Sloyan Bernadette M.

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Last Name
Sloyan
First Name
Bernadette M.
ORCID
0000-0003-0250-0167

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Now showing 1 - 19 of 19
  • Article
    Deep ocean changes near the Western Boundary of the South Pacific Ocean
    (American Meteorological Society, 2013-10) Sloyan, Bernadette M. ; Wijffels, Susan E. ; Tilbrook, Bronte ; Katsumata, Katsuro ; Murata, Akihiko ; Macdonald, Alison M.
    Repeated occupations of two hydrographic sections in the southwest Pacific basin from the 1990s to 2000s track property changes of Antarctic Bottom Water (AABW). The largest property changes—warming, freshening, increase in total carbon, and decrease in oxygen—are found near the basin’s deep western boundary between 50° and 20°S. The magnitude of the property changes decreases with increasing distance from the western boundary. At the deep western boundary, analysis of the relative importance of AABW (γn > 28.1 kg m−3) freshening, heating, or isopycnal heave suggests that the deep ocean stratification change is the result of both warming and freshening processes. The consistent deep ocean changes near the western boundary of the southwest Pacific basin dispel the notion that the deep ocean is quiescent. High-latitude climate variability is being directly transmitted into the deep southwest Pacific basin and the global deep ocean through dynamic deep western boundary currents.
  • Article
    Mixing variability in the Southern Ocean
    (American Meteorological Society, 2015-04) Meyer, Amelie ; Sloyan, Bernadette M. ; Polzin, Kurt L. ; Phillips, Helen E. ; Bindoff, Nathaniel L.
    A key remaining challenge in oceanography is the understanding and parameterization of small-scale mixing. Evidence suggests that topographic features play a significant role in enhancing mixing in the Southern Ocean. This study uses 914 high-resolution hydrographic profiles from novel EM-APEX profiling floats to investigate turbulent mixing north of the Kerguelen Plateau, a major topographic feature in the Southern Ocean. A shear–strain finescale parameterization is applied to estimate diapycnal diffusivity in the upper 1600 m of the ocean. The indirect estimates of mixing match direct microstructure profiler observations made simultaneously. It is found that mixing intensities have strong spatial and temporal variability, ranging from O(10−6) to O(10−3) m2 s−1. This study identifies topographic roughness, current speed, and wind speed as the main factors controlling mixing intensity. Additionally, the authors find strong regional variability in mixing dynamics and enhanced mixing in the Antarctic Circumpolar Current frontal region. This enhanced mixing is attributed to dissipating internal waves generated by the interaction of the Antarctic Circumpolar Current and the topography of the Kerguelen Plateau. Extending the mixing observations from the Kerguelen region to the entire Southern Ocean, this study infers a large water mass transformation rate of 17 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) across the boundary of Antarctic Intermediate Water and Upper Circumpolar Deep Water in the Antarctic Circumpolar Current. This work suggests that the contribution of mixing to the Southern Ocean overturning circulation budget is particularly significant in fronts.
  • Article
    Subantarctic mode water in the southeast Pacific : effect of exchange across the Subantarctic Front
    (John Wiley & Sons, 2013-04-23) Holte, James W. ; Talley, Lynne D. ; Chereskin, Teresa K. ; Sloyan, Bernadette M.
    This study considered cross-frontal exchange as a possible mechanism for the observed along-front freshening and cooling between the 27.0 and 27.3 kg m − 3 isopycnals north of the Subantarctic Front (SAF) in the southeast Pacific Ocean. This isopycnal range, which includes the densest Subantarctic Mode Water (SAMW) formed in this region, is mostly below the mixed layer, and so experiences little direct air-sea forcing. Data from two cruises in the southeast Pacific were examined for evidence of cross-frontal exchange; numerous eddies and intrusions containing Polar Frontal Zone (PFZ) water were observed north of the SAF, as well as a fresh surface layer during the summer cruise that was likely due to Ekman transport. These features penetrated north of the SAF, even though the potential vorticity structure of the SAF should have acted as a barrier to exchange. An optimum multiparameter (OMP) analysis incorporating a range of observed properties was used to estimate the cumulative cross-frontal exchange. The OMP analysis revealed an along-front increase in PFZ water fractional content in the region north of the SAF between the 27.1 and 27.3 kg m − 3 isopycnals; the increase was approximately 0.13 for every 15° of longitude. Between the 27.0 and 27.1 kg m − 3 isopycnals, the increase was approximately 0.15 for every 15° of longitude. A simple bulk calculation revealed that this magnitude of cross-frontal exchange could have caused the downstream evolution of SAMW temperature and salinity properties observed by Argo profiling floats.
  • Article
    Spatial variability of mixing in the Southern Ocean
    (American Geophysical Union, 2005-09-16) Sloyan, Bernadette M.
    Strain variance from standard hydrographic profiles in the southern hemisphere oceans shows that turbulent mixing is vertically and spatially non-uniform. In the South Atlantic, Indian and South Pacific Oceans, enhanced diffusivities are found over rough topography. Consistent with internal tide generated mixing, the water column diffusivity returns to background levels 500 m to 1000 m off the sea floor. In the Southern Ocean, enhanced diffusivities throughout the entire water column below 1500 m are found in the Antarctic Circumpolar Current over complex topography. Differences in the vertical extent of enhanced diffusivity profiles in the Antarctic Circumpolar Current between the parameterizations based on tidal models and topography and of the present estimate of strain variance imply that elevated vertical diffusivity profiles in the Southern Ocean are due to the interaction between the mean geostrophic current and bottom topography.
  • Article
    Revisiting the seasonal cycle of the Timor throughflow: impacts of winds, waves and eddies
    (American Geophysical Union, 2022-04-05) Pena-Molino, Beatriz ; Sloyan, Bernadette M. ; Nikurashin, Maxim ; Richet, Océane ; Wijffels, Susan E.
    The tropical Pacific and Indian Oceans are connected via a complex system of currents known as the Indonesian Throughflow (ITF). More than 30% of the variability in the ITF is linked to the seasonal cycle, influenced by the Monsoon winds. Despite previous efforts, a detailed knowledge of the ITF response to the components of the seasonal forcing is still lacking. Here, we describe the seasonal cycle of the ITF based on new observations of velocity and properties in Timor Passage, satellite altimetry and a high-resolution regional model. These new observations reveal a complex mean and seasonally varying flow field. The amplitude of the seasonal cycle in volume transport is approximately 6 Sv. The timing of the seasonal cycle, with semi-annual maxima (minima) in May and December (February and September), is controlled by the flow below 600 m associated with semi-annual Kelvin waves. The transport of thermocline waters (<300 m) is less variable than the deep flow but larger in magnitude. This top layer is modulated remotely by cycles of divergence in the Banda Sea, and locally through Ekman transport, coastal upwelling, and non-linearities of the flow. The latter manifests through the formation of eddies that reduce the throughflow during the Southeast Monsoon, when is expected to be maximum. While the reduction in transport associated with the eddies is small, its impact on heat transport is large. These non-linear dynamics develop over small scales (<10 km), and without high enough resolution, both observations and models will fail to capture them adequately.
  • Article
    The role of air-sea fluxes in Subantarctic Mode Water formation
    (American Geophysical Union, 2012-03-29) Holte, James W. ; Talley, Lynne D. ; Chereskin, Teresa K. ; Sloyan, Bernadette M.
    Two hydrographic surveys and a one-dimensional mixed layer model are used to assess the role of air-sea fluxes in forming deep Subantarctic Mode Water (SAMW) mixed layers in the southeast Pacific Ocean. Forty-two SAMW mixed layers deeper than 400 m were observed north of the Subantarctic Front during the 2005 winter cruise, with the deepest mixed layers reaching 550 m. The densest, coldest, and freshest mixed layers were found in the cruise's eastern sections near 77°W. The deep SAMW mixed layers were observed concurrently with surface ocean heat loss of approximately −200 W m−2. The heat, momentum, and precipitation flux fields of five flux products are used to force a one-dimensional KPP mixed layer model initialized with profiles from the 2006 summer cruise. The simulated winter mixed layers generated by all of the forcing products resemble Argo observations of SAMW; this agreement also validates the flux products. Mixing driven by buoyancy loss and wind forcing is strong enough to deepen the SAMW layers. Wind-driven mixing is central to SAMW formation, as model runs forced with buoyancy forcing alone produce shallow mixed layers. Air-sea fluxes indirectly influence winter SAMW properties by controlling how deeply the profiles mix. The stratification and heat content of the initial profiles determine the properties of the SAMW and the likelihood of deep mixing. Summer profiles from just upstream of Drake Passage have less heat stored between 100 and 600 m than upstream profiles, and so, with sufficiently strong winter forcing, form a cold, dense variety of SAMW.
  • Article
    Detecting change in the Indonesian Seas
    (Frontiers Media, 2019-06-04) Sprintall, Janet ; Gordon, Arnold L. ; Wijffels, Susan E. ; Feng, Ming ; Hu, Shijian ; Koch-Larrouy, Ariane ; Phillips, Helen E. ; Nugroho, Dwiyoga ; Napitu, Asmi ; Pujiana, Kandaga ; Susanto, R. Dwi ; Sloyan, Bernadette M. ; Yuan, Dongliang ; Riama, Nelly Florida ; Siswanto, Siswanto ; Kuswardani, Anastasia ; Arifin, Zainal ; Wahyudi, A’an J. ; Zhou, Hui ; Nagai, Taira ; Ansong, Joseph ; Bourdalle-Badié, Romain ; Chanut, Jerome ; Lyard, Florent ; Arbic, Brian K. ; Ramdhani, Andri ; Setiawan, Agus
    The Indonesian seas play a fundamental role in the coupled ocean and climate system with the Indonesian Throughflow (ITF) providing the only tropical pathway connecting the global oceans. Pacific warm pool waters passing through the Indonesian seas are cooled and freshened by strong air-sea fluxes and mixing from internal tides to form a unique water mass that can be tracked across the Indian Ocean basin and beyond. The Indonesian seas lie at the climatological center of the atmospheric deep convection associated with the ascending branch of the Walker Circulation. Regional SST variations cause changes in the surface winds that can shift the center of atmospheric deep convection, subsequently altering the precipitation and ocean circulation patterns within the entire Indo-Pacific region. Recent multi-decadal changes in the wind and buoyancy forcing over the tropical Indo-Pacific have directly affected the vertical profile, strength, and the heat and freshwater transports of the ITF. These changes influence the large-scale sea level, SST, precipitation and wind patterns. Observing long-term changes in mass, heat and freshwater within the Indonesian seas is central to understanding the variability and predictability of the global coupled climate system. Although substantial progress has been made over the past decade in measuring and modeling the physical and biogeochemical variability within the Indonesian seas, large uncertainties remain. A comprehensive strategy is needed for measuring the temporal and spatial scales of variability that govern the various water mass transport streams of the ITF, its connection with the circulation and heat and freshwater inventories and associated air-sea fluxes of the regional and global oceans. This white paper puts forward the design of an observational array using multi-platforms combined with high-resolution models aimed at increasing our quantitative understanding of water mass transformation rates and advection within the Indonesian seas and their impacts on the air-sea climate system. Introduction
  • Article
    Internal waves and mixing near the Kerguelen Plateau
    (American Meteorological Society, 2015-12-07) Meyer, Amelie ; Polzin, Kurt L. ; Sloyan, Bernadette M. ; Phillips, Helen E.
    In the stratified ocean, turbulent mixing is primarily attributed to the breaking of internal waves. As such, internal waves provide a link between large-scale forcing and small-scale mixing. The internal wave field north of the Kerguelen Plateau is characterized using 914 high-resolution hydrographic profiles from novel Electromagnetic Autonomous Profiling Explorer (EM-APEX) floats. Altogether, 46 coherent features are identified in the EM-APEX velocity profiles and interpreted in terms of internal wave kinematics. The large number of internal waves analyzed provides a quantitative framework for characterizing spatial variations in the internal wave field and for resolving generation versus propagation dynamics. Internal waves observed near the Kerguelen Plateau have a mean vertical wavelength of 200 m, a mean horizontal wavelength of 15 km, a mean period of 16 h, and a mean horizontal group velocity of 3 cm s−1. The internal wave characteristics are dependent on regional dynamics, suggesting that different generation mechanisms of internal waves dominate in different dynamical zones. The wave fields in the Subantarctic/Subtropical Front and the Polar Front Zone are influenced by the local small-scale topography and flow strength. The eddy-wave field is influenced by the large-scale flow structure, while the internal wave field in the Subantarctic Zone is controlled by atmospheric forcing. More importantly, the local generation of internal waves not only drives large-scale dissipation in the frontal region but also downstream from the plateau. Some internal waves in the frontal region are advected away from the plateau, contributing to mixing and stratification budgets elsewhere.
  • Article
    Antarctic bottom and lower circumpolar deep water circulation in the eastern Indian Ocean
    (American Geophysical Union, 2006-02-15) Sloyan, Bernadette M.
    Net northward transport below γn > 28.1 kgm−3 (≈3200 m) into the Perth Basin of between 4.4 and 5.8 Sv is estimated from a year-long current meter mooring array between the Broken and Naturaliste Plateaus. Northward transport of between 2.0 and 2.5 Sv of Antarctic Bottom Water (γn >28.2 kgm−3), that must upwell within the southern region of the Perth Basin, results in an area-averaged diapycnal velocity and diffusivity of w*=2.5− 3.1× 10−6 ms−1 and κ = 13−15×10−4 m2s−1, respectively. Diffusivity estimates for the Perth Basin are several times larger than area averaged mixing estimates for the abyssal subtropical South Atlantic and Pacific Oceans. However, the dissipation of turbulent kinetic energy required to maintain the abyssal mixing in the Perth basin, ε=O(10−9 Wkg−1), is similar to that required in the South Atlantic Ocean. The area-averaged diffusivity in the Perth Basin does not require unreasonable energy dissipation rates as this ocean basin is only weakly stratified. The abyssal diffuvisity of the Perth Basin results from intense mixing at the basin boundary and in the basin interior over rough topography. The complex bathymetry and low abyssal stratification suggests that the Indian Ocean, for a given energy dissipation, may support a larger meridional overturning circulation than other subtropical basins.
  • Article
    Evolving the physical global ocean observing system for research and application services through international coordination
    (Frontiers Media, 2019-08-06) Sloyan, Bernadette M. ; Wilkin, John L. ; Hill, Katherine Louise ; Chidichimo, Maria Paz ; Cronin, Meghan F. ; Johannessen, Johnny A. ; Karstensen, Johannes ; Krug, Marjolaine ; Lee, Tong ; Oka, Eitarou ; Palmer, Matthew D. ; Rabe, Benjamin ; Speich, Sabrina ; von Schuckmann, Karina ; Weller, Robert A. ; Yu, Weidong
    Climate change and variability are major societal challenges, and the ocean is an integral part of this complex and variable system. Key to the understanding of the ocean’s role in the Earth’s climate system is the study of ocean and sea-ice physical processes, including its interactions with the atmosphere, cryosphere, land, and biosphere. These processes include those linked to ocean circulation; the storage and redistribution of heat, carbon, salt and other water properties; and air-sea exchanges of heat, momentum, freshwater, carbon, and other gasses. Measurements of ocean physics variables are fundamental to reliable earth prediction systems for a range of applications and users. In addition, knowledge of the physical environment is fundamental to growing understanding of the ocean’s biogeochemistry and biological/ecosystem variability and function. Through the progress from OceanObs’99 to OceanObs’09, the ocean observing system has evolved from a platform centric perspective to an integrated observing system. The challenge now is for the observing system to evolve to respond to an increasingly diverse end user group. The Ocean Observations Physics and Climate panel (OOPC), formed in 1995, has undertaken many activities that led to observing system-related agreements. Here, OOPC will explore the opportunities and challenges for the development of a fit-for-purpose, sustained and prioritized ocean observing system, focusing on physical variables that maximize support for fundamental research, climate monitoring, forecasting on different timescales, and society. OOPC recommendations are guided by the Framework for Ocean Observing which emphasizes identifying user requirements by considering time and space scales of the Essential Ocean Variables. This approach provides a framework for reviewing the adequacy of the observing system, looking for synergies in delivering an integrated observing system for a range of applications and focusing innovation in areas where existing technologies do not meet these requirements.
  • Article
    A road map to IndOOS-2 better observations of the rapidly warming Indian Ocean
    (American Meteorological Society, 2020-11-01) Beal, Lisa M. ; Vialard, Jérôme ; Roxy, Mathew Koll ; Li, Jing ; Andres, Magdalena ; Annamalai, Hariharasubramanian ; Feng, Ming ; Han, Weiqing ; Hood, Raleigh R. ; Lee, Tong ; Lengaigne, Matthieu ; Lumpkin, Rick ; Masumoto, Yukio ; McPhaden, Michael J. ; Ravichandran, M. ; Shinoda, Toshiaki ; Sloyan, Bernadette M. ; Strutton, Peter G. ; Subramanian, Aneesh C. ; Tozuka, Tomoki ; Ummenhofer, Caroline C. ; Unnikrishnan, Shankaran Alakkat ; Wiggert, Jerry D. ; Yu, Lisan ; Cheng, Lijing ; Desbruyères, Damien G. ; Parvathi, V.
    The Indian Ocean Observing System (IndOOS), established in 2006, is a multinational network of sustained oceanic measurements that underpin understanding and forecasting of weather and climate for the Indian Ocean region and beyond. Almost one-third of humanity lives around the Indian Ocean, many in countries dependent on fisheries and rain-fed agriculture that are vulnerable to climate variability and extremes. The Indian Ocean alone has absorbed a quarter of the global oceanic heat uptake over the last two decades and the fate of this heat and its impact on future change is unknown. Climate models project accelerating sea level rise, more frequent extremes in monsoon rainfall, and decreasing oceanic productivity. In view of these new scientific challenges, a 3-yr international review of the IndOOS by more than 60 scientific experts now highlights the need for an enhanced observing network that can better meet societal challenges, and provide more reliable forecasts. Here we present core findings from this review, including the need for 1) chemical, biological, and ecosystem measurements alongside physical parameters; 2) expansion into the western tropics to improve understanding of the monsoon circulation; 3) better-resolved upper ocean processes to improve understanding of air–sea coupling and yield better subseasonal to seasonal predictions; and 4) expansion into key coastal regions and the deep ocean to better constrain the basinwide energy budget. These goals will require new agreements and partnerships with and among Indian Ocean rim countries, creating opportunities for them to enhance their monitoring and forecasting capacity as part of IndOOS-2.
  • Article
    Finescale parameterizations of turbulent dissipation
    (John Wiley & Sons, 2014-02-25) Polzin, Kurt L. ; Naveira Garabato, Alberto C. ; Huussen, Tycho N. ; Sloyan, Bernadette M. ; Waterman, Stephanie N.
    This article (1) reviews and clarifies the basic physics underpinning finescale parameterizations of turbulent dissipation due to internal wave breaking and (2) provides advice on the implementation of the parameterizations in a way that is most consistent with the underlying physics, with due consideration given to common instrumental issues. Potential biases in the parameterization results are discussed in light of both (1) and (2), and illustrated with examples in the literature. The value of finescale parameterizations for studies of the large-scale ocean circulation in the presence of common biases is assessed. We conclude that the parameterizations can contribute significantly to the resolution of large-scale circulation problems associated with plausible ranges in the rates of turbulent dissipation and diapycnal mixing spanning an order of magnitude or more.
  • Preprint
    Changes in ocean heat, carbon content, and ventilation : a review of the first decade of GO-SHIP Global Repeat Hydrography
    ( 2015-05-30) Talley, Lynne D. ; Feely, Richard A. ; Sloyan, Bernadette M. ; Wanninkhof, Rik ; Baringer, Molly O. ; Bullister, John L. ; Carlson, Craig A. ; Doney, Scott C. ; Fine, Rana A. ; Firing, Eric ; Gruber, Nicolas ; Hansell, Dennis A. ; Ishii, Masayoshi ; Johnson, Gregory ; Katsumata, K. ; Key, Robert M. ; Kramp, Martin ; Langdon, Chris ; Macdonald, Alison M. ; Mathis, Jeremy T. ; McDonagh, Elaine L. ; Mecking, Sabine ; Millero, Frank J. ; Mordy, Calvin W. ; Nakano, T. ; Sabine, Chris L. ; Smethie, William M. ; Swift, James H. ; Tanhua, Toste ; Thurnherr, Andreas M. ; Warner, Mark J. ; Zhang, Jia-Zhong
    The ocean, a central component of Earth’s climate system, is changing. Given the global scope of these changes, highly accurate measurements of physical and biogeochemical properties need to be conducted over the full water column, spanning the ocean basins from coast to coast, and repeated every decade at a minimum, with a ship-based observing system. Since the late 1970s, when the Geochemical Ocean Sections Study (GEOSECS) conducted the first global survey of this kind, the World Ocean Circulation Experiment (WOCE) and Joint Global Ocean Flux Study (JGOFS), and now the Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP) have collected these “reference standard” data that allow quantification of ocean heat and carbon uptake, and variations in salinity, oxygen, nutrients, and acidity on basin scales. The evolving GO-SHIP measurement suite also provides new global information about dissolved organic carbon, a large bioactive reservoir of carbon.
  • Article
    Adequacy of the ocean observation system for quantifying regional heat and freshwater storage and change
    (Frontiers Media, 2019-08-29) Palmer, Matthew D. ; Durack, Paul J. ; Chidichimo, Maria Paz ; Church, John A. ; Cravatte, Sophie ; Hill, Katherine Louise ; Johannessen, Johnny A. ; Karstensen, Johannes ; Lee, Tong ; Legler, David ; Mazloff, Matthew R. ; Oka, Eitarou ; Purkey, Sarah G. ; Rabe, Benjamin ; Sallee, Jean-Baptiste ; Sloyan, Bernadette M. ; Speich, Sabrina ; von Schuckmann, Karina ; Willis, Josh ; Wijffels, Susan E.
    Considerable advances in the global ocean observing system over the last two decades offers an opportunity to provide more quantitative information on changes in heat and freshwater storage. Variations in these storage terms can arise through internal variability and also the response of the ocean to anthropogenic climate change. Disentangling these competing influences on the regional patterns of change and elucidating their governing processes remains an outstanding scientific challenge. This challenge is compounded by instrumental and sampling uncertainties. The combined use of ocean observations and model simulations is the most viable method to assess the forced signal from noise and ascertain the primary drivers of variability and change. Moreover, this approach offers the potential for improved seasonal-to-decadal predictions and the possibility to develop powerful multi-variate constraints on climate model future projections. Regional heat storage changes dominate the steric contribution to sea level rise over most of the ocean and are vital to understanding both global and regional heat budgets. Variations in regional freshwater storage are particularly relevant to our understanding of changes in the hydrological cycle and can potentially be used to verify local ocean mass addition from terrestrial and cryospheric systems associated with contemporary sea level rise. This White Paper will examine the ability of the current ocean observing system to quantify changes in regional heat and freshwater storage. In particular we will seek to answer the question: What time and space scales are currently resolved in different regions of the global oceans? In light of some of the key scientific questions, we will discuss the requirements for measurement accuracy, sampling, and coverage as well as the synergies that can be leveraged by more comprehensively analyzing the multi-variable arrays provided by the integrated observing system.
  • Article
    Pacific anthropogenic carbon between 1991 and 2017
    (American Geophysical Union, 2019-04-29) Carter, Brendan ; Feely, Richard A. ; Wanninkhof, Rik ; Kouketsu, Shinya ; Sonnerup, Rolf E. ; Pardo, Paula Conde ; Sabine, Christopher L. ; Johnson, Gregory C. ; Sloyan, Bernadette M. ; Murata, Akihiko ; Mecking, Sabine ; Tilbrook, Bronte ; Speer, Kevin G. ; Talley, Lynne D. ; Millero, Frank J. ; Wijffels, Susan E. ; Macdonald, Alison M. ; Gruber, Nicolas ; Bullister, John L.
    We estimate anthropogenic carbon (Canth) accumulation rates in the Pacific Ocean between 1991 and 2017 from 14 hydrographic sections that have been occupied two to four times over the past few decades, with most sections having been recently measured as part of the Global Ocean Ship‐based Hydrographic Investigations Program. The rate of change of Canth is estimated using a new method that combines the extended multiple linear regression method with improvements to address the challenges of analyzing multiple occupations of sections spaced irregularly in time. The Canth accumulation rate over the top 1,500 m of the Pacific increased from 8.8 (±1.1, 1σ) Pg of carbon per decade between 1995 and 2005 to 11.7 (±1.1) PgC per decade between 2005 and 2015. For the entire Pacific, about half of this decadal increase in the accumulation rate is attributable to the increase in atmospheric CO2, while in the South Pacific subtropical gyre this fraction is closer to one fifth. This suggests a substantial enhancement of the accumulation of Canth in the South Pacific by circulation variability and implies that a meaningful portion of the reinvigoration of the global CO2 sink that occurred between ~2000 and ~2010 could be driven by enhanced ocean Canth uptake and advection into this gyre. Our assessment suggests that the accuracy of Canth accumulation rate reconstructions along survey lines is limited by the accuracy of the full suite of hydrographic data and that a continuation of repeated surveys is a critical component of future carbon cycle monitoring.
  • Article
    Global perspectives on observing ocean boundary current systems
    (Frontiers Media, 2019-08-08) Todd, Robert E. ; Chavez, Francisco P. ; Clayton, Sophie A. ; Cravatte, Sophie ; Goes, Marlos Pereira ; Graco, Michelle ; Lin, Xiaopei ; Sprintall, Janet ; Zilberman, Nathalie ; Archer, Matthew ; Arístegui, Javier ; Balmaseda, Magdalena A. ; Bane, John M. ; Baringer, Molly O. ; Barth, John A. ; Beal, Lisa M. ; Brandt, Peter ; Calil, Paulo H. R. ; Campos, Edmo ; Centurioni, Luca R. ; Chidichimo, Maria Paz ; Cirano, Mauro ; Cronin, Meghan F. ; Curchitser, Enrique N. ; Davis, Russ E. ; Dengler, Marcus ; deYoung, Brad ; Dong, Shenfu ; Escribano, Ruben ; Fassbender, Andrea ; Fawcett, Sarah E. ; Feng, Ming ; Goni, Gustavo J. ; Gray, Alison R. ; Gutiérrez, Dimitri ; Hebert, Dave ; Hummels, Rebecca ; Ito, Shin-ichi ; Krug, Marjolaine ; Lacan, Francois ; Laurindo, Lucas ; Lazar, Alban ; Lee, Craig M. ; Lengaigne, Matthieu ; Levine, Naomi M. ; Middleton, John ; Montes, Ivonne ; Muglia, Michael ; Nagai, Takeyoshi ; Palevsky, Hilary I. ; Palter, Jaime B. ; Phillips, Helen E. ; Piola, Alberto R. ; Plueddemann, Albert J. ; Qiu, Bo ; Rodrigues, Regina ; Roughan, Moninya ; Rudnick, Daniel L. ; Rykaczewski, Ryan R. ; Saraceno, Martin ; Seim, Harvey E. ; Sen Gupta, Alexander ; Shannon, Lynne ; Sloyan, Bernadette M. ; Sutton, Adrienne J. ; Thompson, LuAnne ; van der Plas, Anja K. ; Volkov, Denis L. ; Wilkin, John L. ; Zhang, Dongxiao ; Zhang, Linlin
    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.
  • Article
    A sustained ocean observing system in the Indian Ocean for climate related scientific knowledge and societal needs
    (Frontiers Media, 2019-06-28) Hermes, Juliet ; Masumoto, Yukio ; Beal, Lisa M. ; Roxy, Mathew Koll ; Vialard, Jérôme ; Andres, Magdalena ; Annamalai, Hariharasubramanian ; Behera, Swadhin ; D’Adamo, Nick ; Doi, Takeshi ; Feng, Ming ; Han, Weiqing ; Hardman-Mountford, Nick ; Hendon, Harry ; Hood, Raleigh R. ; Kido, Shoichiro ; Lee, Craig M. ; Lee, Tong ; Lengaigne, Matthieu ; Li, Jing ; Lumpkin, Rick ; Navaneeth, K. N. ; Milligan, Ben ; McPhaden, Michael J. ; Ravichandran, M. ; Shinoda, Toshiaki ; Singh, Arvind ; Sloyan, Bernadette M. ; Strutton, Peter G. ; Subramanian, Aneesh C. ; Thurston, Sidney ; Tozuka, Tomoki ; Ummenhofer, Caroline C. ; Unnikrishnan, Shankaran Alakkat ; Venkatesan, Ramasamy ; Wang, Dongxiao ; Wiggert, Jerry D. ; Yu, Lisan ; Yu, Weidong
    The Indian Ocean is warming faster than any of the global oceans and its climate is uniquely driven by the presence of a landmass at low latitudes, which causes monsoonal winds and reversing currents. The food, water, and energy security in the Indian Ocean rim countries and islands are intrinsically tied to its climate, with marine environmental goods and services, as well as trade within the basin, underpinning their economies. Hence, there are a range of societal needs for Indian Ocean observation arising from the influence of regional phenomena and climate change on, for instance, marine ecosystems, monsoon rains, and sea-level. The Indian Ocean Observing System (IndOOS), is a sustained observing system that monitors basin-scale ocean-atmosphere conditions, while providing flexibility in terms of emerging technologies and scientificand societal needs, and a framework for more regional and coastal monitoring. This paper reviews the societal and scientific motivations, current status, and future directions of IndOOS, while also discussing the need for enhanced coastal, shelf, and regional observations. The challenges of sustainability and implementation are also addressed, including capacity building, best practices, and integration of resources. The utility of IndOOS ultimately depends on the identification of, and engagement with, end-users and decision-makers and on the practical accessibility and transparency of data for a range of products and for decision-making processes. Therefore we highlight current progress, issues and challenges related to end user engagement with IndOOS, as well as the needs of the data assimilation and modeling communities. Knowledge of the status of the Indian Ocean climate and ecosystems and predictability of its future, depends on a wide range of socio-economic and environmental data, a significant part of which is provided by IndOOS.
  • Article
    OceanGliders: A component of the integrated GOOS
    (Frontiers Media, 2019-10-02) Testor, Pierre ; de Young, Brad ; Rudnick, Daniel L. ; Glenn, Scott ; Hayes, Daniel J. ; Lee, Craig M. ; Pattiaratchi, Charitha ; Hill, Katherine Louise ; Heslop, Emma ; Turpin, Victor ; Alenius, Pekka ; Barrera, Carlos ; Barth, John A. ; Beaird, Nicholas ; Bécu, Guislain ; Bosse, Anthony ; Bourrin, François ; Brearley, J. Alexander ; Chao, Yi ; Chen, Sue ; Chiggiato, Jacopo ; Coppola, Laurent ; Crout, Richard ; Cummings, James A. ; Curry, Beth ; Curry, Ruth G. ; Davis, Richard F. ; Desai, Kruti ; DiMarco, Steven F. ; Edwards, Catherine ; Fielding, Sophie ; Fer, Ilker ; Frajka-Williams, Eleanor ; Gildor, Hezi ; Goni, Gustavo J. ; Gutierrez, Dimitri ; Haugan, Peter M. ; Hebert, David ; Heiderich, Joleen ; Henson, Stephanie A. ; Heywood, Karen J. ; Hogan, Patrick ; Houpert, Loïc ; Huh, Sik ; Inall, Mark E. ; Ishii, Masao ; Ito, Shin-ichi ; Itoh, Sachihiko ; Jan, Sen ; Kaiser, Jan ; Karstensen, Johannes ; Kirkpatrick, Barbara ; Klymak, Jody M. ; Kohut, Josh ; Krahmann, Gerd ; Krug, Marjolaine ; McClatchie, Sam ; Marin, Frédéric ; Mauri, Elena ; Mehra, Avichal ; Meredith, Michael P. ; Meunier, Thomas ; Miles, Travis ; Morell, Julio M. ; Mortier, Laurent ; Nicholson, Sarah ; O'Callaghan, Joanne ; O'Conchubhair, Diarmuid ; Oke, Peter ; Pallás-Sanz, Enric ; Palmer, Matthew D. ; Park, Jong Jin ; Perivoliotis, Leonidas ; Poulain, Pierre Marie ; Perry, Ruth ; Queste, Bastien ; Rainville, Luc ; Rehm, Eric ; Roughan, Moninya ; Rome, Nicholas ; Ross, Tetjana ; Ruiz, Simon ; Saba, Grace ; Schaeffer, Amandine ; Schönau, Martha ; Schroeder, Katrin ; Shimizu, Yugo ; Sloyan, Bernadette M. ; Smeed, David A. ; Snowden, Derrick ; Song, Yumi ; Swart, Sebastiaan ; Tenreiro, Miguel ; Thompson, Andrew ; Tintore, Joaquin ; Todd, Robert E. ; Toro, Cesar ; Venables, Hugh J. ; Wagawa, Taku ; Waterman, Stephanie N. ; Watlington, Roy A. ; Wilson, Doug
    The OceanGliders program started in 2016 to support active coordination and enhancement of global glider activity. OceanGliders contributes to the international efforts of the Global Ocean Observation System (GOOS) for Climate, Ocean Health, and Operational Services. It brings together marine scientists and engineers operating gliders around the world: (1) to observe the long-term physical, biogeochemical, and biological ocean processes and phenomena that are relevant for societal applications; and, (2) to contribute to the GOOS through real-time and delayed mode data dissemination. The OceanGliders program is distributed across national and regional observing systems and significantly contributes to integrated, multi-scale and multi-platform sampling strategies. OceanGliders shares best practices, requirements, and scientific knowledge needed for glider operations, data collection and analysis. It also monitors global glider activity and supports the dissemination of glider data through regional and global databases, in real-time and delayed modes, facilitating data access to the wider community. OceanGliders currently supports national, regional and global initiatives to maintain and expand the capabilities and application of gliders to meet key global challenges such as improved measurement of ocean boundary currents, water transformation and storm forecast.
  • Article
    Unabated bottom water warming and freshening in the south Pacific Ocean.
    (American Geophysical Union, 2019-02-20) Purkey, Sarah G. ; Johnson, Gregory C. ; Talley, Lynne D. ; Sloyan, Bernadette M. ; Wijffels, Susan E. ; Smethie, William M. ; Mecking, Sabine ; Katsumata, Katsuro
    Abyssal ocean warming contributed substantially to anthropogenic ocean heat uptake and global sea level rise between 1990 and 2010. In the 2010s, several hydrographic sections crossing the South Pacific Ocean were occupied for a third or fourth time since the 1990s, allowing for an assessment of the decadal variability in the local abyssal ocean properties among the 1990s, 2000s, and 2010s. These observations from three decades reveal steady to accelerated bottom water warming since the 1990s. Strong abyssal (z > 4,000 m) warming of 3.5 (±1.4) m°C/year (m°C = 10−3 °C) is observed in the Ross Sea, directly downstream from bottom water formation sites, with warming rates of 2.5 (±0.4) m°C/year to the east in the Amundsen‐Bellingshausen Basin and 1.3 (±0.2) m°C/year to the north in the Southwest Pacific Basin, all associated with a bottom‐intensified descent of the deepest isotherms. Warming is consistently found across all sections and their occupations within each basin, demonstrating that the abyssal warming is monotonic, basin‐wide, and multidecadal. In addition, bottom water freshening was strongest in the Ross Sea, with smaller amplitude in the Amundsen‐Bellingshausen Basin in the 2000s, but is discernible in portions of the Southwest Pacific Basin by the 2010s. These results indicate that bottom water freshening, stemming from strong freshening of Ross Shelf Waters, is being advected along deep isopycnals and mixed into deep basins, albeit on longer timescales than the dynamically driven, wave‐propagated warming signal. We quantify the contribution of the warming to local sea level and heat budgets.