SSS in the North Pacific reveals one notable event in which SSS is locally freshened by intense rainfall. Although SSS pattern shortly after the rainfall reflects atmospheric pattern, its final form reflects ocean dynamic structure; an anticyclonic eddy. Since this anticyclonic eddy was located at SSS front created by precipitation, this eddy stirs the water in a clockwise direction. This eddy stirring was visible for several months. It is expected horizontal transport by mesoscale eddies would play significant role in determining upper ocean salinity structure.

Transitions in bacterial communities along the 2000 km salinity gradient of the Baltic Sea

PubMed Central

Herlemann, Daniel PR; Labrenz, Matthias; Jürgens, Klaus; Bertilsson, Stefan; Waniek, Joanna J; Andersson, Anders F

2011-01-01

Salinity is a major factor controlling the distribution of biota in aquatic systems, and most aquatic multicellular organisms are either adapted to life in saltwater or freshwater conditions. Consequently, the saltwater–freshwater mixing zones in coastal or estuarine areas are characterized by limited faunal and floral diversity. Although changes in diversity and decline in species richness in brackish waters is well documented in aquatic ecology, it is unknown to what extent this applies to bacterial communities. Here, we report a first detailed bacterial inventory from vertical profiles of 60 sampling stations distributed along the salinity gradient of the Baltic Sea, one of world's largest brackish water environments, generated using 454 pyrosequencing of partial (400 bp) 16S rRNA genes. Within the salinity gradient, bacterial community composition altered at broad and finer-scale phylogenetic levels. Analogous to faunal communities within brackish conditions, we identified a bacterial brackish water community comprising a diverse combination of freshwater and marine groups, along with populations unique to this environment. As water residence times in the Baltic Sea exceed 3 years, the observed bacterial community cannot be the result of mixing of fresh water and saltwater, but our study represents the first detailed description of an autochthonous brackish microbiome. In contrast to the decline in the diversity of multicellular organisms, reduced bacterial diversity at brackish conditions could not be established. It is possible that the rapid adaptation rate of bacteria has enabled a variety of lineages to fill what for higher organisms remains a challenging and relatively unoccupied ecological niche. PMID:21472016

Air-sea Forcing and Thermohaline Changes In The Ross Sea.

NASA Astrophysics Data System (ADS)

Fusco, G.; Budillon, G.

Heat exchanges between sea and atmosphere from 1986 to 2000 in the Ross Sea (Antarctica) were computed from climatological data obtained from the European Centre for Medium Range Weather Forecasts. They have been related with the thermo- haline changes observed during 5 hydrological surveys performed between the austral summer 1994-1995 and 2000-2001 in the western sector of the Ross Sea. The esti- mated heat fluxes show extremely strong spatial and temporal variability over all the Ross Sea. As can be expected the largest heat losses occur between May and August, while during the period November-February the heat budget becomes positive. In the first six years of the investigated period the heat loss is very strong with its maximum about 166 Wm-2; while during the period 1992-2000 the yearly heat losses are the lowest. Thermohaline changes in the surface layer (upper pycnocline) of the western Ross Sea follow the expected seasonal pattern of warming and freshening from the be- ginning to the end of the austral summer. The heating changes are substantially lower than the estimated heat supplied by the atmosphere during the summer, which under- lines the importance in this season of the advective component carried by the currents in the total heat budget of this area. The year to year differences are about one or two orders of magnitude smaller than the seasonal changes in the surface layer. In the in- termediate and deep layers, the summer heat and salt variability is of the same order as or one order higher than from one summer to the next. Moreover a freshening of the near bottom layer has been observed, it is consistent with the High Salinity Shelf Water salinity decrease recently detected in the Ross Sea.

Are Surface Waters Around Greenland Getting Saltier in a Warming Climate?

NASA Astrophysics Data System (ADS)

Vinogradova, N. T.; Ponte, R. M.; Piecuch, C. G.; Little, C. M.

2016-02-01

During the past two decades, most surface waters around Greenland ice sheet and in the Nordic Seas became significantly saltier. Given the fact that these waters feed the North Atlantic thermohaline circulation, an increase in surface salinity, which can exceed 0.2 psu in places, might have an important impact on the global ocean circulation and on future projections of the climate state. Surface salinification may seem counter-intuitive to the reported long-term increase in freshwater supply to the region from river discharge and ice melting, sparking debates about whether the freshening of the subpolar gyre has ceased, and whether the recent salinification, if continued, will be able to forestall the projected slowdown of the overturning circulation. Here we assess what controls contemporary salinity changes by examining various terms of the salinity budget, including the dilution effect due to air-sea fluxes of freshwater, fluxes of salt due to sea ice formation/melting, and ocean fluxes of salinity associated with advective and diffusive processes. We use an ocean state estimate produced by the ECCO consortium to consider the budgets over the period 1992-2011. ECCO estimates produce salinity fields close to the observations and, crucial for our purposes, permit closed budget diagnostics of salinity and respective fluxes. The budgets are formulated within the entire water column in order to examine three-dimensional structure of freshwater storage and establish a link between the surface and upper-ocean change in near-Greenland waters. Over the past two decades, patterns of change are evident in all budget terms, with ocean fluxes either offsetting or enhancing surface forcing, including the effects of sea ice dynamics. Interpretation is provided within the context of a changing climate, including intensification of the hydrological cycle and weakening of ocean transports and overturning, as well as natural decadal-to-interdacadal variability present in the

Thin Sea-Ice Thickness as Inferred from Passive Microwave and In Situ Observations

NASA Technical Reports Server (NTRS)

Naoki, Kazuhiro; Ukita, Jinro; Nishio, Fumihiko; Nakayama, Masashige; Comiso, Josefino C.; Gasiewski, Al

2007-01-01

Since microwave radiometric signals from sea-ice strongly reflect physical conditions of a layer near the ice surface, a relationship of brightness temperature with thickness is possible especially during the early stages of ice growth. Sea ice is most saline during formation stage and as the salinity decreases with time while at the same time the thickness of the sea ice increases, a corresponding change in the dielectric properties and hence the brightness temperature may occur. This study examines the extent to which the relationships of thickness with brightness temperature (and with emissivity) hold for thin sea-ice, approximately less than 0.2 -0.3 m, using near concurrent measurements of sea-ice thickness in the Sea of Okhotsk from a ship and passive microwave brightness temperature data from an over-flying aircraft. The results show that the brightness temperature and emissivity increase with ice thickness for the frequency range of 10-37 GHz. The relationship is more pronounced at lower frequencies and at the horizontal polarization. We also established an empirical relationship between ice thickness and salinity in the layer near the ice surface from a field experiment, which qualitatively support the idea that changes in the near-surface brine characteristics contribute to the observed thickness-brightness temperature/emissivity relationship. Our results suggest that for thin ice, passive microwave radiometric signals contain, ice thickness information which can be utilized in polar process studies.

Compositions of surface layers formed on amalgams in air, water, and saline.

PubMed

Hanawa, T; Gnade, B E; Ferracane, J L; Okabe, T; Watari, F

1993-12-01

The surface layers formed on both a zinc-free and a zinc-containing dental amalgam after polishing and aging in air, water, or saline, were characterized using x-ray photoelectron spectroscopy (XPS) to determine the compositions of the surface layers which might govern the release of mercury from amalgam. The XPS data revealed that the formation of the surface layer on the zinc-containing amalgam was affected by the environment in which the amalgam was polished and aged, whereas that on the zinc-free amalgam was not affected. In addition, among the elements contained in amalgam, zinc was the most reactive with the environment, and was preferentially dissolved from amalgam into water or saline. Mercury atoms existed in the metallic state in the surface layer.

Fern Spore Longevity in Saline Water: Can Sea Bottom Sediments Maintain a Viable Spore Bank?

PubMed Central

de Groot, G. Arjen; During, Heinjo

2013-01-01

Freshwater and marine sediments often harbor reservoirs of plant diaspores, from which germination and establishment may occur whenever the sediment falls dry. Therewith, they form valuable records of historical inter- and intraspecific diversity, and are increasingly exploited to facilitate diversity establishment in new or restored nature areas. Yet, while ferns may constitute a considerable part of a vegetation’s diversity and sediments are known to contain fern spores, little is known about their longevity, which may suffer from inundation and - in sea bottoms - salt stress. We tested the potential of ferns to establish from a sea or lake bottom, using experimental studies on spore survival and gametophyte formation, as well as a spore bank analysis on sediments from a former Dutch inland sea. Our experimental results revealed clear differences among species. For Asplenium scolopendrium and Gymnocarpium dryopteris, spore germination was not affected by inundated storage alone, but decreased with rising salt concentrations. In contrast, for Asplenium trichomanes subsp. quadrivalens germination decreased following inundation, but not in response to salt. Germination rates decreased with time of storage in saline water. Smaller and less viable gametophytes were produced when saline storage lasted for a year. Effects on germination and gametophyte development clearly differed among genotypes of A. scolopendrium. Spore bank analyses detected no viable spores in marine sediment layers. Only two very small gametophytes (identified as Thelypteris palustris via DNA barcoding) emerged from freshwater sediments. Both died before maturation. We conclude that marine, and likely even freshwater sediments, will generally be of little value for long-term storage of fern diversity. The development of any fern vegetation on a former sea floor will depend heavily on the deposition of spores onto the drained land by natural or artificial means of dispersal. PMID:24223951

The Last Interglacial Labrador Sea: A Pervasive Millennial Oscillation In Surface Water Conditions Without Labrador Sea Water Formation

NASA Astrophysics Data System (ADS)

Hillaire-Marcel, C.; de Vernal, A.

A multi-proxy approach was developed to document secular to millenial changes of potential density in surface, mesopelagic, and bottom waters of the Labrador Sea, thus allowing to reconstruct situations when winter convection with intermediate or deep water formation occurred in the basin. This approach relies on dinocyst-transfer functions providing estimates of sea-surface temperature and salinity that are used to calibrate past-relationships between oxygen 18 contents in calcite and potential density gradients. The oxygen isotope compositions of epipelagic (Globigerina bul- loides), deeper-dwelling (Neogloboquadrina pachyderma, left coiling), and benthic (Uvigerina peregrina and Cibicides wuellerstorfi) foraminifera, then allow to extrap- olate density gradients between the corresponding water layers. This approach has been tested in surface sediments in reference to modern hydrographic conditions at several sites from the NW North Atlantic, then used to reconstruct past conditions from high resolution studies of cores raised from the southern Greenland Rise (off Cape Farewell). Results indicate that the modern-like regime established during the early Holocene and full developed after 7 ka only. It is marked by weak density gradi- ents between the surface and intermediate water masses, allowing winter convection down to a lower pycnocline between intermediate and deep-water masses, thus the formation of intermediate Labrador Sea Water (LSW). Contrasting with the middle to late Holocene situation, since the last interglacial and throughout the last climatic cycle, a single and dense water mass seems to have occupied the water column below a generally low-density surface water layer, thus preventing deep convection. There- fore, the production of LSW seems to be feature specific to the present interglacial interval that could soon cease to exist, due to global warming, as suggested by recent ocean model experiments and by the fact that it never occurred during the

The SeaDataNet data products: regional temperature and salinity historical data collections

NASA Astrophysics Data System (ADS)

Simoncelli, Simona; Coatanoan, Christine; Bäck, Orjan; Sagen, Helge; Scoy, Serge; Myroshnychenko, Volodymyr; Schaap, Dick; Schlitzer, Reiner; Iona, Sissy; Fichaut, Michele

2016-04-01

Temperature and Salinity (TS) historical data collections covering the time period 1900-2013 were created for each European marginal sea (Arctic Sea, Baltic Sea, Black Sea, North Sea, North Atlantic Ocean and Mediterranean Sea) within the framework of SeaDataNet2 (SDN) EU-Project and they are now available as ODV collections through the SeaDataNet web catalog at http://sextant.ifremer.fr/en/web/seadatanet/. Two versions have been published and they represent a snapshot of the SDN database content at two different times: V1.1 (January 2014) and V2 (March 2015). A Quality Control Strategy (QCS) has been developped and continuously refined in order to improve the quality of the SDN database content and to create the best product deriving from SDN data. The QCS was originally implemented in collaboration with MyOcean2 and MyOcean Follow On projects in order to develop a true synergy at regional level to serve operational oceanography and climate change communities. The QCS involved the Regional Coordinators, responsible of the scientific assessment, the National Oceanographic Data Centers (NODC) and the data providers that, on the base of the data quality assessment outcome, checked and eventually corrected anomalies in the original data. The QCS consists of four main phases: 1) data harvesting from the central CDI; 2) file and parameter aggregation; 3) quality check analysis at regional level; 4) analysis and correction of data anomalies. The approach is iterative to facilitate the upgrade of SDN database content and it allows also the versioning of data products with the release of new regional data collections at the end of each QCS loop. SDN data collections and the QCS will be presented and the results summarized.

Spatial variability of soil salinity in coastal saline soil at different scales in the Yellow River Delta, China.

PubMed

Wang, Zhuoran; Zhao, Gengxing; Gao, Mingxiu; Chang, Chunyan

2017-02-01

The objectives of this study were to explore the spatial variability of soil salinity in coastal saline soil at macro, meso and micro scales in the Yellow River delta, China. Soil electrical conductivities (ECs) were measured at 0-15, 15-30, 30-45 and 45-60 cm soil depths at 49 sampling sites during November 9 to 11, 2013. Soil salinity was converted from soil ECs based on laboratory analyses. Our results indicated that at the macro scale, soil salinity was high with strong variability in each soil layer, and the content increased and the variability weakened with increasing soil depth. From east to west in the region, the farther away from the sea, the lower the soil salinity was. The degrees of soil salinization in three deeper soil layers are 1.14, 1.24 and 1.40 times higher than that in the surface soil. At the meso scale, the sequence of soil salinity in different topographies, soil texture and vegetation decreased, respectively, as follows: depression >flatland >hillock >batture; sandy loam >light loam >medium loam >heavy loam >clay; bare land >suaeda salsa >reed >cogongrass >cotton >paddy >winter wheat. At the micro scale, soil salinity changed with elevation in natural micro-topography and with anthropogenic activities in cultivated land. As the study area narrowed down to different scales, the spatial variability of soil salinity weakened gradually in cultivated land and salt wasteland except the bare land.

Numerical study of electromagnetic scattering from one-dimensional nonlinear fractal sea surface

NASA Astrophysics Data System (ADS)

Xie, Tao; He, Chao; William, Perrie; Kuang, Hai-Lan; Zou, Guang-Hui; Chen, Wei

2010-02-01

In recent years, linear fractal sea surface models have been developed for the sea surface in order to establish an electromagnetic backscattering model. Unfortunately, the sea surface is always nonlinear, particularly at high sea states. We present a nonlinear fractal sea surface model and derive an electromagnetic backscattering model. Using this model, we numerically calculate the normalized radar cross section (NRCS) of a nonlinear sea surface. Comparing the averaged NRCS between linear and nonlinear fractal models, we show that the NRCS of a linear fractal sea surface underestimates the NRCS of the real sea surface, especially for sea states with high fractal dimensions, and for dominant ocean surface gravity waves that are either very short or extremely long.

Analyzing the 2010-2011 La Niña signature in the tropical Pacific sea surface salinity using in situ data, SMOS observations, and a numerical simulation

NASA Astrophysics Data System (ADS)

Hasson, Audrey; Delcroix, Thierry; Boutin, Jacqueline; Dussin, Raphael; Ballabrera-Poy, Joaquim

2014-06-01

The tropical Pacific Ocean remained in a La Niña phase from mid-2010 to mid-2012. In this study, the 2010-2011 near-surface salinity signature of ENSO (El Niño-Southern Oscillation) is described and analyzed using a combination of numerical model output, in situ data, and SMOS satellite salinity products. Comparisons of all salinity products show a good agreement between them, with a RMS error of 0.2-0.3 between the thermosalinograph (TSG) and SMOS data and between the TSG and model data. The last 6 months of 2010 are characterized by an unusually strong tripolar anomaly captured by the three salinity products in the western half of the tropical Pacific. A positive SSS anomaly sits north of 10°S (>0.5), a negative tilted anomaly lies between 10°S and 20°S and a positive one south of 20°S. In 2011, anomalies shift south and amplify up to 0.8, except for the one south of 20°S. Equatorial SSS changes are mainly the result of anomalous zonal advection, resulting in negative anomalies during El Niño (early 2010), and positive ones thereafter during La Niña. The mean seasonal and interannual poleward drift exports those anomalies toward the south in the southern hemisphere, resulting in the aforementioned tripolar anomaly. The vertical salinity flux at the bottom of the mixed layer tends to resist the surface salinity changes. The observed basin-scale La Niña SSS signal is then compared with the historical 1998-1999 La Niña event using both observations and modeling.

Pliocene cooling enhanced by flow of low-salinity Bering Sea water to the Arctic Ocean.

PubMed

Horikawa, Keiji; Martin, Ellen E; Basak, Chandranath; Onodera, Jonaotaro; Seki, Osamu; Sakamoto, Tatsuhiko; Ikehara, Minoru; Sakai, Saburo; Kawamura, Kimitaka

2015-06-29

Warming of high northern latitudes in the Pliocene (5.33-2.58 Myr ago) has been linked to the closure of the Central American Seaway and intensification of North Atlantic Deep Water. Subsequent cooling in the late Pliocene may be related to the effects of freshwater input from the Arctic Ocean via the Bering Strait, disrupting North Atlantic Deep Water formation and enhancing sea ice formation. However, the timing of Arctic freshening has not been defined. Here we present neodymium and lead isotope records of detrital sediment from the Bering Sea for the past 4.3 million years. Isotopic data suggest the presence of Alaskan glaciers as far back as 4.2 Myr ago, while diatom and C37:4 alkenone records show a long-term trend towards colder and fresher water in the Bering Sea beginning with the M2 glaciation (3.3 Myr ago). We argue that the introduction of low-salinity Bering Sea water to the Arctic Ocean by 3.3 Myr ago preconditioned the climate system for global cooling.

Pliocene cooling enhanced by flow of low-salinity Bering Sea water to the Arctic Ocean

PubMed Central

Horikawa, Keiji; Martin, Ellen E.; Basak, Chandranath; Onodera, Jonaotaro; Seki, Osamu; Sakamoto, Tatsuhiko; Ikehara, Minoru; Sakai, Saburo; Kawamura, Kimitaka

2015-01-01

Warming of high northern latitudes in the Pliocene (5.33–2.58 Myr ago) has been linked to the closure of the Central American Seaway and intensification of North Atlantic Deep Water. Subsequent cooling in the late Pliocene may be related to the effects of freshwater input from the Arctic Ocean via the Bering Strait, disrupting North Atlantic Deep Water formation and enhancing sea ice formation. However, the timing of Arctic freshening has not been defined. Here we present neodymium and lead isotope records of detrital sediment from the Bering Sea for the past 4.3 million years. Isotopic data suggest the presence of Alaskan glaciers as far back as 4.2 Myr ago, while diatom and C37:4 alkenone records show a long-term trend towards colder and fresher water in the Bering Sea beginning with the M2 glaciation (3.3 Myr ago). We argue that the introduction of low-salinity Bering Sea water to the Arctic Ocean by 3.3 Myr ago preconditioned the climate system for global cooling. PMID:26119338

Hydrographic observations by instrumented marine mammals in the Sea of Okhotsk

NASA Astrophysics Data System (ADS)

Nakanowatari, Takuya; Ohshima, Kay I.; Mensah, Vigan; Mitani, Yoko; Hattori, Kaoru; Kobayashi, Mari; Roquet, Fabien; Sakurai, Yasunori; Mitsudera, Humio; Wakatsuchi, Masaaki

2017-09-01

The Sea of Okhotsk is a challenging environment for obtaining in situ data and satellite observation in winter due to sea ice cover. In this study, we evaluated the validity of hydrographic observations by marine mammals (e.g., seals and sea lions) equipped with oceanographic conductivity-temperature-depth (CTD) sensors. During 4-yr operations from 2011 to 2014, we obtained total of 997 temperature-salinity profiles in and around the Soya Strait, Iony Island, and Urup Strait. The hydrographic data were mainly obtained from May to August and the maximum profile depth in shelf regions almost reaches to the seafloor, while valuable hydrographic data under sea ice cover were also obtained. In strong thermoclines, the seal-derived data sometimes showed positive biases in salinity with spike-like signal. For these salinity biases, we applied a new thermal mass inertia correction scheme, effectively reducing spurious salinity biases in the seasonal thermocline. In the Soya Strait and the adjacent region, the detailed structure of the Soya Warm Current including the cold-water belt was well identified. Dense water up to 27.0σθ, which can be a potential source of Okhotsk Sea Intermediate Water, has flowed from the Soya Strait into the Sea of Okhotsk in mid-winter (February). In summer, around the Iony Island and Urup Strait, remarkable cold and saline waters are localized in the surface layers. These regions are also characterized by weak stratification, suggesting the occurrence of tidally induced vertical mixing. Thus, CTD-tag observations have a great potential in monitoring data-sparse regions in the Sea of Okhotsk.

Mechanisms of Mixed-Layer Salinity Seasonal Variability in the Indian Ocean

NASA Astrophysics Data System (ADS)

Köhler, Julia; Serra, Nuno; Bryan, Frank O.; Johnson, Benjamin K.; Stammer, Detlef

2018-01-01

Based on a joint analysis of an ensemble mean of satellite sea surface salinity retrievals and the output of a high-resolution numerical ocean circulation simulation, physical processes are identified that control seasonal variations of mixed-layer salinity (MLS) in the Indian Ocean, a basin where salinity changes dominate changes in density. In the northern and near-equatorial Indian Ocean, annual salinity changes are mainly driven by respective changes of the horizontal advection. South of the equatorial region, between 45°E and 90°E, where evaporation minus precipitation has a strong seasonal cycle, surface freshwater fluxes control the seasonal MLS changes. The influence of entrainment on the salinity variance is enhanced in mid-ocean upwelling regions but remains small. The model and observational results reveal that vertical diffusion plays a major role in precipitation and river runoff dominated regions balancing the surface freshwater flux. Vertical diffusion is important as well in regions where the advection of low salinity leads to strong gradients across the mixed-layer base. There, vertical diffusion explains a large percentage of annual MLS variance. The simulation further reveals that (1) high-frequency small-scale eddy processes primarily determine the salinity tendency in coastal regions (in particular in the Bay of Bengal) and (2) shear horizontal advection, brought about by changes in the vertical structure of the mixed layer, acts against mean horizontal advection in the equatorial salinity frontal regions. Observing those latter features with the existing observational components remains a future challenge.

Management scenarios for the Jordan River salinity crisis

USGS Publications Warehouse

Farber, E.; Vengosh, A.; Gavrieli, I.; Marie, Amarisa; Bullen, T.D.; Mayer, B.; Holtzman, R.; Segal, M.; Shavit, U.

2005-01-01

Recent geochemical and hydrological findings show that the water quality of the base flow of the Lower Jordan River, between the Sea of Galilee and the Dead Sea, is dependent upon the ratio between surface water flow and groundwater discharge. Using water quality data, mass-balance calculations, and actual flow-rate measurements, possible management scenarios for the Lower Jordan River and their potential affects on its salinity are investigated. The predicted scenarios reveal that implementation of some elements of the Israel-Jordan peace treaty will have negative effects on the Jordan River water salinity. It is predicted that removal of sewage effluents dumped into the river (???13 MCM/a) will significantly reduce the river water's flow and increase the relative proportion of the saline groundwater flux into the river. Under this scenario, the Cl content of the river at its southern point (Abdalla Bridge) will rise to almost 7000 mg/L during the summer. In contrast, removal of all the saline water (16.5 MCM/a) that is artificially discharged into the Lower Jordan River will significantly reduce its Cl concentration, to levels of 650-2600 and 3000-3500 mg/L in the northern and southern areas of the Lower Jordan River, respectively. However, because the removal of either the sewage effluents or the saline water will decrease the river's discharge to a level that could potentially cause river desiccation during the summer months, other water sources must be allocated to preserve in-stream flow needs and hence the river's ecosystem. ?? 2005 Elsevier Ltd. All rights reserved.

Long-terms Change of Sea Surface Temperature in the South China Sea

NASA Astrophysics Data System (ADS)

Park, Y. G.; Choi, A.

2016-02-01

Using the Hadley Centre Global Sea Ice and Sea Surface Temperature (HadISST) the long term trend in the South China Sea (SCS) sea surface temperature (SST) between 1950 and 2008 is investigated. Both in winter and summer SST was increased by comparable amounts, but the warming patterns and the governing processes was different. During winter warming rate was greater in the deep basin in the central part, while during summer near the southern part. In winter the net heat flux into the sea was increased and could contribute to the warming. The pattern of the heat flux, however, was different from that of the warming. The heat flux was increased over the coastal area where warming was weaker, but decreased in deeper part where warming was stronger. The northeasterly monsoon wind weakened to lower the shoreward Ekman transport and the sea surface height gradient. The cyclonic gyre that transports cold northern water to south was weakened to warm the ocean. The effect manifested more strongly southward western boundary currents, and subsequently cold advection. In summer the net surface heat flux, however, was reduced and could not contribute to the warming. Over the southern part of the ocean the weakening of the southwesterly summer monsoon reduced southeastward Ekman transport, which is antiparallel to the mean SST gradient. Firstly, southeastward cold advection is reduced to warm the surface near the southeastern boundary of the SCS. The upwelling southeast of Vietnam was also weakened to raise the SST east of Vietnam. Thus the weakening of the wind in each season was the ultimate cause of the warming, but the responses of the ocean that lead to the warming were different.

Low salinity and high-level UV-B radiation reduce single-cell activity in antarctic sea ice bacteria.

PubMed

Martin, Andrew; Hall, Julie; Ryan, Ken

2009-12-01

Experiments simulating the sea ice cycle were conducted by exposing microbes from Antarctic fast ice to saline and irradiance regimens associated with the freeze-thaw process. In contrast to hypersaline conditions (ice formation), the simulated release of bacteria into hyposaline seawater combined with rapid exposure to increased UV-B radiation significantly reduced metabolic activity.

Measurement of Near-Surface Salinity, Temperature and Directional Wave Spectra using a Novel Wave-Following, Lagrangian Surface Contact Buoy

NASA Astrophysics Data System (ADS)

Boyle, J. P.

2016-02-01

Results from a surface contact drifter buoy which measures near-surface conductivity ( 10 cm depth), sea state characteristics and near-surface water temperature ( 2 cm depth) are described. This light (< 750 gram), wave-following discus buoy platform has a hull diameter of 25 cm and a thickness of approximately 3 cm. The buoy is designed to allow for capsize events, but remains top up because it is ballasted for self-righting. It has a small above-surface profile and low windage, resulting in near-Lagrangian drift characteristics. It is autonomous, with low power requirements and solar panel battery recharging. Onboard sensors include an inductive toroidal conductivity probe for salinity measurement, a nine-degrees-of-freedom motion package for derivation of directional wave spectra and a thermocouple for water temperature measurement. Data retrieval for expendable, ocean-going operation uses an onboard Argos transmitter. Scientific results as well as data processing algorithms are presented from laboratory and field experiments which support qualification of buoy platform measurements. These include sensor calibration experiments, longer-term dock-side biofouling experiments during 2013-2014 and a series of short-duration ocean deployments in the Gulf Stream in 2014. In addition, a treatment method will be described which appears to minimize the effects of biofouling on the inductive conductivity probe when in coastal surface waters. Due to its low cost and ease of deployment, scores, perhaps hundreds of these novel instruments could be deployed from ships or aircraft during process studies or to provide surface validation for satellite-based measurements, particularly in high precipitation regions.

On the Balancing of the SMOS Ocean Salinity Retrieval Cost Function

NASA Astrophysics Data System (ADS)

Sabia, R.; Camps, A.; Portabella, M.; Talone, M.; Ballabrera, J.; Gourrion, J.; Gabarró, C.; Aretxabaleta, A. L.; Font, J.

2009-04-01

The Soil Moisture and Ocean Salinity (SMOS) mission will be launched in mid 2009 to provide synoptic sea surface salinity (SSS) measurements with good temporal resolution [1]. To obtain a proper estimation of the SSS fields derived from the multi-angular brightness temperatures (TB) measured by the Microwave Interferometric Radiometer by Aperture Synthesis (MIRAS) sensor, a comprehensive inversion procedure has been defined [2]. Nevertheless, several salinity retrieval issues remain critical, namely: 1) Scene-dependent bias in the simulated TBs, 2) L-band forward geophysical model function definition, 3) Auxiliary data uncertainties, 4) Constraints in the cost function (inversion), especially in salinity term, and 5) Adequate spatio-temporal averaging. These issues will have to be properly addressed in order to meet the proposed accuracy requirement of the mission: a demanding 0.1 psu (practical salinity units) after averaging in a 30-day and 2°x2° spatio-temporal boxes. The salinity retrieval cost function minimizes the difference between the multi-angular measured SMOS TBs (yet simulated, so far) and the modeled TBs, weighted by the corresponding radiometric noise of the measurements. Furthermore, due to the fact that the minimization problem is both non-linear and ill-posed, background reference terms are needed to nudge the solution and ensuring convergence at the same time [3]. Constraining terms in SSS, sea surface temperature (SST) and wind speed are considered with their respective uncertainties. Moreover, whether SSS constraints have to be included or not as part of the retrieval procedure is still a matter of debate. On one hand, neglecting background reference information on SSS might prevent from retrieving salinity with the prescribed accuracy or at least within reasonable error. Conversely, including constraints in SSS, relying for instance on the climatology, may force the retrieved value to be too close to the reference prior values, thus

Scottish saline lagoons: Impacts and challenges of climate change

NASA Astrophysics Data System (ADS)

Angus, Stewart

2017-11-01

The majority of Scotland's saline lagoons are located on the low-lying coastlines of the Western Isles and the northern archipelagos of Orkney and Shetland, where recorded annual relative sea level rise rates are among the highest in Scotland. The sediment-impounded lagoons of Orkney and Shetland will either lose their impoundment and become incorporated in marine coastal waters, or become increasingly saline, as relative sea levels rise. The rock-basin lagoons of the Western Isles will retain their restricted exchange with the sea but will also become more saline with rising sea level. Specialist lagoonal organisms tend to have wide salinity tolerances but may succumb to competition from marine counterparts. In all areas, there are sufficient fresh-water inland water bodies with potential to be captured as lagoons to compensate for loss of extent and number, but the specialist lagoon biota tend to have limited dispersal powers. It is thus possible that they will be unable to transfer to their analogue sites before existing lagoons become fully marine, giving conservation managers the problem of deciding on management options: leave natural processes to operate without interference, manage the saline inflow to maintain the current salinity regime, or translocate lagoon organisms perceived as threatened by rising salinities. Timing of conversion and capture is unpredictable due to local topography and complications caused by variable stratification.

The Dead Sea

NASA Technical Reports Server (NTRS)

2006-01-01

The Dead Sea is the lowest point on Earth at 418 meters below sea level, and also one of the saltiest bodies of water on Earth with a salinity of about 300 parts-per-thousand (nine times greater than ocean salinity). It is located on the border between Jordan and Israel, and is fed by the Jordan River. The Dead Sea is located in the Dead Sea Rift, formed as a result of the Arabian tectonic plate moving northward away from the African Plate. The mineral content of the Dead Sea is significantly different from that of ocean water, consisting of approximately 53% magnesium chloride, 37% potassium chloride and 8% sodium chloride. In the early part of the 20th century, the Dead Sea began to attract interest from chemists who deduced that the Sea was a natural deposit of potash and bromine. From the Dead Sea brine, Israel and Jordan produce 3.8 million tons potash, 200,000 tons elemental bromine, 45,000 tons caustic soda, 25, 000 tons magnesium metal, and sodium chloride. Both countries use extensive salt evaporation pans that have essentially diked the entire southern end of the Dead Sea.

With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet.

ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping, and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop

Hydrographic survey in the dying Aral Sea

NASA Astrophysics Data System (ADS)

Zavialov, P. O.; Kostianoy, A. G.; Emelianov, S. V.; Ni, A. A.; Ishniyazov, D.; Khan, V. M.; Kudyshkin, T. V.

2003-07-01

We report the results of a hydrographic survey conducted in November, 2002, in the Uzbekistan part of the western basin of the dying Aral Sea. There were very few hydrographic measurements in this region since at least early 1990s. The salinity in the western deep basin of the Aral Sea varied from about 82 psu at the surface to over 94 psu at the bottom. The absolute lake surface level was about 30.5 m. Hence, the observed salinity values were much higher, and the level much lower, than expected according to earlier predictions. The density in the western basin exhibited an extremely strong stratification of ~11 kg/m3 per ~20 m in the bottom layer. The picnocline was accompanied by a temperature inversion whose magnitude was ~4°C. The observed density stratification effectively isolating the lower part of the water column from surface exchanges may be responsible for the increase of summer SSTs and evaporation rates reported in previous studies. We discovered the hydrogen sulphide contamination in the bottom layer whose upper limit was at the depth of approximately 22 m. Estimates suggest that the western basin salinization occurs not only because of the local evaporation, but also because of the assimilation of the saltier eastern basin water in the course of the interbasin exchange through the connecting channel. The satellite imagery analysis, in particular the Maximum Cross-Correlation method, suggests that the circulation pattern in the Aral Sea in its present limits is cyclonic under the eastern winds that are predominant in the region throughout the year.

Arctic Sea Ice Classification and Mapping for Surface Albedo Parameterization in Sea Ice Modeling

NASA Astrophysics Data System (ADS)

Nghiem, S. V.; Clemente-Colón, P.; Perovich, D. K.; Polashenski, C.; Simpson, W. R.; Rigor, I. G.; Woods, J. E.; Nguyen, D. T.; Neumann, G.

2016-12-01

A regime shift of Arctic sea ice from predominantly perennial sea ice (multi-year ice or MYI) to seasonal sea ice (first-year ice or FYI) has occurred in recent decades. This shift has profoundly altered the proportional composition of different sea ice classes and the surface albedo distribution pertaining to each sea ice class. Such changes impacts physical, chemical, and biological processes in the Arctic atmosphere-ice-ocean system. The drastic changes upset the traditional geophysical representation of surface albedo of the Arctic sea ice cover in current models. A critical science issue is that these profound changes must be rigorously and systematically observed and characterized to enable a transformative re-parameterization of key model inputs, such as ice surface albedo, to ice-ocean-atmosphere climate modeling in order to obtain re-analyses that accurately reproduce Arctic changes and also to improve sea ice and weather forecast models. Addressing this challenge is a strategy identified by the National Research Council study on "Seasonal to Decadal Predictions of Arctic Sea Ice - Challenges and Strategies" to replicate the new Arctic reality. We review results of albedo characteristics associated with different sea ice classes such as FYI and MYI. Then we demonstrate the capability for sea ice classification and mapping using algorithms developed by the Jet Propulsion Laboratory and by the U.S. National Ice Center for use with multi-sourced satellite radar data at L, C, and Ku bands. Results obtained with independent algorithms for different radar frequencies consistently identify sea ice classes and thereby cross-verify the sea ice classification methods. Moreover, field observations obtained from buoy webcams and along an extensive trek across Elson Lagoon and a sector of the Beaufort Sea during the BRomine, Ozone, and Mercury EXperiment (BROMEX) in March 2012 are used to validate satellite products of sea ice classes. This research enables the mapping

Calving seismicity from iceberg-sea surface interactions

USGS Publications Warehouse

Bartholomaus, T.C.; Larsen, C.F.; O'Neel, S.; West, M.E.

2012-01-01

Iceberg calving is known to release substantial seismic energy, but little is known about the specific mechanisms that produce calving icequakes. At Yahtse Glacier, a tidewater glacier on the Gulf of Alaska, we draw upon a local network of seismometers and focus on 80 hours of concurrent, direct observation of the terminus to show that calving is the dominant source of seismicity. To elucidate seismogenic mechanisms, we synchronized video and seismograms to reveal that the majority of seismic energy is produced during iceberg interactions with the sea surface. Icequake peak amplitudes coincide with the emergence of high velocity jets of water and ice from the fjord after the complete submergence of falling icebergs below sea level. These icequakes have dominant frequencies between 1 and 3 Hz. Detachment of an iceberg from the terminus produces comparatively weak seismic waves at frequencies between 5 and 20 Hz. Our observations allow us to suggest that the most powerful sources of calving icequakes at Yahtse Glacier include iceberg-sea surface impact, deceleration under the influence of drag and buoyancy, and cavitation. Numerical simulations of seismogenesis during iceberg-sea surface interactions support our observational evidence. Our new understanding of iceberg-sea surface interactions allows us to reattribute the sources of calving seismicity identified in earlier studies and offer guidance for the future use of seismology in monitoring iceberg calving.

Precise orbit computation and sea surface modeling

NASA Technical Reports Server (NTRS)

Wakker, Karel F.; Ambrosius, B. A. C.; Rummel, R.; Vermaat, E.; Deruijter, W. P. M.; Vandermade, J. W.; Zimmerman, J. T. F.

1991-01-01

The research project described below is part of a long-term program at Delft University of Technology aiming at the application of European Remote Sensing satellite (ERS-1) and TOPEX/POSEIDON altimeter measurements for geophysical purposes. This program started in 1980 with the processing of Seasat laser range and altimeter height measurements and concentrates today on the analysis of Geosat altimeter data. The objectives of the TOPEX/POSEIDON research project are the tracking of the satellite by the Dutch mobile laser tracking system MTLRS-2, the computation of precise TOPEX/POSEIDON orbits, the analysis of the spatial and temporal distribution of the orbit errors, the improvement of ERS-1 orbits through the information obtained from the altimeter crossover difference residuals for crossing ERS-1 and TOPEX/POSEIDON tracks, the combination of ERS-1 and TOPEX/POSEIDON altimeter data into a single high-precision data set, and the application of this data set to model the sea surface. The latter application will focus on the determination of detailed regional mean sea surfaces, sea surface variability, ocean topography, and ocean currents in the North Atlantic, the North Sea, the seas around Indonesia, the West Pacific, and the oceans around South Africa.

Tidal Marshes across a Chesapeake Bay Subestuary Are Not Keeping up with Sea-Level Rise

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beckett, Leah H.; Baldwin, Andrew H.; Kearney, Michael S.

Sea-level rise is a major factor in wetland loss worldwide, and inmuch of Chesapeake Bay (USA) the rate of sea-level rise is higher than the current global rate of 3.2 mmyr -1 due to regional subsidence.Marshes along estuarine salinity gradients differ in vegetation composition, productivity, decomposition pathways, and sediment dynamics, andmay exhibit different responses to sea-level rise. Coastal marshes persist by building vertically at rates at or exceeding regional sea-level rise. In one of the first studies to examine elevation dynamics across an estuarine salinity gradient, we installed 15 surface elevation tables (SET) and accretion marker-horizon plots (MH) in tidalmore » freshwater, oligohaline, and brackish marshes across a Chesapeake Bay subestuary. Over the course of four years, wetlands across the subestuary decreased 1.8 ± 2.7 mmyr -1 in elevation on average, at least 5 mmyr -1 below that needed to keep pace with global sea-level rise. Elevation change rates did not significantly differ among themarshes studied, and ranged from-9.8 ± 6.9 to 4.5 ± 4.3 mmyr -1. Surface accretion of depositedmineral and organic matter was uniformly high across the estuary (~9–15 mmyr -1), indicating that elevation loss was not due to lack of accretionary input. Position in the estuary and associated salinity regime were not related to elevation change or surface matter accretion. In conclusion, previous studies have focused on surface elevation change inmarshes of uniformsalinity (e.g., salt marshes); however, our findings highlight the need for elevation studies inmarshes of all salinity regimes and different geomorphic positions, and warn that brackish, oligohaline, and freshwater tidal wetlands may be at similarly high risk of submergence in some estuaries.« less

Tidal Marshes across a Chesapeake Bay Subestuary Are Not Keeping up with Sea-Level Rise

DOE PAGES

Beckett, Leah H.; Baldwin, Andrew H.; Kearney, Michael S.; ...

2016-07-28

Sea-level rise is a major factor in wetland loss worldwide, and inmuch of Chesapeake Bay (USA) the rate of sea-level rise is higher than the current global rate of 3.2 mmyr -1 due to regional subsidence.Marshes along estuarine salinity gradients differ in vegetation composition, productivity, decomposition pathways, and sediment dynamics, andmay exhibit different responses to sea-level rise. Coastal marshes persist by building vertically at rates at or exceeding regional sea-level rise. In one of the first studies to examine elevation dynamics across an estuarine salinity gradient, we installed 15 surface elevation tables (SET) and accretion marker-horizon plots (MH) in tidalmore » freshwater, oligohaline, and brackish marshes across a Chesapeake Bay subestuary. Over the course of four years, wetlands across the subestuary decreased 1.8 ± 2.7 mmyr -1 in elevation on average, at least 5 mmyr -1 below that needed to keep pace with global sea-level rise. Elevation change rates did not significantly differ among themarshes studied, and ranged from-9.8 ± 6.9 to 4.5 ± 4.3 mmyr -1. Surface accretion of depositedmineral and organic matter was uniformly high across the estuary (~9–15 mmyr -1), indicating that elevation loss was not due to lack of accretionary input. Position in the estuary and associated salinity regime were not related to elevation change or surface matter accretion. In conclusion, previous studies have focused on surface elevation change inmarshes of uniformsalinity (e.g., salt marshes); however, our findings highlight the need for elevation studies inmarshes of all salinity regimes and different geomorphic positions, and warn that brackish, oligohaline, and freshwater tidal wetlands may be at similarly high risk of submergence in some estuaries.« less

Seasonal variation of hydrographic and nutrient fields during the US JGOFS Arabian Sea Process Study

NASA Astrophysics Data System (ADS)

Morrison, J. M.; Codispoti, L. A.; Gaurin, S.; Jones, B.; Manghnani, V.; Zheng, Z.

Between September 1994 and December 1995, the US JGOFS Arabian Sea Process Experiment collected extensive, high quality hydrographic data (temperature, salinity, dissolved oxygen and nutrients) during all seasons in the northern Arabian Sea. An analysis of this unique data suite suggests the presence of many features that are described in the canonical literature, but these new data provided the following insights. Although the seasonal evolution of mixed-layer depths was in general agreement with previous descriptions, the deepest mixed-layer depths in our data occurred during the late NE Monsoon instead of the SW Monsoon. The region exhibits considerable mesoscale variability resulting in extremely variable temperature-salinity (TS) distributions in the upper 1000 db. This mesoscale variability is readily observed in satellite imaging, in the high resolution data taken by a companion ONR funded project, and in underway ADCP data. The densest water reaching the sea surface during coastal upwelling appeared to have maximum offshore depths of ˜150 m and σθ's close to the core value (˜25) for the saline Arabian Sea Water (ASW), but salinities in these upwelling waters were relatively low. The densest water found at the sea surface during late NE Monsoon conditions has σθ's>24.8 and relatively high salinities, suggesting that they are a source for the ASW salinity maximum. Persian Gulf Water (PGW) with a core σθ of 26.6 forms a widespread salinity maximum. Despite the considerable extent of this feature, Persian Gulf outflow water, with a salinity (4) of ˜39 at its source, can only be a minor contributor. Within the standard US JGOFS sampling grid, maximum salinities on this surface are ˜36.8 at stations near the Gulf, falling to values as low as ˜35.3 at the stations farthest removed from its influence. Even at our standard stations closest to the Gulf (N-1 and N-2), the high-salinity, low-nutrient Persian Gulf water has only a modest direct effect on

Oxygen isotope ranking of late Eocene and Oligocene planktonic foraminifers: Implications for Oligocene sea-surface temperatures and global ice-volume

USGS Publications Warehouse

Poore, R.Z.; Matthews, R.K.

1984-01-01

Oxygen isotope analyses of late Eocene and Oligocene planktonic foraminifers from low and middle latitude sites in the Atlantic Basin show that different species from the same samples can yield significantly different isotopic values. The range of isotopic values observed between species is greatest at low-latitudes and declines poleward. Many planktonic foraminifers exhibit a systematic isotopic ranking with respect to each other and can therefore be grouped on the basis of their isotopic ranking. The isotopic ranking of some taxa, however, appears to vary geographically and/or through time. Isotopic and paleontologic data from DSDP Site 522 indicate that commonly used isotopic temperature scales underestimate Oligocene sea surface temperatures. We suggest these temperature scales require revision to reflect the presence of Oligocene glaciation. Comparison of isotopic and paleontologic data from Sites 522, 511 and 277 suggests cold, low-salinity surface waters were present in high southern latitudes during the early Oligocene. Lowsalinity, high latitude surface waters could be caused by Eocene/Oligocene paleogeography or by the production of warm saline bottom water. ?? 1984.

Understanding the Dynamics of the South Indian Ocean Sea Surface Salinity Maximum Pool From Argo, Rama, Aquarius, SMOS & Other Satellites

NASA Astrophysics Data System (ADS)

Menezes, V. V.; Phillips, H. E.

2016-02-01

Subtropical salinity maximum regions are particularly important because the salty subtropical underwater (STW) is formed by subduction of surface waters in these areas. In all oceans, the STW is transported equatorward from the formation region and are tightly related to the Subtropical-Tropical Cell. In the South Indian Ocean (SIO), the salinity maximum pool is further poleward (25S-38S) and eastward (60E-120E). It significantly impacts the circulation of the eastern basin, because the STW forms a strong haline front with the fresh Indonesian Throughflow waters. This haline front overwhelms the temperature contribution establishing the eastward Eastern Gyral Current, an important upstream source for the Leeuwin Current. In the present work, we analyze the variability of the SSS maximum pool using Aquarius and SMOS satellites, an Argo gridded product and the RAMA mooring located at 25S-100E. OAFLUX, 3B42 TRMM, Ascat/Quikscat winds and OSCAR products complement this study. The salinity maximum pool has a strong seasonal cycle of contraction (min in Oct) and expansion (max in April), and most of this variation occurs in the pool poleward side. Advection and entrainment control the contraction, while expansion is due to atmospheric forcing (E-P). From 2004 to 2014, a clear reduction in the pool area is identified, which might be related to a decadal variability. In this case, the variation is in the equatorward side of the pool. Processes controlling this long-term variability are being investigated.

Combined Effects of the North Atlantic Oscillation and the Arctic Oscillation on Sea Surface Temperature in the Alborán Sea

PubMed Central

Báez, José C.; Gimeno, Luis; Gómez-Gesteira, Moncho; Ferri-Yáñez, Francisco; Real, Raimundo

2013-01-01

We explored the possible effects of the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) on interannual sea surface temperature (SST) variations in the Alborán Sea, both separately and combined. The probability of observing mean annual SST values higher than average was related to NAO and AO values of the previous year. The effect of NAO on SST was negative, while that of AO was positive. The pure effects of NAO and AO on SST are obscuring each other, due to the positive correlation between them. When decomposing SST, NAO and AO in seasonal values, we found that variation in mean annual SST and mean winter SST was significantly related to the mean autumn NAO of the previous year, while mean summer SST was related to mean autumn AO of the previous year. The one year delay in the effect of the NAO and AO on the SST could be partially related to the amount of accumulated snow, as we found a significant correlation between the total snow in the North Alborán watershed for a year with the annual average SST of the subsequent year. A positive AO implies a colder atmosphere in the Polar Regions, which could favour occasional cold waves over the Iberian Peninsula which, when coupled with precipitations favoured by a negative NAO, may result in snow precipitation. This snow may be accumulated in the high peaks and melt down in spring-summer of the following year, which consequently increases the runoff of freshwater to the sea, which in turn causes a diminution of sea surface salinity and density, and blocks the local upwelling of colder water, resulting in a higher SST. PMID:23638005

Low pCO2 under sea-ice melt in the Canada Basin of the western Arctic Ocean

NASA Astrophysics Data System (ADS)

Kosugi, Naohiro; Sasano, Daisuke; Ishii, Masao; Nishino, Shigeto; Uchida, Hiroshi; Yoshikawa-Inoue, Hisayuki

2017-12-01

In September 2013, we observed an expanse of surface water with low CO2 partial pressure (pCO2sea) (< 200 µatm) in the Chukchi Sea of the western Arctic Ocean. The large undersaturation of CO2 in this region was the result of massive primary production after the sea-ice retreat in June and July. In the surface of the Canada Basin, salinity was low (< 27) and pCO2sea was closer to the air-sea CO2 equilibrium (˜ 360 µatm). From the relationships between salinity and total alkalinity, we confirmed that the low salinity in the Canada Basin was due to the larger fraction of meltwater input (˜ 0.16) rather than the riverine discharge (˜ 0.1). Such an increase in pCO2sea was not so clear in the coastal region near Point Barrow, where the fraction of riverine discharge was larger than that of sea-ice melt. We also identified low pCO2sea (< 250 µatm) in the depth of 30-50 m under the halocline of the Canada Basin. This subsurface low pCO2sea was attributed to the advection of Pacific-origin water, in which dissolved inorganic carbon is relatively low, through the Chukchi Sea where net primary production is high. Oxygen supersaturation (> 20 µmol kg-1) in the subsurface low pCO2sea layer in the Canada Basin indicated significant net primary production undersea and/or in preformed condition. If these low pCO2sea layers surface by wind mixing, they will act as additional CO2 sinks; however, this is unlikely because intensification of stratification by sea-ice melt inhibits mixing across the halocline.

Biofilm-like properties of the sea surface and predicted effects on air-sea CO2 exchange

NASA Astrophysics Data System (ADS)

Wurl, Oliver; Stolle, Christian; Van Thuoc, Chu; The Thu, Pham; Mari, Xavier

2016-05-01

Because the sea surface controls various interactions between the ocean and the atmosphere, it has a profound function for marine biogeochemistry and climate regulation. The sea surface is the gateway for the exchange of climate-relevant gases, heat and particles. Thus, in order to determine how the ocean and the atmosphere interact and respond to environmental changes on a global scale, the characterization and understanding of the sea surface are essential. The uppermost part of the water column is defined as the sea-surface microlayer and experiences strong spatial and temporal dynamics, mainly due to meteorological forcing. Wave-damped areas at the sea surface are caused by the accumulation of surface-active organic material and are defined as slicks. Natural slicks are observed frequently but their biogeochemical properties are poorly understood. In the present study, we found up to 40 times more transparent exopolymer particles (TEP), the foundation of any biofilm, in slicks compared to the underlying bulk water at multiple stations in the North Pacific, South China Sea, and Baltic Sea. We found a significant lower enrichment of TEP (up to 6) in non-slick sea surfaces compared to its underlying bulk water. Moreover, slicks were characterized by a large microbial biomass, another shared feature with conventional biofilms on solid surfaces. Compared to non-slick samples (avg. pairwise similarity of 70%), the community composition of bacteria in slicks was increasingly (avg. pairwise similarity of 45%) different from bulk water communities, indicating that the TEP-matrix creates specific environments for its inhabitants. We, therefore, conclude that slicks can feature biofilm-like properties with the excessive accumulation of particles and microbes. We also assessed the potential distribution and frequency of slick-formation in coastal and oceanic regions, and their effect on air-sea CO2 exchange based on literature data. We estimate that slicks can reduce CO2

Carbon speciation at the air-sea interface during rain

NASA Astrophysics Data System (ADS)

McGillis, Wade; Hsueh, Diana; Takeshita, Yui; Donham, Emily; Markowitz, Michele; Turk, Daniela; Martz, Todd; Price, Nicole; Langdon, Chris; Najjar, Raymond; Herrmann, Maria; Sutton, Adrienne; Loose, Brice; Paine, Julia; Zappa, Christopher

2015-04-01

This investigation demonstrates the surface ocean dilution during rain events on the ocean and quantifies the lowering of surface pCO2 affecting the air-sea exchange of carbon dioxide. Surface salinity was measured during rain events in Puerto Rico, the Florida Keys, East Coast USA, Panama, and the Palmyra Atoll. End-member analysis is used to determine the subsequent surface ocean carbonate speciation. Surface ocean carbonate chemistry was measured during rain events to verify any approximations made. The physical processes during rain (cold, fresh water intrusion and buoyancy, surface waves and shear, microscale mixing) are described. The role of rain on surface mixing, biogeochemistry, and air-sea gas exchange will be discussed.

Near-surface Salinity and Temperature Structure Observed with Dual-Sensor Drifters in the Subtropical South Pacific

NASA Astrophysics Data System (ADS)

Dong, Shenfu; Goni, Gustavo; Volkov, Denis; Lumpkin, Rick; Foltz, Gregory

2017-04-01

Three surface drifters equipped with temperature and salinity sensors at 0.2 m and 5 m depths were deployed in April/May 2015 in the subtropical South Pacific Ocean with the objective of measuring near-surface salinity differences seen by satellite and in situ sensors and examining the causes of the differences. Measurements from these drifters indicate that, on average, water at a depth of 0.2 m is about 0.013 psu fresher than at 5 m and about 0.024°C warmer. Events with large temperature and salinity differences between the two depths often occur when surface winds are weak. In addition to the expected surface freshening and cooling during rainfall events, surface salinification occurs under weak wind conditions when there is strong surface warming that enhances evaporation and upper ocean stratification. Further examination of the drifter measurements demonstrate that (i) the amount of surface freshening and vertical salinity gradient heavily depend on wind speed during rain events, (ii) salinity differences between 0.2 m and 5 m are positively correlated with the corresponding temperature differences, and (iii) temperature exhibits a diurnal cycle at both depths, whereas the diurnal cycle of salinity is observed only at 0.2 m when the wind speed is less than 4 m/s. Its phase is consistent with diurnal changes in surface temperature-induced evaporation. Below a wind speed of 6 m/s, the amplitudes of the diurnal cycles of temperature at both depths decrease with increasing wind speed. Wind speed also affects the phasing of the diurnal cycle of T5m with the time of maximum T5m increasing gradually with decreasing wind speed. Wind speed does not affect the phasing of the diurnal cycle of T0.2m. At 0.2 m and 5 m, the diurnal cycle of temperature also depends on surface solar radiation, with the amplitude and time of diurnal maximum increasing as solar radiation increases.

Colloid transport in porous media: impact of hyper-saline solutions.

PubMed

Magal, Einat; Weisbrod, Noam; Yechieli, Yoseph; Walker, Sharon L; Yakirevich, Alexander

2011-05-01

The transport of colloids suspended in natural saline solutions with a wide range of ionic strengths, up to that of Dead Sea brines (10(0.9) M) was explored. Migration of microspheres through saturated sand columns of different sizes was studied in laboratory experiments and simulated with mathematical models. Colloid transport was found to be related to the solution salinity as expected. The relative concentration of colloids at the columns outlet decreased (after 2-3 pore volumes) as the solution ionic strength increased until a critical value was reached (ionic strength > 10(-1.8) M) and then remained constant above this level of salinity. The colloids were found to be mobile even in the extremely saline brines of the Dead Sea. At such high ionic strength no energetic barrier to colloid attachment was presumed to exist and colloid deposition was expected to be a favorable process. However, even at these salinity levels, colloid attachment was not complete and the transport of ∼ 30% of the colloids through the 30-cm long columns was detected. To further explore the deposition of colloids on sand surfaces in Dead Sea brines, transport was studied using 7-cm long columns through which hundreds of pore volumes were introduced. The resulting breakthrough curves exhibited a bimodal shape whereby the relative concentration (C/C(0)) of colloids at the outlet rose to a value of 0.8, and it remained relatively constant (for the ∼ 18 pore volumes during which the colloid suspension was flushed through the column) and then the relative concentration increased to a value of one. The bimodal nature of the breakthrough suggests different rates of colloid attachment. Colloid transport processes were successfully modeled using the limited entrapment model, which assumes that the colloid attachment rate is dependent on the concentration of the attached colloids. Application of this model provided confirmation of the colloid aggregation and their accelerated attachment during

Decadal trends in Red Sea maximum surface temperature.

PubMed

Chaidez, V; Dreano, D; Agusti, S; Duarte, C M; Hoteit, I

2017-08-15

Ocean warming is a major consequence of climate change, with the surface of the ocean having warmed by 0.11 °C decade -1 over the last 50 years and is estimated to continue to warm by an additional 0.6 - 2.0 °C before the end of the century 1 . However, there is considerable variability in the rates experienced by different ocean regions, so understanding regional trends is important to inform on possible stresses for marine organisms, particularly in warm seas where organisms may be already operating in the high end of their thermal tolerance. Although the Red Sea is one of the warmest ecosystems on earth, its historical warming trends and thermal evolution remain largely understudied. We characterized the Red Sea's thermal regimes at the basin scale, with a focus on the spatial distribution and changes over time of sea surface temperature maxima, using remotely sensed sea surface temperature data from 1982 - 2015. The overall rate of warming for the Red Sea is 0.17 ± 0.07 °C decade -1 , while the northern Red Sea is warming between 0.40 and 0.45 °C decade -1 , all exceeding the global rate. Our findings show that the Red Sea is fast warming, which may in the future challenge its organisms and communities.

Satellite altimetry in sea ice regions - detecting open water for estimating sea surface heights

NASA Astrophysics Data System (ADS)

Müller, Felix L.; Dettmering, Denise; Bosch, Wolfgang

2017-04-01

The Greenland Sea and the Farm Strait are transporting sea ice from the central Arctic ocean southwards. They are covered by a dynamic changing sea ice layer with significant influences on the Earth climate system. Between the sea ice there exist various sized open water areas known as leads, straight lined open water areas, and polynyas exhibiting a circular shape. Identifying these leads by satellite altimetry enables the extraction of sea surface height information. Analyzing the radar echoes, also called waveforms, provides information on the surface backscatter characteristics. For example waveforms reflected by calm water have a very narrow and single-peaked shape. Waveforms reflected by sea ice show more variability due to diffuse scattering. Here we analyze altimeter waveforms from different conventional pulse-limited satellite altimeters to separate open water and sea ice waveforms. An unsupervised classification approach employing partitional clustering algorithms such as K-medoids and memory-based classification methods such as K-nearest neighbor is used. The classification is based on six parameters derived from the waveform's shape, for example the maximum power or the peak's width. The open-water detection is quantitatively compared to SAR images processed while accounting for sea ice motion. The classification results are used to derive information about the temporal evolution of sea ice extent and sea surface heights. They allow to provide evidence on climate change relevant influences as for example Arctic sea level rise due to enhanced melting rates of Greenland's glaciers and an increasing fresh water influx into the Arctic ocean. Additionally, the sea ice cover extent analyzed over a long-time period provides an important indicator for a globally changing climate system.

A laboratory investigation into microwave backscattering from sea ice. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Bredow, Jonathan W.

1989-01-01

The sources of scattering of artificial sea ice were determined, backscatter measurements semi-quantitatively were compared with theoretical predictions, and inexpensive polarimetric radars were developed for sea ice backscatter studies. A brief review of the dielectric properties of sea ice and of commonly used surface and volume scattering theories is presented. A description is provided of the backscatter measurements performed and experimental techniques used. The development of inexpensive short-range polarimetric radars is discussed. The steps taken to add polarimetric capability to a simple FM-W radar are considered as are sample polarimetric phase measurements of the radar. Ice surface characterization data and techniques are discussed, including computation of surface rms height and correlation length and air bubble distribution statistics. A method is also presented of estimating the standard deviation of rms height and correlation length for cases of few data points. Comparisons were made of backscatter measurements and theory. It was determined that backscatter from an extremely smooth saline ice surface at C band cannot be attributed only to surface scatter. It was found that snow cover had a significant influence on backscatter from extremely smooth saline ice at C band.

Physical characteristics of summer sea ice across the Arctic Ocean

USGS Publications Warehouse

Tucker, W. B.; Gow, A.J.; Meese, D.A.; Bosworth, H.W.; Reimnitz, E.

1999-01-01

Sea ice characteristics were investigated during July and August on the 1994 transect across the Arctic Ocean. Properties examined from ice cores included salinity, temperature, and ice structure. Salinities measured near zero at the surface, increasing to 3-4??? at the ice-water interface. Ice crystal texture was dominated by columnar ice, comprising 90% of the ice sampled. Surface albedos of various ice types, measured with radiometers, showed integrated shortwave albedos of 0.1 to 0.3 for melt ponds, 0.5 for bare, discolored ice, and 0.6 to 0.8 for a deteriorated surface or snow-covered ice. Aerial photography was utilized to document the distribution of open melt ponds, which decreased from 12% coverage of the ice surface in late July at 76??N to almost none in mid-August at 88??N. Most melt ponds were shallow, and depth bore no relationship to size. Sediment was pervasive from the southern Chukchi Sea to the north pole, occurring in bands or patches. It was absent in the Eurasian Arctic, where it had been observed on earlier expeditions. Calculations of reverse trajectories of the sediment-bearing floes suggest that the southernmost sediment was entrained during ice formation in the Beaufort Sea while more northerly samples probably originated in the East Siberian Sea, some as far west as the New Siberian Islands.

Black Sea outflow response to Holocene meltwater events.

PubMed

Herrle, Jens O; Bollmann, Jörg; Gebühr, Christina; Schulz, Hartmut; Sheward, Rosie M; Giesenberg, Annika

2018-03-06

During the Holocene, North American ice sheet collapse and rapid sea-level rise reconnected the Black Sea with the global ocean. Rapid meltwater releases into the North Atlantic and associated climate change arguably slowed the pace of Neolithisation across southeastern Europe, originally hypothesized as a catastrophic flooding that fueled culturally-widespread deluge myths. However, we currently lack an independent record linking the timing of meltwater events, sea-level rise and environmental change with the timing of Neolithisation in southeastern Europe. Here, we present a sea surface salinity record from the Northern Aegean Sea indicative of two meltwater events at ~8.4 and ~7.6 kiloyears that can be directly linked to rapid declines in the establishment of Neolithic sites in southeast Europe. The meltwater events point to an increased outflow of low salinity water from the Black Sea driven by rapid sea level rise >1.4 m following freshwater outbursts from Lake Agassiz and the final decay of the Laurentide ice sheet. Our results shed new light on the link between catastrophic sea-level rise and the Neolithisation of southeastern Europe, and present a historical example of how coastal populations could have been impacted by future rapid sea-level rise.

Incorporating future change into current conservation planning: Evaluating tidal saline wetland migration along the U.S. Gulf of Mexico coast under alternative sea-level rise and urbanization scenarios

USGS Publications Warehouse

Enwright, Nicholas M.; Griffith, Kereen T.; Osland, Michael J.

2015-11-02

In this study, the U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, quantified the potential for landward migration of tidal saline wetlands along the U.S. Gulf of Mexico coast under alternative future sea-level rise and urbanization scenarios. Our analyses focused exclusively on tidal saline wetlands (that is, mangrove forests, salt marshes, and salt flats), and we combined these diverse tidal saline wetland ecosystems into a single grouping, “tidal saline wetland.” Collectively, our approach and findings can provide useful information for scientists and environmental planners working to develop future-focused adaptation strategies for conserving coastal landscapes and the ecosystem goods and services provided by tidal saline wetlands. The primary product of this work is a public dataset that identifies locations where landward migration of tidal saline wetlands is expected to occur under alternative future sea-level rise and urbanization scenarios. In addition to identifying areas where landward migration of tidal saline wetlands is possible because of the absence of barriers, these data also identify locations where landward migration of these wetlands could be prevented by barriers associated with current urbanization, future urbanization, and levees.

Hydrographic characterization of southeast Arabian Sea during the wane of southwest monsoon and spring intermonsoon.

PubMed

Vimal Kumar, K G; Dinesh Kumar, P K; Smitha, B R; Habeeb Rahman, H; Josia, Jacob; Muraleedharan, K R; Sanjeevan, V N; Achuthankutty, C T

2008-05-01

Seasonal variation of the hydrography along the southeast Arabian Sea is described using data collected onboard FORV Sagar Sampada in September--October 2003 (later phase of Southwest monsoon, SWM) and March--April 2004 (Spring inter monsoon, SIM). During the later phase of the SWM, upwelling was in the withdrawal phase and the frontal structure was clearer in the northern sections (13 and 15 degrees N lat) indicating strong upwelling in the area. The driving force of upwelling is identified as the combination of alongshore wind stress and remote forcing with a latitudinal variability. Although a more prominent upwelling was found in the north, a maximum surface Chlorophyll-a was found in the south (10 degrees N). During the SIM, the area was characterized by oligotrophic water with relatively high Sea Surface Temperature (>29 degrees C) and low salinity (33.8 to 35.4). During March, the surface hydrography was found to be controlled mainly by the intrusion of low-saline waters from the south, while during September by the high saline water from the north. The presence of various water masses [Arabian Sea High Salinity Water (ASHSW), Persian Gulf Water (PGW), Red Sea Water (RSW)] and their seasonal variations in the region is discussed and their decreasing influence towards the south is noted during both periods of observation. During the SWM, the dynamic topography showed the equator-ward flow of the West India Coastal Current (WICC) at the surface and a pole-ward coastal under current at sub-thermocline depth. During the SIM, surface circulation revealed the WICC flowing pole-ward north of 13 degrees N, but equator-ward flow in the south, with a clockwise circulation around the Lakshadweep High.

Satellite observed salinity distributions at high latitudes in the Northern Hemisphere: A comparison of four products

NASA Astrophysics Data System (ADS)

Garcia-Eidell, Cynthia; Comiso, Josefino C.; Dinnat, Emmanuel; Brucker, Ludovic

2017-09-01

Global surface ocean salinity measurements have been available since the launch of SMOS in 2009 and coverage was further enhanced with the launch of Aquarius in 2011. In the polar regions where spatial and temporal changes in sea surface salinity (SSS) are deemed important, the data have not been as robustly validated because of the paucity of in situ measurements. This study presents a comparison of four SSS products in the ice-free Arctic region, three using Aquarius data and one using SMOS data. The accuracy of each product is assessed through comparative analysis with ship and other in situ measurements. Results indicate RMS errors ranging between 0.33 and 0.89 psu. Overall, the four products show generally good consistency in spatial distribution with the Atlantic side being more saline than the Pacific side. A good agreement between the ship and satellite measurements was also observed in the low salinity regions in the Arctic Ocean, where SSS in situ measurements are usually sparse, at the end of summer melt seasons. Some discrepancies including biases of about 1 psu between the products in spatial and temporal distribution are observed. These are due in part to differences in retrieval techniques, geophysical filtering, and sea ice and land masks. The monthly SSS retrievals in the Arctic from 2011 to 2015 showed variations (within ˜1 psu) consistent with effects of sea ice seasonal cycles. This study indicates that spaceborne observations capture the seasonality and interannual variability of SSS in the Arctic with reasonably good accuracy.

Nudging the Arctic Ocean to quantify Arctic sea ice feedbacks

NASA Astrophysics Data System (ADS)

Dekker, Evelien; Severijns, Camiel; Bintanja, Richard

2017-04-01

It is well-established that the Arctic is warming 2 to 3 time faster than rest of the planet. One of the great uncertainties in climate research is related to what extent sea ice feedbacks amplify this (seasonally varying) Arctic warming. Earlier studies have analyzed existing climate model output using correlations and energy budget considerations in order to quantify sea ice feedbacks through indirect methods. From these analyses it is regularly inferred that sea ice likely plays an important role, but details remain obscure. Here we will take a different and a more direct approach: we will keep the sea ice constant in a sensitivity simulation, using a state-of -the-art climate model (EC-Earth), applying a technique that has never been attempted before. This experimental technique involves nudging the temperature and salinity of the ocean surface (and possibly some layers below to maintain the vertical structure and mixing) to a predefined prescribed state. When strongly nudged to existing (seasonally-varying) sea surface temperatures, ocean salinity and temperature, we force the sea ice to remain in regions/seasons where it is located in the prescribed state, despite the changing climate. Once we obtain fixed' sea ice, we will run a future scenario, for instance 2 x CO2 with and without prescribed sea ice, with the difference between these runs providing a measure as to what extent sea ice contributes to Arctic warming, including the seasonal and geographical imprint of the effects.

Ocean Salinity Variance and the Global Water Cycle.

NASA Astrophysics Data System (ADS)

Schmitt, R. W.

2012-12-01

Ocean salinity variance is increasing and appears to be an indicator of rapid change in the global water cycle. While the small terrestrial water cycle does not reveal distinct trends, in part due to strong manipulation by civilization, the much larger oceanic water cycle seems to have an excellent proxy for its intensity in the contrasts in sea surface salinity (SSS). Change in the water cycle is arguably the most important challenge facing mankind. But how well do we understand the oceanic response? Does the ocean amplify SSS change to make it a hyper-sensitive indicator of change in the global water cycle? An overview of the research challenges to the oceanographic community for understanding the dominant component of the global water cycle is provided.

Twentieth century sea surface temperature and salinity variations at Timor inferred from paired coral δ18O and Sr/Ca measurements

NASA Astrophysics Data System (ADS)

Cahyarini, Sri Yudawati; Pfeiffer, Miriam; Nurhati, Intan Suci; Aldrian, Edvin; Dullo, Wolf-Christian; Hetzinger, Steffen

2014-07-01

The Indonesian Throughflow (ITF), which represents the global ocean circulation connecting the Pacific Warm Pool to the Indian Ocean, strongly influences the Indo-Pacific climate. ITF monitoring since the late 1990s using mooring buoys have provided insights on seasonal and interannual time scales. However, the absence of longer records limits our perspective on its evolution over the past century. Here, we present sea surface temperature (SST) and salinity (SSS) proxy records from Timor Island located at the ITF exit passage via paired coral δ18O and Sr/Ca measurements spanning the period 1914-2004. These high-resolution proxy based climate data of the last century highlights improvements and cautions when interpreting paleoclimate records of the Indonesian region. If the seasonality of SST and SSS is not perfectly in phase, the application of coral Sr/Ca thermometry improves SST reconstructions compared to estimates based on coral δ18O only. Our records also underline the importance of ocean advection besides rainfall on local SSS in the region. Although the El Niño/Southern Oscillation (ENSO) causes larger anomalies relative to the Indian Ocean Dipole (IOD), Timor coral-based SST and SSS records robustly correlate with IOD on interannual time scales, whereas ENSO only modifies Timor SST. Similarly, Timor SST and SSS are strongly linked to Indian Ocean decadal-scale variations that appear to lead Timor oceanographic conditions by about 1.6-2 years. Our study sheds new light on the complex signatures of Indo-Pacific climate modes on SST and SSS dynamics of the ITF. This article was corrected on 8 AUG 2014. See the end of the full text for details.

Detection of subsurface-intensified eddies from observations of the sea-surface: a case study for Mediterranean Water Eddies in a long-term high-resolution simulation

NASA Astrophysics Data System (ADS)

Ciani, Daniele; Carton, Xavier; Barbosa Aguiar, Ana Claudia; Peliz, Alvaro; Bashmachnikov, Igor; Ienna, Federico; Chapron, Bertrand

2017-04-01

Subsurface-intensified eddies are ubiquitous in the world ocean. They can be generated by exchanges of water masses between semi-enclosed evaporation basins and the open ocean or by deep convection. Past and recent studies have shown that these eddies are carriers of large amounts of heat and salt, that they are coherent over inter-annual timescales and that they can migrate for several thousands of miles from their origination areas towards the open ocean. Hence, subsurface-intensified eddies can influence the three-dimensional distribution of oceanic tracers at global scale. The synoptic knowledge of the eddies positions and mean pathways is then crucial for evaluating temperature and salinity budgets in the world ocean. At present day, satellite sensors constitute the ideal tool for the synoptic and global scale observations of the ocean. Since they only provide informations on the oceanic surface, we characterized the signatures that subsurface eddies generate at the sea-surface, to determine the extent to which they can be isolated from the surrounding surface turbulence and be considered as a trace of an underlying eddy. We studied the surface signature of subsurface-intensified anticyclones (Mediterranean Water Eddies - Meddies) in a realistic, long-term (20 years) and high resolution simulation (dx = 3 km) based on the ROMS model. The novelty and advantage of this approach is given by the simultaneous availability of the full 3D eddies characteristics, the ones of the background ocean and of the sea-surface (in terms of sea-surface height, temperature and salinity). This also allowed us to speculate on a synergy between different satellite observations for the automatic detection of subsurface eddies from space. The along trajectory properties and surface signatures of more than 90 long-lived Meddies were analyzed. We showed that the Meddies constantly generate positive anomalies in sea-surface height and that these anomalies are principally related to the

Analyses of Sea Surface Height, Bottom Pressure and Acoustic Travel Time in the Japan/East Sea

DTIC Science & Technology

2006-01-01

ANALYSES OF SEA SURFACE HEIGHT, BOTTOM PRESSURE AND ACOUSTIC TRAVEL TIME IN THE JAPAN/EAST SEA BY YONGSHENG XU A DISSERTATION SUBMITTED IN PARTIAL...COVERED 00-00-2006 to 00-00-2006 4. TITLE AND SUBTITLE Analyses of Sea Surface Height, Bottom Pressure and Acoustic Travel Time in the Japan/East Sea...1999 to July 2001. The PIESs recorded hourly vertical acoustic travel time and pressure, which are respectively good proxies of baroclinic and

Salinity Remote Sensing and the Study of the Global Water Cycle

NASA Technical Reports Server (NTRS)

Lagerloef, G. S. E.; LeVine, David M.; Chao, Y.; Colomb, F. Raul; Font, J.

2007-01-01

The SMOS and AquariusISAC-D satellite missions will begin a new era to map the global sea surface salinity (SSS) field and its variability from space within the next twothree years. They will provide critical data needed to study the interactions between the ocean circulation, global water cycle and climate. Key scientific issues to address are (1) mapping large expanses of the ocean where conventional SSS data do not yet exist, (2) understanding the seasonal and interannual SSS variations and the link to precipitation, evaporation and sea-ice patterns, (3) links between SSS and variations in the oceanic overturning circulation, (4) air-sea coupling processes in the tropics that influence El Nino, and (4) closing the marine freshwater budget. There is a growing body of oceanographic evidence in the form of salinity trends that portend significant changes in the hydrologic cycle. Over the past several decades, highlatitude oceans have become fresher while the subtropical oceans have become saltier. This change is slowly spreading into the subsurface ocean layers and may be affecting the strength of the ocean's therrnohaline overturning circulation. Salinity is directly linked to the ocean dynamics through the density distribution, and provides an important signature of the global water cycle. The distribution and variation of oceanic salinity is therefore attracting increasing scientific attention due to the relationship to the global water cycle and its influence on circulation, mixing, and climate processes. The oceans dominate the water cycle by providing 86% of global surface evaporation (E) and receiving 78% of global precipitation (P). Regional differences in E-P, land runoff, and the melting or freezing of ice affect the salinity of surface water. Direct observations of E-P over the ocean have large uncertainty, with discrepancies between the various state-of-the-art precipitation analyses of a factor of two or more in many regions. Quantifying the climatic

An atlas of monthly mean distributions of GEOSAT sea surface height, SSMI surface wind speed, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1988

NASA Technical Reports Server (NTRS)

Halpern, D.; Zlotnicki, V.; Newman, J.; Brown, O.; Wentz, F.

1991-01-01

Monthly mean global distributions for 1988 are presented with a common color scale and geographical map. Distributions are included for sea surface height variation estimated from GEOSAT; surface wind speed estimated from the Special Sensor Microwave Imager on the Defense Meteorological Satellite Program spacecraft; sea surface temperature estimated from the Advanced Very High Resolution Radiometer on NOAA spacecrafts; and the Cartesian components of the 10m height wind vector computed by the European Center for Medium Range Weather Forecasting. Charts of monthly mean value, sampling distribution, and standard deviation value are displayed. Annual mean distributions are displayed.

The impact of land and sea surface variations on the Delaware sea breeze at local scales

NASA Astrophysics Data System (ADS)

Hughes, Christopher P.

The summertime climate of coastal Delaware is greatly influenced by the intensity, frequency, and location of the local sea breeze circulation. Sea breeze induced changes in temperature, humidity, wind speed, and precipitation influence many aspects of Delaware's economy by affecting tourism, farming, air pollution density, energy usage, and the strength, and persistence of Delaware's wind resource. The sea breeze front can develop offshore or along the coastline and often creates a near surface thermal gradient in excess of 5°C. The purpose of this dissertation is to investigate the dynamics of the Delaware sea breeze with a focus on the immediate coastline using observed and modeled components, both at high resolutions (~200m). The Weather Research and Forecasting model (version 3.5) was employed over southern Delaware with 5 domains (4 levels of nesting), with resolutions ranging from 18km to 222m, for June 2013 to investigate the sensitivity of the sea breeze to land and sea surface variations. The land surface was modified in the model to improve the resolution, which led to the addition of land surface along the coastline and accounted for recent urban development. Nine-day composites of satellite sea surface temperatures were ingested into the model and an in-house SST forcing dataset was developed to account for spatial SST variation within the inland bays. Simulations, which include the modified land surface, introduce a distinct secondary atmospheric circulation across the coastline of Rehoboth Bay when synoptic offshore wind flow is weak. Model runs using high spatial- and temporal-resolution satellite sea surface temperatures over the ocean indicate that the sea breeze landfall time is sensitive to the SST when the circulation develops offshore. During the summer of 2013 a field campaign was conducted in the coastal locations of Rehoboth Beach, DE and Cape Henlopen, DE. At each location, a series of eleven small, autonomous thermo-sensors (i

Patterns of ecological specialization among microbial populations in the Red Sea and diverse oligotrophic marine environments

PubMed Central

Thompson, Luke R; Field, Chris; Romanuk, Tamara; Ngugi, David; Siam, Rania; El Dorry, Hamza; Stingl, Ulrich

2013-01-01

Large swaths of the nutrient-poor surface ocean are dominated numerically by cyanobacteria (Prochlorococcus), cyanobacterial viruses (cyanophage), and alphaproteobacteria (SAR11). How these groups thrive in the diverse physicochemical environments of different oceanic regions remains poorly understood. Comparative metagenomics can reveal adaptive responses linked to ecosystem-specific selective pressures. The Red Sea is well-suited for studying adaptation of pelagic-microbes, with salinities, temperatures, and light levels at the extreme end for the surface ocean, and low nutrient concentrations, yet no metagenomic studies have been done there. The Red Sea (high salinity, high light, low N and P) compares favorably with the Mediterranean Sea (high salinity, low P), Sargasso Sea (low P), and North Pacific Subtropical Gyre (high light, low N). We quantified the relative abundance of genetic functions among Prochlorococcus, cyanophage, and SAR11 from these four regions. Gene frequencies indicate selection for phosphorus acquisition (Mediterranean/Sargasso), DNA repair and high-light responses (Red Sea/Pacific Prochlorococcus), and osmolyte C1 oxidation (Red Sea/Mediterranean SAR11). The unexpected connection between salinity-dependent osmolyte production and SAR11 C1 metabolism represents a potentially major coevolutionary adaptation and biogeochemical flux. Among Prochlorococcus and cyanophage, genes enriched in specific environments had ecotype distributions similar to nonenriched genes, suggesting that inter-ecotype gene transfer is not a major source of environment-specific adaptation. Clustering of metagenomes using gene frequencies shows similarities in populations (Red Sea with Pacific, Mediterranean with Sargasso) that belie their geographic distances. Taken together, the genetic functions enriched in specific environments indicate competitive strategies for maintaining carrying capacity in the face of physical stressors and low nutrient availability. PMID

Patterns of ecological specialization among microbial populations in the Red Sea and diverse oligotrophic marine environments.

PubMed

Thompson, Luke R; Field, Chris; Romanuk, Tamara; Ngugi, David; Siam, Rania; El Dorry, Hamza; Stingl, Ulrich

2013-06-01

Large swaths of the nutrient-poor surface ocean are dominated numerically by cyanobacteria (Prochlorococcus), cyanobacterial viruses (cyanophage), and alphaproteobacteria (SAR11). How these groups thrive in the diverse physicochemical environments of different oceanic regions remains poorly understood. Comparative metagenomics can reveal adaptive responses linked to ecosystem-specific selective pressures. The Red Sea is well-suited for studying adaptation of pelagic-microbes, with salinities, temperatures, and light levels at the extreme end for the surface ocean, and low nutrient concentrations, yet no metagenomic studies have been done there. The Red Sea (high salinity, high light, low N and P) compares favorably with the Mediterranean Sea (high salinity, low P), Sargasso Sea (low P), and North Pacific Subtropical Gyre (high light, low N). We quantified the relative abundance of genetic functions among Prochlorococcus, cyanophage, and SAR11 from these four regions. Gene frequencies indicate selection for phosphorus acquisition (Mediterranean/Sargasso), DNA repair and high-light responses (Red Sea/Pacific Prochlorococcus), and osmolyte C1 oxidation (Red Sea/Mediterranean SAR11). The unexpected connection between salinity-dependent osmolyte production and SAR11 C1 metabolism represents a potentially major coevolutionary adaptation and biogeochemical flux. Among Prochlorococcus and cyanophage, genes enriched in specific environments had ecotype distributions similar to nonenriched genes, suggesting that inter-ecotype gene transfer is not a major source of environment-specific adaptation. Clustering of metagenomes using gene frequencies shows similarities in populations (Red Sea with Pacific, Mediterranean with Sargasso) that belie their geographic distances. Taken together, the genetic functions enriched in specific environments indicate competitive strategies for maintaining carrying capacity in the face of physical stressors and low nutrient availability.

High frequency acoustic propagation under variable sea surfaces

NASA Astrophysics Data System (ADS)

Senne, Joseph

This dissertation examines the effects of rough sea surfaces and sub-surface bubbles on high frequency acoustic transmissions. Owing to the strong attenuation of electromagnetic waves in seawater, acoustic waves are used in the underwater realm much in the same way that electromagnetic waves are used in the atmosphere. The transmission and reception of acoustic waves in the underwater environment is important for a variety of fields including navigation, ocean observation, and real-time communications. Rough sea surfaces and sub-surface bubbles alter the acoustic signals that are received not only in the near-surface water column, but also at depth. This dissertation demonstrates that surface roughness and sub-surface bubbles notably affect acoustic transmissions with frequency ranges typical of underwater communications systems (10-50 kHz). The influence of rough surfaces on acoustic transmissions is determined by modeling forward propagation subject to sea surface dynamics that vary with time scales of less than a second to tens of seconds. A time-evolving rough sea surface model is combined with a rough surface formulation of a parabolic equation model for predicting time-varying acoustic fields. Linear surface waves are generated from surface wave spectra, and evolved in time using a Runge-Kutta integration technique. This evolving, range-dependent surface information is combined with other environmental parameters and fed into the acoustic model, giving an approximation of the time-varying acoustic field. The wide-angle parabolic equation model manages the rough sea surfaces by molding them into the boundary conditions for calculations of the near-surface acoustic field. The influence of sub-surface bubbles on acoustic transmissions is determined by modeling the population of bubbles near the surface and using those populations to approximate the effective changes in sound speed and attenuation. Both range-dependent and range-independent bubble models are

Rapid subtropical North Atlantic salinity oscillations across Dansgaard-Oeschger cycles.

PubMed

Schmidt, Matthew W; Vautravers, Maryline J; Spero, Howard J

2006-10-05

Geochemical and sedimentological evidence suggest that the rapid climate warming oscillations of the last ice age, the Dansgaard-Oeschger cycles, were coupled to fluctuations in North Atlantic meridional overturning circulation through its regulation of poleward heat flux. The balance between cold meltwater from the north and warm, salty subtropical gyre waters from the south influenced the strength and location of North Atlantic overturning circulation during this period of highly variable climate. Here we investigate how rapid reorganizations of the ocean-atmosphere system across these cycles are linked to salinity changes in the subtropical North Atlantic gyre. We combine Mg/Ca palaeothermometry and oxygen isotope ratio measurements on planktonic foraminifera across four Dansgaard-Oeschger cycles (spanning 45.9-59.2 kyr ago) to generate a seawater salinity proxy record from a subtropical gyre deep-sea sediment core. We show that North Atlantic gyre surface salinities oscillated rapidly between saltier stadial conditions and fresher interstadials, covarying with inferred shifts in the Tropical Atlantic hydrologic cycle and North Atlantic overturning circulation. These salinity oscillations suggest a reduction in precipitation into the North Atlantic and/or reduced export of deep salty thermohaline waters during stadials. We hypothesize that increased stadial salinities preconditioned the North Atlantic Ocean for a rapid return to deep overturning circulation and high-latitude warming by contributing to increased North Atlantic surface-water density on interstadial transitions.

Impact of topography on groundwater salinization due to ocean surge inundation

NASA Astrophysics Data System (ADS)

Yu, Xuan; Yang, Jie; Graf, Thomas; Koneshloo, Mohammad; O'Neal, Michael A.; Michael, Holly A.

2016-08-01

Sea-level rise and increases in the frequency and intensity of ocean surges caused by climate change are likely to exacerbate adverse effects on low-lying coastal areas. The landward flow of water during ocean surges introduces salt to surficial coastal aquifers and threatens groundwater resources. Coastal topographic features (e.g., ponds, dunes, barrier islands, and channels) likely have a strong impact on overwash and salinization processes, but are generally highly simplified in modeling studies. To understand topographic impacts on groundwater salinization, we modeled a theoretical overwash event and variable-density groundwater flow and salt transport in 3-D using the fully coupled surface and subsurface numerical simulator, HydroGeoSphere. The model simulates the coastal aquifer as an integrated system considering overland flow, coupled surface and subsurface exchange, variably saturated flow, and variable-density groundwater flow. To represent various coastal landscape types, we simulated both synthetic fields and real-world coastal topography from Delaware, USA. The groundwater salinization assessment suggested that the topographic connectivity promoting overland flow controls the volume of aquifer that is salinized. In contrast, the amount of water that can be stored in surface depressions determines the amount of seawater that infiltrates the subsurface and the time for seawater to flush from the aquifer. Our study suggests that topography has a significant impact on groundwater salinization due to ocean surge overwash, with important implications for coastal land management and groundwater vulnerability assessment.

Distribution and sources of dissolved black carbon in surface waters of the Chukchi Sea, Bering Sea, and the North Pacific Ocean

NASA Astrophysics Data System (ADS)

Nakane, Motohiro; Ajioka, Taku; Yamashita, Youhei

2017-05-01

Pyrogenic carbon, also called black carbon (BC), is an important component in the global carbon cycle. BC produced by biomass burning or fossil fuel combustion is transported to oceans by the atmosphere or rivers. However, environmental dynamics (i.e., major sources and sinks) of BC in marine environments have not been well documented. In this study, dissolved BC (DBC) collected from surface waters of the Chukchi Sea, the Bering Sea, and the subarctic and subtropical North Pacific were analyzed using the benzene polycarboxylic acid (BPCA) method. The DBC concentration and the ratio of B5CA and B6CA to all BPCAs (an index of the DBC condensation degree) ranged from 4.8 to 15.5 µg-C L-1 and from 0.20 to 0.43, respectively, in surface waters of the Chukchi/Bering Seas and the North Pacific Ocean. The concentration and condensation degree of DBC in the Chukchi/Bering Seas were higher and more variable than those in the subarctic and subtropical North Pacific, which implies that the major factors controlling DBC distribution were different in these marine provinces. In the Chukchi/Bering Seas, the DBC concentration was negatively correlated to salinity but positively correlated to chromophoric dissolved organic matter (CDOM) quantity and total dissolved lignin phenol concentration estimated by CDOM parameters. These correlations indicated that the possible major source of DBC in the Chukchi/Bering Seas was Arctic rivers. However, in the North Pacific, where riverine inputs are negligible for most sampling sites, DBC was possibly derived from the atmosphere. Although spectral slopes of CDOM at 275-295 nm (an index of the photodegradation degree of CDOM) differed widely between the subarctic and subtropical North Pacific, the concentration and condensation degrees of DBC were similar between the subarctic and subtropical North Pacific, which suggests that photodegradation was not the only major factor controlling DBC distribution. Therefore, DBC distributions of the

Sea level and turbidity controls on mangrove soil surface elevation change

USGS Publications Warehouse

Lovelock, Catherine E.; Fernanda Adame, Maria; Bennion, Vicki; Hayes, Matthew; Reef, Ruth; Santini, Nadia; Cahoon, Donald R.

2015-01-01

Increases in sea level are a threat to seaward fringing mangrove forests if levels of inundation exceed the physiological tolerance of the trees; however, tidal wetlands can keep pace with sea level rise if soil surface elevations can increase at the same pace as sea level rise. Sediment accretion on the soil surface and belowground production of roots are proposed to increase with increasing sea level, enabling intertidal habitats to maintain their position relative to mean sea level, but there are few tests of these predictions in mangrove forests. Here we used variation in sea level and the availability of sediments caused by seasonal and inter-annual variation in the intensity of La Nina-El Nino to assess the effects of increasing sea level on surface elevation gains and contributing processes (accretion on the surface, subsidence and root growth) in mangrove forests. We found that soil surface elevation increased with mean sea level (which varied over 250 mm during the study) and with turbidity at sites where fine sediment in the water column is abundant. In contrast, where sediments were sandy, rates of surface elevation gain were high, but not significantly related to variation in turbidity, and were likely to be influenced by other factors that deliver sand to the mangrove forest. Root growth was not linked to soil surface elevation gains, although it was associated with reduced shallow subsidence, and therefore may contribute to the capacity of mangroves to keep pace with sea level rise. Our results indicate both surface (sedimentation) and subsurface (root growth) processes can influence mangrove capacity to keep pace with sea level rise within the same geographic location, and that current models of tidal marsh responses to sea level rise capture the major feature of the response of mangroves where fine, but not coarse, sediments are abundant.

Coherent mesoscale eddies in the North Atlantic subtropical gyre: 3-D structure and transport with application to the salinity maximum

NASA Astrophysics Data System (ADS)

Amores, Angel; Melnichenko, Oleg; Maximenko, Nikolai

2017-01-01

The mean vertical structure and transport properties of mesoscale eddies are investigated in the North Atlantic subtropical gyre by combining historical records of Argo temperature/salinity profiles and satellite sea level anomaly data in the framework of the eddy tracking technique. The study area is characterized by a low eddy kinetic energy and sea surface salinity maximum. Although eddies have a relatively weak signal at surface (amplitudes around 3-7 cm), the eddy composites reveal a clear deep signal that penetrates down to at least 1200 m depth. The analysis also reveals that the vertical structure of the eddy composites is strongly affected by the background stratification. The horizontal patterns of temperature/salinity anomalies can be reconstructed by a linear combination of a monopole, related to the elevation/depression of the isopycnals in the eddy core, and a dipole, associated with the horizontal advection of the background gradient by the eddy rotation. A common feature of all the eddy composites reconstructed is the phase coherence between the eddy temperature/salinity and velocity anomalies in the upper ˜300 m layer, resulting in the transient eddy transports of heat and salt. As an application, a box model of the near-surface layer is used to estimate the role of mesoscale eddies in maintaining a quasi-steady state distribution of salinity in the North Atlantic subtropical salinity maximum. The results show that mesoscale eddies are able to provide between 4 and 21% of the salt flux out of the area required to compensate for the local excess of evaporation over precipitation.

Detailed real-time infrared radiation simulation applied to the sea surface

NASA Astrophysics Data System (ADS)

Zhang, Xuemin; Wu, Limin; Long, Liang; Zhang, Lisha

2018-01-01

In this paper, the infrared radiation characteristics of sea background have been studied. First, MODTRAN4.0 was used to calculate the transmittance of mid-infrared and far-infrared, and the solar spectral irradiance, the atmospheric and sea surface radiation. Secondly, according to the JONSWAP sea spectrum model, the different sea conditions grid model based on gravity wave theory was generated. The spectral scattering of the sun and the atmospheric background radiation was studied. The total infrared radiation of the sea surface was calculated. Finally, the infrared radiation of a piece of sea surface was mapped to each pixel of the detector, and the infrared radiation is simulated. The conclusion is that solar radiance has a great influence on the infrared radiance. When the detector angle is close to the sun's height angle, there will be bright spots on the sea surface.

Fresh Water River discharges as observed by SMOS in the Arabian Sea and the Bay of Bengal

NASA Astrophysics Data System (ADS)

Olmedo, Estrella; Ballabrera-Poy, Joaquim; Turiel, Antonio

2017-04-01

The Bay of Bengal (BoB) and the Arabian Sea (AS) are two peculiar regions in the Indian Ocean exhibiting a wide range of Sea Surface Salinity (SSS) values. In the BoB, the strong summer monsoon rainfall and the continental run-offs into these semi-enclosed basins result in an intense dilution of the surface seawater in the northern part of the Bay, thereby inducing some of the lowest SSS water masses found in the tropical belt. In the AS, because of the intense variability associated with the monsoon cycle, water mass structure in the upper layers of the AS shows enormous variability in the space and time. As such, the role of the salinity in these regions is crucial in the ocean dynamics of these regions. After more than 7 years in orbit, the Soil Moisture and Ocean Salinity (SMOS) mission [1] continues to provide a series of salinity data that could be used to monitor the SSS variations in these climatically relevant regions, provided that systematic errors due to land contamination are reduced. Recently-developed algorithms for SSS retrieval [2] have improved the filtering criteria and the mitigation of the systematic bias, providing coherent SSS retrievals close to the land masses. In this work we have analyzed the SSS in 2-degree boxes located at the mouth of the main rivers in the BoB: Ganges-Brahmaputra, Irrawady, Mahanadi, Godovari; and in the AS: Indus. We have first tried to validate the SMOS salinity retrievals with in situ measurements. Since there is few available in situ data, we have also compared the climatological SSS behavior derived from SMOS with the ones provided by the World Ocean Atlas [3]. We have also compared the SMOS SSS data with historical data of discharges [4] and [5], ocean currents from the Ocean Surface Current Analyses Real-time (OSCAR) [6], Sea Surface Temperature from Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) [7],[8] and [9] and Chlorophyll data [10]. The conclusion of this work is that, when the proper

Sea ice ecosystems.

PubMed

Arrigo, Kevin R

2014-01-01

Polar sea ice is one of the largest ecosystems on Earth. The liquid brine fraction of the ice matrix is home to a diverse array of organisms, ranging from tiny archaea to larger fish and invertebrates. These organisms can tolerate high brine salinity and low temperature but do best when conditions are milder. Thriving ice algal communities, generally dominated by diatoms, live at the ice/water interface and in recently flooded surface and interior layers, especially during spring, when temperatures begin to rise. Although protists dominate the sea ice biomass, heterotrophic bacteria are also abundant. The sea ice ecosystem provides food for a host of animals, with crustaceans being the most conspicuous. Uneaten organic matter from the ice sinks through the water column and feeds benthic ecosystems. As sea ice extent declines, ice algae likely contribute a shrinking fraction of the total amount of organic matter produced in polar waters.

Total Mercury in Surface and Deep Waters in the Western and Eastern Mediterranean Sea

NASA Astrophysics Data System (ADS)

Varde', M.; Cofone, F.; Servidio, A.; Rosselli, A.; Hedgecock, I. M.; Ammoscato, I.; Mannarino, V.; Sprovieri, F.; Gensini, M.; Pirrone, N.

2014-12-01

In the framework of the Italian National Research Council (CNR) Med-Oceanor measurement program and as part of the Global Mercury Observation System (GMOS) objectives, we performed two cruise campaigns with the CNR's Research Vessel (RV) Urania, in the western and eastern Mediterranean Basin, in the summers of 2012 and 2013. Total Mercury (THg) concentration in seawater was systematically measured at different depths from the sea bottom to the surface. A total of 155 surface and deep seawater samples at 25 selected stations were collected during the cruise campaigns using a stainless-steel rosette system on which 24 Niskin bottles (10L) were mounted. Continuous monitoring of temperature, conductivity, salinity and oxygen with depth were obtained by CTD measurements. All fluorinated containers were cleaned prior to use following GMOS SOPs. The chemical reagents used were suitable for ultra-trace Hg analysis. After sampling, samples were preserved by adding HCl solution to the sample bottles, which were refrigerated during transportation and analyzed within four weeks of the end of the oceanographic campaign. Sea water samples were analyzed in the laboratory following the US-EPA 1631 method revision E (US-EPA, 2002). To assess the critical issues related to mercury (Hg) contamination and to prevent leakage of Hg through volatilization we used all necessary precautions for sampling, sample stabilization, preservation and subsequent analysis in the laboratory. Quality assurance and quality control were performed using transport blanks, laboratory blanks and use of seawater certified reference materials. The accuracy of the analytical procedures for the determination of THg in sea water was corroborated by participation in a global inter-laboratory comparison study for THg in natural waters. THg concentrations in surface and deep waters found in the Mediterranean basin during the last two cruise campaigns Med-Oceanor as well as the THg measurements in sea water

The conservative behavior of dissolved organic carbon in surface waters of the southern Chukchi Sea, Arctic Ocean, during early summer

PubMed Central

Tanaka, Kazuki; Takesue, Nobuyuki; Nishioka, Jun; Kondo, Yoshiko; Ooki, Atsushi; Kuma, Kenshi; Hirawake, Toru; Yamashita, Youhei

2016-01-01

The spatial distribution of dissolved organic carbon (DOC) concentrations and the optical properties of dissolved organic matter (DOM) determined by ultraviolet-visible absorbance and fluorescence spectroscopy were measured in surface waters of the southern Chukchi Sea, western Arctic Ocean, during the early summer of 2013. Neither the DOC concentration nor the optical parameters of the DOM correlated with salinity. Principal component analysis using the DOM optical parameters clearly separated the DOM sources. A significant linear relationship was evident between the DOC and the principal component score for specific water masses, indicating that a high DOC level was related to a terrigenous source, whereas a low DOC level was related to a marine source. Relationships between the DOC and the principal component scores of the surface waters of the southern Chukchi Sea implied that the major factor controlling the distribution of DOC concentrations was the mixing of plural water masses rather than local production and degradation. PMID:27658444

North Atlantic near-surface salinity contrasts and intra-basin water vapor transfer