Oceanography | September 2022
Oceanography
THE OFFICIAL MAGAZINE OF THE OCEANOGRAPHY SOCIETY
VOL.35, NO.2, SEPTEMBER 2022
BIO-INSPIRED OCEAN EXPLORATION
TRANSFORMING THE FUTURE OF MARINE AQUACULTURE // OVERVIEW OF THE PEACH PROGRAM
FINDING A THESIS TOPIC // DIY pySAS: AUTONOMOUS SOLAR TRACKING SYSTEM
Oceanography | Vol.35, No.2
VOL. 35, NO. 2, SEPTEMBER 2022
POWERING
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Oceanography | September 2022
contents
VOL. 35, NO. 2, SEPTEMBER 2022
REGULAR ISSUE FEATURES
06
Overview of the Processes Driving Exchange at Cape Hatteras Program
By H.E. Seim, D. Savidge, M. Andres, J. Bane, C. Edwards, G. Gawarkiewicz, R. He,
R.E. Todd, M. Muglia, J. Zambon, L. Han, and S. Mao
18
The NSF Graduate Fellowship Program: An Analysis of Awards in the
Ocean Sciences by Gender and Career Stage, 1996–2021
By S.B. Cook, G. Muller-Parker, and C.B. Cook
26
Transforming the Future of Marine Aquaculture: A Circular Economy
Approach
By C.H. Greene, C.M. Scott-Buechler, A.L.P. Hausner, Z.I. Johnson, X.G. Lei,
and M.E. Huntley
ROGER REVELLE COMMEMORATIVE LECTURE
35
Bio-Inspired Ocean Exploration
By N.W. Xu and J.O. Dabiri
DEPARTMENTS
03
QUARTERDECK. Seeking Outstanding Feature Articles: First Results of
the Oceanography Survey
By E.S. Kappel
04
FROM THE TOS JEDI COMMITTEE. Broadening Participation in TOS
Through Honors Nominations and Awards
By F. Muller-Karger, E. Bhatt, and E. Meyer-Gutbrod
49
WORKSHOP REPORT. Characterization and Speciation of Marine
Materials Using Synchrotron Probes: Guidelines for New Users
By R. Jones, S. Nicholas, P. Northrup, B.C. Bostick, C. Hoffman, W. Hu, P.J. Lam,
A. Leri, B.M. Toner, and B.S. Twining
55
DIY OCEANOGRAPHY. pySAS: Autonomous Solar Tracking System for
Surface Water Radiometric Measurements
By N. Haëntjens, K. Forsythe, B. Denholm, J. Loftin, and E. Boss
60
OCEAN EDUCATION. Broadening Participation Through Research
Experiences in Marine Science: An Early-Admit Immersive College
Course Provides Experiential, Place-Based Scientific Training for
Hawai‘i High School Students
By M.A.J. Rivera, C.M. Ambrosino, M.M. Manning, S. Leon Soon, Y.M. Rii,
and K.D. Gorospe
72
NAVIGATING GRAD SCHOOL. Finding a Thesis Topic
By P.J.S. Franks
78
THE OCEANOGRAPHY CLASSROOM. Collaborative Sketching to
Support Sensemaking: If You Can Sketch It, You Can Explain It
By K. Daae and M.S. Glessmer
81
CAREER PROFILES. Patrick Drupp, Deputy Legislative Director, Sierra
Club • Candice Hall, Research Oceanographer, US Army Engineer
Research and Development Center, and PhD Candidate, University of
Cape Town
06
60
26
35
Oceanography | September 2022
Oceanography | Vol.35, No.2
Oceanography | Vol.34, No.3
Oceanography | Vol.35, No.2
The Oceanography Society was founded in 1988 to advance
oceanographic research, technology, and education, and
to disseminate knowledge of oceanography and its appli-
cation through research and education. TOS promotes
the broad understanding of oceanography, facilitates con-
sensus building across all the disciplines of the field, and
informs the public about ocean research, innovative tech-
nology, and educational opportunities throughout the spec-
trum of oceanographic inquiry.
OFFICERS
PRESIDENT: Andone Lavery
PRESIDENT-ELECT: Deborah Bronk
PAST-PRESIDENT: Martin Visbeck
SECRETARY: Allison Miller
TREASURER: Susan Banahan
COUNCILORS
AT-LARGE: Mona Behl
APPLIED TECHNOLOGY: Larry Mayer
BIOLOGICAL OCEANOGRAPHY: Kim S. Bernard
CHEMICAL OCEANOGRAPHY: Galen McKinley
EARLY CAREER: Erin Satterthwaite
EDUCATION: Sara Harris
GEOLOGICAL OCEANOGRAPHY: Laura Guertin
OCEAN DATA SCIENCE: Vicki Ferrini
OCEAN SCIENCE AND POLICY: Leopoldo C. Gerhardinger
PHYSICAL OCEANOGRAPHY: LuAnne Thompson
STUDENT REPRESENTATIVE: Josette McLean
EXECUTIVE DIRECTOR
Jennifer Ramarui
CORPORATE AND INSTITUTIONAL
MEMBERS
Baker Donelson » bakerdonelson.com
Integral Consulting Inc. » integral-corp.com
Metocean Solutions » metocean.co.nz
National Oceanography Centre » noc.ac.uk
RBR » rbr-global.com
Sea-Bird Scientific » seabird.com
Sequoia » sequoiasci.com
US Arctic Research Commission » arctic.gov
tos.org
EDITOR
Ellen S. Kappel, Geosciences Professional Services Inc.
ASSISTANT EDITOR
Vicky Cullen
DESIGN/PRODUCTION
Johanna Adams
ASSOCIATE EDITORS
Claudia Benitez-Nelson, University of South Carolina
Ian Brosnan, NASA Ames Research Center
Grace Chang, Integral Consulting Inc.
Philip N. Froelich, Duke University
Charles H. Greene, University of Washington
Amelia Shevenell, University of South Florida
William Smyth, Oregon State University
Peter Wadhams, University of Cambridge
Oceanography contains peer-reviewed articles that chronicle
all aspects of ocean science and its applications. The journal
presents significant research, noteworthy achievements, excit-
ing new technology, and articles that address public policy and
education and how they are affected by science and technol-
ogy. The overall goal of Oceanography is cross- disciplinary
communication in the ocean sciences.
Oceanography (Print ISSN 1042-8275; Online ISSN 2377-617X)
is published by The Oceanography Society, 1 Research Court,
Suite 450-117, Rockville, MD 20850 USA. Oceanography arti-
cles are licensed under a Creative Commons Attribution 4.0
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distribution, and reproduction in any medium or format as long
as users cite the materials appropriately, provide a link to the
Creative Commons license, and indicate the changes that were
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cles are included in the Creative Commons license unless indi-
cated otherwise in a credit line to the material. If the material is
not included in the article’s Creative Commons license, users
will need to obtain permission directly from the license holder
to reproduce the material. Please contact Jennifer Ramarui at
info@tos.org for further information.
Oceanography
tos.org/oceanography
Oceanography | Vol.35, No.2
Oceanography | September 2022
CONTACT US
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ON THE COVER
The concept of biology-inspired engi-
neering has emerged as a powerful tool
to complement traditional engineering
approaches to technology development.
The specific swimming features of jellyfish,
for example, may be used for bio-inspired
ocean exploration. Read more on page 35.
Photo credit: istock.com/VictorHuang
UPCOMING SPECIAL ISSUES
• The New Arctic Ocean
• GEOTRACES
• Near-Inertial Shear and Kinetic Energy in
the North Atlantic Experiment (NISKINE)
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50 Years of Innovative Research in
Oceanography
• Building Diversity, Equity, and Inclusion
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• Sea Grant
Over the summer, TOS conducted a survey of its membership, asking questions
about how readers primarily access Oceanography (paper or online), what con-
tent they read the most, what subjects we should cover in the future, and whether
they anticipate publishing an article in Oceanography in the next three years. The
main purpose of the survey was to see if, on the magazine’s 35th anniversary, we
needed to make some adjustments to maintain our readership. With the more
than 100 responses submitted, spanning all career levels, I am pleased to report
that overall, survey respondents seem to be content with our current format, and
they offered many excellent thoughts on topics Oceanography should cover in the
future and areas where we could do better.
While we are still digesting the responses to the survey, one significant miscon-
ception has come to light. Several of the responses to the question, “Do you plan
to publish in Oceanography in the next three years,” suggest that there is a percep-
tion, though we don’t know how widespread, that Oceanography only publishes
scientific articles under the special issue banner, that we don’t accept manuscript
submissions that fall outside of special issue topics. That is not the case. Nearly
every issue contains at least a couple of peer-reviewed articles under the “Regular
Issue Feature” banner as well as other non-special issue, peer-reviewed content
in such categories as Breaking Waves, Ocean Education, DIY Oceanography, and
Hands-On Oceanography. In fact, this issue contains only articles that were sub-
mitted to Oceanography outside of any special issue designation.
In an effort to bring clarity to the sorts of article submissions we hope to receive
and the pathway to submission, this year we overhauled our Author Guidelines
(https://tos.org/oceanography/guidelines). For example, we write that, “Feature
articles can include review papers that summarize the current state of knowledge
of a particular topic, synthesis papers that discuss new findings and how they
significantly revise our thinking about a topic, and more traditional scientific
research papers from across the full spectrum of oceanography and marine tech-
nology.” And subjects for Breaking Waves articles “have the potential to move
the field of oceanography forward or in new directions.” The guidelines contain
information on all of the other categories of articles that we publish as well.
I strongly encourage you to consider submitting a manuscript to our peer-
reviewed, open access journal that is—to quote the Oceanography guidelines
again—“of broad interest to our readership,” which ranges from ocean science
students to emeritus professors and industry professionals. Such articles will
allow TOS to strengthen its commitment to promoting cross-disciplinary com-
munication in the ocean sciences. Act now—don’t wait for a next special issue
that is in your research area!
ARTICLE DOI. https://doi.org/10.5670/oceanog.2022.215
QUARTERDECK
SEEKING OUTSTANDING
FEATURE ARTICLES
FIRST RESULTS OF THE OCEANOGRAPHY SURVEY
Ellen S. Kappel, Editor
Oceanography | Vol.35, No.2
BROADENING
PARTICIPATION IN TOS
THROUGH HONORS NOMINATIONS AND AWARDS
The Oceanography Society (TOS) Honors
Program provides opportunities for its
members to amplify the Society’s val-
ues (https://tos.org/about) and to recog-
nize and celebrate the accomplishments
of colleagues. However, individual and
systemic biases can affect the nomina-
tion and selection process. In fall 2021,
the TOS Council postponed a cycle of the
Honors Program due to lack of diversity
in nominees (https://tos.org/tos-news-
june-2022). The TOS JEDI Committee
(https://tos.org/diversity) is considering
ways to generate a large and diverse pool
of nominees by embedding TOS’s justice,
equity, diversity, and inclusion goals into
the honors and awards process. This arti-
cle highlights some of those suggestions
and invites TOS members to weigh in.
As of 2022, TOS has three honors cate-
gories: Fellows, Medals, and Awards. The
oldest honors offered by the Society are
the Munk Award (established in 1993),
the Jerlov Award (established in 2000),
and The Oceanography Society Fellows
(established in 2004). The other medals
(Wallace S. Broecker, Mary Sears) and
awards (Mentoring, Early Career, and
Ocean Observing) are relatively new.
The nomination criteria for all awards
(https://tos.org/honors) at present focus
on a nominee’s impactful, innovative,
and/or transformative contributions to
original research; impact in educating
and mentoring students and early career
scientists; and their significant interdisci-
plinary and/or collaborative research. It is
sobering that to date, the lists of awardees
remain predominantly from a particular
demographic—White men from North
America or Europe. For example, of the
13 Munk Awardees, 12 are White men.
Of the 11 Jerlov Awardees, 10 are White
men. Of the 45 TOS Fellows, 31 are White
men. While other societies in oceanogra-
phy also predominantly honor men, the
gender statistics for TOS honors are the
least diverse (Legg et al., 2022).
Part of the reason for the lack of diver-
sity in nominations may be how TOS
members and nomination supporters
interpret merit. For example, when one
of us (FM-K) attempted to nominate a
female scientist from a developing nation
for a specific TOS medal, he was not able
to obtain letters of support. Scientists
from renowned institutions in developed
nations agreed that her contributions
were multiple and commendable, but also
felt that this nominee would likely not be
considered by TOS because she could
not be equated to one of the people rep-
resented by a named medal. This experi-
ence suggests that there may be unwrit-
ten rules preventing many of our peers
from being nominated, let alone selected,
for these awards. We suggest that TOS
can more clearly articulate its values in
a redesigned process that is sensitive at a
number of different levels, such as indi-
vidual identity, socioeconomic status,
culture, and geography.
We offer six initial suggestions that
may help open the TOS nomination
and awards process to broader sets of
contributions and contributors. These
suggestions are consistent with efforts to
reconsider awards processes in other geo-
science societies (e.g., Holmes et al., 2020;
Ali et al., 2021).
1. Focus the award guidelines on the
holistic essence of a career. Criteria
could introduce a more comprehen-
sive definition of achievement beyond
the publication record alongside the
overarching value of a person’s efforts
to improve community well-being
at local, regional, national, and/or
international levels.
2. Change the nomination guidelines
to better support individuals at each
stage in the honors and awards pro-
cess. Simplify the package that nom-
inators provide and allow supporters
to sign on and/or add a short con-
curring letter. Guarantee need-based
support for awardees, such as travel
and lodging to attend the award cer-
emony, meeting registration fees, and
interpretation services.
3. Allow nominations of non-TOS mem-
bers for all TOS honors. Clearly, there
are many TOS members who deserve
honors and awards, but TOS mem-
bers should not be restricted to look-
ing only inside the Society to cele-
brate excellent role models. This is an
important mechanism to highlight the
fact that our Society has broader val-
ues and real-world commitments. It
may also serve as a new avenue for
membership recruitment for nomi-
nees and their networks.
FROM THE TOS JEDI COMMITTEE
By Frank Muller-Karger, EeShan Bhatt, and Erin Meyer-Gutbrod
Oceanography | September 2022
4. Implement a waiting period (three
years or more) before awarding TOS
honors to people who have received
similar awards from TOS or other
societies. This action would increase
the chances of diversifying the pool of
people who are selected for honors.
5. Expand the number of named med-
als to reflect the diversity of those who
have made life-long contributions to
ocean science, conservation, educa-
tion, and access. These medals may
be named after individuals from com-
munities that have been historically or
currently targeted by or excluded from
academic circles in developed coun-
tries. If so, TOS must first build rela-
tionships with these communities and
bestow awards jointly. It is of utmost
importance that new awards have sim-
ilar prestige as existing ones.
6. To mitigate implicit bias, commit to an
ongoing review of the Honors process
every three to five years. TOS should
regularly reevaluate procedures, such
as award publicity, nomination pack-
age guidelines, award criteria, and
nomination and selection commit-
tee
procedures,
against
evolving
best practices. TOS should also pro-
mote implicit bias training for mem-
bers of the Nomination and Selection
Committees and make these types of
training programs a benefit of TOS
membership. TOS may consider offer-
ing this training openly and for broad
community participation, for even
greater impact on advancing diversity
and inclusion in ocean science.
Implementing solutions that will
enable TOS to recognize the many people
who help advance science, education, and
society is not easy. For example, those
from less-resourced countries encoun-
ter many barriers in developing a career
in marine science (Osborne et al., 2022).
The broader TOS community can help
identify and participate in a process to
achieve changes in the honors nominat-
ing and selection process that will result
in positive outcomes for the Society, its
membership, and our individual net-
works. We encourage everyone to nom-
inate role models in our networks and to
volunteer for TOS committees. We invite
you to work with The Oceanography
Society’s JEDI Committee to improve the
awards process to recognize individuals,
groups, and activities anywhere and at all
scales. Please send any ideas or feedback
to JEDIcochair@tos.org. In doing so, you
will help move us closer to the ideals we
hold as a Society.
REFERENCES
Ali, H.N., S.L. Sheffield, J.E. Bauer, R.P. Caballero-
Gill, N.M. Gasparini, J. Libarkin, K.K. Gonzales,
J. Willenbring, E. Amir-Lin, J. Cisneros, and
D. Desai. 2021. An actionable anti-racism
plan for geoscience organizations. Nature
Communications 12:3794, https://doi.org/10.1038/
s41467-021-23936-w.
Holmes, M.A., L. Myles, and B. Schneider. 2020.
Diversity and equality in honours and awards pro-
grams— Steps towards a fair representation of
membership. Advances in Geosciences 53:41–51,
https://doi.org/10.5194/adgeo-53-41-2020.
Legg, S., C. Wang, E. Kappel, and L. Thompson. 2022.
Gender equity in oceanography. Annual Review
of Marine Science 15, https://doi.org/10.1146/
annurev-marine-032322-100357.
Osborne, T., C. Pattiaratchi, and E. Meyer-Gutbrod.
2022. Limited opportunities and numerous barri-
ers to ocean science careers in under-resourced
nations. Oceanography, https://doi.org/10.5670/
oceanog.2022.117.
AUTHORS
Frank Muller-Karger (carib@usf.edu) is Professor,
College of Marine Science, University of South
Florida, St. Petersburg, FL, USA. EeShan
Bhatt is Postdoctoral Investigator, Woods Hole
Oceanographic Institution, Woods Hole, MA, USA.
Erin Meyer-Gutbrod is Assistant Professor, University
of South Carolina, Columbia, SC, USA.
ARTICLE CITATION
Muller-Karger, F., E. Bhatt, and E. Meyer-Gutbrod.
2022. Broadening participation in TOS
through honors nominations and awards.
Oceanography 35(2):4–5, https://doi.org/10.5670/
oceanog.2022.216.
COPYRIGHT & USAGE
This is an open access article made available under
the terms of the Creative Commons Attribution 4.0
International License (https://creativecommons.org/
licenses/by/4.0/), which permits use, sharing, adapta-
tion, distribution, and reproduction in any medium or
format as long as users cite the materials appropri-
ately, provide a link to the Creative Commons license,
and indicate the changes that were made to the
original content.
In this Oceanography section, contributing
authors share all of the relevant information
on a homemade sensor or instrument so that
others can build, or build upon, it. The short
articles also showcase how this technology
was used successfully in the field.
Call for Contributions
Oceanography guest editors Melissa Omand
and Emmanuel Boss are seeking contribu-
tions to DIY Oceanography. Contributions
should include a list of the materials and
costs, instructions on how to build, and
any blueprints and codes (those could be
deposited elsewhere). See Oceanography’s
Author Guidelines page for detailed informa-
tion on submission requirements.
https://tos.org/oceanography/guidelines
See the Collection
Go to the DIY Oceanography web page to
view the complete collection of articles.
• pySAS: Autonomous Solar Tracking
System for Surface Water Radiometric
Measurements
• An Optical Imaging System for Capturing
Images in Low-Light Aquatic Habitats
Using Only Ambient Light
• A Simple and Inexpensive Method
for Manipulating Dissolved Oxygen in
the Lab
• The Pressure of In Situ Gases Instrument
(PIGI) for Autonomous Shipboard
Measurement of Dissolved O2 and N2 in
Surface Ocean Waters
• Inlinino: A Modular Software Data Logger
for Oceanography
https://tos.org/diy-oceanography
Oceanography | September 2022
Oceanography | Vol.35, No.2
OVERVIEW OF THE PROCESSES
DRIVING EXCHANGE AT
CAPE HATTERAS PROGRAM
By Harvey E. Seim, Dana Savidge, Magdalena Andres, John Bane, Catherine Edwards, Glen Gawarkiewicz,
Ruoying He, Robert E. Todd, Michael Muglia, Joseph Zambon, Lu Han, and Shun Mao
REGULAR ISSUE FEATURE
Drone photo of a PEACH meteorological buoy being
serviced using the work boat from R/V Armstrong.
Photo credit: John McCord, Coastal Studies Institute,
East Carolina University
Oceanography | Vol.35, No.2
Oceanography | September 2022
INTRODUCTION
The program called Processes driving
Exchange At Cape Hatteras (PEACH)
uses observations and models to study
exchanges of seawater and its constitu-
ents between the continental shelf and the
open ocean near Cape Hatteras, North
Carolina, through a US National Science
Foundation-funded collaboration among
principal investigators at the University
North Carolina at Chapel Hill, Skidaway
Institute of Oceanography (University of
Georgia), Woods Hole Oceanographic
Institution, North Carolina State Uni-
versity, and the Coastal Studies Institute
at East Carolina University. Boundaries
between subtropical and subpolar oce-
anic gyres are characterized by confluent
western boundary currents in the open
ocean and convergence in the adjacent
shelf and slope waters. Strong forcing typ-
ical of midlatitude western ocean mar-
gins modulate the resulting net export of
shelf waters and complex, bidirectional
shelf-deep ocean exchanges. Exchanges
between the shelf and the open ocean are
central to global carbon budgets, marine
ecosystem dynamics, larval and pollut-
ant transports, and modulation of storm
tracks and intensity, and thus have signif-
icant environmental, economic, and soci-
etal implications.
Recent examples of anomalous forcing
along the US East Coast underscore the
importance of understanding the dynam-
ics that control exchange between the open
ocean and the continental shelf at the con-
fluence of the North Atlantic gyres near
Cape Hatteras (Figure 1). Large deviations
in Gulf Stream position relative to the
typical meander envelope (Gawarkiewicz
et al., 2012), extreme wintertime wind
stress and buoyancy fluxes (K. Chen
et al., 2014), accelerated shelf warming
(Forsyth et al., 2015), and sea level rise
north of Cape Hatteras (Sallenger et al.,
2012; Andres et al., 2013) have been doc-
umented in recent years. Such trends are
potential harbingers of larger shifts in
atmospheric and oceanic forcing, yet their
effects on shelf-open ocean exchange are
not well understood. Developing better
understanding and predictive capacity are
central goals of PEACH. Early results, dis-
cussed below, both confirm expectations
and provide surprises about the region’s
physical oceanography. Beyond the Gulf
Stream, a documentary film produced by
Kyle Lawrence-Maddux based on PEACH
cruise activities, was shown at the 2020
Woods Hole Film Festival and is available
at https://vimeo.com/279906819.
BACKGROUND
The most prominent feature of the
mean circulation in the PEACH study
area is the Gulf Stream (orange curve
in Figure 1a), the subtropical west-
ern boundary current in the Northwest
Atlantic. It carries components of both
wind-driven and overturning circula-
tion (Meinen et al., 2010; Buckley and
Marshall, 2016), so its strength is coupled
to both the deep-reaching thermohaline
circulation and the surface-intensified
flows driven by the basin-wide wind field.
Largely unconstrained by topography,
the Gulf Stream transitions from a shelf-
adjacent boundary-trapped current along
the South Atlantic Bight (SAB, which
extends from Cape Canaveral to Cape
Hatteras) to a separated jet northeast of
Cape Hatteras. The Gulf Stream’s tempo-
ral and spatial changes in offshore posi-
tion, flow orientation, and transport are
discussed more fully below.
ABSTRACT. The Processes driving Exchange At Cape Hatteras (PEACH) program
seeks to better understand seawater exchanges between the continental shelf and the
open ocean near Cape Hatteras, North Carolina. This location is where the Gulf Stream
transitions from a boundary-trapped current to a free jet, and where robust along-shelf
convergence brings cool, relatively fresh Middle Atlantic Bight and warm, salty South
Atlantic Bight shelf waters together, forming an important and dynamic biogeographic
boundary. The magnitude of this convergence implies large export of shelf water to the
open ocean here. Background on the oceanography of the region provides motivation
for the study and gives context for the measurements that were made. Science ques-
tions focus on the roles that wind forcing, Gulf Stream forcing, and lateral density gra-
dients play in driving exchange. PEACH observational efforts include a variety of fixed
and mobile observing platforms, and PEACH modeling included two different resolu-
tions and data assimilation schemes. Findings to date on mean circulation, the nature
of export from the southern Middle Atlantic Bight shelf, Gulf Stream variability, and
position variability of the Hatteras Front are summarized, together with a look ahead
to forthcoming analyses.
Gulf Stream
20 m
60 m
200 m
Cape
Hatteras
37°N
36°N
35°N
34°N
77°W
76°W
75°W
74°W
MAB Shelf Water
Diamond Shoals
Shelfbreak Jet
45°N
40°N
35°N
30°N
25°N
80°W
75°W
70°W
65°W
100 m
500 m
500 m
4000 m
4000 m
100 m
Gulf Stream
Slope Sea Gyre
Deep Western
Boundary Current
Shelfbreak Jet
Hatteras Front
MAB Shelf Water
SAB Shelf Water
After Schmitz, 1996 and
Csanady and Hamilton, 1988
MAB
SAB
30'
76°W
30'
75°W
30'
74°W
30'
30'
35°N
30'
36°N
30'
37°N
2,000
1,000
200
100
50
30
0
Depth (m)
Spray Gliders
Slocum Gliders
CPIES
ADCP+CTD
Met+ADCP+CTD
Articulating Profler
NDBC Moorings
CODAR Sites
WERA Sites
Altimeter Tracks
SAB S
helf W
ater
el
FIGURE 1. (a) Schematic depiction of circulation in the Northwest Atlantic and (b) zoom in on the
Cape Hatteras region. SAB = South Atlantic Bight. MAB = Mid-Atlantic Bight. Created by Anna
Boyette, after Schmitz (1996) and Csanady and Hamilton (1988)
Oceanography | Vol.35, No.2
Counterclockwise mean circulation
(black curves in Figure 1a) in the Slope
Sea separates the Mid-Atlantic Bight
(MAB shelf extends from Cape Hatteras
to Cape Cod) from the mean path of the
separated Gulf Stream, downstream of
Cape Hatteras (Csanady and Hamilton,
1988). The Slope Sea is generally filled
with cooler and fresher waters than are
found in the Gulf Stream. The Deep
Western Boundary Current (blue-gray
path) flows equatorward through the
study area, carrying components of the
North Atlantic Deep Water at depths
between 1,000 m and 3,000 m, as part of
the deep limb of the Atlantic Meridional
Overturning Circulation (Toole et al.,
2017). It crosses underneath the Gulf
Stream off Cape Hatteras, allowing for
complicated interactions between the
deep and upper components of North
Atlantic circulation (Pickart and Smethie,
1993; Spall, 1996).
On the MAB shelf, the mean flow is
equatorward (blue arrows in Figure 1a)
from Georges Bank to Cape Hatteras,
including flow over the continental shelf
(Lentz, 2008) and in a narrow shelf-
break jet (purple in Figure 1a; Linder
and Gawarkiewicz, 1998), each of which
carries about 0.25 Sv (1 Sverdrup [Sv]
= 106 m3 s–1; Linder and Gawarkiewicz,
1998; K. Chen and He, 2015). These
waters originate as far north as the
Labrador Sea (Chapman and Beardsley,
1989). Shoreward of the Gulf Stream, in
the SAB south of Cape Hatteras, there is
thought to be mean poleward flow (light
green arrow in Figure 1a; Lee et al., 1991;
Blanton et al., 2003), particularly off the
northernmost part (Savidge and Bane,
2001; Savidge and Savidge, 2014). The
adjacent Gulf Stream strongly influences
SAB shelf circulation and hydrography,
and with limited river discharge into the
SAB, shelf water is difficult to distinguish
from Gulf Stream waters based on tem-
perature and salinity alone. However,
striking differences between Gulf Stream
and SAB biogeochemical properties
can develop through bio-mediated epi-
sodic shelf processes with timescales that
appear to align with shelf residence times
(Menzel, 1993; Savidge and Savidge,
2014). In the immediate vicinity of Cape
Hatteras, a multiyear mooring data set
from the early 1990s illustrated per-
sistent along-shelf convergence of MAB
and SAB shelf waters at Cape Hatteras
(Figure 2d) in both means and daily data
(Savidge and Bane, 2001). The MAB and
SAB salinity and temperature contrasts
form the Hatteras Front (Figure 1b),
whose along-shelf density gradient sup-
ports cross-shelf geostrophic flow within
the Front (Savidge and Austin, 2007).
These circulation features affect the
PEACH study region across a range of
spatial and temporal scales. Of particu-
lar interest to PEACH are wave-like lat-
eral meanders in the Gulf Stream’s path
that form nearly continuously and prop-
agate along the SAB, with largest ampli-
tude downstream of the Charleston
Bump (~31°N; Figure 2a). The crests and
troughs of the meanders and their associ-
ated frontal eddies move downstream at
speeds of 20–60 km day–1 with roughly
weekly period (Bane and Dewar, 1988).
Eddy decay regions off Georgia and
approaching Cape Hatteras are associated
with elongation of frontal features, off-
shore transport of momentum and heat,
and onshore transport of nutrients (Lee
et al., 1991). Measurements of currents
along the SAB shelf adjacent to the Gulf
36°N
38°N
40°N
42°N
76°W
74°W
72°W
70°W
28
22
16
10
°C
74°48'W
74°42'W
74°36'W
100
200
100
200
100
200
Depth (m)
100
200
–0.10
–0.05
0.00
0.05
0.10
Along-Shore
Velocity (m s–1)
24.5
25.0
25.5
26.0
26.5
27.0
Potential Density
(kg m–3)
33.5
34.0
34.5
35.0
35.5
Salinity
10
12
14
16
18
Potential
Temperature (°C)
74°W
5 cm s–1
75°W
76°W
77°W
35°N
36°N
37°N
FIGURE 2. (a) Sea surface temperature (SST) image offshore of the South Atlantic Bight (SAB) with
Gulf Stream meander crests (C) and troughs (T) labeled, and a white star marking the position of the
Charleston Bump. MAB = Mid-Atlantic Bight. CCR = Cold Core Rings. Image from Rutgers University
(b) SST image of the Gulf Stream and Slope Sea offshore of the Mid-Atlantic Bight shelf. Image
from Rutgers University (c) Average shelfbreak temperature, salinity, density, and along-shelf veloc-
ity during PEACH measured along the cross-shelf section in Figure 3. After Todd (2020), Figure 7
(d) Mean flow convergence near Cape Hatteras. From Savidge and Bane (2001)
30
26
22
18
14
°C
36°N
34°N
32°N
30°N
28°N
82°W
80°W
78°W
76°W
74°W