Posts Tagged ‘oceans’
“It is by the deep, hidden currents that the oceans are made one”*…
A significant part of the earth’s climate infrastructure is under threat. New research suggests the Atlantic Meridional Overturning Circulation (or AMOC) could weaken by half this century with wide ranging consequences for weather, food, and sea levels across the world. Alison Smart and Charlotte Venner unpack the past and ponder the future of this critical ocean current…
London, England, and Quebec City, Canada sit at roughly the same latitude (51°N and 47°N, respectively) but have vastly different climates. Historically, Quebec City had 99 freezing days in an average year—weather you might expect from its relative proximity to the Arctic—but London only experienced three freezing days in an average year, despite being slightly further north. This difference is largely due to an ocean current called the Atlantic Meridional Overturning Circulation (AMOC), which distributes warmth from the Tropics via the Atlantic Ocean.
Now, impacts from climate change are weakening the AMOC, and it could collapse entirely in the near future. AMOC collapse would rapidly make regions of the Northern Hemisphere with historically mild weather colder and harsher, while triggering irreversible changes in the global climate.
The AMOC is both the product of a stable climate and a factor in maintaining weather patterns around the planet. To plan for future scenarios, we need to first understand how the AMOC works and what might happen if it collapses…
[Smart and Venner explain the AMOC and outline the ways in which it shapes the climate of regions around the world…]
… Even minor weakening of the AMOC can significantly impact local climates, as has happened several times in the past 12,000 years. A “Little Ice Age” occurred in Europe in the Middle Ages, likely connected to a disruption in the AMOC. Just a slight slowdown in the AMOC could make Europe colder overall, disrupt global precipitation patterns from South America to India, and worsen drought in Africa.
The more freshwater pours into the ocean, and the more ocean temperatures rise, the weaker the AMOC becomes—until, at some threshold, it could stop moving altogether.
It is possible that the AMOC will collapse entirely if warming continues. There is no agreed-upon global average temperature at which collapse becomes certain, but there are signals we can track and historical examples we can examine to predict the likelihood of collapse…
… The consequences of total AMOC collapse would be far-reaching, severe, and irreversible on timescales relevant to humans. AMOC collapse would cool parts of the Northern Hemisphere and warm parts of the Southern Hemisphere by multiple degrees Celsius and drastically alter weather around the world.
In Europe, winter temperatures would drop, cold snaps could increase, and winter storms would intensify. A 2025 research letter found that, even if global warming reached 2°C, AMOC collapse would make Europe colder than it is today, creating extreme winters in Northwestern Europe in which record cold might reach -20°C (-4°F) in London and -50°C (-58°F) in Scandinavia. Even milder cold days would increase, with approximately 150 to 180 frost days per year in Utrecht, Netherlands, compared to a historic average of about 53. Precipitation would likely shift and decrease, potentially drying out some parts of Europe and making others wetter.
Around the world, other climates would change, likely in less extreme ways.
- North America. The East Coast of North America would likely experience rapid sea level rise as the gravitational pull of the AMOC weakens, as well as cooler conditions, with some parts of Eastern Canada and the North Atlantic coast cooling by several degrees Celsius, erratic storms, weather variability, and more intense hurricanes.
- Tropics & South America. Without the AMOC, the ITCZ would shift south, potentially leading to drying in the Northern Tropics and parts of the Amazon and wetter conditions in the Southern Tropics.
- Africa. Because of the shift in the ITCZ, West Africa and the Sahel would be much drier, experiencing severe and frequent drought and reduced rainy seasons. The Sahel could possibly transition from a semi-arid climate to hot dry desert.
- Asia. Because of the shift in the ITCZ, weakened and more erratic monsoons in Asia would lead to increased drought and a higher risk of extreme precipitation events.
These changes may occur rapidly, create climate risks, and cause systemic disruption in affected regions. The collapse of the AMOC would also be a tipping point in the global climate, meaning that the changes would likely be difficult, if not impossible, to reverse on human timescales.
Once the AMOC passes a critical threshold of weakening, called a tipping point, it would continue to weaken until it collapses. AMOC collapse could also create systemic impacts that activate other tipping points as well as feedback loops that could generate further warming.
For example, if AMOC collapse contributed to changes like a permanent dieback of the Amazon Rainforest or increased ice loss, those changes would generate their own warming effect on Earth’s climate. A 2026 paper suggests that AMOC collapse would result in substantial carbon release from oceans and add around 0.2°C in additional atmospheric warming.
Reducing greenhouse gas emissions may slow warming enough to reduce weakening and delay collapse. If collapse begins, it is unlikely we could stop it. There is no feasible technological way to reengineer ocean currents…
A bracing, but important read: “A complete guide to the Atlantic Meridional Overturning Circulation (AMOC).”
See also: “What would happen if the Atlantic Meridional Overturning Circulation (AMOC) collapses? How likely is it?”
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As we put on our sailin’ shoes, we might send interconnected birthday greetings to Andrew Sharrett; he was born on this date in 1946. An archaeologist, his application of world-systems theory to questions of change on large, often global, scale made him one of the most influential archaeologists of the late 20th/early 21st centuries. Sharrett is best known for his theory of the secondary products revolution; but his work touched on a broad range of fundamental human developmental issues: global migration and colonization, the spread of agriculture, the development of metallurgy and urbanism, and the development of new forms of consumption, to name a few. All of those dynamics were, as Sharrett observed, shaped in significant ways by the climatic conditions in which they unfolded.
“We can only sense that in the deep and turbulent recesses of the sea are hidden mysteries far greater than any we have solved.”*…
A new study finds that the vast majority of the deep sea floor remains undocumented. Nell Greenfieldboyce report…
Bizarre creatures like vampire squid and blobfish make their home in the dark, cold, depths of the deep sea, but most of this watery realm remains a complete mystery.
That’s because humans have seen less than 0.001% of the globe’s deep seafloor, according to a new study.
In fact, the area of the deep seafloor that’s been directly visualized is roughly equivalent to the state of Rhode Island, researchers report in the journal Science Advances.
Maps created with tools like sonar can show the shape of the seafloor, but it’s much harder to send cameras down beyond 200 meters, or more than 656 feet, where sunlight begins to fade rapidly and the waters turn cold and dark. This is the region of the ocean that’s considered “deep.”
“The fact of the matter is, when you’re down there with a remotely operated vehicle or other sort of deep-submergence vehicle, you can only see a very tiny bit of the deep sea floor at any one time,” says Katy Croff Bell of the nonprofit Ocean Discovery League, who led this new research…
… To try to get a better accounting of the total area of the deep seafloor that’s been observed so far, she and her colleagues created a database of all known efforts. They found records of more than 43,000 trips down, starting in 1958, with everything from robotic vehicles to human-driven subs to simple landers that didn’t move around.
It turns out that most of the exploratory expeditions occurred within 200 nautical miles of the United States, Japan, and New Zealand. Those three countries, along with France and Germany, led nearly all of the efforts.
As a result, scientists really haven’t seen a very representative sample of what’s going on around the globe…
… Bell says we don’t know what habitats might yet be discovered — and that even though the deep ocean might be out of sight and out of mind for most people, the currents down there bring oxygen and key nutrients up towards the surface.
“All of these things are connected, and impact us in so many different ways,” she says.
What little has been explored beneath the deep ocean suggests that it can have dramatically different ecosystems that support very different kinds of living things. Already, in the ocean, explorers have seen hot hydrothermal vents, alkaline vents, and cold seeps.
“But given how little we’ve seen and how biased it is, we can’t really give you a global map of all the habitats of the deep sea, because we just haven’t been to all of them,” she says.
Past explorations to the deep have revealed completely unexpected forms of life. For example, in the 1970’s, researchers discovered microbes at hydrothermal vents that did not depend at all on the sun and photosynthesis, and instead got their energy from chemical reactions.
“That was completely revolutionary and completely rewrote all the science books,” she says.
Geologist and deep sea expert Jeffrey Karson of Syracuse University, who wasn’t part of this research team, says this is the first time he’s ever seen a well-documented number that really encapsulates what’s been seen of the deep ocean floor so far.
He would have assumed the area seen by humanity was less than 1% of the total, he says, but was still surprised the faction would be “such a tiny number.”
“We’re spending a lot of money to try to understand other planets, maybe planets outside of our solar system. And yet right here on our own planet, we know so little of what’s going on in this area that covers about two-thirds of our planet,” says Karson. “Almost every time we go there, we learn something new and exciting, and many of our discoveries on the seafloor have been serendipitous. So, you know, we’re feeling our way in the dark, literally, there.”..
We’re asleep to the deep: “Humans still haven’t seen 99.999% of the deep seafloor,” from @ngreenfieldboyce.bsky.social and @npr.org.
* Rachel Carson, The Sea Around Us (1951)
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As we dive deep, we might spare a thought for Robert S. Dietz; he died on this date in 1995. A marine geologist, geophysicist, and oceanographer with the United States Coast and Geodetic Survey, he developed (in 1961) a theory of seafloor spreading (a term he coined), in which new crustal material continually upwells from the Earth’s depths along the mid-ocean ridges and spreads outward at a rate of several inches per year.
“There is a limit to thinking about even a small piece of something monumental”*…
Still, we can try…
Via Jason Kottke, who is reminded…
of Ben Terrett’s calculation of how many helveticas from here to the Moon and my subsequent calculations about the point size of the Earth and the Moon (50.2 billion and 13.7 billion, respectively).
* Jeff VanderMeer, Annihilation
As we size up scale, we might recall that it was on this date (the feast day of St. Mary Magdalene) in 1342, that Central Europe’s worst flood ever occurred. Following the passage of a Genoa low, the rivers Rhine, Moselle, Main, Danube, Weser, Werra, Unstrut, Elbe, Vltava, and their tributaries inundated large areas. Many towns such as Cologne, Mainz, Frankfurt am Main, Würzburg, Regensburg, Passau, and Vienna were seriously damaged, with water levels exceeding those of the 2002 European floods. Even the river Eider north of Hamburg flooded the surrounding land; indeed, the affected area extended to Carinthia and northern Italy.
“Who that goeth on Pilgrimage but would have one of these Maps about him, that he may look when he is at a stand, which is the way he must take?*…
Carta Marina, by Olaus Magnus, 1539
Johannes Gutenberg printed his first Bible in 1455, and the first published sailing directions appeared thirty-five years later. Print media encouraged the divergence of navigational information from material discussing the commercial prospects of trade at various ports. Printing promoted the widespread distribution of geographic and hydrographic information, including maps, to readers throughout Europe at a time when literacy was on the rise and the spreading use of vernacular languages made such works available to non-scholars…
Europe’s explorers actively sought and exploited both academic knowledge and geographic experience in their systematic search for new trade routes. Use of the sea ultimately rested on reliable knowledge of the ocean. Fresh appreciation for empirical evidence fueled recognition of the value of experience, and the process of exploration included mechanisms for accumulating and disseminating new geographic knowledge to form the basis for future navigation.
At the outset of the discovery of the seas, portolan charts recorded actual experiences at sea. These navigational aids provided mariners with compass direction and estimated the distance between coastal landmarks or harbors. Utterly novel for their time, portolans were the first charts to attempt to depict scale. Portolans created by fourteenth- and fifteenth-century explorers document Portuguese and Spanish discovery of Atlantic islands and the African coast and helped subsequent mariners retrace their steps. Accuracy of portolans was best over shorter distances, and they became less useful when navigators steered offshore.
In contrast to creators of portolans, armchair cartographers compiled world maps of little use for actual navigation but which reflected shifting knowledge of oceans. While manuscript maps had been produced alongside written manuscripts since antiquity, the earliest known printed map was included in an encyclopedia of 1470. It represents the world schematically within a circle, in which the three continents of Asia, Europe, and Africa are surrounded by an ocean river and separated from each other by horizontal and vertical rivers that form a T shape—hence the name “T-O” to describe this kind of map. Other early maps were based on Ptolemy’s work, on biblical stories or other allegories, or occasionally on portolans…
Although the majority of medieval maps and nautical charts of the Age of Discovery did not include sea monsters, the ones that do reveal both a rise of general interest in marvels and wonders and a specific concern for maritime activities that took place at sea, including in far distant oceans. The more exotic creatures are often positioned on maps at the edge of the Earth, conveying a sense of mystery and danger and perhaps discouraging voyages in those areas. Images of octopuses or other monsters attacking ships would seem to be warning of dangers to navigation…
An excerpt from a fascinating essay on how cartographers saw the– mostly blue– world in the Age of Discovery; read it in full at “Mapping the Oceans.”
* John Bunyan, The Pilgrim’s Progress
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As we find our way, we might light a birthday candle for Sir Francis Bacon– English Renaissance philosopher, lawyer, linguist, composer, mathematician, geometer, musician, poet, painter, astronomer, classicist, philosopher, historian, theologian, architect, father of modern science (The Baconian– aka The Scientific– Method), and patron of modern democracy, whom some allege was the illegitimate son of Queen Elizabeth I of England (and other’s, the actual author of Shakespeare’s plays)… He was in any event born on this date in 1561.
Bacon (whose Essays were, in a fashion, the first “management book” in English) was, in Alexander Pope’s words, “the greatest genius that England, or perhaps any country, ever produced.” He probably did not actually write the plays attributed to Shakespeare (as a thin, but long, line of enthusiasts, including Mark Twain and Friedrich Nietzsche, believed). But Bacon did observe, in a discussion of sedition that’s as timely today as ever, that “the remedy is worse than the disease.”
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