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Hurricane Dorian: Why are more extreme storms stalling?
The Category 5 hurricane was moving at speeds of about 1 mph over the Bahamas on Sunday and Monday.
- Hurricane Dorian is one of the strongest Atlantic hurricanes on record, with wind speeds of more than 200 mph.
- The storm was moving slowly over the Bahamas as a result of clashing high- and low-pressure systems.
- It's unclear whether climate change is causing shifts in large-scale wind patterns, but scientists generally agree that warmer temperatures are causing storms to become stronger.
Hurricane Dorian became on Sunday the strongest hurricane to ever hit the Bahamas, pummelling islands with 200-mph winds and more than 20 feet of coastal flooding. At its strongest point, the Category 5 storm — the most severe ranking — floated nearly motionless over the islands, inching along at about 1 mph as it dropped more than 2 feet of rain. At least five people in the Bahamas were killed by the storm.
By Monday, Dorian was a Category 4 storm. On Tuesday, the slow-moving hurricane had lost much of its steam and was downranked to Category 2. But Dorian has grown in size if not force, and it's expected to move northerly over the Atlantic, parallel with the coast of Florida and, later, Georgia and the Carolinas. Violent winds have already struck parts of Florida, and officials in multiple states have already ordered thousands of residents to evacuate.
The core of Dorian is finally moving away from Grand Bahama Island. At 1 pm Dorian was located 50 mi N of Freeport… https://t.co/z4GakuHlWO— NWS Eastern Region (@NWS Eastern Region)1567530851.0
"I can't decide for you, but I'm asking you, as the mayor of Savannah: Please attempt to get out of town as best you can, and come back in a few days and begin your life over and move forward," Eddie DeLoach, mayor of Savannah, Georgia, said in a public appearance Monday night, according to The Savannah Morning News.
For now, the main focus of residents and officials in the storm's path is safety, rescue and, eventually, reconstruction. But for scientists who study storms and climate change, Dorian's intensity and brutal sluggishness highlight how warming temperatures are changing the nature of extreme storms around the globe.
A pattern of stalling hurricanes
In recent years, scientists have identified a pattern: Severe hurricanes are not only becoming stronger and more common, but many are also moving more slowly and even stalling, as Hurricane Harvey did over Houston for days in 2017, dumping 60 inches of rain in the process. A study published in June by NASA and NOAA scientists showed that the average forward speed of North Atlantic hurricanes has slowed from 11.5 mph in 1944 to 9.6 mph in 2017.
So, is climate change making hurricanes slower? It's too early to say for sure, and the issue is still an area of debate among climate scientists. In the case of Dorian, the violent storm stalled above the Bahamas because, somewhat ironically, the atmosphere was too calm; a clash between high- and low-pressure systems caused the weather pattern to come to a standstill.
"Was it caused by climate change?" is the most common question when we hear about an extreme event. But when it com… https://t.co/XtckqQCmNa— Prof. Katharine Hayhoe (@Prof. Katharine Hayhoe)1567272551.0
But scientists generally believe that warmer temperatures in the Arctic are likely playing a part in slowing down wind patterns, as NOAA hurricane expert Jim Kossin, co-author of the June study, told InsideClimate News:
"...in the broadest sense, global warming makes the global atmospheric circulation slow down," he said. "There is a lot of evidence to suggest this is more than just natural variability."
How exactly warmer temperatures affect wind patterns is a complicated issue that needs further research. But there's little debate among climate scientists as to whether climate change is making storms worse and more common.
"The environment for all such storms has changed because of climate change," Kevin Trenberth, a climate scientist with the National Center for Atmospheric Research, told Inside ClimateNews. "The oceans are warmer, especially in the upper 100 meters, which is most important for such storms," Trenberth said. "This makes available more energy via water vapor for the storms and makes for more activity: more intensity, bigger and longer lasting storms, with heavier rainfalls."
An open letter predicts that a massive wall of rock is about to plunge into Barry Arm Fjord in Alaska.
- A remote area visited by tourists and cruises, and home to fishing villages, is about to be visited by a devastating tsunami.
- A wall of rock exposed by a receding glacier is about crash into the waters below.
- Glaciers hold such areas together — and when they're gone, bad stuff can be left behind.
The Barry Glacier gives its name to Alaska's Barry Arm Fjord, and a new open letter forecasts trouble ahead.
Thanks to global warming, the glacier has been retreating, so far removing two-thirds of its support for a steep mile-long slope, or scarp, containing perhaps 500 million cubic meters of material. (Think the Hoover Dam times several hundred.) The slope has been moving slowly since 1957, but scientists say it's become an avalanche waiting to happen, maybe within the next year, and likely within 20. When it does come crashing down into the fjord, it could set in motion a frightening tsunami overwhelming the fjord's normally peaceful waters .
The Barry Arm Fjord
Camping on the fjord's Black Sand Beach
Image source: Matt Zimmerman
The Barry Arm Fjord is a stretch of water between the Harriman Fjord and the Port Wills Fjord, located at the northwest corner of the well-known Prince William Sound. It's a beautiful area, home to a few hundred people supporting the local fishing industry, and it's also a popular destination for tourists — its Black Sand Beach is one of Alaska's most scenic — and cruise ships.
Not Alaska’s first watery rodeo, but likely the biggest
Image source: whrc.org
There have been at least two similar events in the state's recent history, though not on such a massive scale. On July 9, 1958, an earthquake nearby caused 40 million cubic yards of rock to suddenly slide 2,000 feet down into Lituya Bay, producing a tsunami whose peak waves reportedly reached 1,720 feet in height. By the time the wall of water reached the mouth of the bay, it was still 75 feet high. At Taan Fjord in 2015, a landslide caused a tsunami that crested at 600 feet. Both of these events thankfully occurred in sparsely populated areas, so few fatalities occurred.
The Barry Arm event will be larger than either of these by far.
"This is an enormous slope — the mass that could fail weighs over a billion tonnes," said geologist Dave Petley, speaking to Earther. "The internal structure of that rock mass, which will determine whether it collapses, is very complex. At the moment we don't know enough about it to be able to forecast its future behavior."
Outside of Alaska, on the west coast of Greenland, a landslide-produced tsunami towered 300 feet high, obliterating a fishing village in its path.
What the letter predicts for Barry Arm Fjord
Moving slowly at first...
Image source: whrc.org
"The effects would be especially severe near where the landslide enters the water at the head of Barry Arm. Additionally, areas of shallow water, or low-lying land near the shore, would be in danger even further from the source. A minor failure may not produce significant impacts beyond the inner parts of the fiord, while a complete failure could be destructive throughout Barry Arm, Harriman Fiord, and parts of Port Wells. Our initial results show complex impacts further from the landslide than Barry Arm, with over 30 foot waves in some distant bays, including Whittier."
The discovery of the impeding landslide began with an observation by the sister of geologist Hig Higman of Ground Truth, an organization in Seldovia, Alaska. Artist Valisa Higman was vacationing in the area and sent her brother some photos of worrying fractures she noticed in the slope, taken while she was on a boat cruising the fjord.
Higman confirmed his sister's hunch via available satellite imagery and, digging deeper, found that between 2009 and 2015 the slope had moved 600 feet downhill, leaving a prominent scar.
Ohio State's Chunli Dai unearthed a connection between the movement and the receding of the Barry Glacier. Comparison of the Barry Arm slope with other similar areas, combined with computer modeling of the possible resulting tsunamis, led to the publication of the group's letter.
While the full group of signatories from 14 organizations and institutions has only been working on the situation for a month, the implications were immediately clear. The signers include experts from Ohio State University, the University of Southern California, and the Anchorage and Fairbanks campuses of the University of Alaska.
Once informed of the open letter's contents, the Alaska's Department of Natural Resources immediately released a warning that "an increasingly likely landslide could generate a wave with devastating effects on fishermen and recreationalists."
How do you prepare for something like this?
Image source: whrc.org
The obvious question is what can be done to prepare for the landslide and tsunami? For one thing, there's more to understand about the upcoming event, and the researchers lay out their plan in the letter:
"To inform and refine hazard mitigation efforts, we would like to pursue several lines of investigation: Detect changes in the slope that might forewarn of a landslide, better understand what could trigger a landslide, and refine tsunami model projections. By mapping the landslide and nearby terrain, both above and below sea level, we can more accurately determine the basic physical dimensions of the landslide. This can be paired with GPS and seismic measurements made over time to see how the slope responds to changes in the glacier and to events like rainstorms and earthquakes. Field and satellite data can support near-real time hazard monitoring, while computer models of landslide and tsunami scenarios can help identify specific places that are most at risk."
In the letter, the authors reached out to those living in and visiting the area, asking, "What specific questions are most important to you?" and "What could be done to reduce the danger to people who want to visit or work in Barry Arm?" They also invited locals to let them know about any changes, including even small rock-falls and landslides.
What makes some people more likely to shiver than others?
Some people just aren't bothered by the cold, no matter how low the temperature dips. And the reason for this may be in a person's genes.
Eating veggies is good for you. Now we can stop debating how much we should eat.
- A massive new study confirms that five servings of fruit and veggies a day can lower the risk of death.
- The maximum benefit is found at two servings of fruit and three of veggies—anything more offers no extra benefit according to the researchers.
- Not all fruits and veggies are equal. Leafy greens are better for you than starchy corn and potatoes.