Why the Oceans Matter

[GordMay]

Why the ocean matters [to everyone, but especially to Cruisers]
Our oceans are not only victims of pollution & climate change, they are also a vital part of the solution(s).

The ocean, which makes up more than 70 percent of the planet’s surface, is where life on Earth first emerged. It continues to allow life to flourish, both in the waters, and on land: marine phytoplankton have produced about half of the world’s oxygen, meaning every second breath we take, came from the ocean.

The ocean has greatly slowed the rate of climate change. It is a powerful carbon sink [takes in more carbon than it releases]. Absorbing a quarter of the carbon dioxide (CO2), released, since humans started burning fossil fuels. At the surface, the ocean absorbs and releases heat, as well as carbon dioxide; the phytoplankton living near the top of the water column absorb as much carbon dioxide, through photosynthesis, as the world’s forests and plants do.
It has also trapped an estimated 90% of the excess heat, created by climate warming gasses.

But, at a cost.
The ocean has also warmed, lost oxygen and acidified, currents are changing, and sea levels are rising. To continue along this path not only threatens marine ecosystems, but also, the future ability of the ocean to indirectly support life.

And, of course, the oceans are ‘home’, to many of us Cruisers.

UNESCO State of the Ocean Report 2022 (Last update:20 April 2023)
➥ https://unesdoc.unesco.org/ark:/48223/pf0000381921


A two-part documentary, from Naked Science*

“How Humans Are Shaping The Destiny Of Our Oceans” ~ Naked Science
➥ https://youtu.be/7SxNcMqjc04

“In unprecedented ways, humans are changing our seas and the life within. Ocean Autopsy takes us on a journey to carry out an 'autopsy' on the ocean itself, where leading oceanographer Dr Helen Czerski, along with zoologist Dr George McGavin, will reveal the startling changes it's undergoing.

Two thirds of our planet is covered in water, split into five distinct oceans, but in reality, they are part of one huge global water system. This system has been instrumental in shaping our destiny for millions of years. But now, in the 21st century, it's humankind that is shaping the destiny of our oceans. In this first episode, we look at the impact that pollution is having on the quality of our ocean water as well as the damage it is doing to our wildlife, such as dolphins.”

Are We Destroying The Ocean For Future Generations?” ~ Naked Science
➥ https://youtu.be/WUJKlYt0HUc

“In the second and final part of this documentary, we continue to look at the impact that the rest of our human footprint is having on the world as whole as well as the ocean. Will we be able to restore the ocean by 2030? What will the consequences be for the future generations? In unprecedented ways, humans are changing our seas and the life within. Ocean Autopsy takes us on a journey to carry out an 'autopsy' on the ocean itself, where leading oceanographer Dr Helen Czerski, along with zoologist Dr George McGavin, will reveal the startling changes it's undergoing.”

* Subscribe to Naked Science, the channel dedicated to bringing you the world of science and technology. ➥ http://goo.gl/wpc2Q1

[denverd0n]

Unfortunately, I suspect that anyone who needs to be TOLD that the oceans matter, is someone who won't really care.

[GordMay]

Originally Posted by denverd0n

Unfortunately, I suspect that anyone who needs to be TOLD that the oceans matter, is someone who won't really care.

Perhaps, some might be interested in WHY/HOW* the Oceans matter. [66 views, in < 10 min.]
Perhaps not.

* In what manner - the mechanisms.

"It's not that the wind is blowing - it's what the wind is blowing" ~ Ron White

[GordMay]

A minor ocean warming, could cause a rapid shift in ocean currents, imperiling the Ross Ice Shelf [world’s largest], and coastal cities

Several thousand years ago, the Ross Ice Shelf, and the glaciers feeding it, thinned dramatically, causing sea level to rise.
A new study [1], suggests this was triggered by a rearrangement of ocean currents, set off by a minor amount of ocean warming [half a degree Celsius].

Many people assumed the Ross Ice Shelf had been stable since the close of the last ice age, roughly 12,000 years ago. But, in 2018, scientists reported [2] that it and the glaciers behind it had substantially thinned, and retreated, before eventually growing back.

A few years later, glaciologists reported [3] that this temporary retreat was actually caused by a slight warming, from 7,000 to 1,600 years ago.

If the Ross Ice Shelf retreated today, it would open a crucial back door to the West Antarctic Ice Sheet [already losing substantial ice from Thwaites and Pine Island Glaciers]. allowing warm ocean currents to melt it, from two sides. If the sheet melted entirely, it would raise sea levels enough to put Miami; Newark, N.J.; Charleston, S.C.; and the Bahamas underwater, at high tide [ruining many docks, and deepening all our anchorages].

Currently, the Ross Ice Shelf is shielded from that melting, by a natural oceanic conveyor belt. It operates just beyond the shelf’s outer, ocean-facing edge. As ocean water migrates through this area, bitter-cold air causes its surface to freeze, forming a steady procession of metre-thick sea ice.

As the sea ice forms, it ejects salt. The water beneath it becomes saltier and denser, and sinks. Roughly 30,000 cubic kilometres of this cold, dense water forms each year — more than four times the annual flow of the Amazon River. It sinks to the seafloor like a steady waterfall where the outer edge of the ice shelf meets the ocean, blocking the entry of warm water from further north. That’s why we see low melt rates there, today.

The researchers found [1] that just 0.4°C or 0.5°C of ocean warming would have greatly slowed the formation of sea ice, in front of the Ross Ice Shelf. This would have weakened the cold, salty waterfall, protecting the ice shelf, allowing warmer water further off the coastline to intrude under it.

If this happened today, it would commit humanity to a gradual, but dramatic, rise in sea level, over the coming centuries. The glaciers behind the Ross Ice Shelf hold enough ice to raise sea level by roughly 2 metres.

[1] “Ocean cavity regime shift reversed West Antarctic grounding line retreat in the late Holocene” ~ by Daniel P. Lowry et al
➥ https://www.nature.com/articles/s41467-024-47369-3

[2]“Extensive retreat and re-advance of the West Antarctic Ice Sheet during the Holocene” ~ by J. Kingslake et al
➥ https://www.nature.com/articles/s415...ciencenews.org

[3] “Did Holocene climate changes drive West Antarctic grounding line retreat and readvance?” ~ by Sarah U. Neuhaus et al
➥ https://tc.copernicus.org/articles/15/4655/2021/

[rls8r]

Good stuff, GordMay, thanks! Glad to see such topics making their way to Cruisers Forum. My undergraduate degree is in Marine Sciences and I later studied some oceanography under Prof. Heinrich Holland in the mid-70s. All this is near and dear to my heart (and psyche).

It's good that you mention the Antarctic situation, but another interesting physical phenomenon that may be adversely influenced by human activities is the potential melting of the Greenland ice sheet and its effect on the Meridional Overturning Circulation. Changing that circulation could have very serious consequences for Europe (and elsewhere) beyond sea level rise.

Getting away from the scientific aspects of why oceans are important, I think that sociological and historical aspects also are interesting. I always thought it interesting that Benjamin Franklin 'discovered' the Gulf Stream after being puzzled by why mail seemed to take longer to get from England to the Colonies than it did for merchant ships to get from the Colonies to England.

It's also interesting why the Grand Banks fisheries were so plentiful, and why Wood's Hole Oceanographic Institute (one of the finest in the world) is located where it is. Try reading Mark Kurlansky's Cod: A Biography of the Fish that Changed the World. Note that one of the ten Articles of the Treaty of Paris (1783) - which officially ended the Revolutionary War and formed the United States from the Colonies - ensured that Americans could continue to take fish from the Grand Banks and other Newfoundland banks. That's how important those fisheries were to the Colonists. Sad to think that cod fishing was halted in Newfoundland in the early 1990s due to depletion of stock. Cod were placed on the Endangered Species list in 2000 and are still listed as 'vulnerable' to extinction.

On another note ... you may be interested in picking up a copy (or an audible book) of Simon Winchester's Atlantic. He also wrote one about the Pacific, but I didn't find it as interesting as he focused a lot on the wars and entrepreneurs associated with the Pacific rather than the ocean.

Thanks again!

[GordMay]

Originally Posted by rls8r

“... Sad to think that cod fishing was halted in Newfoundland in the early 1990s due to depletion of stock. Cod were placed on the Endangered Species list in 2000 and are still listed as 'vulnerable' to extinction...”

Indeed; however, I’d have phrased it a little differently:
“Sad to think that overfishing [& and natural and fishing-induced changes to the ecosystem] depleted the cod stock [97% since the early 1970s, and more than 99% since the early 1960s] ...”

“Assessment and Update Status Report on the Atlantic Cod in Canada” ~ by COSEWIC
➥ https://www.sararegistry.gc.ca/virtu...ntic_cod_e.pdf

“Newfoundland and Labrador population - Endangered
Laurentian North population - Threatened
Maritimes population - Special Concern
Arctic population - Special Concern
...”