The Mediterranean’s Summer Heat Wave

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

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

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

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

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

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

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

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.”

Explore Zealandia

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]

Heinrich C. Berann

Henrich C. Berann, “Panorama of Denali,” 1994. U.S. National Park Service.

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.

Mapping Doggerland

The Guardian looks at efforts to map Doggerland, a prehistoric area of land in the North Sea between Britain and continental Europe that was submerged by rising sea levels at the end of the last ice age. “Using seabed mapping data the team plans to produce a 3D chart revealing the rivers, lakes, hills and coastlines of the country. Specialist survey ships will take core sediment samples from selected areas to extract millions of fragments of DNA from the buried plants and animals.”


I’ve been meaning to read Soundings, Hali Felt’s biography of Marie Tharp, since it came out in 2012. Since then I’ve seen a flurry of articles, interviews, videos and other tributes concerning Tharp, whose reputation, which grew during her lifetime, continues to grow in the 12 years since her death in 2006 at the age of 86.

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.

Physiographic Diagram: Atlantic Ocean

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

About the Spilhaus Projection

Le Cartographe

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).

Marie Tharp on the BBC World Service

Still another profile of ocean cartographer Marie Tharp, this time from the BBC World Service’s Witness program: it’s a nine-minute audio clip called “Mapping the Ocean’s Secrets.” [Osher]

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.”