Observed Ocean Bottom Temperature Variability at Four Sites in the Northwestern Argentine Basin: Evidence of Decadal Deep/Abyssal Warming Amidst Hourly to Interannual Variability During 2009–2019

Consecutive multiyear records of hourly ocean bottom temperature measurements are merged to produce new decade-long time series at four depths ranging from 1,360 to 4,757 m within the northwest Argentine Basin at 34.5°S. Energetic temperature variations are found at a wide range of time scales. All sites exhibit fairly linear warming trends of approximately 0.02–0.04°C per decade over the period 2009–2019, although the trends are only statistically different from zero at the two deepest sites at depths of ~4,500–4,800 m. Near-bottom temperatures from independent conductivity-temperature-depth profiles collected at these same locations every 6–24 months over the same decade show roughly consistent trends. Based on the distribution of spectral energies at the deepest sites and a Monte Carlo-style analysis, sampling at least once per year is necessary to capture the significant warming trends over this decade to within 50% error bars at a 95% confidence limit.Fil: Meinen, Christopher S.. National Ocean And Atmospheric Administration; Estados UnidosFil: Perez, Renellys C.. National Ocean And Atmospheric Administration; Estados UnidosFil: Dong, Shenfu. National Ocean And Atmospheric Administration; Estados UnidosFil: Piola, Alberto Ricardo. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; Argentina. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Campos, Edmo. Universidade de Sao Paulo; Brasil. American University Of Sharjah.; Emiratos Árabes Unido

Brazil Current volume transport variability during 2009-2015 from a longterm moored array at 34.5°S

The Brazil Current, the western limb of the subtropical gyre of the South Atlantic Ocean, is one of the major Western Boundary Currents of the global ocean. Here, we present the first multiyear continuous daily time series of Brazil Current absolute volume transport obtained using 6+ years of observations from a line of four pressure-recording inverted echo sounders (PIES) deployed at 34.5°S. The array was augmented in December 2012 with two current meter-equipped PIES and in December 2013 with a moored Acoustic Doppler Current Profiler on the upper continental slope. The Brazil Current is bounded by the sea surface and the neutral density interface separating South Atlantic Central Water and Antarctic Intermediate Water, which is on average at a reference pressure of 628 ± 46 dbar, and it is confined west of 49.5°W. The Brazil Current has a mean strength of −14.0 ± 2.8 Sv (1 Sv ≡ 106 m3 s−1; negative indicates southward flow) with a temporal standard deviation of 8.8 Sv and peak-to-peak range from −41.7 to +20 Sv. About 80% of the absolute transport variance is concentrated at periods shorter than 150 days with a prominent peak at 100 days. The baroclinic component accounts for 85% of the absolute transport variance, but the barotropic variance is not negligible. The baroclinic and barotropic transports are uncorrelated, demonstrating the need to measure both transport components independently. Given the energetic high frequency transport variations, statistically significant seasonal to interannual variability and trends have yet to be detected.Fil: Chidichimo, María Paz. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; Argentina. Centre National de la Recherche Scientifique. Institut de Recherche pour le Developpement. Département Ecologie, Biodiversité et Fonctionnement des Ecosystèmes Continentaux; FranciaFil: Piola, Alberto Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; Argentina. Centre National de la Recherche Scientifique. Institut de Recherche pour le Developpement. Département Ecologie, Biodiversité et Fonctionnement des Ecosystèmes Continentaux; FranciaFil: Meinen, Christopher S.. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentina. National Ocean And Atmospheric Administration; Estados UnidosFil: Perez, Renellys. National Ocean And Atmospheric Administration; Estados UnidosFil: Campos, Edmo. Universidade de Sao Paulo; Brasil. American University Of Sharjah.; Emiratos Árabes UnidosFil: Dong, Shenfu. National Ocean And Atmospheric Administration; Estados UnidosFil: Lumpkin, Rick. National Ocean And Atmospheric Administration; Estados UnidosFil: Garzoli, S. L.. National Ocean And Atmospheric Administration; Estados Unido

Antarctic Bottom Water Sensitivity to Spatio‐Temporal Variations in Antarctic Meltwater Fluxes

Ice sheet melting into the Southern Ocean can change the formation and properties of the Antarctic Bottom Water (AABW). Ocean models often mimic ice sheet melting by adding freshwater fluxes in the Southern Ocean under diverse spatial distributions. We use a global ocean and sea-ice model to explore whether the spatial distribution and magnitude of meltwater fluxes can alter AABW properties and formation. We find that a realistic spatially varying meltwater flux sustains AABW with higher salinities compared to simulations with uniform meltwater fluxes. Finally, we show that increases in ice sheet melting above 12% since 1958 can trigger AABW freshening rates similar to those observed in the Southern Ocean since 1990, suggesting that the increasing Antarctic meltwater discharge can drive the observed AABW freshening

Autonomous multi-platform observations during the Salinity Processes in the Upper-ocean Regional Study

Author Posting. © The Oceanography Society, 2017. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 30, no. 2 (2017): 38–48, doi:10.5670/oceanog.2017.218.The Salinity Processes in the Upper-ocean Regional Study (SPURS) aims to understand the patterns and variability of sea surface salinity. In order to capture the wide range of spatial and temporal scales associated with processes controlling salinity in the upper ocean, research vessels delivered autonomous instruments to remote sites, one in the North Atlantic and one in the Eastern Pacific. Instruments sampled for one complete annual cycle at each of these two sites, which are subject to contrasting atmospheric forcing. The SPURS field programs coordinated sampling from many different platforms, using a mix of Lagrangian and Eulerian approaches. This article discusses the motivations, implementation, and first results of the SPURS-1 and SPURS-2 programs.SPURS is supported by multiple NASA grants, with important additional contributions from the US National Science Foundation, NOAA, and the Office of Naval Research, as well as international agencies. SVP drifters are deployed with support from NASA and the NOAA funded Global Drifter Program at the Lagrangian Drifter Laboratory of the Scripps Institution of Oceanography. SVP-S2 drifters are provided by NOAA-AOML and NASA. PRAWLER mooring development is supported by NOAA’s Office of Oceanic and Atmospheric Research, Ocean Observing and Monitoring Division, and by NOAA/PMEL

Highly variable upper and abyssal overturning cells in the South Atlantic

The Meridional Overturning Circulation (MOC) is a primary mechanism driving oceanic heat redistribution on Earth, thereby affecting Earth’s climate and weather. However, the full-depth structure and variability of the MOC are still poorly understood, particularly in the South Atlantic. This study presents unique multiyear records of the oceanic volume transport of both the upper (~3100 meters) overturning cells based on daily moored measurements in the South Atlantic at 34.5°S. The vertical structure of the time-mean flows is consistent with the limited historical observations. Both the upper and abyssal cells exhibit a high degree of variability relative to the temporal means at time scales, ranging from a few days to a few weeks. Observed variations in the abyssal flow appear to be largely independent of the flow in the overlying upper cell. No meaningful trends are detected in either cell.Fil: Kersalé, Marion. National Ocean And Atmospheric Administration; Estados Unidos. University of Miami; Estados UnidosFil: Meinen, Christopher S.. National Ocean And Atmospheric Administration; Estados UnidosFil: Perez, Renellys C.. National Ocean And Atmospheric Administration; Estados UnidosFil: Le Hénaff, Matthieu. National Ocean And Atmospheric Administration; Estados Unidos. University of Miami; Estados UnidosFil: Valla, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; ArgentinaFil: Lamont, Tarron. University of Cape Town; SudáfricaFil: Sato, Olga T.. Universidade de Sao Paulo; BrasilFil: Dong, Shenfu. National Ocean And Atmospheric Administration; Estados UnidosFil: Terre, T.. University of Brest; Francia. Centre National de la Recherche Scientifique; FranciaFil: van Caspel, M.. Universidade de Sao Paulo; BrasilFil: Chidichimo, María Paz. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; ArgentinaFil: van den Berg, Marcel Alexander. Department of Environmental Affairs; SudáfricaFil: Speich, Sabrina. University Of Cape Town; SudáfricaFil: Piola, Alberto Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ecole Normale Superieure. Laboratoire de Meteorologie Dynamique; Francia. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; Argentina. Universidad de Buenos Aires; ArgentinaFil: Campos, Edmo. Universidade de Sao Paulo; Brasil. American University Of Sharjah.; Emiratos Árabes UnidosFil: Ansorge, Isabelle. University of Cape Town; SudáfricaFil: Volkov, Denis L.. University of Miami; Estados Unidos. National Ocean And Atmospheric Administration; Estados UnidosFil: Lumpkin, Rick. National Ocean And Atmospheric Administration; Estados UnidosFil: Garzoli, S. L.. University of Miami; Estados Unidos. National Ocean And Atmospheric Administration; Estados Unido

XBT Science: Assessment of Instrumental Biases and Errors

Expendable bathythermograph (XBT) data were the major component of the ocean temperature profile observations from the late 1960s through the early 2000s, and XBTs still continue to provide critical data to monitor surface and subsurface currents, meridional heat transport, and ocean heat content. Systematic errors have been identified in the XBT data, some of which originate from computing the depth in the profile using a theoretically and experimentally derived fall-rate equation (FRE). After in-depth studies of these biases and discussions held in several workshops dedicated to discussing XBT biases, the XBT science community met at the Fourth XBT Science Workshop and concluded that XBT biases consist of 1) errors in depth values due to the inadequacy of the probe motion description done by standard FRE and 2) independent pure temperature biases. The depth error and temperature bias are temperature dependent and may depend on the data acquisition and recording system. In addition, the depth bias also includes an offset term. Some biases affecting the XBT-derived temperature profiles vary with manufacturer/probe type and have been shown to be time dependent. Best practices for historical XBT data corrections, recommendations for future collection of metadata to accompany XBT data, impact of XBT biases on scientific applications, and challenges encountered are presented in this manuscript. Analysis of XBT data shows that, despite the existence of these biases, historical XBT data without bias corrections are still suitable for many scientific applications, and that bias-corrected data can be used for climate research

Warming Trend in Antarctic Bottom Water in the Vema Channel in the South Atlantic

The excess heat absorbed from the atmosphere has increased the temperature in the upper layers of the ocean (<2,000 m). In the abyss, infrequently repeated ship sections, deep Argo float measurements, and sparse moored observations have found signs of warming in the Southwest Atlantic, possibly linked to changes in the Weddell Sea. We present a new moored temperature time series sampled near the bottom in the Vema Channel, from February 2019 to August 2020. Together with historical data, the combined record confirms the warming of the abyssal waters, with an increase of 0.059°C in potential temperature between January 1991 and August 2020, embedded within intense high-frequency variability. Moreover, the data suggest the possibility of an accelerated warming, with a change in the temperature trend from 0.0016°C yr−1, between the early 1990s and 2005, to 0.0026°C yr−1 afterwards

More than 50 years of successful continuous temperature section measurements by the global expendable bathythermograph network, its integrability, societal benefits, and future

The first eXpendable BathyThermographs (XBTs) were deployed in the 1960s in the North Atlantic Ocean. In 1967 XBTs were deployed in operational mode to provide a continuous record of temperature profile data along repeated transects, now known as the Global XBT Network. The current network is designed to monitor ocean circulation and boundary current variability, basin-wide and trans-basin ocean heat transport, and global and regional heat content. The ability of the XBT Network to systematically map the upper ocean thermal field in multiple basins with repeated trans-basin sections at eddy-resolving scales remains unmatched today and cannot be reproduced at present by any other observing platform. Some repeated XBT transects have now been continuously occupied for more than 30 years, providing an unprecedented long-term climate record of temperature, and geostrophic velocity profiles that are used to understand variability in ocean heat content (OHC), sea level change, and meridional ocean heat transport. Here, we present key scientific advances in understanding the changing ocean and climate system supported by XBT observations. Improvement in XBT data quality and its impact on computations, particularly of OHC, are presented. Technology development for probes, launchers, and transmission techniques are also discussed. Finally, we offer new perspectives for the future of the Global XBT Network

Global perspectives on observing ocean boundary current systems

Ocean boundary current systems are key components of the climate system, are home to highly productive ecosystems, and have numerous societal impacts. Establishment of a global network of boundary current observing systems is a critical part of ongoing development of the Global Ocean Observing System. The characteristics of boundary current systems are reviewed, focusing on scientific and societal motivations for sustained observing. Techniques currently used to observe boundary current systems are reviewed, followed by a census of the current state of boundary current observing systems globally. The next steps in the development of boundary current observing systems are considered, leading to several specific recommendations.Fil: Todd, Robert E.. Woods Hole Oceanographic Institution; Estados UnidosFil: Chavez, Francisco. Monterey Bay Aquarium Research Institute; Estados UnidosFil: Clayton, Sophie. Old Dominion University; Estados UnidosFil: Cravatte, Sophie E.. Centre National de la Recherche Scientifique. Institut de Recherche pour le Développement; Francia. Universite de Toulouse; FranciaFil: Goes, Marlos P.. University of Miami; Estados UnidosFil: Graco, Michelle I.. Instituto del Mar del Peru; PerúFil: Lin, Xiaopei. Ocean University of China; ChinaFil: Sprintall, Janet. University of California; Estados UnidosFil: Zilberman, Nathalie V.. University of California; Estados UnidosFil: Archer, Matthew. California Institute of Technology; Estados UnidosFil: Arístegui, Javier. Universidad de Las Palmas de Gran Canaria; EspañaFil: Balmaseda, Magdalena A.. European Centre for Medium-Range Weather Forecasts; Reino UnidoFil: Bane, John M.. University of North Carolina; Estados UnidosFil: Baringer, Molly O.. Atlantic Oceanographic and Meteorological Laboratory ; Estados UnidosFil: Barth, John A.. State University of Oregon; Estados UnidosFil: Beal, Lisa M.. University of Miami; Estados UnidosFil: Brandt, Peter. Geomar-Helmholtz Centre for Ocean Research Kiel; AlemaniaFil: Calil, Paulo H.. Universidade Federal do Rio Grande; BrasilFil: Campos, Edmo. Universidade de Sao Paulo; BrasilFil: Centurioni, Luca R.. University of California; Estados UnidosFil: Chidichimo, María Paz. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; ArgentinaFil: Cirano, Mauro. Universidade Federal do Rio de Janeiro; BrasilFil: Cronin, Meghan F.. National Oceanic and Atmospheric Administration. Pacific Marine Environmental Laboratory; Estados UnidosFil: Curchitser, Enrique N.. Rutgers University; Estados UnidosFil: Davis, Russ E.. University of California; Estados UnidosFil: Dengler, Marcus. Geomar-Helmholtz Centre for Ocean Research Kiel; AlemaniaFil: DeYoung, Brad. Memorial University of Newfoundland; CanadáFil: Dong, Shenfu. University of Miami; Estados UnidosFil: Escribano, Ruben. Universidad de Concepción; ChileFil: Fassbender, Andrea J.. Monterey Bay Aquarium Research Institute; Estados Unido