December 2025 | Oceanography
Oceanography
THE OFFICIAL MAGAZINE OF THE OCEANOGRAPHY SOCIETY
VOL. 38, NO. 4, DECEMBER 2025
TRAINING LEADERS FOR SEAGOING
POLAR OCEANOGRAPHY
COST-CONSCIOUS MEASUREMENTS OFF BANGLADESH
AIR-CUSHION TRAVEL FOR SCIENCE MISSIONS IN POLAR REGIONS
TEN PRESSING QUESTIONS (AND ANSWERS) ABOUT MARINE FUNGI
AND MORE…
IN THIS ISSUE
Oceanography | Vol. 38, No. 4
POWERING SCIENCE-BASED DECISIONS
FOR A BETTER OCEAN.
December 2025 | Oceanography
contents VOL. 38, NO. 4, DECEMBER 2025
5 QUARTERDECK. A Look Behind the Curtain at Tales from the Deep: Stories of Scientific Ocean Drilling
By E.S. Kappel
7 ESSAY. Tales from the Deep: Audio Narratives from the Scientific Ocean Drilling Community
By L. Guertin
10 FEATURE ARTICLE. Cost-Conscious Measurements in the Coastal Waters of Bangladesh
By R. Loodh, D. Chaudhuri, E. D’Asaro, and M.M. Hoque
20 FEATURE ARTICLE. Training Leaders for Seagoing Polar Oceanography
By L. Juranek and E. Eidam
30 FEATURE ARTICLE. Exploring Air Cushion Travel for Science Missions Over Arctic Sea Ice and
Antarctic Ice Shelves, 2008–2025
By J.K. Hall and Y. Kristoffersen
40 MEETING REPORT. Ten Pressing Questions (and Answers) About Marine Fungi and Opportunities for
Collaborations in the Ocean Sciences
By A.S. Amend, N. Gunde-Cimerman, M.A. Coelho, C.A. Durkin, C. Ettinger, H. Gifford, A.S. Gladfelter, C. Gostinčar,
L. Granit, I. Grigoriev, M.H. Gutiérrez, K.J.E. Hickman, T.Y. James, A.C. Jones, R. Levi, M. David-Palma, X. Peng,
C.A. Quandt, T. Rämä, L. Vargas-Gastélum, S. Whitner, A. Williams, O. Yarden, A. Yenewodage, and G. Zahn
50 OCEAN EDUCATION. The Student Seaglider Center: A Model Student-Run Laboratory for Scalable
Training and Authentic Research Experiences in Marine Science
By S.K. Seroy, L. Airola, A.R. Rupan, C. Kohlman, F. Stahr, and C.C. Eriksen
56 THE OCEANOGRAPHY CLASSROOM. Developing a Scholarly Approach and Contributing to
Conversations About Teaching and Learning
By M.S. Glessmer, K. Daae, O. Førland, and R. Kordts
63 CAREER PROFILES. Grantly Galland, Project Director, International Fisheries, The Pew Charitable Trusts •
Tammy Silva, Research Marine Ecologist, Stellwagen Bank National Marine Sanctuary, NOAA Office of
National Marine Sanctuaries
A small traditional fishing boat operating in
coastal waters near Cox’s Bazar, Bangladesh.
See the article by Loodh et al. on p. 10 for details.
Photo credit: Rupak Loodh
Oceanography | Vol. 38, No. 4
ON THE COVER
Recovery of a gravity core on a
co-chief scientist training cruise aboard
R/V Sikuliaq offshore Seward, Alaska,
in June 2023. See the article by
Juranek and Eidam on p. 20 for details.
Photo credit: John Farrell
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one other former JR onboard outreach officer at the IMPACT
workshop, and I asked her if she wanted to be a part of this project.
Before I even finished explaining my idea, she said “count me in!” I
then reached out to one other former outreach officer, and the three
of us were an organizing board that discussed what the collection
would look like, attended virtual training through StoryCorps, and
then launched our first episode on November 21, 2022. Most of the
early conversations were with people I sailed with on International
Ocean Discovery Program (IODP) Expedition 390, as well as with
other former outreach officers. I still use the first two outreach offi-
cers from the beginning of the project as an advisory board and
run ideas by them. Just like the incredible community that develops
among the scientists who sail together, the outreach officers are also
committed to continuing education and outreach post-expedition
and work together on new and continuing projects.
How did you come up with the logo for the project?
The small life ring logo and the overall graphic featuring JOIDES
Resolution came from my association with an introductory-
level physics course at another institution in the area (Drexel
University). In the course, students were required to complete
an interdisciplinary, real-world project that related their major to
an area of physical science. I knew I wanted some branding for
Tales from the Deep, so I became a “client” for a pair of students
in the course. I provided potential design ideas and overall infor-
mation about this audio narrative project. After several email
exchanges, I could not be more pleased not only with the design
but also that it came from students.
Did you know about the StoryCorps project when
you started?
I learned about StoryCorps several years ago when my Penn State
campus adopted a common read book for the entire student body
titled This I Believe. The book was a collection of personal stories
from a cross section of individuals who represented different loca-
tions, social status, and careers, and there was a short correspond-
ing audio series on National Public Radio (NPR). I invited my stu-
dents to generate their own This I Believe stories through audio,
knowing that audio can add a more personal and emotional com-
ponent to a narrative than just reading text. In looking for exam-
ples of personal audio narratives online, the StoryCorps website
quickly appeared in my search.
A LOOK BEHIND THE CURTAIN AT
TALES FROM THE DEEP: STORIES OF
SCIENTIFIC OCEAN DRILLING
In this issue of Oceanography, Laura Guertin describes her inspi-
ration for launching the audio narrative project Tales from the
Deep: Stories of Scientific Ocean Drilling, and she provides links
to many of the conversations she has recorded with shipboard
and shore-based participants. Projects like this are not new in the
ocean sciences, but the recorded oral histories are often done with
senior scientists and compiled as historical documentation by
individual institutions—Woods Hole Oceanographic Institution,
Scripps Institution of Oceanography, and Lamont-Doherty Earth
Observatory, among others, have such oral history archives.
Transcripts are often the only thing available for many of these
oral histories, and several have restricted access. One of the great
things about Tales from the Deep is that the stories provide var-
ied perspectives, from early career scientists to senior scientists,
and from folks who sailed on the various scientific drilling ves-
sels and platforms over the years to onshore support staff and pro-
gram managers. Some of the narratives contain funny stories while
others are more serious. The recordings are all openly accessible to
anyone with an internet connection.
Thinking that others might be inspired to launch similar proj-
ects after reading Laura’s essay and listening to some of the record-
ings, I share below Laura’s responses to a series of questions I asked
regarding how she went from an idea to a much-accessed web page
of recordings that are archived in the US Library of Congress.
—
Your essay talks about how your scientific ocean drilling
storytelling project was an outgrowth of student-
generated audio narratives you assigned as coursework.
How did the scientific ocean drilling project come about?
Did you need to seek some help from others to launch the
project? Did you first line up several conversations with
people you sailed with?
In just days after I returned home from my JOIDES Resolution
(JR) expedition, I headed to Washington, DC, for the Advancing
Scientific Ocean Drilling IMPACT workshop (June 2022). The
workshop focused on increasing broader impacts for scientific
ocean drilling, and I remember being in a breakout session on
storytelling. As I had recently disembarked from the JR, many of the
questions asked by schoolchildren and museum audiences during
ship-to-shore virtual tours were still swirling around in my head—
questions about living and working at sea, for example. There was
QUARTERDECK
Oceanography | Vol. 38, No. 4
How did you decide to place the Tales from the Deep
collection on the StoryCorps website?
There were several features that attracted me to the StoryCorps
website. First, it is an existing collection with a large audience
of listeners. By adding our conversations to this online archive,
people beyond our scientific ocean drilling community have the
opportunity to discover this unique collection and to learn more
about the human side of working in this discipline. The record-
ings are also freely available, can be downloaded, and have a tran-
script automatically generated. This means no one needs a sub-
scription service, and individuals, especially classroom teachers,
can easily access the audio files. Because StoryCorps partners
with the American Folklife Center at the Library of Congress in
Washington, DC, to archive their collection, I decided to have our
Tales from the Deep recordings on this platform.
How often do you interview people?
I aim for one to two people per month. I try to be as flexible as pos-
sible with individual schedules—for example, the beginning and
end of semesters are a very busy time for many involved in the sci-
entific ocean drilling community (including myself), so I do have
several weeks where I step away from the recording and editing
phase of the project. But I always have email inquiries out there,
inviting people to participate and scheduling recordings.
What kinds of costs are involved with such a project?
The biggest cost is time. My time is involved with the communi-
cations, scheduling, recording, editing, getting the thumbs-up to
post online, and then sharing out the new additions to the collec-
tion through (my limited) social media channels. For the people
participating, I ask them to block off 45 minutes on their calendar
so we can test the audio quality before recording, and to leave us
enough time to ensure the full story or stories they want to share
are captured.
There is no budget for this project, but I do not mind donating
my time to capturing these voices and the dynamic conversations
around scientific ocean drilling. Because I have so much fun doing
this project, and there are no absolute deadlines for when the next
audio must be posted online, the flexibility I have makes this proj-
ect also very enjoyable.
The StoryCorps platform is free, so there are no costs associated
with adding our recordings to their collection.
What software do you need and what skills have you
developed that enable you to work on this project?
Though I look forward soon to starting live face-to-face recordings,
to date, all the recordings have been completed through Zoom. I
do not keep the video piece of the recording but ask that we keep
our cameras on for a more fluid conversation. I only download the
audio piece and do a first round of editing in GarageBand, then
move over to Adobe Podcast for some final touches.
I have now recorded over 50 conversations, and my skills have
certainly developed over the project. I am much better at taking
notes during the conversation in order to ask follow-up questions.
I also have learned to be patient during the recordings, allowing
my guests to share a complete story before I insert comments or
laughter. It is still a tricky balance making sure the recording comes
across as a conversation and not an interview—which is why I
don’t send along a long list of questions I am going to ask ahead of
time. Although that is a best practice for professional podcasters,
I do not want the dialogue to sound so structured and scripted.
Do you do anything to get the word out? Do you know
whether more than people related to scientific ocean
drilling are accessing and listening to the audio files?
I know that people I have recorded are doing their own dissemina-
tion of their conversations with family and friends. I have received
a few heartwarming stories from scientists who reported sharing
a link with family members that resulted in opening the door to
unprecedented conversations with their relatives about science
and being a scientist.
In addition, I was contacted last year by staff of the Learning
and Engagement Department at StoryCorps, who noticed that
Tales from the Deep is a “thriving community” and wanted to know
more about this project, as they found it inspiring, and also very
different from the other communities in the StoryCorps Archive.
In fact, Tales from the Deep has been a Featured Community on the
front page of the StoryCorps Archive for over a year now!
I have presented about Tales from the Deep at the fall meeting
of the American Geophysical Union and at the Ocean Sciences
Meeting, and I will continue to spread the word about this unique
collection and how it is important not only to our community but
also as a contribution to ocean science.
—
If you enjoyed reading about this project and listening to some
of the recorded conversations, please share the link to Tales from
the Deep widely. As Laura mentions at the end of her essay, she is
happy to answer any questions you might have about the project or
to schedule an online conversation about your experience with sci-
entific ocean drilling. Contact Laura at (guertin@psu.edu).
Ellen S. Kappel, Editor
ARTICLE DOI. https://doi.org/10.5670/oceanog.2025.e404
December 2025 | Oceanography
December 2025 | Oceanography
Audio Narratives from the Scientific Ocean Drilling Community
ESSAY
This quote is from an online conversation I recorded with
Maya Pincus when she was about to join JOIDES Resolution
as the onboard outreach officer for International Ocean
Discovery Program (IODP) Expedition 397T (Return to
the Walvis Ridge Hotspot, September 2022). I was com-
fortably sitting in my university office in Pennsylvania
(USA) with complete freedom to come and go, while
Maya was isolated in a hotel room in Cape Town, South
Africa, for a one-week mandatory quarantine period
before boarding the drilling vessel.
Why record a conversation on precautions and proce-
dures required before heading out to sea during an active
time of the COVID-19 pandemic? The motivation is sim-
ilar to that for recording the anxiety young scientists
may feel before joining their first research cruise, or how
someone handles the news of the loss of a family mem-
ber while miles offshore. Although the scientific research
conducted at sea is fully documented, where are the
stories collected about living and working at sea? As Maya
mentions, there are additional preparation, activities, and
emotions involved before, during, and even after expedi-
tions “so that we can make the important parts happen.”
I am a university professor with a background in
marine geology and geophysics. With part of my research
focused on geoscience education, like Maya, I was
attracted to the idea of sailing for two months as an
onboard outreach officer on the scientific ocean drilling
vessel JOIDES Resolution (JR). Taking responsibility for
By Laura Guertin
I think when someone goes on an [ocean] expedition…no one really
remembers the quarantine as what stands out. But it’s part of what we
did so that we could make the important parts happen.
— Maya Pincus, Tales from the Deep
Listen to the full interview recorded on September 8, 2022
Oceanography | Vol. 38, No. 4
posting on social media, authoring blog posts, and conducting live
ship-to-shore video tours with classrooms and community groups
across the world sounded appealing, so I applied and was accepted
to sail on IODP Expedition 390 (South Atlantic Transect 1) in
April/June 2022.
Using an iPad to facilitate the live video satellite connections,
I thoroughly enjoyed each of the ship-to-shore sessions. I would
talk to remote audiences while walking around the ship, sharing
my iPad screen to show everyone freshly collected core material
and the view from the ship’s bridge. I would also conduct live con-
versations where scientists could discuss their research. I was pre-
pared for this educational responsibility. But what I was not pre-
pared for was the flood of questions I received during and after the
remote ship tours that had nothing to do with our deep-sea inves-
tigation. No matter what the ages of the groups I connected with,
individuals and classrooms were asking: Do you need to know how
to swim to be an oceanographer? Is it easy to make friends at sea?
What if your birthday happens on the ship? And more.
One question I received made the biggest impact on me and
really led to the development of the audio narrative collection Tales
from the Deep: Stories of Scientific Ocean Drilling. During one of
my tours, a fourth-grade girl walked up to her teacher’s computer,
leaned into the video camera, and asked “what if you have a food
allergy?” The student quickly walked away from the computer, but I
was gushing with excitement to respond to her inquiry. I explained
that I have a food allergy to tomatoes, a very common ingredi-
ent in sauces and condiments. But the Camp Boss (the head of the
ship’s galley) and the entire kitchen staff worked with me imme-
diately when I boarded the ship and made sure I was included in
every meal with non-tomato items to choose from.
I reflected on that young student’s question quite a bit during
the remainder of my expedition. I realized that she was potentially
viewing a food allergy, possibly her own, as an invisible barrier to
participating in an ocean expedition, or perhaps even pursuing a
career as an oceanographer. There are websites that have profiles of
scientists that describe pathways to becoming a professional in the
field. There are also websites, conferences, and journal articles that
disseminate the scientific outcomes of analyses collected on deep-
sea samples. But so far as I could tell, especially in the scientific
ocean drilling community, there was no collection of personal sto-
ries from onshore and offshore scientists and staff related to living
and working at sea, along with the support necessary to carry out
There’s a team of people around the world who
are working on these materials to try and uncover
new information that we think matters.
— Melissa Berke, Tales from the Deep
Listen to the full interview recorded on April 17, 2025
At our science crossover meetings, if you went
over your 5 minutes, you would get oinked at by
the [Secret Santa] pirate pig.
— Stephen Phillips, Tales from the Deep
Listen to the full interview recorded on November 25, 2024
What I hadn’t experienced is actually how we
collect that [ODP and DSDP] data…
— Andrew McIntyre, Tales from the Deep
Listen to the full interview recorded on October 4, 2022
December 2025 | Oceanography
Do you have a story related to scientific ocean drilling to con-
tribute? Maybe it is a similar story to that of Patty Stranding, who
first learned about scientific ocean drilling through an under-
graduate research experience. Or you may have a reflection like
Larry Krissek’s as he details how, despite the advances in technol-
ogy, core descriptions will always need a human eye. All individ-
uals and topics are welcome, especially from non-US scientists
and crew who sailed on Glomar Challenger, Chikyū, and mission-
specific platforms, and those who have also played shore-based
roles in support of scientific ocean drilling. Whether it be a one-
time connection to scientific ocean drilling, or discussion of a
24-year career such as Kevin Grigar reflects upon, your story is an
important piece of the history of scientific ocean drilling.
Please contact me (guertin@psu.edu) with any questions and if
you are interested in scheduling a 30-minute online conversation.
All recorded conversations go through a round of editing and are
sent back to the speaker for approval before being uploaded to the
StoryCorps Archive.
AUTHOR
Laura Guertin (guertin@psu.edu), The Pennsylvania State University - Brandywine, PA,
USA. Laura was the TOS Geological Oceanography Councilor from 2022 to 2024.
ARTICLE CITATION
Guertin, L. 2025. Tales from the Deep: Audio narratives from the Scientific Ocean
Drilling community. Oceanography 38(4):7–9, https://doi.org/10.5670/oceanog.2025.
e405.
COPYRIGHT & USAGE
This is an open access article made available under the terms of the Creative
Commons Attribution 4.0 International License, which permits use, sharing, adapta-
tion, 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 made to the original content.
the science, aside from 10 short stories contributed by shipboard
scientists that were included in the December 2006 Oceanography
special issue on The Impact of the Ocean Drilling Program.
I have been integrating audio storytelling assignments into
my university courses for over a decade, where students generate
audio narratives about our course content. After sailing on JOIDES
Resolution, I was motivated to start a collection of audio conversa-
tions focusing on the people involved with scientific ocean drill-
ing. Titled Tales from the Deep: Stories of Scientific Ocean Drilling,
the collection contains the voices of scientists and staff who have
sailed on the various scientific ocean drilling vessels and plat-
forms over the years, along with tales from those who work in
land-based support offices. The collection currently has over
50 recorded conversations and is freely available online through
the StoryCorps Archive. The independent nonprofit organization
StoryCorps is then preserving these recordings for continued pub-
lic availability at the American Folklife Center at the Library of
Congress in Washington, DC.
Most of the conversations have been lighthearted. Jeffrey Ryan
shares what happened after he saw his shredded luggage come
off on the belt at Japan’s Narita International Airport right before
joining JOIDES Resolution. Tracy Quan talks about the ship-wide
search for a new watch battery after her battery died only two
weeks into her expedition. Yi Wang describes sharing a cultural
birthday celebration with those on board. And Chieh Peng and
Etienne Claasen noted that crossing over the International Date
Line had them work the same day twice, but only get paid once.
But some of the conversations strike a more serious note.
Suzanne O’Connell discusses the three medical evacuations she
witnessed sailing on three different expeditions. Keir Becker
describes joining Glomar Challenger just as the Iran Hostage
Crisis began, and Tim Bralower describes being aboard JOIDES
Resolution during the collapse of the World Trade Center tow-
ers in New York City. Aidan Leetz spoke with me from the same
ship right after they received the news that JOIDES Resolution
would no longer be participating in the International Ocean
Discovery Program.
Importantly, these conversations capture the roles of so many
unsung people whose efforts have always been critical to conduct-
ing scientific ocean drilling research. You can listen to the voices
of Sidney Hemming and Priyank Jaiswal as they describe how
drilling in international waters may never have happened with-
out the behind-the-scenes work of such individuals. You can also
learn about the roles TOS Executive Director Jenny Ramarui and
Director of Publications Ellen Kappel played in scientific ocean
drilling—both worked in the Joint Oceanographic Institutions
office and tell not only how the office operated in the earliest days
of the internet but also how the Joint Oceanographic Institutions
office was the starting point of The Oceanography Society. Both
also had quite the experience related to a helicopter getting lost on
its way to the JR…
Oceanography | Vol. 38, No. 4
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Oceanography | Vol. 38, No. 4
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COST-CONSCIOUS
MEASUREMENTS
IN THE COASTAL WATERS OF BANGLADESH
By Rupak Loodh, Dipanjan Chaudhuri, Eric D’Asaro, and Md Minarul Hoque
Bangladeshi scientists on board a
sampan while returning from data collection.
Photo credit: Md Sultanul Azim Mahi
FEATURE ARTICLE
December 2025 | Oceanography
11
INTRODUCTION
BAY OF BENGAL
The South Asian Monsoon impacts the livelihoods of one-fourth
of the world’s population, particularly those living around the
Bay of Bengal (BoB). The seasonal rainfall and river inflows
contribute significant freshwater flux of 1.6 m yr–1 (Bhat et al.,
2001; Vinayachandran et al., 2002; Sengupta et al., 2006), result-
ing in the development of a thin, salinity-stratified surface layer
in the northern and central BoB (Figure 1a). This layer has two
important effects: (1) it increases the number of monsoonal con-
vective systems that deliver rain to central India (Waliser et al.,
2003; Goswami, 2012; Samanta et al., 2018), and (2) it contrib-
utes to the intensification of destructive tropical cyclones in the
BoB (Sengupta et al., 2008; Balaguru et al., 2012, 2014; Neetu et al.,
2012; Chaudhuri et al., 2019).
Furthermore, the BoB is vital for controlling maritime access
to the Far East, affecting major shipping routes that facilitate 25%
of global trade. Given its growing strategic importance, key stake-
holders such as the United States, China, India, and Japan are mak-
ing substantial investments to ensure the maritime security and
stability that is essential for maintaining a continuous flow of
energy resources and trade opportunities (Chaudhury and Pant,
2024; Ranjan and Attanayake, 2024).
OCEAN OBSERVING NETWORK
A network of BOB moored buoys (Figure 1d) includes, at any given
time, approximately six Ocean Moored buoy Network for Northern
Indian Ocean (OMNI) buoys (including one in the Andaman Sea)
that are maintained by the National Institute of Ocean Technology
(NIOT) of India (Venkatesan et al., 2013), along with four RAMA
ABSTRACT. The northern Bay of Bengal plays a crucial role in regional climate, human activities, and ecological diversity, but it is
unstudied by oceanographers. In 2022, the Bangladesh Oceanographic Research Institute began to address this important problem by
initiating a project to collect in situ data off the coast of Cox’s Bazar, Bangladesh. We report the initial results from winter 2022–23 here.
High-resolution spatial measurements of ocean temperature, salinity, and horizontal velocities were made using modern sensors adapted
to local boats. During this period, the coastal seas display sharp salinity-dominated density fronts, prominent temperature inversions,
and partially compensated water masses. We hypothesize that these characteristics result from the stirring and mixing of cold and fresh
water from local rivers, and warm and salty water from the central Bay of Bengal, creating distinct water masses on the Bangladeshi
shelf. Future work aims to continue to modernize the capabilities of Bangladeshi oceanography through international collaborations,
emphasizing state-of-the-art instrumentation, experimental design, and data analysis. These activities combine in a novel “cost-conscious
oceanography” approach, pointing toward an innovative solution for the Global South to address data gaps in uncharted coastal seas.
FIGURE 1. (a) Annual mean sea surface salinity from the World Ocean Atlas 2018 (WOA18; Garcia et al., 2019). The white square locates the Bay of Bengal.
(b) Daytime 4 km resolution NOAA/Advanced Very High Resolution Radiometer (AVHRR) sea surface temperature (SST, °C) is plotted for December 19, 2022;
blank white areas are clouds. (c) Daytime pass of Soil Moisture Active Passive Satellite (SMAP) swath over the Bay of Bengal on December 20, 2022. (d) Map
showing the locations of Argo floats during 2008–2021 (gray) in the Bay of Bengal. The green line shows the 50 m depth contour, and the blue lines indi-
cate 3000 m, 2000 m, 1000 m, and 500 m depths. Four black stars and a square indicate the positions of the buoys maintained by the National Institute of
Ocean Technology (NIOT) and NOAA’s Pacific Marine Environmental Laboratory in the Bay of Bengal. The red square in the head bay represents the sam-
pling area within the unexplored continental shelf near the city of Cox’s Bazar. (e) In this zoom into the coastal sampling area, red dots indicate the locations
of 60 CTD stations taken during 2021–2022 by the Bangladesh Oceanographic Research Institute (BORI) that are discussed here. Green and blue dashed
lines plot depth contours of 30 m and 10 m, respectively.
Oceanography | Vol. 38, No. 4
12
(Research Moored Array for African-Asian-Australian Monsoon
Analysis and Prediction) moorings operated by the US National
Oceanic and Atmospheric Administration (NOAA) in collab-
oration with India (McPhaden et al., 2009). These buoys collect
high-resolution data on upper ocean conditions, including tem-
perature, salinity (conductivity), currents at various depths, and
surface meteorological data such as wind, humidity, pressure, tem-
perature, rainfall, and radiation. Some buoys also collect wave
parameters. In addition, India organizes several scientific oceano-
graphic cruises yearly to enhance understanding of the interactions
between oceanic and atmospheric processes that affect climate,
extreme weather events, ecosystems, and human populations.
The US Office of Naval Research (ONR), in collaboration with
India, Sri Lanka, Thailand, and the Maldives, has conducted
three significant observational programs in the BoB over the past
10 years (Wijesekera et al., 2016; Shroyer et al., 2021). These pro-
grams primarily took place in international waters below 20°N,
notably excluding two key countries, Bangladesh and Myanmar.
As a result, the northeastern portion of the BoB remains one of the
unexplored frontiers of our planet, holding immense potential for
future research and discovery. It is an “aqua incognito.”
MOTIVATION
Bangladesh is a riverine country located on the northern coast
of the BoB. It encompasses the confluence of the Ganges,
Brahmaputra, and Meghna Rivers, which discharge substan-
tial amounts of fresh water (about 0.04 Sv) into the vast and rel-
atively flat waters of the northeastern Bengal shelf. Modern phys-
ical oceanography increasingly relies on satellite remote sensing
for continuous ocean sampling. However, clouds can hinder the
retrieval of infrared sea surface temperature (SST) data in coastal
areas (Figure 1b). Although microwave remote sensing is not
affected by cloud cover, satellite-derived, microwave-based SST
measurements are often compromised by land contamination due
to antenna side lobes within approximately 50 km of the coast
(Wentz et al., 2000; Donlon et al., 2007; Pearson et al., 2018).
Furthermore, sea surface salinity measurements obtained through
satellite remote sensing may exhibit significant systematic errors
near coastal regions (Figure 1c) and in areas affected by radio fre-
quency interference (Boutin et al., 2021). Recently, salinity data
from NASA’s Soil Moisture Active Passive Satellite (SMAP) were
contaminated throughout the BoB, likely due to radio frequency
interference in multiple microwave channels following the out-
break of civil war in Myanmar.
Coastal seas also lack depth-resolved in situ temperature and
salinity measurements, as robotic floats, such as those in the
international Argo program, require a parking depth of 1,000 m
(Roemmich et al., 2009) and cannot operate in such shallow depths
as those around Cox’s Bazar. (However, a few Argo floats that have
entered the northern BoB continental shelf [Figure 1d] have pro-
vided valuable information about water mass characteristics).
These factors result in the poor understanding of the north con-
tinental shelf of the BoB that motivates the effort described here to
collect more data in this region.
In 2020, the Bangladesh Oceanographic Research Institute
(BORI) launched a coastal observation program to tackle the
challenges associated with coastal oceanography research. The
Bangladesh Government supports this program to establish sus-
tained monitoring of several oceanic variables. Under the frame-
work of the blue economy, BORI’s continuous efforts across all
branches of oceanography hold promise for discovering potential
resources for fisheries and renewable energy from ocean sources.
STUDYING THE AQUA INCOGNITO
Our study focuses on the northern coastal area of the BoB near
the city of Cox’s Bazar, located approximately 120 km south
of the Karnaphuli River and 200 km southeast of the Ganga-
Brahmaputra-Megna River mouth (Figure 1e). We chose this site
because of its proximity to the institute, which facilitates logis-
tics movements and local support. Because BORI has no seagoing
ocean vessel, we rely on local fishing boats. So far, our observa-
tions have only been possible during winter as the sea becomes too
rough during the southwest summer monsoon.
BOAT
Our sampling was conducted using a wooden fishing boat (locally
called a sampan) of a type that is ubiquitous in the Cox’s Bazaar
coastal area (Figure 2a); ten to 15 fishermen usually fish for seven
to 10 days using sampans. The choice of this boat was based on its
suitability for the local conditions and its stability in the water. It
is 12.8 m in length, with a maximum width of 3.66 m and a draft
of 2.1 m. Powered by a 32 HP engine, the boat cruises at 9 km per
hour and has a carrying capacity of 12 tons. Sampling trips usu-
ally commence at 7 a.m. local time and return at sunset at 5 p.m.,
The first area of success encompasses the development of an indigenous
method for measuring coastal oceans with modern sensors and the collection
of unprecedented data in uncharted waters by Bangladeshi scientists
December 2025 | Oceanography
13
covering roughly 100 km and 10 sampling stations. The daily cost
of using the boat is about $400.
At each sampling station, the boat driver (locally called majhee)
skillfully stabilized the boat using the Global Positioning System
(GPS) position, ensuring a smooth sampling process. We utilized
Android-based GPS software, specifically GeoTracker and Google
Maps, which offer an accuracy range of 3 m to 10 m. We use pre-
marked nylon rope with a depth indicator and an echo sounder
for depth information. After each conductivity-temperature-depth
(CTD) and acoustic Doppler current profiler (ADCP) operation,
we extract data from the sensor and conduct a data quality check
on the boat, ensuring the accuracy and credibility of our results.
The average rolling and pitching at each station measured by the
inbuilt motion sensor in the Aquadopp ADCP are 10° and 12°,
respectively, suggesting calm sea conditions and a stable boat.
INSTRUMENTS AND METHODS
After extensive discussions, we carefully selected the instruments
to be used in this study. Our main focus was to ensure that the
chosen instruments were all usable from an ordinary fishing
boat without a deployment platform and that had proven reli-
ability. All instruments were procured under BORI’s Research &
Development project 2020–2022, with recommendations from an
expert committee comprised of experienced oceanographic sci-
entists. Table 1 lists detailed information about each instrument.
The total cost for procuring all the instruments was approximately
$50,000 USD.
Our study used two CTD sensors: the CTD90M from Sea & Sun
Technology and the Star-Oddi sensor. The CTD90M, known for
its high quality and accuracy, was our primary instrument for cal-
ibrating the other CT sensors. Its conductivity cell features a natu-
rally flushed design similar to the RBR Concertos “combined CT”
cell, which has a co-located temperature sensor (Pt100). We
selected continuous profiling modes, acquiring data at seven sam-
ples per second. The CTD profiles were secured to a steel cage
with a 1.7-liter Niskin water sampler. Our team of technicians
and scientists deployed and recovered the CTD by hand for each
cast from the side of the vessel, using pre-labeled nylon rope for
assistance (Figure 2b).
TABLE 1. List of instruments.
EQUIPMENT
MAKE/MODEL
PARAMETER
RESOLUTION
ACCURACY
RANGE
CTD90M
Sea & Sun Technology
Temperature
0.0005°C
±0.002°C
–2–60°C
Conductivity
0.005 mS cm–1
±0.01 mS cm–1
0–300 mS cm–1
Pressure
0.002% FS
0.05% FS
0–200 bar
DST CT
Star-Oddi
Temperature
0.032°C
±0.1°C
–1–40°C
Conductivity
0.03 mS cm–1
±0.1 mS cm–1
3–68 m S cm–1
Aquadopp 600 kHz
Nortek
Zonal meridional velocity
1 cm s–1
±1% of the measured value
±5.75 m s–1
Niskin-Type Plastic Water Sampler
HYDRO-BIOS
FIGURE 2. These photos show the platform, instruments, and data collection procedure used in this study. Gray arrows point to (a) the fishing boat used,
(b) CTD sensors, (c) an ADCP, and (d) a thermosalinograph.
Oceanography | Vol. 38, No. 4
14
Over a span of five days, the team successfully collected
57 profiles. The average descent and ascent rate of the CTD frame
was 0.07 m s–1, with each complete CTD operation taking approx-
imately 6 to 8 minutes. We processed each CTD profile by aver-
aging data at 25 cm intervals. Slight differences in temperature
and salinity values were observed between the upcast and down-
cast profiles, probably due to advection. Because we did not have a
commercial thermosalinograph installed on a dedicated research
vessel, we innovatively developed a new method to measure fine-
scale horizontal gradients of near-surface temperature and salin-
ity. First, we placed one conductivity/temperature logger, along
with one temperature logger manufactured by Star-Oddi, inside
a small cage made of satin stainless steel. These compact sen-
sors, which are high-pressure tolerant and have long battery lives,
are among the smallest CT loggers on the market, measuring
less than 5 cm.
Next, for flotation, we attached the cage to two five-liter plastic
containers. Finally, we deployed the setup behind the boat using
a 20-meter-long rope, which helped us avoid the wake generated
by the boat. We used a depressor weight attached to a one-meter-
long rope connected to the cage to ensure the sensors remained
submerged while towing. We called this arrangement the “cost-
conscious thermosalinograph” (Figure 2d). The sensors were pro-
grammed to record data at two-minute intervals, resulting in a fine
horizontal resolution of 150 m for temperature and salinity in the
upper 1 m of the water column.
We used the Aquadopp 600 kHz ADCP to measure the horizon-
tal velocities in the upper ocean. At each CTD station, we securely
mounted the ADCP on a pole extending over the side of the boat,
facing downward (Figure 2c). The ADCP was deployed at a depth
of 2 m and was configured to sample in 1 m vertical bins with
a 1 sec sampling interval. We processed the velocity data using
Nortek’s AquaPro software. To minimize measurement error, we
averaged all the velocity data over a period of five to 10 minutes.
RESULTS
COASTAL MEASUREMENTS
Figure 3a,b shows the surface temperature and salinity in
Bangladesh’s coastal waters on five days: December 19, 22, 23,
and 24 in 2022 and January 14, 2023. The northern waters, influ-
enced by riverine sources, are colder (24°C compared to 29°C) and
less saline (12 psu compared to 32 psu) than those in the southern
part of the study. The depth-averaged currents flow from the south,
bringing warmer and saltier water to the region (see Figure 3c).
Strong stratification is observed in northern waters, with an
average buoyancy frequency (N 2) of 10–3 s–2 at depths of 2–4 m
(Figure 3g). In contrast, the southern waters show evidence of
well-mixed conditions. The data also indicate a temperature inver-
sion north of 22°N (Figure 3d), where the subsurface layers are
warmer than the surface. This phenomenon is consistent with pre-
vious studies (Vinayachandran et al., 2002; Thadathil et al., 2016;
Masud-Ul-Alam et al., 2022) and is particularly pronounced
within the upper 10 m of the water column.
FIGURE 3. (a) Temperature and (b) salinity measurements taken at a depth of 2 m. (c) Flow patterns along the Cox’s Bazar coast during the measurement
periods, with different colors representing different days. Depth-latitude profiles are plotted along A to B within the dashed-line box in panel a for (d) poten-
tial temperature (θ, °C), (e) salinity (S, psu), (f) potential density (σθ, kg m–3), (g) square of the Brunt-Väisälä buoyancy frequency (N2, s−2), and (h) meridional
velocity (V m s–1) as measured on December 23 and 24, 2022.
December 2025 | Oceanography
15
The inversion primarily arises from surface cooling associated
with the “Western Disturbance” (Dimri and Chevuturi, 2016).
In a shallow mixed layer, like the one observed here, much of the
incoming atmospheric heat escapes into the subsurface ocean as
shortwave radiation, which further intensifies the temperature
inversion. Notably, salinity plays a more critical role than tempera-
ture in influencing the stability of the water column (Figure 3e–g).
Throughout the recorded data, distinct temperature and salinity
fronts are visible, raising intriguing questions about mixing pro-
cesses and thermodynamics in this region.
OBSERVATIONS ON DECEMBER 19, 2022
We present evidence of partially density-compensated submeso-
scale surface fronts (Figure 4c,d) with lateral scales ranging from
1 km to 10 km, based on in situ observations in the coastal region,
along with NOAA Visible Infrared Imaging Radiometer Suite
(VIIRS) satellite SST data with a resolution of 0.12 × 0.9 km. A
notable observation by the satellite recorded at 1 a.m. local time
on December 20, 2022, reveals a 50 km filament of warm water
located just east and south of the coasts of Bangladesh and
Myanmar (see Figure 4a,b). This warm filament is approximately
5 km wide and has an SST 2°C higher than the surrounding waters.
The northern side of the filament has a mushroom-like appearance
and forms a front with the incoming colder river water. Although
we collected data in the area eight hours before the satellite passed
(Figure 4b), the filament remained in place, suggesting that mix-
ing occurs slowly.
Temperature-salinity (T-S) plots at various depths and differ-
ent latitudes (Figure 4c,d) show two distinct water masses in the
coastal waters of Bangladesh during winter. The northern water is
primarily “minty” (Jackett and McDougall, 1985; Flament, 2002),
meaning it is cold (24°C) and fresh (12 psu) river water that has
been carried along the coast. As it moves, it mixes with the “spicy”1
warm (29°C) and salty (32 psu) waters of the BoB, resulting in the
formation of different types of coastal water (Figure 4c,d). A com-
bination of vertical (M1and M2 in Figure 4c) and horizontal mix-
ing (M3 in Figure 4c) can explain the distribution of temperature
and salinity on the continental shelf. Vertical mixing occurs on the
surface or bottom, probably due to surface cooling or tidal influ-
ences, while intermediate depths are more susceptible to horizon-
tal mixing (Figure 4c,d).
1 In oceanography, “spice” describes water masses with varying salinity and temperature along isopycnals, measured in density units and nearly orthogonal
to potential density. Cold and fresh water is called “minty,” while warm and salty water is known as “spicy,” both having the same density.
FIGURE 4. (a) NOAA Visible Infrared Imaging Radiometer Suite (VIIRS) SST (°C) for January 19, 2022. Blank areas are clouds
or land. (b) A magnified view shows SST in the vicinity of the Bangladesh coast near Cox’s Bazar. CTD locations are marked
by squares. The evolution of temperature and salinity (TS) in the coastal ocean is shown with colors indicating (c) measure-
ment depths and (d) latitudes. The three straight lines labeled M1, M2, and M3 represent resultant water masses formed due
to the mixing of minty river water and spicy ocean water.
Oceanography | Vol. 38, No. 4
16
LATERAL VARIATIONS AND FRONTS ALONG BOAT TRACK
Our measurements on December 19, 2022, began at 7 a.m. local
time, continued until 5 p.m., and were made in a 60 km rectan-
gular loop (Figure 5a). That day, we completed a time series of
measurements of vertical profiles, including temperature, salin-
ity, and horizontal velocities at 10 different stations (Figure 5a).
We deployed our cost-conscious thermosalinograph behind our
boat to capture the initial insights into horizontal temperature and
salinity variability. The thermosalinograph collected continuous
data, and a comparison with near-surface temperature and salinity
from the CTD instrument indicates that the salinity measurements
from the thermosalinograph are generally reliable (Figure 5f,g).
Note that we used different sampling patterns during the other
four days (see Figure 4c).
On December 19, 2022, the along-track temperature and salin-
ity measurements indicate that we crossed two prominent sharp
fronts (Figure 5b–d). The data show that coastal waters are the
coldest and saltiest, measuring 24°C and 30 psu, while the waters
farther away are warmer and fresher, at 26°C and 26.5 psu. Between
these zones, we find the warmest and saltiest waters, with a tem-
perature of 27°C and a salinity of 31.5 psu (Figure 5b–d).
Horizontal density gradients are prevalent throughout the mea-
surement period, reaching a minimum within the first 20 km
(along-track distance) off the coast due to temperature and salin-
ity compensation (Figure 5d,e). In contrast, a sharp, dynam-
ically active front is observed farther from the coast (between
20 to 30 km) with a significant lateral density difference of
4 kg m–3 over a spatial scale of 4 km. These observations suggest
FIGURE 5. (a) Local time (hours) of measurement for surface (b) potential temperature (θ; °C) and (c) salinity (S; psu)
data collected on December 19, 2022, from a fishing boat. Open squares (black) show the locations of ten CTD
stations. Surface (d) potential temperature (blue) and salinity (red), and (e) potential density (green) are plotted
along the boat’s track. The three horizontal lines (gray) in panel (d) represent three different types of water mass
(I, II, and III). (f,g) Scatterplots show temperature (f) and salinity (g) as measured by a Star-Oddi sensor (TSO) within a
10-minute window, centered around each CTD profile (TCT D), averaged over the depth range of 0–2 m. The error
bars represent one standard deviation of the measurements. Dashed lines in panels a and b represent the 1:1 line.
Probability density functions (PDFs) for (h) the horizontal salinity ( dx
dS, psu, red) and temperature absolute gradi-
ents ( dx
dT,°C, blue) and (i) the potential density absolute gradient ( dx
dp, kg m–3, green) collected along the boat tracks
during five days of coastal measurements. The gray vertical lines in panel e mark the CTD stations along the boat
track. The blue, red, and green vertical lines in panels (h) and (i) mark the median of the probability density func-
tions for the horizontal potential temperature, salinity, and potential density gradients.
December 2025 | Oceanography
17
the presence of submesoscale fronts in this region, consistent with
previous studies conducted in the open bay (Sengupta et al., 2016;
Jaeger and Mahadevan, 2018). The magnitude of the lateral gradi-
ent of temperature, salinity, and potential density along the boat
track exceeds 0.05 l/km (l ≡ °C, psu, kg m–3) about 15%, 25%, and
19% of the time (Figure 5h,i).
VERTICAL STRATIFICATION AND SHEAR
Temperature and salinity profiles have been plotted at selected
locations A2, near the coast, and D3, at the front, (both indicated
in Figure 5a) along the track (Figure 6) to illustrate the verti-
cal structure and variability of the upper ocean. The D3 profile
displays a double pycnocline structure, with peaks in the verti-
cal density gradient occurring between depths of 6 m and 8 m
and 11 m and 13 m (Figure 6h). This vertical density gradient
is stabilized by a salinity gradient as riverine water creates a
salinity difference of 5 psu between the surface and bottom lay-
ers (Figure 6f). This stabilization counteracts the destabilizing
effect of the temperature gradient, where the surface layer is 4°C
colder than the warmer subsurface layer (Figure 6f). Such a tem-
perature inversion is commonly observed in the Bay of Bengal
during winter (Thadathil et al., 2016; Vinayachandran et al., 2002;
Masud-Ul-Alam et al., 2022).
In contrast, the A2 profile represents a relatively well-mixed
layer (Figure 6a). A negative Brunt-Väisälä buoyancy frequency
squared value N 2 in the depth range of 5–8 m (Figure 6c) indicates
a vertical density overturn, suggesting substantial vertical mix-
ing near the coast (Figure 6b). The estimations of reduced shear2
(RSH = SH 2 − 4N 2) further support these observations. A reduced-
shear value greater than zero (RSH > 0) indicates active turbulence,
while a value less than zero (RSH < 0) suggests a lack of turbu-
lence. Figure 6e,j shows that strong stratification resists signifi-
cant shear, contributing to the stability of the D3 profile, whereas
shear-induced mixing and weak stratification lead to a well-mixed
layer at A2. Notably, both profiles exhibit partially vertically com-
pensated water masses.
DISCUSSION
Co-located measurements of temperature, salinity, and horizontal
velocity provide valuable insights into the variability of tempera-
ture and salinity and the vertical shear structure in Bangladesh’s
coastal waters. The vertical resolution of the data ranges from
0.25 m to 1 m, while the horizontal resolution averages around
300 m, sufficient to capture submesoscale features (1–20 km).
The study reveals the presence of sharp, salinity-dominated
near-surface density fronts that are sometimes partially compen-
2 The Richardson number criterion, defined as —
N2
SH2 < 0.25, is often used to identify mixing events in the ocean. Reduced shear, derived from the above crite-
rion, is expressed as SH2 − 4N2. If this value is positive, it means that the shear is strong enough to cause mixing. If the value is negative, it indicates that
the stratification is stronger, allowing the layers to remain stable.
FIGURE 6. Plots show profiles of (a,f) potential temperature (θ, blue, °C) and salinity (S, red; psu), (b,g) potential
density (σθ, green, kg m–3), (c,h) square of the Brunt-Väisälä buoyancy frequency (N2, maroon, s−2), (d,i) square
of the shear (SH2, yellow, s−2), and (e,j) reduced shear (SH2−4N2, gray). Thin lines in panels f, g, and h repre-
sent similar quantities, but in panels a, b, and c.
Oceanography | Vol. 38, No. 4
18
sated by temperature differences. The largest gradient exceeds
4 kg m–3 over a distance of 4 km. Furthermore, the data indicate
large temperature inversions, which are common in the open bay
during winter.
The findings also highlight the complex pathways and mix-
ing patterns of river water in the ocean. For example, a narrow
10 km-wide coastal jet transports salty water into the northern
BoB shelves, maintaining the salt balance. We hypothesize that this
jet is a seasonal phenomenon occurring in winter, which helps pre-
vent the shelves from becoming fresher.
To illustrate these concepts, we can consider an idealized budget
for salt mixing expressed as
VS
FV ∆S
dt
dS
(1)
where dt
dS is the overall change in salinity on the shelf, FV = vh2w
is the volume flow, v is the meridional velocity, h2 is depth, w is
width, ∆S = SI − SF, SI is the salinity of the BoB, SF is the salin-
ity of the shelf sea, and VS is the volume of the shelf where the
depth is less than 10 m (see Figure 3e). Our measurements indi-
cate that v = 0.5 m s–1, h2 = 20 m, w = 10 km, VS = 9 × 109 m3,
SI = 32 psu, and SF = 12 psu (see Figure 3). By substituting these
values into Equation 1, we estimate that dt
dS is 2 psu/day, suggesting
that the shelf water rapidly freshens by mixing with water from the
local rivers as it moves northward. More generally, this suggests
that many of the properties of the shelf water—salinity, oxygen,
nutrient concentration, and plankton—are strongly influenced by
similar balances between open ocean and riverine inputs, and that
these might change rapidly as this balance shifts due to variations
in either input or the mixing rate. We can explore this hypothesis
in future studies.
CONCLUSIONS
The northern shelves of the BoB associated with the mouth of the
Ganga-Brahmaputra-Meghna Rivers are among the least sampled
areas in the upper ocean. The establishment of BORI in 2018, along
with the goals set by the Bangladesh government, marked a sig-
nificant step toward a systematic scientific observation program.
This initiative aligns with the country’s vision of a blue economy
by 2028, focusing on collecting data on the physical, chemical, bio-
logical, and geological aspects of the ocean. It will also monitor
coastal conditions, create a regional ocean model for the northern
BoB, and help restore coral habitats.
We have succeeded in two main areas. The first area of success
encompasses the development of an indigenous method for mea-
suring coastal oceans with modern sensors and the collection of
unprecedented data in uncharted waters by Bangladeshi scientists.
There are three key reasons for this success. (1) Instead of devel-
oping low-cost sensors, BORI initially purchased modern instru-
ments, thanks to initial government funding of $50,000. (2) BORI
also offered support in terms of logistics, operations, and infra-
structure development by setting up laboratories and data cen-
ters, ensuring the long-term success of our coastal observation
programs. (3) Collaboration between oceanographers from BORI
and the Applied Physics Laboratory, University of Washington, in
buying instruments, designing experiments, and processing data
played an important role in our success. This enthusiasm and
eagerness, bolstered by expert training, will pave the way for “cost-
conscious oceanography,” a new frontier for developing countries
in the Global South that cannot afford expensive ocean obser-
vation programs. Similar future observational efforts will help
address data gaps in many areas of the global ocean, ultimately
aiding in more accurate sea predictions.
The second area of success is that, from an oceanographic per-
spective, our work provides unique insights into the rich upper-
ocean temperature-salinity variability and vertical shear structure
in Bangladesh’s coastal waters. These findings suggest complex
pathways and mixing patterns of river water in the ocean. Ongoing
efforts to collect additional variables, such as oxygen, chlorophyll,
turbidity, and tides, are explicitly important for the effective man-
agement of coastal resources.
REFERENCES
Balaguru, K., P. Chang, R. Saravanan, L.R. Leung, Z. Xu, M. Li, and J.-S. Hsieh. 2012.
Ocean barrier layers’ effect on tropical cyclone intensification. Proceedings of
the National Academy of Sciences of the United States of America 109(36):
14,343–14,347, https://doi.org/10.1073/pnas.1201364109.
Balaguru, K., S. Taraphdar, L.R. Leung, and G.R. Foltz. 2014. Increase in the inten-
sity of postmonsoon Bay of Bengal tropical cyclones. Geophysical Research
Letters 41(10):3,594–3,601, https://doi.org/10.1002/2014GL060197.
Bhat, G.S., S. Gadgil, P.V. Hareesh Kumar, S.R. Kalsi, P. Madhusoodanan, V.S.N. Murty,
C.V.K. Prasada Rao, V. Ramesh Babu, L.V.G. Rao, R.R. Rao, and others. 2001.
BOBMEX: The Bay of Bengal Monsoon Experiment. Bulletin of the American
Meteorological Society 82(10):2,217–2,244, https://doi.org/10.1175/1520-0477(2001)
082<2217:BTBOBM>2.3.CO;2.
The second area of success is that, from an oceanographic perspective,
our work provides unique insights into the rich upper-ocean temperature-salinity
variability and vertical shear structure in Bangladesh’s coastal waters.