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Recent observations indicate that ice-ocean interaction drives much of the recent increase in mass loss from the Greenland Ice Sheet; however, the role of ocean forcing in driving past glacier change is poorly understood. To extend the observational record and our understanding of the ocean-cryosphere link, we used a multi-proxy approach that combines new data from proglacial lake sediments, 14C-dated in situ moss that recently emerged from beneath cold-based ice caps, and 10Be ages to reconstruct centennial-scale records of mountain glacier activity for the past ~10 k.y. in West Greenland. Proglacial lake sediment records and 14C dating of moss indicate the onset of Neoglaciation in West Greenland at ca. 5 ka with substantial snowline lowering and glacier expansion at ca. 3.7 ka followed by additional ice expansion phases at ca. 2.9, ca. 1.7, and ca. 1.4 ka and during the Little Ice Age. We find that widespread glacier growth at ca. 3.7 ka in West Greenland coincides with marked cooling and reduced strength of the West Greenland Current in Disko Bugt. The transition to cooler ocean conditions at ca. 3.7 ka identified in Disko Bugt is registered by marine proxy data farther afield in East Greenland and on the northwestern Icelandic shelf, implying large-scale paleoceanographic changes across the North Atlantic during this interval. The similarity between glacier change on West Greenland and multiple marine and terrestrial records across the North Atlantic suggests that glaciers are strongly influenced by changes in ocean circulation and consequently implies that the ocean-cryosphere teleconnection is a persistent feature of the Arctic system. [ABSTRACT FROM AUTHOR]

The stable carbon isotope composition of dissolved inorganic carbon (δ13CDIC) in seawater was measured in samples collected during June"July 2014 in the subpolar North Atlantic. Sample collection was carried out on the RRS James Clark Ross cruise JR302, part of the 'Radiatively Active Gases from the North Atlantic Region and Climate Change' (RAGNARoCC) research programme. The observed δ13CDIC values for cruise JR302 fall in a range from 0.07 ° to +1.95 °, relative to the Vienna Peedee Belemnite standard. From duplicate samples collected during the cruise, the 1σ precision for the 341 results is 0.08 °, which is similar to our previous work and other studies of this kind. We also performed a cross-over analysis using nearby historical δ13CDIC data, which indicated that there were no significant systematic offsets between our measurements and previously published results. We also included seawater reference material (RM) produced by A. G. Dickson (Scripps Institution of Oceanography, USA) in every batch of analysis, enabling us to improve upon the calibration and quality-control procedures from a previous study. The δ13CDIC is consistent within each RM batch, although its value is not certified. We report δ13CDIC values of 1.15 ± 0.03 ° and 1.27 ± 0.05 ° for batches 141 and 144 respectively. Our JR302 δ13CDIC data can be used " along with measurements of other biogeochemical variables " to constrain the processes that control DIC in the interior ocean, in particular the oceanic uptake of anthropogenic carbon dioxide and the biological carbon pump. Our δ13CDIC results are available from the British Oceanographic Data Centre - doi:10.5285/22235f1a-b7f3-687f-e053-6c86abc0c8a6. [ABSTRACT FROM AUTHOR]

The stable carbon isotope composition of dissolved inorganic carbon (δ13C-DIC) can be used toquantify fluxes within the carbon system. For example, knowing the δ13C-DIC signature of the inorganic carbon pool can help to describe the exchange between ocean and atmosphere as well as the amount of anthropogenic carbon in the water column. The measurements can also be used for evaluating modeled carbon fluxes, for making basin wide estimates, studying seasonal and interannual variability or decadal trends in interior ocean biogeochemistry. For all these purposes, it is not only important to have a sufficient amount of data, but these data must also be internally consistent and of high quality. In this study, we present a δ13C-DIC dataset for the North Atlantic, which has undergone secondary quality control. The data originate from oceanographic research cruises between 1981 and 2012. During a primary quality control step based on simple range tests obviously bad data were flagged. In a second quality control step, biases between measurements from different cruises were quantified through a crossover analysis using nearby data of the respective cruises and absolute values of biased cruises were adjusted in the data product. the crossover analysis was possible for 22 of the 29 cruises in our dataset and adjustments were applied to 10 of these. The internal accuracy of this dataset is 0.017 °. The dataset is available via CDIAC at 10.3334/CDIAC/OTG.NAC13v1. [ABSTRACT FROM AUTHOR]

As part of the CONCEPTS (Canadian Operational Network of Coupled Environmental PredicTion Systems) initiative, a high-resolution (1/12°) ice-ocean regional model is developed covering the North Atlantic and the Arctic oceans. The long-term objective is to provide Canada with short-term ice-ocean predictions and hazard warnings in ice-infested regions. To evaluate the modelling component (as opposed to the analysis - or data-assimilation - component, which is not covered in this contribution), a series of hindcasts for the period 2003-2009 is carried out, forced at the surface by the Canadian GDPS reforecasts (Smith et al., 2014). These hindcasts test how the model represents upper ocean characteristics and ice cover. Each hindcast implements a new aspect of the modelling or the ice-ocean coupling. Notably, the coupling to the multi-category ice model CICE is tested. The hindcast solutions are then assessed using a verification package under development, including in situ and satellite ice and ocean observations. The conclusions are as follows: (1) the model reproduces reasonably well the time mean, variance and skewness of sea surface height; (2) the model biases in temperature and salinity show that while the mean properties follow expectations, the Pacific Water signature in the Beaufort Sea is weaker than observed; (3) the modelled freshwater content of the Arctic agrees well with observational estimates; (4) the distribution and volume of the sea ice are shown to be improved in the latest hindcast due to modifications to the drag coefficients and to some degree to the ice thickness distribution available in CICE; (5) nonetheless, the model still overestimates the ice drift and ice thickness in the Beaufort Gyre. [ABSTRACT FROM AUTHOR]

We examine the variability of near-surface salinity in a 10° x 10° region of the eastern North Atlantic, the location of the first part of the Salinity Processes in the Upper-ocean Regional Study (SPURS-1). The data used were collected over a two-year period, largely by a group of two types of profiling floats equipped with sensors that record high-resolution temperature and salinity measurements in the upper few meters of the water column. By comparing the SPURS-1 measurements to observations in the area from previous decades, we examine variability at time scales ranging from a few hours (mostly consisting of rainfall-driven decreases in salinity) to diurnal cycles in temperature and salinity, seasonal variability and the annual cycle, and finally to decadal-scale changes. The relationship of near-surface salinity to the hydrological cycle suggests a continuous spectrum of variability in this cycle from hours to decades. [ABSTRACT FROM AUTHOR]

Within the North Atlantic subtropical gyre lies a salinity maximum region, relatively constant in time, yet forced by a seasonally varying strong evaporation zone located several degrees south and advected by wind-driven Ekman currents and geostrophic gyre currents and eddies. Large-scale calculations using in situ salinities to quantify salt divergence in the mixed layer, together with freshwater flux products, cannot account for the observed surface salinity signature. Small-scale and vertical processes must complete the budget. The Aquarius satellite system, launched in June 2011, now provides sea surface salinity observations every seven days at approximately 100 km spacing. Here, we reexamine the surface freshwater balance in the salinity maximum region, the location of the Salinity Processes in the Upper-ocean Regional Study (SPURS) campaign, from a satellite-sensed perspective. Advection of surface salinity by Ocean Surface Current Analyses Real-time (OSCAR) satellite-based surface currents is investigated for the whole region as well as within two boxes that isolate the salinity maximum and the maximum evaporation regions. Locations of imbalance, variability of surface salinity forcing terms, and areas of potential transport and redistribution are explored using satellite observations. A discussion then considers the vertical pathways by which surface waters reach and exchange salinity with the deep ocean, thus contributing to the signal seen at the surface. [ABSTRACT FROM AUTHOR]

Surface salinity variations and processes affecting surface salinity in the high-salinity region of the subtropical North Atlantic (the SPURS-1 area) are investigated by combining data from in situ observations and satellite remote-sensing measurements. On temporal average, the surface freshwater flux term (evaporation minus precipitation) in the SPURS-1 region increases mixed-layer salinity. Oceanic advection plays the largest role in compensating this salinity increase. On seasonal time scales, mixed-layer salinity increases from April to August and decreases from September to March. This seasonal evolution of the mixed-layer salinity is largely controlled by the freshwater flux term, with vertical entrainment playing a secondary role. The domain-averaged oceanic advection and diffusion terms do not show significant seasonal cycles. The sum of all estimated salinity budget terms largely captures salinity variations on interannual time scales. Unlike the seasonal cycle, variations in freshwater flux, oceanic advection, and vertical entrainment all contribute to interannual variations in surface salinity. Oceanic advection plays a larger role in salinity changes during 2008-2012, whereas the surface freshwater flux term dominates surface salinity evolution during 2004-2007 and in 2013. Although evaporation in the SPURS-1 region dominates the mean freshwater flux, precipitation plays a larger role in interannual variations of the freshwater flux. Separating the advection term into geostrophic and Ekman components indicates that the Ekman component dominates the total advection term. The effect of Ekman advection on salinity changes in the SPURS-1 region is closely linked to the spatial distribution of salinity anomalies. Therefore, it is important to understand large-scale forcing changes. [ABSTRACT FROM AUTHOR]

The Aquarius satellite mission and Salinity Processes in the Upper-ocean Regional Study (SPURS) are providing the scientific community with new insights into the role seawater salinity plays in the Earth system. Aquarius and SPURS scientists and engineers, working with the University of Maine-based Salinity Public Engagement and Communications team, developed webinars that focused on how these programs' findings increase knowledge about topics such as the water cycle, ocean circulation, and climate. Direct involvement of research scientists and engineers was key to the success of these efforts. These experts learned how to use interactive concept maps to "deconstruct" scientific content into simpler graphical formats for their presentations. A benefit to webinar participants, presenters, and facilitators was that they honed their critical thinking skills. In addition, the webinars allow people traditionally not represented in science, technology, engineering and math to gain better access to high-quality NASA materials. Post-event audience evaluation data provide valuable feedback on the impacts of sharing the results of ocean salinity research beyond the scientific community. [ABSTRACT FROM AUTHOR]

Knowledge of the intensity and spatial-temporal distribution of rainfall over the ocean is critical in understanding the global hydrological cycle. However, rain has proven difficult to measure over the ocean due to problems associated with platform motion and flow distortion combined with the spatial and temporal variability of rainfall itself. Underwater acoustical rain gauges avoid these issues by using the loud and distinctive underwater sound generated by raindrops on the ocean surface to detect and quantify rainfall. Here, the physics and operation of and results from an instrument that uses underwater ambient sound to measure rainfall rate and wind speed are presented. Passive Aquatic Listener (PAL) instruments were mounted on a buoy deployed at Ocean Station P and on 13 Argo profilers that were deployed as part of the US National Aeronautics and Space Administration-sponsored Salinity Processes in the Upper-ocean Regional Study (SPURS) field experiment in the North Atlantic Ocean. The PALs provide near-continuous measurements of rain rate and wind speed during the two-year period over the SPURS study region defined by the Argo profilers. Comparisons of PAL data with rain and wind measured by other techniques, including direct in situ observations and satellite measurements, show good agreement for both rain rate and wind speed. [ABSTRACT FROM AUTHOR]

We investigated a 100 x 100 km high-salinity region of the North Atlantic subtropical gyre during the Sub-Tropical Atlantic Surface Salinity Experiment/Salinity Processes in the Upper-ocean Regional Study (STRASSE/SPURS) cruise from August 21, 2012, to September 9, 2012. Results showed great variability in sea surface salinity (SSS; over 0.3 psu) in the mesoscale, over 7 cm of total evaporation, and little diapycnal mixing below 36 m depth, the deepest mixed layers encountered. Strong currents in the southwestern part of the domain, and the penetration of freshwater, suggest that advection contributed greatly to salinity evolution. However, it was further observed that a smaller cyclonic structure tucked between the high SSS band and the strongest currents contributed to the transport of high SSS water along a narrow front. Cross-frontal transport by mixing is also a possible cause of summertime reduction of SSS. The observed structure was also responsible for significant southward salt transport over more than 200 km. [ABSTRACT FROM AUTHOR]

The North Atlantic subtropical salinity maximum harbors the saltiest surface waters of the open world ocean. Subduction of these waters gives rise to Subtropical Underwater, spreading the high-salinity signature over the entire basin. The Salinity Processes in the Upper-ocean Regional Study (SPURS) is aimed at understanding the physics controlling the thermohaline structure in the salinity maximum region. A combination of moored and autonomous float observations is used here to describe the vertical water mass interleaving in the area. Seasonal intensification of interleaving in late spring and the abundance of small-scale thermohaline intrusions point to an important role for submesoscale processes in the initial subduction and subsequent evolution of Subtropical Underwater. [ABSTRACT FROM AUTHOR]

The Global Drifter Program deployed a total of 144 Lagrangian drifters drogued at 15 m depth, including 88 equipped with salinity sensors, in support of the first Salinity Processes in the Upper-ocean Regional Study (SPURS-1) in the subtropical North Atlantic Ocean with the goal of measuring salt fluxes associated with surface currents. The quality-controlled data set consists of 996,583 salinity observations collected between August 2012 and April 2014. A comparison of the drifter salinities with Aquarius satellite sea surface salinity (SSS) data shows that the lifespan of the salinity sensor fitted to the drifters is of the order of one year. The salinity and velocity data from the drifters were used to validate salt transport divergence computed with satellite products, with satellite salinity taken from the standard Aquarius v3.0 data set. The results indicate good agreement between the two independent methods, and also demonstrate that the effect of the eddy field combined with SSS variability at the surface dominates the signal. SSS variability within spatial bins as compared to Aquarius-beam footprints measured by drifters can be in excess of 0.1 psu. This result suggests that careful evaluation of the representation error is required when single-point in situ measurements, such as those collected by Argo floats, are used to validate spatially averaged Aquarius salinity data. [ABSTRACT FROM AUTHOR]

We developed the data management system for the US National Aeronautics and Space Administration-sponsored Salinity Processes in the Upper-ocean Regional Study (SPURS) Atlantic field campaign (SPURS-1). Data management support means more than simply collecting and archiving static data sets. It involves a complex mixture of data visualization, interaction with principal investigators, Web development, public outreach, quality assurance, and archiving for posterity. [ABSTRACT FROM AUTHOR]

The article investigates the changes in ocean subsurface salinity in 2013. Topics discussed include the average gridded salinity anomalies at standard depths from the surface to 2,000 meters, the zonally-averaged difference between salinities in the Pacific Ocean and the long-term averages, and the increased salinity reported in the subtropical and tropical North Atlantic and the in the subpolar North Atlantic.

The article highlights trends in meridional overturning circulation (MOC) in the North Atlantic Ocean in 2013. Topics discussed include the mean variability of the MOC, the variability of transported properties, and the strength of the MOC. The lack of consistent trend in the MOC during the year is noted.