Alfred Tennyson wrote:We are not now that strength which in old days
Moved earth and heaven, that which we are, we are;
One equal temper of heroic hearts,
Made weak by time and fate, but strong in will
To strive, to seek, to find, and not to yield.
Newfie wrote:A floating mass of seaweed stretching from West Africa to the Gulf of Mexico is now the biggest seaweed bloom in the world, according to satellite observations.
The algal explosion in the Atlantic Ocean and Caribbean Sea could signify a new normal, say US scientists.
Deforestation and fertiliser use are among the factors thought to be driving the growth
https://www.bbc.com/news/science-environment-48869100
For long periods animals in ancient oceans could live only in shallow surface waters, above vast 'dead zones' inhabited only by anoxic bacteria, writes Richard Pancost. Human activity is now creating immense new dead zones, and global warming could be helping as it reduces vertical mixing of waters. Could this be the beginning of something big?
Maryland scientists have been warning of a growing "dead zone" in the Chesapeake Bay. Now the numbers are in, confirming their dire warnings were correct.
Natural Resources Department data shows an area with little to no oxygen spread to 2 cubic miles (8 cubic kilometers) by late July, making it one of the worst in decades. By comparison, July dead zones averaged about 1.35 cubic miles (6 cubic kilometers) for the past 35 years. The worst section includes the lower Potomac and Patuxent rivers and much of the Bay, from Baltimore to the mouth of the York River.
University of Maryland environmental scientists say heavy rains washed wastewater and agricultural runoff into the bay and produced oxygen-stealing algae. Scientists fear it could harm crabs, oysters and the state's seafood industry
When he introduced carbon dioxide at greater rates, he found that once the levels crossed a critical threshold, the carbon cycle reacted with a cascade of positive feedbacks that magnified the original trigger, causing the entire system to spike, in the form of severe ocean acidification.
The system did, eventually, return to equilibrium, after tens of thousands of years in today’s oceans — an indication that, despite a violent reaction, the carbon cycle will resume its steady state.
This pattern matches the geological record, Rothman found. The characteristic rate exhibited by half his database results from excitations above, but near, the threshold. Environmental disruptions associated with mass extinction are outliers — they represent excitations well beyond the threshold. At least three of those cases may be related to sustained massive volcanism.
“When you go past a threshold, you get a free kick from the system responding by itself,” Rothman explains. “The system is on an inexorable rise. This is what excitability is, and how a neuron works too.”
Although carbon is entering the oceans today at an unprecedented rate, it is doing so over a geologically brief time. Rothman’s model predicts that the two effects cancel: Faster rates bring us closer to the threshold, but shorter durations move us away.
Insofar as the threshold is concerned, the modern world is in roughly the same place it was during longer periods of massive volcanism.
In other words, if today’s human-induced emissions cross the threshold and continue beyond it, as Rothman predicts they soon will, the consequences may be just as severe as what the Earth experienced during its previous mass extinctions.
dohboi wrote:Ancient 'dead seas' offer a stark warning for our own future
http://www.theecologist.org/blogs_and_c ... uture.html
QuoteFor long periods animals in ancient oceans could live only in shallow surface waters, above vast 'dead zones' inhabited only by anoxic bacteria, writes Richard Pancost. Human activity is now creating immense new dead zones, and global warming could be helping as it reduces vertical mixing of waters. Could this be the beginning of something big?
While the changes are widespread in the Arctic, the effect on wildlife is acute in the eastern shelf of the Bering Sea, which yields more than 40% of the annual U.S. fish and shellfish catch.
“The changes going on have the potential to influence the kinds of fish products you have available to you, whether that’s fish sticks in the grocery store or shellfish at a restaurant,” said Rick Thoman, a meteorologist in Alaska and one of the report’s authors.
Earlier this year, he was reading the Bear’s log from June 1918. It had set out to resupply the remote Alaskan outpost at Point Barrow, but heavy ice forced it to turn back. Purves looked at maps published by the National Snow and Ice Data Center, a U.S. government agency based in Boulder, Colorado, to see where the ice was in June 2019. What he found was sobering.
“The ice in 2019 was more than 650 miles north of where it was on the same day in 1918,” he says. “You sit there and you think: Whoa.”
Purves feels most people have yet to grasp the gravity of climate change. “I’m 72, and I’m thinking I’ll still live to see a summer with no ice in the Arctic Ocean,” he says. “Will that be enough to wake people up? I really don’t know.”
For today's world, the findings could portend an ominous development. The undersea carbon reservoirs released greenhouse gas to the atmosphere as oceans warmed, the study shows, and today the ocean is heating up again due to humanmade global warming.
If undersea carbon reservoirs are upset again, they would emit a huge new source of greenhouse gases, exacerbating climate change. Temperature increases in the ocean are on pace to reach that tipping point by the end of the century. For example, a big carbon reservoir beneath the western Pacific near Taiwan is already within a few degrees Celsius of destabilizing.
Moreover, the phenomenon is a threat unaccounted for in climate model projections. Undersea carbon dioxide reservoirs are relatively recent discoveries and their characteristics and history are only beginning to be understood.
…
"The grand challenge is we don't have estimates of the size of these or which ones are particularly vulnerable to destabilization," Stott said. "It's something that needs to be determined."
In many cases, the carbon reservoirs are bottled up by their hydrate caps. But those covers are sensitive to temperature changes. As oceans warm, the caps can melt, a development the paper warns would lead to a double wallop for climate change -- a new source of geologic carbon in addition to the humanmade greenhouse gases.
Oceans absorb nearly all the excess energy from the Earth's atmosphere, and as a result they have been warming rapidly in recent decades. Over the past quarter-century, Earth's oceans have retained 60 percent more heat each year than scientists previously had thought, other studies have shown. Throughout the marine water column, ocean heat has increased for the last 50 years. The federal government's Climate Science Special Report projected a global increase in average sea surface temperatures of up to 5 degrees Fahrenheit by the end of the century, given current emissions rates. Temperature gains of that magnitude throughout the ocean could eventually destabilize the geologic hydrate reservoirs, Stott said.
"The last time it happened, climate change was so great it caused the end of the ice age. Once that geologic process begins, we can't turn it off," Stott said.
…
Said Stott: "Discoveries of accumulations of liquid, hydrate and gaseous carbon dioxide in the ocean has not been accounted for because we didn't know these reservoirs existed until recently, and we didn't know they affected global change in a significant way.
"This study shows that we've been missing a critical component of the marine carbon budget. It shows these geologic reservoirs can release large amounts of carbon from the oceans. Our paper makes the case that this process has happened before and it could happen again."
The geological record contains numerous examples of “greenhouse periods” and ocean acidification episodes, where the spreading of corrosive (CO2-enriched) bottom waters enhances the dissolution of CaCO3 minerals delivered to the seafloor or contained within deep-sea sediments.
The dissolution of sedimentary CaCO3 neutralizes excess CO2, thus preventing runaway acidification, and acts as a negative-feedback mechanism in regulating atmospheric CO2 levels over timescales of centuries to millennia. We report an observation-based indication and quantification of significant CaCO3 dissolution at the seafloor caused by man-made CO2.
This dissolution is already occurring at various locations in the deep ocean, particularly in the northern Atlantic and near the Southern Ocean, where the bottom waters are young and rich in anthropogenic CO2.
Along with McClintock he acted as adviser to Scott's Antarctic expeditions. His papers contain a letter that has eerie relevance to the climate trends of today. In 1911, he read a report of Scott's first expedition to the South Pole and told one member that ‘the only serious omission … is that of the marvellous retrocession of the Barrier since Ross mapped it. To me this appears the most momentous change known to be brought about in the Antarctic in little more than half a century. I have seen doubts cast upon Ross's demarcation of the sea front of the Barrier–but that is ridiculous, he was a first-rate naval surveyor …’ 10
The Barrier had shrunk at the rate of approximately one mile per year. The clean white world that Hooker had visited so long ago was already starting to dissolve.
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