Category: Oceans

Deep Learning Applied to Satellite Imagery Reveals Untracked Ships

Published on by Jonathan Crowe
Maps showing registered and unregistered fishing vessels near Spain, Morocco, Sicily and Tunisia.
Excerpt from Fig. 2 of Paolo et al., “Satellite mapping reveals extensive industrial activity at sea,” Nature 625 (2024).

Speaking of AI-assisted global monitoring: researchers affiliated with Global Fishing Watch have revealed that the global fishing, transport and energy fleets are a lot bigger than expected. They were able to compare the locations of ships carrying AIS transponders with satellite imagery, to which deep learning was applied to classify ships. They conclude that something like three-quarters of industrial fishing vessels, and thirty percent of transport and energy vessels, go untracked. This isn’t necessarily so much about clandestine activity—in many regions ships, especially fishing boats, simply aren’t required to be tracked—but it can, among other things, reveal illegal fishing in protected areas. Results of the study were published in Nature last month. Global Fishing Watch also has an interactive map. [The Verge]

‘Cartographically Speaking, Water Sucks’

Published on by Jonathan Crowe

Last October, on her Huge If True YouTube channel, Cleo Abram explored the state of deep ocean mapping, why it lags behind our mapping of, say, Mars, and what’s being done to chart the ocean floor at a higher resolution than currently exists (e.g. the Seabed 2030 project). All told this is a good and enthusiastic primer for the relatively uninitiated (though I do have to quibble with the statement that Marie Tharp’s maps have “largely been forgotten by history,” but then I’ve seen rather a lot about Marie Tharp’s maps and am a bit of an outlier).

Mapping Global Sea Levels at Even Finer Resolution

Published on by Jonathan Crowe

Launched in December 2022, the Surface Water and Ocean Topography (SWOT) satellite measures ocean surface topography—i.e., sea surface height. It recently completed its first full 21-day science orbit, which is represented in the above animated globe.

The animation shows sea surface height anomalies around the world: Red and orange indicate ocean heights that were higher than the global mean sea surface height, while blue represents heights lower than the mean. Sea level differences can highlight ocean currents, like the Gulf Stream coming off the U.S. East Coast or the Kuroshio current off the east coast of Japan. Sea surface height can also indicate regions of relatively warmer water—like the eastern part of the equatorial Pacific Ocean during an El Niño—because water expands as it warms.

Sea surface height has been measured by earlier satellites (previously); SWOT does so at a much greater level of detail.

The Deepest Map

Published on by Jonathan Crowe

Book cover: The Deepest MapOut today from HarperCollins (and Goose Lane in Canada): The Deepest Map: The High-Stakes Race to Chart the World’s Oceans by Laura Trethewey. “Scientists, investors, militaries, and private explorers are competing in this epic venture to obtain an accurate reading of this vast terrain and understand its contours and environment. In The Deepest Map, Laura Trethewey chronicles this race to the bottom. Following global efforts around the world, she documents Inuit-led crowdsourced mapping in the Arctic as climate change alters the landscape, a Texas millionaire’s efforts to become the first man to dive to the deepest point in each ocean, and the increasingly fraught question of whether and how to mine the deep sea.” Amazon (Canada, UK), Bookshop.

Marie Tharp as Google Doodle

Published on by Jonathan Crowe

Google Doodle of Marie Tharp (screenshot)

Marie Tharp is the subject of today’s Google Doodle, with an interactive narration of her life story. That story—how Tharp’s pioneering work mapping the ocean floor helped prove the theory of continental drift—is familiar to long-time readers of this blog: this is the 12th post I’ve made about the legendary cartographer. But someone is going to be one of today’s lucky 10,000 because of this, and that’s not a bad thing.

Ortelius was a Google Doodle in May 2018.

Extent of Tongan Eruption Revealed by New Seafloor Maps

Published on by Jonathan Crowe
Hunga Tonga-Hunga Ha'apai 3D bathymetry map
NIWA/Nippon Foundation TESMaP

Scientists have now mapped the seafloor around the Hunga Tonga-Hunga Ha‘apai volcano, and as a result we have learned just how massive the January 2022 eruption was. By comparing their soundings with 2017 data, they determined that at least 9.5 km3 of material was discharged. Debris was found 80 km from the volcano, and the volcano’s caldera has been replaced by a cavern 850 m deep. More from the NIWA media release and from ABC (Australia).

Previously: Remotely Operated Vessel Maps Tonga Caldera.

The Mediterranean’s Summer Heat Wave

Published on by Jonathan Crowe

Europe’s summer heat wave wasn’t just felt on land; the Mediterranean Sea saw surface temperatures as much as 5°C above the average. The ESA’s animated map, above, shows the difference between sea surface temperatures from March to August 2022 and the 1985-2005 average for those months. The redder, the hotter than average. [ESA]

Climate Change Could Affect Maritime Boundaries

Published on by Jonathan Crowe

Sea level rise and coral reef destruction could have an impact on international boundaries, according to a study by University of Sydney researchers published in Environmental Research Letters. Coral reefs form the basis for a number of claims on maritime zones, which could suddenly be in doubt if reef destruction or changes to a reef’s low-water line erase that basis. Press release.

The Gough Map and the Lost Islands of Cardigan Bay

Published on by Jonathan Crowe

Gough MapA paper in Atlantic Geoscience is basically arguing that the Gough Map offers evidence that the Welsh legend of the sunken kingdom of Cantre’r Gwaelod —a sort of Welsh Atlantis—is real. Actually, no. Not quite. That’s clickbait—and the headline for the BBC News story about the study.

In their paper, the complete text of which is available online, physical geographer Simon Haslett and professor of Celtic David Willis are trying to reconstruct the post-glacial evolution of Wales’s Cardigan Bay using historical and folklore sources as well as bathymetric data and geological evidence. (It’s pretty obvious which author contributed what.) The Gough Map shows two islands that don’t correlate to any real island in Cardigan Bay; the study suggests that the islands may have in fact existed and have since been lost to flooding, erosion and other post-glacial changes to the shorelines. There are several submarine highs in the bay that may match up with the lost islands. The paper hypothesizes that the Cantre’r Gwaelod legend is a folk memory from when the coast was much different: that there were islands in Cardigan Bay, that they disappeared during the human era, and this legend is one of their traces.

In other words, a bit different from taking an old map at entirely too much face value (which, to be sure, has been enough of a thing that it was first to mind when I saw the story). They’re using the map and the legend to try and figure out the shoreline’s history—not using the map to prove the legend.

Remotely Operated Vessel Maps Tonga Caldera

Published on by Jonathan Crowe
Aerial view of the Hunga-Tonga Hunga-Ha’apai (HT-HH) volcano, showing new multibeam depth data overlaid on a satellite image of the islands (deep depths in blue, shallow depths in red).
SEA-KIT/NIWA-Nippon Foundation TESMaP survey team

As part of the Tonga Eruption Seabed Mapping Project, a robotic vessel has conducted a bathymetric survey of the Hunga Tonga-Hunga Ha‘apai volcano’s underwater caldera. Said volcano, you will recall, erupted spectacularly last January. The 12-metre vessel, USV Maxlimer, was controlled remotely from 16,000 km away, and carried sensors to measure the state of the seabed, temperature, salinity, turbidity, dissolved oxygen and chemical plumes. More at the press release. BBC News coverage.

Previously: The Rise and Fall of Hunga Tonga-Hunga Ha‘apai; Hunga Tonga-Hunga Ha‘apai, Before and After; How Satellites Revealed the Hunga-Tonga Hunga-Ha‘apai Eruption.

Mapping Marine Microplastics

Published on by Jonathan Crowe
Maps of microplastics concentrations
NASA Earth Observatory (Joshua Stevens)

NASA Earth Observatory: “Researchers at the University of Michigan (UM) recently developed a new method to map the concentration of ocean microplastics around the world. The researchers used data from eight microsatellites that are part of the Cyclone Global Navigation Satellite System (CYGNSS) mission. Radio signals from GPS satellites reflect off the ocean surface, and CYGNSS satellites detect those reflections. Scientists then analyze the signals to measure the roughness of the ocean surface. These measurements provide scientists with a means to derive ocean wind speeds, which is useful for studying phenomena like hurricanes. It turns out that the signals also reveal the presence of plastic.”

Mapping Shallow Seafloors with Satellite Data

Published on by Jonathan Crowe
Seafloor map of Bermuda
David Lagomasino/East Carolina University

NASA Earth Observatory summarizes recent work in using satellite data to improve our maps of shallow seafloors—where the situation changes more often than traditional sonar methods can track—by, among other things, using a laser altimeter system on one of NASA’s satellites.

In 2021, Nathan Thomas and Lola Fatoyinbo of NASA’s Goddard Space Flight Center, along with colleagues from three countries, took another step by mating ICESat-2 measurements with images from Copernicus Sentinel-2 to derive bathymetry at better resolution. The team mapped the shallows down a depth of 26 meters (85 feet) around Biscayne Bay in Florida, the Gulf of Chania in Crete, and the island of Bermuda.

Thomas and colleagues compared their satellite-derived bathymetry with maps made from traditional topographic surveys, multibeam sonar, and nautical soundings. Their new maps had a resolution of 10 meters, improving upon the current 115-meter resolution dataset for Crete and the 30- to 90-meter datasets for Florida and Bermuda. The existing data for Florida and Bermuda are composites of lots of sources spanning 63 years, while the ICESat-2/Sentinel-2 maps offer a contemporary assessment of underwater structure.

See also this earlier Earth Observatory item from last year. (Deep water bathymetry is another thing: light can’t get down that far. But out-of-date soundings are less impactful on shipping.)

More on Marie Tharp

Published on by Jonathan Crowe

A new article on the life and career of Marie Tharp, written by our friend Betsy Mason, was published by Science News earlier this month. Plenty has been written about Tharp, whose work mapping the ocean floor helped provide the evidence for continental drift: numerous articles, a 2012 biography, two books for children just last year. But that doesn’t mean that there aren’t still people who still haven’t heard of her, and should.

Marie Tharp at 100

Published on by Jonathan Crowe

July 30 marks the 100th anniversary of the birth of pioneering ocean cartographer Marie Tharp, whose seafloor maps provided evidence of continental drift. Columbia University’s Earth Institute is marking the event with blog posts, interviews, workshops and other social media and multimedia activity. See, for example, this overview of her legacy by Marie Denoia Aronsohn and a reprint of Tharp’s own piece, “Connect the Dots: Mapping the Seafloor and Discovering the Mid-ocean Ridge.”

The anniversary probably explains why two books about Tharp, aimed at children, are coming out this year:

Ocean Speaks: How Marie Tharp Revealed the Ocean’s Biggest Secret
by Jess Keating
Tundra Books, 30 Jun 2020
Amazon (Canada, UK) | Apple Books | Bookshop


Marie’s Ocean
by Josie James
Henry Holt, 22 Sep 2020
Amazon (Canada, UK) | Apple Books

Add those to Robert Burleigh’s Solving the Puzzle Under the Sea: Marie Tharp Maps the Ocean Floor (2016), also aimed at young readers, and Hali Felt’s 2012 biography of Tharp (for adults), Soundings, which I review here.

Older posts about Marie Tharp can be found here.

Update, July 30: Suzanne O’Connell at The Conversation: “As a geoscientist, I believe Tharp should be as famous as Jane Goodall or Neil Armstrong. Here’s why.”