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).

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.

Well, that’s one way to visualize the rate of continental drift.

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.

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.

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]

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.

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.

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.”

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.)

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.”

Zealandia (Te Riu-a-Māui) is the name given to a proposed, and largely submerged eighth continent, of which New Zealand (Aotearoa) is the largest above-water remnant. Explore Zealandia is geoscience company GNS Science’s web portal to their maps of this largely submerged continent, including bathymetry, tectonics, and other data; the data is also available for download. [WAML]

I can’t believe that, other than a brief mention in 2010, I’ve never written anything about the cartographic artist Heinrich C. Berann (1917-1992), whose work includes panoramic paintings for National Geographic and, in his later years, for the National Park Service. (To be honest, they remind me of Jim Niehues’s ski resort maps, but that surely should be the other way around.) He also worked with Marie Tharp and Bruce Heezen to turn their physiographic maps of the ocean floor into works of art.

Some links: Kottke looks at his panoramic paintings; so did All Over the Map last year. Also last year, The Map Designer has examples from Berann’s entire career. This site is maintained by one of Berann’s grandsons.

The bare bones of Tharp’s story are therefore fairly well known: while mapping the floor of the Atlantic Ocean, she discovered the presence of the Mid-Atlantic Ridge—and, more specifically, its rift valley, providing tangible evidence of continental drift. Because continental drift was at that point considered to be a crackpot theory, it took some doing for Tharp’s discovery to be accepted; and when it was her contributions were to some extent minimized.

While Felt’s book is positioned as a biography, its strength is in the details of that pivotal discovery: how and where it was made, and by whom, and in what context. Tharp’s work was not done in a vacuum, and how and why she was where she was is important. Felt sets the stage for us: not only does she take us through Tharp’s early childhood and rather variegated education and her arrival in 1948 at the Lamont Observatory, she gives us a short history of that Observatory, of the theory of continental drift, of her colleagues—notably her lifelong collaborator (and possibly life partner) Bruce Heezen and Observatory director (and sometime antagonist) Maurice Ewing. More than anything else, Soundings provides context for Tharp’s discovery: by the time we’re done, we know how important it was, and why. We’ve been well briefed.

Felt is less successful in building a portrait of Tharp herself. Some areas of her non-work life—her childhood, family and college education, for example—are extremely well covered, but other areas have considerable gaps, particularly those involving her personal life. The nature of Tharp’s relationship with Heezen is only hinted at, as is an early, unsuccessful marriage to someone else. Her later life, supported by a motley gang of eccentrics called Tharpophiles, is also incompletely covered. The elisions, however unintended, are frustrating. I suspect the author was a prisoner of her source material, which in places she follows very closely; I would have liked it if more had been done to fill in the gaps.

Soundings was published in hardcover by Henry Holt in 2012. It’s available in paperback and ebook from Picador.

Amazon | iBooks

This image went a bit viral earlier this week. Some context. It’s from an August 2015 blog post at Le Cartographe, in which Alexandre Nicolas discussed (and rendered, above) a projection produced in 1942 by South African oceanographer Athelstan Spilhaus. In Spilhaus’s oceanic projection, centred on Antarctica, the world’s oceans form a single, uninterrupted body of water. Which, you know, it is. The continents form the edges of the map; there is … some … spatial distortion. As Alexandre wrote in 2015, “This projection is rarely used and it’s a real shame!”

Previously: The Penguin Projection (speaking of Antarctica-centred projections).

On the WMS Facebook group, Bert Johnson had this to say about this latest profile: “Hers is a standout story, but I wish some of these journalists who keep running these would spend some time and effort discussing some of the other women—known and unknown—who made contributions and helped open the doors of cartography to women.”

This short video does a good job explaining the coastline paradox, which basically results from coastlines being fractal, and the length of a coastline can vary quite a lot depending on the method you use to measure it. More at Mental Floss. [WMS]

NASA Earth Observatory:

Global sea level rise has been accelerating in recent decades, according to a new study based on 25 years of NASA and European satellite data. This acceleration has been driven mainly by increased ice melting in Greenland and Antarctica, and it has the potential to double the total sea level rise projected by 2100[. …]

The rate of sea level rise has risen from about 2.5 millimeters (0.1 inch) per year in the 1990s to about 3.4 millimeters (0.13 inches) per year today. These increases have been measured by satellite altimeters since 1992, including the TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3 missions, which have been jointly managed by NASA, France’s Centre national d’etudes spatiales (CNES), the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), and the U.S. National Oceanic and Atmospheric Administration (NOAA). The maps on this page depict the changes in sea level observed by those satellites between 1992 and 2014.

The Australian government has released high-resolution sea floor map data of the Great Barrier Reef; the data improves the view of the relief by a factor of eight, from 250-metre resolution to 30-metre resolution. The result of a collaboration between James Cook University, Geoscience Australia and the Australian Hydrographic Service, the data “can be used for policy, planning and scientific work. For example, this data is an important input for oceanographic modelling, which we can use to enhance our knowledge of climate change impacts, marine biodiversity, and species distribution.” Press release, data files.

Comparing century-old maps of kelp beds in the Pacific Northwest to modern aerial surveys, a University of Chicago professor was able to track the long-term abundance and health of the beds, which in most cases remained remarkably constant: Journal of Ecology article. The kelp bed maps, made from surveys in 1911 and 1912, were the result of U.S. concern about the nation’s potash supply, which in the runup to World War I was largely imported from Germany. The kelp beds were, for some reason, seen as an alternative fertilizer source. That plan never came to fruition, but the maps remained, to be put to use for an entirely different purpose more than a century after they were made. [WMS]

Audobon Alaska’s Ecological Atlas of the Bering, Chukchi, and Beaufort Seas maps the environment, biota and wildlife in the three seas surrounding the Bering Strait, as well as the human activity that puts them at risk. The cartography is by Daniel Huffman and not by coincidence excellent. It’s available for download as PDF files, either chapter-by-chapter or a whopping 125-megabyte single download; a print copy costs $125 with shipping and handling. [NACIS]

In the 1770s British surveyor George Gauld mapped the Florida Keys, taking careful note of the location and depth of Florida reefs. A study published last month in Science Advances compares Gauld’s maps with modern-day satellite imagery and concludes that half of the area occupied by coral in the eighteenth century has disappeared. As the Washington Post reports, the cause of the coral’s disappearance is unclear, though several potential human and natural factors are put forward. [WMS]

Marie Tharp, who died in 2006, has never been more in the public eye. This short film for the Royal Institution, animated by Rosanna Wan and narrated by Helen Czerski, is the fourth profile I’ve seen of her within the past year. [National Geographic]