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This visualization shows total sea level change between 1992 and 2014, based on data collected from the TOPEX/Poseidon, Jason-1, and Jason-2 satellites. Blue regions are where sea level has gone down, and orange/red regions are where sea level has gone up. Since 1992, seas around the world have risen an average of nearly 3 inches. The color range for this visualization is -7 cm to +7 cm (-2.76 inches to +2.76 inches), though measured data extends above and below 7cm(2.76 inches). This particular range was chosen to highlight variations in sea level change.
The oceans have heaved up and down as world temperatures have waxed
and waned, but as new research tracking the past 2,800 years shows,
never during that time did the seas rise as sharply or as suddenly as
has been the case during the last century.
The new study, the culmination of a decade of work by three teams of
farflung scientists, has charted what they called an “acceleration” in
sea level rise that’s triggering and worsening flooding in coastlines
around the world.
The findings also warn of much worse to come.
The scientists reported in a paper published Monday in
Proceedings of the National Academy of Sciences that they have greater
than 95 percent certainty that at least half of more than 5 inches of
sea level rise they detected during the 20th century was directly caused
by global warming.
“During the past millennia, sea level has never risen nearly as fast as during the last century,” said Stefan Rahmstorf,
a physics professor at Potsdam University in Germany, one of 10 authors
of the paper.
“That was to be expected, since global warming inevitably
leads to rising seas.”
By trapping heat, rising concentrations of atmospheric pollution are
causing glaciers and ice sheets to melt into seas, lifting high tides
ever higher.
Globally, average temperatures have risen about 1°C (nearly 2°F) since the 1800s.
The expansion of warming ocean water was blamed in a recent study for about half of sea level rise during the past decade.
Changes in sea level vary around the world and over time, because of
the effects of ocean cycles, volcanic eruptions and other phenomenon.
But the hastening pace of sea level rise is being caused by climate
change.
“The new sea level data confirm once again just how unusual the age
of modern global warming, due to our greenhouse gas emissions, is,”
Rahmstorf said.
“They also demonstrate that one of the most dangerous
impacts of global warming, namely rising seas, is well underway.”
Were it not for the effects of global warming, the researchers
concluded that sea levels might actually have fallen during the 20th
century.
At the very least, they would have risen far less than was
actually the case.
A report published by Climate Central on Monday, the result of an
analysis based in part on the findings in Monday’s paper, concluded that
climate change was to blame for three quarters of the coastal floods
recorded in the U.S. from 2005 to 2014, mostly high tide floods.
That
was up from less than half of floods in the 1950s.
“I think this is really a first placing of human fingerprints on coastal floods, and thousands of them,” said Ben Strauss,
vice president for sea level and climate impacts at Climate Central.
Strauss led the analysis, which also involved government and academic
researchers.
Governments and communities have been slow to respond to the crisis
of rising seas, though efforts to adapt to the changes underway are now
being planned around the world.
“There’s a definite recognition among people who weren’t talking
about sea level rise 5 years ago that it’s something to be concerned
about,” said Laura Tam, a policy director at SPUR, which is an urban
planning think-tank based in San Francisco.
“And something that needs to
be planned for.”
A high-profile effort to track long-term changes in sea levels was
based on analysis of sediment layers at a single location in North
Carolina. Published in 2011,
that study produced a chart of sea levels that bounced up and down over
time, changing with global temperatures, and then ticked sharply upward
as industrialization triggered global warming.
“North Carolina basically showed us that this could be done,” said Andrew Kemp, a sea level scientist at Tuft’s University.
He was a co-author of both Monday’s paper and the paper published in 2011.
Monday’s paper combined the data from North Carolina with similar
analyses from 23 other locations around the world plus data from tide
gauges. Rob DeConto,
a professor at UMass Amherst who researches prehistoric climates, and
who was not involved with the study, described the report as a “nice
job” that “used a lot more data than anybody else has used in a study
like this.”
The analysis goes further than explaining historical sea level rise.
It includes worrying projections for the future.
By extending their findings to future scenarios, the scientists
showed that the amount of land that could be inundated in the coming
years will depend heavily on whether humanity succeeds in slashing
pollution from fuel burning, deforestation and farming.
The Paris Agreement negotiated in December aims
to do just that, with nations agreeing to take voluntary steps to
reduce the amount of pollution they release after 2020.
It could take
decades, though, before that untested approach is revealed to have been a
success, a failure, or something in between.
Coastal cities will face greater threat than anticipated
Even If humans quickly stop polluting the atmosphere, potentially
keeping a global temperature rise to well below 2°C (3.8°F) compared
with preindustrial times — a major goal of the Paris climate agreement —
seas may still rise by an additional 9 inches to 2 feet this century,
the study concluded. That would trigger serious flooding in some areas,
and worsen it in others.
Under the worst-case scenario investigated, if pollution continues
unabated, and if seas respond to ongoing warming by rising at the
fastest rates considered likely, sea levels could rise more than 4 feet
this century alone, wiping out coastal infrastructure and driving
communities inland.
The problem would be made far worse if the Antarctic or Greenland ice sheets collapse — something that’s difficult to forecast.
Their projections for future sea level rise were similar to those published in 2013 by scientists convened by the United Nations, following the Intergovernmental Panel on Climate Change’s most recent assessment of climate science.
They also closely matched projections that were coincidentally published in a separate paper in the same journal on Monday.
The similarity of the other papers’ projections “strengthens the confidence” in the findings, said Robert Kopp, a Rutgers University climate scientist who led the analysis.
The convergence of the findings in Monday’s papers was a “nice result,” said Matthias Mengel,
a researcher at at Potsdam University who coauthored the other sea
level rise study released Monday. He led a team of sea level scientists
who took a different approach than Kopp’s team to projecting future sea
levels.
Mengel’s team projected future sea levels by combining the results of
models that anticipate changes to icebergs, ice sheets and ocean
expansion in the years ahead, and used those findings to predict sea
levels.
For years, different approaches to projecting future sea level rise
have arrived at different results, but the gap has recently been
closing, which Mengel described as “a really good sign for sea level
science” — even if it’s ominous news for humanity.
An article in Saturday’s New York Times (Connecticut Rock Pile Known as Negro Heads May Get a New Name) described efforts
to rename a small island near New Haven Connecticut.
The island,
actually more of a “rock pile”, has long been known as Negro Heads, and
bears that name on the official nautical charts for Long Island Sound.
A buoy in Long Island Sound near Branford, Conn., that marks the rock formation known as Negro Heads.
Andrew Sullivan for The New York Times
The feature is a local landmark off the town of Branford, and has a warning buoy according to the Times story.
Here are closeup views of Branford from a 2014 nautical chart.
The rocks have been marked by buoys since at least 1846, but the name changed.
The newspaper article noted that the rock pile used to have a more
offensive name, and that it was changed to the present name “between the
1830s and 1880s”. That covers a large date range, so I looked through my collection of
Coast Survey charts to see if I could find the older name and get a
closer date for the name change.
I found the old name (Nigger Heads) in
1846 and the new name in 1855.
I was surprised to find the change made
so early – before the Civil War.
The oldest 80,000 scale chart for the New Haven area is the 1846
chart which covers Long Island Sound from New Haven east to the
Connecticut River.
A closeup view shows that the rocks were called
“Nigger Heads” at that time.
Plum Island to Stratford Shoal 1846 1:80,000
Middle Part of Long Island Sound (USCGS)
On the 1855 map we see the name change to the current “Negro Heads”.
Plum Island to Stratford Shoal 1855 1:80,000
Middle Part of Long Island Sound (USCGS)
Before I found the evidence, I was imaging that the new name might have
appeared much later in the century during the Reconstruction period.
We
don’t know who made the change, or whether it was the subject of much
discussion at the time. The map’s title tells us that it was published
by the US Coast Survey.
The “Sailing Directions” on each chart had the same usage.
While the official charts showed the new name from 1855 to the present, common usage may not have changed.
Note this 1903 article found online about a sailing trip along the shoreline:
Scientists have released the first audio recordings taken from the deepest point on Earth's surface, Challenger Deep, at the bottom of the Mariana Trench.
Filled with strange moans, low rumbles, and the occasional
high-pitched screech, the soundbites below shed rare light on the dark
world that lies 10.9 km (6.7 miles) below the crushing weight of the
Pacific Ocean... and they're somehow both haunting and beautiful at the
same time.
Mariana Trench with the GeoGarage platform (NGA chart)
On the whole, we know very little about what goes on inside the Mariana Trench, located at the bottom of the Pacific Ocean around 322 km (200 miles) southwest of Guam, mostly because it's so difficult for us to get to.
But Robert Dziak, an oceanographer with the US National Oceanic and Atmospheric Administration (NOAA), figured that even if we couldn't explore the trench ourselves for long periods of time, we might be able to eavesdrop on it.
So his team dropped a titanium-encased hydrophone down to Challenger Deep, the trench's deepest point, and kept it recording for 23 days straight.
Below are some of the strange sounds that came back, including whales calls, which are made by a mix of baleen and toothed (odontocete) whales:
The first thing you'll notice is that, for somewhere with 16,000 pounds per square inch (PSI) of pressure crushing down from above, and where the Sun never shines, the deepest point on Earth is a lot noisier than you'd expect.
That's because sound waves travel an incredibly long way in water, turning Challenger Deep into something of an echo chamber for sounds from miles around.
In one of the recordings you can clearly hear the propellor of a boat travelling across the surface 10.9 km (6.7 miles) away, and another day the researchers captured the distinctive rustling of a category four typhoon raging overhead.
Not to mention the frequent rumbling of earthquakes.
"I was surprised by just how cleanly we can record whales, ships, and all sorts of activity taking place at the surface," Dziak told Maddie Stone over at Gizmodo.
Here's what it sounds like when a boat passes 10.9 km (6.7 miles) over your head:
And here's a magnitude 5 earthquake rumbling near Guam on 16 July 2015:
This is a baleen whale's calls right before and after the same quake:
The hydrophone was able to survive at those depths and continue recording for more than three weeks thanks to clever engineering.
"The pressure at that depth is incredible," said Haru Matsumoto, an engineer from Oregon State University who worked on the hydrophone.
"We had to drop the hydrophone mooring down through the water column at no more than five metres per second to be sure the hydrophone, which is made of ceramic, would survive the rapid pressure change."
But although the soundbites give us fascinating insight into the Mariana Trench, that wasn't the sole purpose of the mission - the NOAA is hoping to use the recordings to establish a baseline for ambient noise in the deepest part of the Pacific Ocean.
That way they can determine in future if human-created noise in the ocean is getting louder, and begin to assess how that might affect marine animals that use sound to communicate, navigate and feed, such as whales and dolphins.
Dziak is now hoping to go back to the Mariana Trench soon to do more recording, and would also love to explore the deep areas of the Arctic Ocean that are beginning to become accessible as the polar ice caps shrink.
"It is akin to sending a deep-space probe to the outer Solar System," Dziak told Gizmodo. "We’re sending out a deep-ocean probe to the unknown reaches of inner space."
Contemplate that while you listen to the call of baleen whale, possibly a humpback or blue whale, echoing in the deepest place on Earth:
