Rossby H. Thomas
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ArticleThe scientific and societal uses of global measurements of subsurface velocity(Frontiers Media, 2019-07-24) Szuts, Zoltan B. ; Bower, Amy S. ; Donohue, Kathleen A. ; Girton, James B. ; Hummon, Julia M. ; Katsumata, Katsuro ; Lumpkin, Rick ; Ortner, Peter B. ; Phillips, Helen E. ; Rossby, H. Thomas ; Shay, Lynn Keith ; Sun, Charles ; Todd, Robert E.Ocean velocity defines ocean circulation, yet the available observations of subsurface velocity are under-utilized by society. The first step to address these concerns is to improve visibility of and access to existing measurements, which include acoustic sampling from ships, subsurface float drifts, and measurements from autonomous vehicles. While multiple programs provide data publicly, the present difficulty in finding, understanding, and using these data hinder broader use by managers, the public, and other scientists. Creating links from centralized national archives to project specific websites is an easy but important way to improve data discoverability and access. A further step is to archive data in centralized databases, which increases usage by providing a common framework for disparate measurements. This requires consistent data standards and processing protocols for all types of velocity measurements. Central dissemination will also simplify the creation of derived products tailored to end user goals. Eventually, this common framework will aid managers and scientists in identifying regions that need more sampling and in identifying methods to fulfill those demands. Existing technologies are capable of improving spatial and temporal sampling, such as using ships of opportunity or from autonomous platforms like gliders, profiling floats, or Lagrangian floats. Future technological advances are needed to fill sampling gaps and increase data coverage.
ArticleMore than 50 years of successful continuous temperature section measurements by the global expendable bathythermograph network, its integrability, societal benefits, and future(Frontiers Media, 2019-07-24) Goni, Gustavo J. ; Sprintall, Janet ; Bringas, Francis ; Cheng, Lijing ; Cirano, Mauro ; Dong, Shenfu ; Domingues, Ricardo ; Goes, Marlos Pereira ; Lopez, Hosmay ; Morrow, Rosemary ; Rivero, Ulises ; Rossby, H. Thomas ; Todd, Robert E. ; Trinanes, Joaquin ; Zilberman, Nathalie ; Baringer, Molly O. ; Boyer, Tim ; Cowley, Rebecca ; Domingues, Catia M. ; Hutchinson, Katherine ; Kramp, Martin ; Mata, Mauricio M. ; Reseghetti, Franco ; Sun, Charles ; Udaya Bhaskar, T. V. S. ; Volkov, Denis L.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.
Working PaperThe North Atlantic current system : a scientific report, 19-20 April 1993, Woods Hole Oceanographic Institution, Woods Hole, MA 02543(Woods Hole Oceanographic Institution, 1993) Malanotte-Rizzoli, Paola ; Rossby, H. ThomasOn April 19-20, 1993 a two-day workshop was held at the Woods Hole Oceanographic Institution on "The North Atlantic Current (NAC) System". The workshop, which was sponsored by NSF/NOAA/ONR reflected a growing sense of excitement and interest in the oceanographic community in the NAC system and its role in the large scale circulation of the North Atlantic Ocean and Climate of the adjoining landmasses. The presence of the North Atlantic Current with its warm waters at such high latitudes, and its role in both the wind-driven and thermohaline circulations makes it unique amongst the Western Boundary Currents of the oceans. Being on the one hand part of the wind-driven circulation and on the other hand the upper branch of the "Global Conveyor Belt", the North Atlantic current is indeed an enigma, suggesting fundamental issues about the nature of the coupling between the two 'roles' of the current that will need to be addressed. But it was also clear from the workshop discussions that there remain considerable uncertainty about the basic structure of the NAC. A high level of interest in these questions was evident at the workshop. The lectures, presentations, and the discussion sessions where observational and modelling issues were debated, brought out many ideas for the development and focus of future research of the NAC and surrounding waters. This report is intended to provide not only a synopsis of the lectures, papers, and ideas that were discussed, but also a scientific statement from the workshop reflecting a growing consensus for initiating a coordinated research effort in the region.
Technical ReportA quasi-Lagrangian study of mid-ocean variability using long range SOFAR floats(Woods Hole Oceanographic Institution, 1976-04) Rossby, H. Thomas ; Voorhis, Arthur D. ; Webb, Douglas C.Twenty neutrally buoyant SOFAR floats were used in the Mid-Ocean Dynamics Experiment (MODE) to study the structure and variability of the deep ocean currents. The floats were clustered so that the pattern of motions could be resolved (mapping and pattern recognition). A number of float trajectories are shown and the very individual character of their signature is emphasized. Some floats remain nearly stationary for a year whereas others will cover hundreds of kilometers to the south or west in just a few months. Superposition of all trajectories in the spaghetti diagram is shown to reveal considerable organization of the "eddy" field in the MODE area and is thought to be caused by the near presence of the Blake-Bahama Outer Ridge to the west. There is considerable asymmetry to the float dispersal with floats rapidly scattering to the south and west, but not to the north and east even though the r .m.s. velocities are a factor 3 to 6 times greater than the mean drift. The evolution and dispersal of the float cluster is illustrated in a set of figures in each of which a 12 day segment of all float trajectories is displayed. At times their mobility and relative motion is shown to be associated with onset of sudden swirls and regions of large horizontal shear, features that are not evident from the analysis of individual trajectories. Cluster averages of the float velocities and kinetic energy, computed weekly and plotted as a function of time, show substantial variability. Much better averages are obtained by limiting the cluster to floats within a geographical region. As the spaghetti diagram indicates and the following paper discusses in more detail there exist substantial geographical variations in the average kinetic energy levels. These may be in some way caused topographically by the close proximity to the continental margin. Whatever the reason they caution us to reexamine the notion that the scale of variation of the second order eddy statistics is large compared to the eddies themselves, at least in the MODE-I area. Ten floats also contained a system to record the local pressure, temperature and vertical currents. The pressure and temperature yield data concerning low frequency vertical displacements and the vertical current meters measure the internal wave sea state which is shown to be remarkably constant.
ArticleAXIS—an Autonomous Expendable Instrument System(American Meteorological Society, 2017-12-28) Fratantoni, David M. ; O’Brien, Jeff ; Flagg, Charles Noel ; Rossby, H. ThomasExpendable bathythermographs (XBT) to profile upper-ocean temperatures from vessels in motion have been in use for some 50 years now. Developed originally for navy use, they were soon adapted by oceanographers to map out upper-ocean thermal structure and its space–-time variability from both research vessels and merchant marine vessels in regular traffic. These activities continue today. This paper describes a new technology—the Autonomous Expendable Instrument System (AXIS)—that has been developed to provide the capability to deploy XBT probes on a predefined schedule, or adaptively in response to specific events without the presence of an observer on board. AXIS is a completely self-contained system that can hold up to 12 expendable probes [XBTs, XCTDs, expendable sound velocimeter (XSV)] in any combination. A single-board Linux computer keeps track of what probes are available, takes commands from ashore via Iridium satellite on what deployment schedule to follow, and records and forwards the probe data immediately with a time stamp and the GPS position. This paper provides a brief overview of its operation, capabilities, and some examples of how it is improving coverage along two lines in the Atlantic.
ArticleOleander is more than a flower twenty-five years of oceanography aboard a merchant vessel(Oceanography Society, 2019-09-05) Rossby, H. Thomas ; Flagg, Charles Noel ; Donohue, Kathleen A. ; Fontana, Sandra ; Curry, Ruth G. ; Andres, Magdalena ; Forsyth, Jacob S. T.Since late fall 1992, CMV Oleander III has been measuring upper ocean currents during its weekly trips between Bermuda and Port Elizabeth, New Jersey, by means of an acoustic Doppler current profiler installed in its hull. The overarching objective of this effort has been to monitor transport in the Gulf Stream and surrounding waters. With 25 years of observation in hand, we note that the Gulf Stream exhibits significant year-to-year variations but no evident long-term trend in transport. We show how these data have enabled studies of oceanic variability over a very wide range of scales, from a few kilometers to the full 1,000 km length of its route. We report that the large interannual variations in temperature on the continental shelf are negatively correlated with flow from the Labrador Sea, but that variability in the strength of this flow cannot account for a longer-term warming trend observed on the shelf. Acoustic backscatter data offer a rich trove of information on biomass activities over a wide range of spatial and temporal scales. A peek at the future illustrates how the new and newly equipped Oleander will be able to profile currents to greater depths and thereby contribute to monitoring the strength of the meridional overturning circulation.
PreprintDiscrete eddies in the northern North Atlantic as observed by looping RAFOS floats( 2004-10-29) Shoosmith, Deborah R. ; Richardson, Philip L. ; Bower, Amy S. ; Rossby, H. ThomasRAFOS float trajectories near the 27.5 density level were analyzed to investigate discrete eddies in the northern North Atlantic with the objective of determining their geographical distribution and characteristics. Floats that made two or more consecutive loops in the same direction (loopers) were considered to have been in an eddy. Overall 15% (24 float years) of the float data were in loopers. One hundred and eight loopers were identified in 96 different eddies. Roughly half of the eddies were cyclonic (49%) and half were anticyclonic (51%), although the percentages varied in different regions. A few eddies were quasi-stationary for long times, one for over a year in the Iceland Basin, and many others clearly translated, often in the direction of the general circulation as observed by non-looping floats. Several floats were trapped in eddies in the vicinity of the North Atlantic Current just upstream (west) of the Charlie Gibbs (52ºN) and Faraday (50ºN) Fracture Zones, which seem to be preferred routes for flow crossing the mid-Atlantic ridge. Five floats looped in four anticyclones which translated southwestward away from the eastern boundary near the Goban Spur (47ºN-50ºN). These could have been weak meddies forming from remnants of warm salty Mediterranean Water advected northward along the eastern boundary.