The Seabed 2030 project announced on Saturday that “27.3% of the world’s ocean floor has now been mapped to modern standards. The increase in data represents more than four million square kilometres of newly mapped seafloor—an area roughly equivalent to the entire Indian subcontinent.” The above map shows the progress to date, with new bathymetric data added over the past year indicated in red. Data compiled by this project is freely available via GEBCO’s global grid.
The National Maritime Museum in Greenwich, London has a new attraction. “The Ocean Map is a giant, 440m2 floor map that turns our view of the world inside out. While most world maps focus on countries and continents, the Ocean Map is all about water.” You can probably see where this is going: the Museum’s floor map uses the Spilhaus projection. Here’s a preview from before the hall in which it’s situated reopened on June 7:
I'm genuinely SO excited about the new ocean map that will be at the heart of the National Maritime Museum in Greenwich when this hall reopens on June 7th. It's an unusual ocean-focussed map with so much detail, and it's just brilliant. 🌊🌊 Here's a sneak peak.www.rmg.co.uk/stories/ocea…
Because geologic features like seamounts and abyssal hills have more mass than their surroundings, they exert a slightly stronger gravitational pull that creates small, measurable bumps in the sea surface above them. These subtle gravity signatures help researchers predict the kind of seafloor feature that produced them.
[…] Through repeated observations, the satellite is sensitive enough to pick up these minute differences, with centimeter-level accuracy, in sea surface height caused by the features below. David Sandwell, a geophysicist at Scripps Institution of Oceanography, and his colleagues used a year’s worth of SWOT data to focus on seamounts, abyssal hills, and underwater continental margins, where continental crust meets oceanic crust.
[…] Areas of decreased gravity (purple) are affiliated with depressions on the seafloor, while areas of increased gravity (green) indicate the locations of more massive, elevated features.
Only about a quarter of the seafloor has been mapped with traditional sonar methods, so you can see how a gap is being filled here. Next up is calculating the depth of the features being detected through this method.
Pacific nations like Fiji, Kiribati and Tuvalu will face at least 15 cm of sea level rise over the next 30 years, according to a NASA analysis. “In addition to the overall analysis, the agency’s sea level team produced high-resolution maps showing which areas of different Pacific Island nations will be vulnerable to high-tide flooding—otherwise known as nuisance flooding or sunny day flooding—by the 2050s. Released on Sept. 23, the maps outline flooding potential in a range of emissions scenarios, from best-case to business-as-usual to worst-case.” [Universe Today]
A feature article by Cullen Murphy in The Atlantic’s November 2024 issue [Apple News +] explores the oceanic pole of inaccessibility—the point on the globe furthest from any land. Known as Point Nemo, it’s at a spot in the South Pacific nearly 2,700 km from the nearest island where the weather is beyond fierce, the water so lacking in nutrients it’s a biological desert, and the closest human beings are often the astronauts in the International Space Station, which passes 250 km overhead every day. (That’s not a coincidence, by the way: Point Nemo will eventually be the ISS’s final resting place. The surrounding oceans have become a spaceship graveyard, a preferred target for controlled deorbits, precisely because they’re so far from land.)
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]
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).
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.
Out 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 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.
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).
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]
Out today from 
