Deep Floats Reveal Complex Ocean Circulation Patterns

Ramsey, A.T.S.; Furey, Heather H.; Bower, Amy

doi:10.1029/2018eo105549

Cited by 3 publications

(6 citation statements)

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“…This applies to most of the depths occupied by the deep limb of the AMOC, especially in the SA, where there has been only one deep float study (Brazil Basin). Figure shows all the available acoustically tracked subsurface float trajectories in the Atlantic, color‐coded by depth (see Ramsey et al, , for more details of the data distribution, an extension to the global view). The deep eastern North Atlantic, where recent studies suggest that a sizeable southward export of NADW may occur, perhaps as part of an eastern‐basin‐only overturning circulation, is another region that deserves more attention.…”

Section: Discussionmentioning

confidence: 99%

“…Subsurface float trajectories binned by depth, from left to right: 0‐1,000 m; 1,000‐2,000m; and 2,000m and deeper. Data source is the AOML PhOD subsurface drifter database, which currently houses all subsurface data collected through end of 2015 (Ramsey et al, ; https://www.aoml.noaa.gov/phod/float_traj/).…”

Section: Discussionmentioning

confidence: 99%

“…In large numbers such as these, floats and drifters can be used to map out mean currents over large areas. But even single trajectories are valuable as they may reveal a previously unknown flow pathway or transport mechanism (Ramsey et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Lagrangian Views of the Pathways of the Atlantic Meridional Overturning Circulation

et al. 2019

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The Lagrangian method—where current location and intensity are determined by tracking the movement of flow along its path—is the oldest technique for measuring the ocean circulation. For centuries, mariners used compilations of ship drift data to map out the location and intensity of surface currents along major shipping routes of the global ocean. In the mid‐20th century, technological advances in electronic navigation allowed oceanographers to continuously track freely drifting surface buoys throughout the ice‐free oceans and begin to construct basin‐scale, and eventually global‐scale, maps of the surface circulation. At about the same time, development of acoustic methods to track neutrally buoyant floats below the surface led to important new discoveries regarding the deep circulation. Since then, Lagrangian observing and modeling techniques have been used to explore the structure of the general circulation and its variability throughout the global ocean, but especially in the Atlantic Ocean. In this review, Lagrangian studies that focus on pathways of the upper and lower limbs of the Atlantic Meridional Overturning Circulation (AMOC), both observational and numerical, have been gathered together to illustrate aspects of the AMOC that are uniquely captured by this technique. These include the importance of horizontal recirculation gyres and interior (as opposed to boundary) pathways, the connectivity (or lack thereof) of the AMOC across latitudes, and the role of mesoscale eddies in some regions as the primary AMOC transport mechanism. There remain vast areas of the deep ocean where there are no direct observations of the pathways of the AMOC.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Lagrangian Views of the Pathways of the Atlantic Meridional Overturning Circulation

et al. 2019

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“…Lagrangian tracks of RAFOS-style float trajectories from many regional studies are now archived and publicly available (Ramsey et al, 2018). Originally compiled by the WOCE Subsurface Float Data Assembly Center in Woods Hole, this comprehensive database is now maintained by NOAA/AOML 9 .…”

Section: Subsurface Float Driftsmentioning

confidence: 99%

“…The GOCD has also created archiveready velocity file formats suitable for many platforms and sensors. A second database, also released in the past year, archives subsurface float tracks (Ramsey et al, 2018; see description in section "Data Access"). Although studies with acoustically tracked floats have predominantly been done in the Atlantic Basin ( Figure 2C) to study regional circulation, the compilation of these data now permits additional studies, from comparative analyses to basin-wide model validation studies.…”

Section: Data Accessmentioning

confidence: 99%

The Scientific and Societal Uses of Global Measurements of Subsurface Velocity

et al. 2019

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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.

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Improved Acoustic Tracking of RAFOS-Enabled Profiling Floats through the New Software Package artoa4argo

Hancock,

Boebel

2024

Journal of Atmospheric and Oceanic Technology

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In sea ice covered polar oceans, profiling Argo floats are often unable to surface for 9 months or longer, rendering acoustic RAFOS (Ranging And Fixing Of Sound) tracking the only method to obtain unambiguous under-ice positions. Tracking RAFOS-enabled floats has historically relied on the ARTOA3 software, which had originally been tailored towards non-profiling floats in regions featuring the SOFAR (SOund Fixing And Ranging) channel with acoustic ranges of approximately 1000km. However, in sea ice covered regions, RAFOS tracking is challenged due to: (a) reduced acoustic ranges of RAFOS signals, and (b) enhanced uncertainties in float and sound source clock offsets. A new software, built on methodologies of previous ARTOA versions, called artoa4argo, has been created to overcome these issues by exploiting additional float satellite fixes, resolving ambiguous float positions when tracking with only two sources and systematically resolving float and sound source clock offsets. To gauge the performance of artoa4argo, 21 RAFOS-enabled profiling floats deployed in the Weddell Sea during 2008-2012 were tracked. These have previously been tracked in independent studies with a Kalman Smoother and a Multi-Constraint method. artoa4argo improves tracking by automating and streamlining methods. Although artoa4argo does not necessarily produce positions for every timestep, which the Kalman Smoother and Multi-Constraint methods do, whenever a track location is available, it outperforms both methods.

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Deep Floats Reveal Complex Ocean Circulation Patterns

Abstract: Acoustically tracked floats drift far below the ocean’s surface, providing fresh discoveries about deep-sea currents. A new archive gathers decades’ worth of float data into a central repository.

Cited by 3 publications

References 0 publications

Lagrangian Views of the Pathways of the Atlantic Meridional Overturning Circulation

Lagrangian Views of the Pathways of the Atlantic Meridional Overturning Circulation

The Scientific and Societal Uses of Global Measurements of Subsurface Velocity

Improved Acoustic Tracking of RAFOS-Enabled Profiling Floats through the New Software Package artoa4argo

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