A global algorithm for estimating Absolute Salinity

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. <br><br> 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<sup>−1</sup> in the northernmost North Pacific. Here we provide an algorithm for estimating Absolute Salinity Anomaly for any location (<i>x, y, p</i>) in the world ocean. <br><br> 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)

Collection and processing of shipboard ADCP velocities from the Barents Sea Polar Front Experiment

The Barents Sea Polar Front Experiment was a combined physical oceanography and acoustic tomography field study which took place from 6-26 August 1992. Both shipboard and moored data were collected in a 80 x 70 km experimental region on the south flank of Sptisbergen Bank about 60 km east of Bear Island. Of principal interest in this report are the data from an Acoustic Doppler Current Profier (ADCP) which was operated continuously during the experimental period as a part of the shipboard instrumentation aboard the USNS Barlett. The data from eight current meters deployed on three moorings in the experimental region are used to supplement the ADCP analysis. Preliminary results showed that velocities in the experimental region were dominated by semi-diurnal tides. The strong tidal oscilations dictated the use of a tide removal scheme to extract a steady flow component from the space-time grid of ADCP velocities. This report describes the configuration and operation of the ADCP, the space-time sampling grid on which the data were collected, the determination of absolute velocity from the ADCP measurements, and the application and results of a tide removal technique which allowed estimation of the sub-tidal flow.Funding was provided by the Office of Naval Research under Grant No. NOOOI4-90-J-1359

Eddy heat fluxes from direct current measurements of the Antarctic Polar Front in Shag Rocks Passage

Determining meridional heat flux in the Southern Ocean is critical to the accurate understanding and model simulation of the global ocean. Mesoscale eddies provide a significant but poorly-defined contribution to this transport. An eighteen-month deep-water current meter array deployment in Shag Rocks Passage (53°S, 48°W) between May 2003 and November 2004 provides estimates of the eddy flux of heat across the Polar Front. We calculate a statistically nonzero (99% level), vertically coherent local poleward heat flux of 12.0 ± 5.8 kW m-2 within the eddy frequency band at ~2750 m depth. Exceeding previous deep-water estimates by up to an order of magnitude, this highlights the large spatial variation in flux estimates and illustrates that constriction of circumpolar fronts facilitates large eddy transfers of heat southwards

Application of a nested-grid ocean circulation model to a shallow coastal embayment: Verification against observations

A nested-grid ocean circulation modeling system is used to study the response of Lunenburg Bay in Nova Scotia, Canada, to local wind-forcing, tides, remotely generated waves, and buoyancy forcing in the summer and fall of 2003. Quantitative comparisons between observations and model results demonstrate that the modeling system reproduces reasonably well the observed sea level, temperature, salinity, and currents in the bay. Numerical results reveal that the spatial and temporal variability of temperature and salinity in the bay during the study period is mainly forced by the local wind stress and surface heat/freshwater fluxes, with some contribution from tidal circulation. In particular, the local heat balance on the monthly timescale is dominated by cooling due to vertical advection and warming due to horizontal advection and net surface heat flux, while high-frequency variations (timescales of 1–30 days) are mainly associated with vertical advection, i.e., wind-induced upwelling and downwelling. There is also a strong baroclinic throughflow over the deep water region outside Lunenburg Bay that is strongly influenced by wind-forcing. The vertically integrated momentum balance analysis indicates a modified geostrophic balance on the monthly timescale and longer, and is dominated by the pressure term and wind minus bottom stress in the high-frequency band

Historic 2005 toxic bloom of Alexandrium fundyense in the west Gulf of Maine : 1. In situ observations of coastal hydrography and circulation

Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): C07039, doi:10.1029/2007JC004601.An extensive Alexandrium fundyense bloom occurred along the coast of the Gulf of Maine in late spring and early summer 2005. To understand the physical aspects of bloom's initiation and development, in situ observations from both a coast-wide ship survey and the coastal observing network were used to characterize coastal circulation and hydrography during that time period. Comparisons between these in situ observations and their respective long-term means revealed anomalous ocean conditions during May 2005: waters were warmer and fresher coast-wide owing to more surface heating and river runoff; coastal currents were at least 2 times stronger than their climatological means. Surface winds were also anomalous in the form of both episodic bursts of northeast winds and a downwelling-favorable mean condition. These factors may have favored more vigorous along-shore transport and nearshore aggregation of toxic A. fundyense cells (a red tide) in 2005.Research support was provided through the Woods Hole Center for Oceans and Human Health, National Science Foundation (NSF) grant OCE-0430723 and National Institute of Environmental Health Science (NIEHS) grant 1-P50-ES012742-01, ECOHAB program through NSF grant OCE-9808173 and NOAA grant NA96OP0099, and GOMTOX program through NOAA NA06NOS4780245

Skill tests of three-dimensional tidal currents in a global ocean model: A look at the North Atlantic

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92458/1/jgr_timkoetal_northatlatnictidalcurrentskilltest_2012.pd

Calculating Reynolds stresses from ADCP measurements in the presence of surface gravity waves using the cospectra-fit method

Author Posting. © American Meteorological Society, 2010. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 27 (2010): 889-907, doi:10.1175/2009JTECHO682.1.Recently, the velocity observations of acoustic Doppler current profilers (ADCPs) have been successfully used to estimate turbulent Reynolds stresses in estuaries and tidal channels. However, the presence of surface gravity waves can significantly bias stress estimates, limiting application of the technique in the coastal ocean. This work describes a new approach to estimate Reynolds stresses from ADCP velocities obtained in the presence of waves. The method fits an established semiempirical model of boundary layer turbulence to the measured turbulent cospectra at frequencies below those of surface gravity waves to estimate the stress. Applied to ADCP observations made in weakly stratified waters and variable significant wave heights, estimated near-bottom and near-surface stresses using this method compared well with independent estimates of the boundary stresses in contrast to previous methods. Additionally, the vertical structure of tidal stress estimated using the new approach matched that inferred from a linear momentum balance at stress levels below the estimated stress uncertainties. Because the method makes an estimate of the horizontal turbulent length scales present as part of the model fit, these results can also enable a direct correction for the mean bias errors resulting from instrument tilt, if these scales are long relative to the beam separation.AK acknowledges support from the WHOI Coastal Ocean Institute, and SL acknowledges support from NSF Ocean Science Grant OCE-0548961

Genetic Deletion of PGF2α-FP Receptor Exacerbates Brain Injury Following Experimental Intracerebral Hemorrhage

Background: The release of inflammatory molecules such as prostaglandins (e.g., PGF2α) is associated with brain damage following an intracerebral hemorrhagic (ICH) stroke; however, the role of PGF2α and its cognate FP receptor in ICH remains unclear. This study focused on investigating the role of the FP receptor as a target for novel neuroprotective drugs in a preclinical model of ICH, aiming to investigate the contribution of the PGF2α-FP axis in modulating functional recovery and anatomical outcomes following ICH.Results: Neurological deficit scores in FP−/− mice were significantly higher compared to WT mice 72 h after ICH (6.1 ± 0.7 vs. 3.1 ± 0.8; P < 0.05). Assessing motor skills, the total time mice stayed on the rotating rod was significantly less in FP−/−mice compared to WT mice 24 h after ICH (27.0 ± 7.5 vs. 52.4 ± 11.2 s; P < 0.05). Using grip strength to quantify forepaw strength, results showed that the FP−/− mice had significantly less strength compared to WT mice 72 h after ICH (96.4 ± 17.0 vs. 129.6 ± 5.9 g; P < 0.01). In addition to the behavioral outcomes, histopathological measurements were made. In Cresyl violet stained brain sections, the FP−/− mice showed a significantly larger lesion volume compared to the WT (15.0 ± 2.2 vs. 3.2 ± 1.7 mm3; P < 0.05 mice.) To estimate the presence of ferric iron in the peri-hematoma area, Perls' staining was performed, which revealed that FP−/− mice had significantly greater staining than the WT mice (186.3 ± 34.4% vs. 86.9 ± 13.0% total positive pixel counts, P < 0.05). Immunoreactivity experiments on brain sections from FP−/− and WT mice post-ICH were performed to monitor changes in microgliosis and astrogliosis using antibodies against Iba1 and GFAP respectively. These experiments showed that FP−/− mice had a trend toward greater astrogliosis than WT mice post-ICH.Conclusion: We showed that deletion of the PGF2α FP receptor exacerbates behavioral impairments and increases lesion volumes following ICH compared to WT-matched controls.Detailed mechanisms responsible for these novel results are actively being pursued

Horizontal patterns of water temperature and salinity in an estuarine tidal channel: Ria de Aveiro

This work presents results from two complementary and interconnected approaches to study water temperature and salinity patterns in an estuarine tidal channel. This channel is one of the four main branches of the Ria de Aveiro, a shallow lagoon located in the Northwest coast of the Iberian Peninsula. Longitudinal and cross-sectional fields of water temperature and salinity were determined by spatial interpolation of field measurements. A numerical model (Mohid) was used in a 2D depth-integrated mode in order to compute water temperature and salinity patterns. The main purpose of this work was to determine the horizontal patterns of water temperature and salinity in the study area, evaluating the effects of the main forcing factors. The field results were depth-integrated and compared to numerical model results. These results obtained using extreme tidal and river runoff forcing, are also presented. The field results reveal that, when the river flow is weak, the tidal intrusion is the main forcing mechanism, generating saline and thermal fronts which migrate with the neap/spring tidal cycle. When the river flow increases, the influence of the freshwater extends almost as far as the mouth of the lagoon and vertical stratification is established. Results of numerical modelling reveal that the implemented model reproduces quite well the observed horizontal patterns. The model was also used to study the hydrology of the study area under extreme forcing conditions. When the model is forced with a low river flow (1 m3 s−1) the results confirm that the hydrology is tidally dominated. When the model is forced with a high river flow (1,000 m3 s−1) the hydrology is dominated by freshwater, as would be expected in such an area