Ninety percent of the heat from global warming occurs in the Ocean, which is leading to a regime shift in the Arctic where billions of animals in the deep cold eco-system perish in massive die-offs. At the same time, species unable to establish themselves in previously icy waters move in. This eco-system that had been stable for thousands of years while able to survive brief shifts in temperatures is in the midst of "an irreversible transition."
Susanne Rust writes in the LA Times.
Forces profound and alarming are reshaping the upper reaches of the North Pacific and Arctic oceans, breaking the food chain that supports billions of creatures and one of the world's most important fisheries.
In the last five years, scientists have observed animal die-offs of unprecedented size, scope and duration in the waters of the Beaufort, Chukchi and northern Bering seas, while recording the displacement and disappearance of entire species of fish and ocean-dwelling invertebrates. The ecosystem is critical for resident seals, walruses and bears, as well as migratory gray whales, birds, sea lions and numerous other animals.
Historically long stretches of record-breaking ocean heat and loss of sea ice have fundamentally changed this ecosystem from bottom to top and top to bottom, say researchers who study its inhabitants. Not only are algae and zooplankton affected, but now apex predators such as killer whales are moving into areas once locked away by ice—gaining unfettered access to a spoil of riches.
Scientists describe what's going on as less an ecosystem collapse than a brutal "regime shift"—an event in which many species may disappear, but others will replace them.
Scientists have reported the deaths of migrating gray whales, seals, walrus, sea lions along with "large die-offs—or "wrecks," as avian biologists call them—in dozens of seabird species including horned puffins, black-legged kittiwakes, and shearwaters."
Due to the "cold pool" in the Bering Sea, which prevented non-native species from moving into the deep cold water of the Bering Sea for thousands of years, it has weakened. The result is that species such as snow crab and Arctic cod are disappearing while Sub-Arctic species move in vast numbers to replace them.
Non-native species introduce diseases that native species have never faced before. Orca now swims freely in the Arctic ocean; they kill narwhals and beluga because they no longer have enough sea ice to protect them from annihilation by predation. Algae blooms, the base of the food chain, is becoming denser, more toxic and, increasing in frequency.
"We're used to change around here," said Alexus Kwatchka, a commercial fisherman who has navigated Alaskan waters for more than 30 years. He noted some years are cold, some are warm; sometimes all of the fish seem to be in one area for a few years, and then resettle elsewhere.
This fall has been extremely cold in Alaska; the town of Kotzebue, in the northwest, hit minus-31 degrees on Nov. 28—the record low for that date. This follows several years of record-setting warmth in the region.
What is new, said Kwatchka, is the persistence of this change. It's not like it gets super warm for one or two years and then goes back to normal, he said. Now the changes last, and he said he's encountering things he's never seen before—such as gray whales feeding along the beaches of Kodiak, or swimming in packs.
Dozens of scientists validated Kwatchka's observations, describing these periods of intense ocean heat and cooling as "stanzas," which are growing more extreme and lasting longer than those of the past.
That's a problem, said Duffy-Anderson, because the longer you stress a system, the deeper and broader the impacts—and therefore the harder for it to bounce back.
Because of intensive heating from climate change, the ice-cold waters of the Arctic are unlikely to recover from the damage humans caused. The world will be an uglier and sadder place because of it.
Guest post: The threat of high-probability ocean 'tipping points'
The ocean is a giant reservoir of heat and carbon. Since the beginning of the industrial revolution, the oceans have taken up around 30-40% of the carbon dioxide (CO2) and 93% of the heat added to the atmosphere through human activity.
Without ocean uptake, the scale of atmospheric warming would already be much larger. But this comes with a high cost in the form of ocean warming, acidification – where the alkaline ocean becomes more acidic – and deoxygenation – where the oxygen content of the ocean falls.
The potential impact of these processes on the marine environment is well documented. However, in some cases, they could trigger a number of regional tipping points with potentially widespread consequences for marine ecosystems and ocean functioning.
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