Dever Mathieu

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  • Article
    Accuracy and long-term stability assessment of inductive conductivity cell measurements on Argo Floats
    (American Meteorological Society, 2020-12-01) Nezlin, Nikolay P. ; Dever, Mathieu ; Halverson, Mark ; Leconte, Jean-Michel ; Maze, Guillaume ; Richards, Clark G. ; Shkvorets, Igor ; Zhang, Rui ; Johnson, Greg
    This study demonstrates the long-term stability of salinity measurements from Argo floats equipped with inductive conductivity cells, which have extended float lifetimes as compared to electrode-type cells. New Argo float sensor payloads must meet the demands of the Argo governance committees before they are implemented globally. Currently, the use of CTDs with inductive cells designed and manufactured by RBR, Ltd., has been approved as a Global Argo Pilot. One requirement for new sensors is to demonstrate stable measurements over the lifetime of a float. To demonstrate this, data from four Argo floats in the western Pacific Ocean equipped with the RBRargo CTD sensor package are analyzed using the same Owens–Wong–Cabanes (OWC) method and reference datasets as the Argo delayed-mode quality control (DMQC) operators. When run with default settings against the standard DMQC Argo and CTD databases, the OWC analysis reveals no drift in any of the four RBRargo datasets and, in one case, an offset exceeding the Argo target salinity limits. Being a statistical tool, the OWC method cannot strictly determine whether deviations in salinity measurements with respect to a reference hydrographic product (e.g., climatologies) are caused by oceanographic variability or sensor problems. So, this study furthermore investigates anomalous salinity measurements observed when compared with a reference product and demonstrates that anomalous values tend to occur in regions with a high degree of variability and can be better explained by imperfect reference data rather than sensor drift. This study concludes that the RBR inductive cell is a viable option for salinity measurements as part of the Argo program.
  • Article
    Static and dynamic performance of the RBRargo3 CTD
    (American Meteorological Society, 2022-10-01) Dever, Mathieu ; Owens, W. Brechner ; Richards, Clark G. ; Wijffels, Susan E. ; Wong, Annie P. S. ; Shkvorets, Igor ; Halverson, Mark ; Johnson, Greg
    The static and dynamic performances of the RBRargo3 are investigated using a combination of laboratory-based and in situ datasets from floats deployed as part of an Argo pilot program. Temperature and pressure measurements compare well to co-located reference data acquired from shipboard CTDs. Static accuracy of salinity measurements is significantly improved using 1) a time lag for temperature, 2) a quadratic pressure dependence, and 3) a unit-based calibration for each RBRargo3 over its full pressure range. Long-term deployments show no significant drift in the RBRargo3 accuracy. The dynamic response of the RBRargo3 demonstrates the presence of two different adjustment time scales: a long-term adjustment O(120) s, driven by the temperature difference between the interior of the conductivity cell and the water, and a short-term adjustment O(5–10) s, associated to the initial exchange of heat between the water and the inner ceramic. Corrections for these effects, including dependence on profiling speed, are developed.
  • Article
    Frontal dynamics of a buoyancy‐driven coastal current : quantifying buoyancy, wind, and isopycnal tilting influence on the Nova Scotia Current
    (John Wiley & Sons, 2018-07-28) Dever, Mathieu ; Skagseth, Øystein ; Drinkwater, Ken F. ; Hebert, David
    The focus of this study is on the relative roles of winds and buoyancy in driving the Nova Scotia Current (NSC) utilizing detailed hydrographic glider transects along the Halifax Line. We define a Hydrographic Wind Index (HWI) using a simplistic two‐layer model to represent the NSC and its frontal system. The HWI is based on local characteristics of the density front extracted from the glider data (e.g., frontal slope). The impact of wind‐driven isopycnal tilting on the frontal slope is estimated and corrected for to accurately scale the buoyancy‐driven component of the NSC. Observations from independent current profilers deployed across the NSC confirm that the HWI captures the low‐frequency variability of the NSC. The monthly wind‐driven flow is estimated to represent between 1.0% (±0.1%) and 48% (±1%) of the total alongshore currents, with a yearly mean of about 36% (±1%). We demonstrate that using local conditions is more appropriate to the study of buoyancy‐driven currents ranging over distances on the order of urn:x-wiley:jgrc:media:jgrc22972:jgrc22972-math-0001(100 km), compared to the traditional approach based on upstream conditions. Contrary to the traditional approach, the HWI is not affected by the advective time lag associated with the downshelf propagation of the buoyant water coming from the upstream source. However, the HWI approach requires high‐resolution data sets, as errors on the estimates of the buoyancy‐ and wind‐driven flows become large as the sampling resolution decreases. Despite being data intensive, we argue that the HWI is also applicable to multisource currents, where upstream conditions are difficult to define.
  • Technical Report
    UCTD and EcoCTD Observations from the CALYPSO Pilot Experiment (2018): Cruise and Data Report
    (Woods Hole Oceanographic Institution, 2019-01) Dever, Mathieu ; Freilich, Mara ; Hodges, Benjamin A. ; Farrar, J. Thomas ; Lanagan, Thomas ; Mahadevan, Amala
    From May 27, 2018 to June 02, 2018, a scientific campaign was conducted in the Alboran Sea as part of an ONR Departmental Research Initiative, CALYPSO. The pilot cruise involved two ships: the R/V Socib, tasked with sampling fixed lines repeatedly, and the NRV Alliance that surveyed along the trajectory of Lagrangian platforms. A large variety of assets were deployed from the NRV Alliance, with the objective to identify coherent Lagrangian pathways from the surface ocean to interior. As part of the field campaign, an Underway-CTD (UCTD) system was used to measure vertical profiles of salinity, temperature and other properties while steaming, to achieve closely spaced measurements in the horizontal along the ship's track. Both a UCTD probe and an biooptically augmented probe, named EcoCTD, were deployed. The EcoCTD collects concurrent physical and bio-optical observations. This report focuses exclusively on the data collected by these two underway systems. It describes th e datasets collected during the pilot cruise, as well as the important processing steps developed for the EcoCTD.
  • Working Paper
    Pump it Up workshop report
    (Woods Hole Oceanographic Institution, 2017-10-20) Buesseler, Ken O. ; Adams, Allan ; Bellingham, James G. ; Dever, Mathieu ; Edgcomb, Virginia P. ; Estapa, Margaret L. ; Frank, Alex ; Gallager, Scott M. ; Govindarajan, Annette F. ; Horner, Tristan J. ; Hunter, Jon ; Jakuba, Michael V. ; Kapit, Jason ; Katija, Kakani ; Lawson, Gareth L. ; Lu, Yuehan ; Mahadevan, Amala ; Nicholson, David P. ; Omand, Melissa M. ; Palevsky, Hilary I. ; Rauch, Chris ; Sosik, Heidi M. ; Ulmer, Kevin M. ; Wurgaft, Eyal ; Yoerger, Dana R.
    A two-day workshop was conducted to trade ideas and brainstorm about how to advance our understanding of the ocean’s biological pump. The goal was to identify the most important scientific issues that are unresolved but might be addressed with new and future technological advances.
  • Article
    EcoCTD for profiling oceanic physical-biological properties from an underway ship
    (American Meteorological Society, 2020-05-08) Dever, Mathieu ; Freilich, Mara ; Farrar, J. Thomas ; Hodges, Benjamin A. ; Lanagan, Thomas ; Baron, Andrew J. ; Mahadevan, Amala
    The study of ocean dynamics and biophysical variability at submesoscales of O(1) km and O(1) h raises several observational challenges. To address these by underway sampling, we recently developed a towed profiler called the EcoCTD, capable of concurrently measuring both hydrographic and bio-optical properties such as oxygen, chlorophyll fluorescence, and optical backscatter. The EcoCTD presents an attractive alternative to currently used towed platforms due to its light footprint, versatility in the field, and ease of deployment and recovery without cranes or heavy-duty winches. We demonstrate its use for gathering high-quality data at submesoscale spatiotemporal resolution. A dataset of bio-optical and hydrographic properties, collected with the EcoCTD during field trials in 2018, highlights its scientific potential for the study of physical–biological interactions at submesoscales.
  • Article
    Size-differentiated export flux in different dynamical regimes in the ocean
    (American Geophysical Union, 2021-02-17) Dever, Mathieu ; Nicholson, David P. ; Omand, Melissa M. ; Mahadevan, Amala
    Export of Particulate Organic Carbon (POC) is mainly driven by gravitational sinking. Thus, traditionally, it is thought that larger, faster-sinking particles make up most of the POC export flux. However, this need not be the case for particles whose sinking speeds are comparable to the vertical velocities of a dynamic flow field that can influence the descent rate of particles. Particles with different settling speeds are released in two process-oriented model simulations of an upper ocean eddying flow in the Northeast Pacific to evaluate the impact of (1) ocean dynamics on the respective contribution of the different sinking-velocity classes to POC export, and (2) the particle number size-spectrum slope. The analysis reveals that the leading export mechanism changes from gravitationally driven to advectively driven as submesoscale dynamics become more active in the region. The vertical velocity associated with submesoscale dynamics enhances the contribution of slower-sinking particles to POC export flux by a factor ranging from 3 to 10, especially where the relative abundance of small particles is large (i.e., steep particle size-spectrum slope). Remineralization generally decreases the total amount of biomass exported, but its impact is weaker in dynamical regimes where submesoscale dynamics are present and export is advectively driven. In an advectively driven export regime, remineralization processes counter-intuitively enhance the role of slower-sinking particles to the point where these slower-sinking velocity classes dominate the export, therefore challenging the traditional paradigm for POC export. This study demonstrates that slow-sinking particles can be a significant contribution, and at times, even dominate the export flux.
  • Technical Report
    CALYPSO 2019 Cruise Report: field campaign in the Mediterranean
    (Woods Hole Oceanographic Institution, 2020-01) Mahadevan, Amala ; D'Asaro, Eric A. ; Allen, John T. ; Almaraz García, Pablo ; Alou-Font, Eva ; Aravind, Harilal Meenambika ; Balaguer, Pau ; Caballero, Isabel ; Calafat, Noemi ; Carbornero, Andrea ; Casas, Benjamin ; Castilla, Carlos ; Centurioni, Luca R. ; Conley, Margaret ; Cristofano, Gino ; Cutolo, Eugenio ; Dever, Mathieu ; Enrique Navarro, Angélica ; Falcieri, Francesco ; Freilich, Mara ; Goodwin, Evan ; Graham, Raymond ; Guigand, Cedric ; Hodges, Benjamin A. ; Huntley, Helga ; Johnston, T. M. Shaun ; Lankhorst, Matthias ; Lermusiaux, Pierre F. J. ; Lizaran, Irene ; Mirabito, Chris ; Miralles, A. ; Mourre, Baptiste ; Navarro, Gabriel ; Ohmart, Michael ; Ouala, Said ; Ozgokmen, Tamay M. ; Pascual, Ananda ; Pou, Joan Mateu Horrach ; Poulain, Pierre Marie ; Ren, Alice ; Tarry, Daniel R. ; Rudnick, Daniel L. ; Rubio, M. ; Ruiz, Simon ; Rypina, Irina I. ; Tintore, Joaquin ; Send, Uwe ; Shcherbina, Andrey Y. ; Torner, Marc ; Salvador-Vieira, Guilherme ; Wirth, Nikolaus ; Zarokanellos, Nikolaos
    This cruise aimed to identify transport pathways from the surface into the interior ocean during the late winter in the Alborán sea between the Strait of Gibraltar (5°40’W) and the prime meridian. Theory and previous observations indicated that these pathways likely originated at strong fronts, such as the one that separates salty Mediterranean water and the fresher water in owing from the Atlantic. Our goal was to map such pathways and quantify their transport. Since the outcropping isopycnals at the front extend to the deepest depths during the late winter, we planned the cruise at the end of the Spring, prior to the onset of thermal stratification of the surface mixed layer.