Tag: Alaska

A Powerful Earthquake In Alaska Didn’t Trigger A Big Tsunami

Last Tuesday night, a magnitude 7.9 earthquake struck southeast of Kodiak Island in the Gulf of Alaska, prompting a tsunami warning that forced people to flee to higher grounds in the middle of the night.

Fortunately, the tsunami waves were less than a foot high, and the advisories were canceled a little after 4AM local time. So why was Alaska so lucky?

Powerful quakes that happen out at sea are known to cause destructive tsunamis. In 2011, a magnitude 9 earthquake in northeastern Japan triggered waves as high as 126 feet, killing nearly 20,000 people.




In 2004, a similarly strong quake off the coast of Indonesia caused a tsunami that killed more than 200,000 people.

Alaska also has a history of strong earthquakes: in 1964, the state experienced the most powerful quake ever recorded in the US, a 9.2 magnitude tremor followed by a tsunami that killed over 100 people.

Earthquakes occur because the Earth’s crust is divided into plates. These plates can move smoothly against each other or become stuck.

When they become stuck, they build up strain over time, until one day, the plates unstick, releasing energy that causes an earthquake.

Just south of Alaska, the Pacific plate is sliding underneath the North American plate, an area called the subduction zone. That’s why the state is highly seismic, Blakeman tells said.

Last Tuesday night’s earthquake generated because of all the strain building up on the subduction zone, but it did not occur exactly on a fault where the Pacific Ocean seafloor is sliding under the North American plate, Blakeman says.

Instead, the quake occurred a little farther out, in a place where the fault is moving horizontally.

This type of quake, called a strike-slip earthquake, is less likely to trigger large tsunamis, and this is probably why Alaska only saw waves of less than a foot, according to Blakeman.

When earthquakes happen on the subduction zone itself, where one plate is pushing down while the other is going up, then high waves form.

To get a tsunami, you have to have substantial vertical movement on the seabed,” Blakeman says. Those types of earthquakes were responsible for the massive tsunamis in Japan and Indonesia.

Aftershocks in Alaska could continue for weeks or months, Blakeman says. If the quakes generate from the same zone as last night, then large tsunamis should not be expected.

But because the state sits by the Pacific-North America plate boundary, it’s normal that new earthquakes will happen in the future. When and where, exactly?

That’s impossible to say. Earthquakes are so complicated that scientists aren’t able to predict them — at least not yet. “Since we can’t predict them, all we can do is be prepared,” Blakeman says.

Please like, share and tweet this article.

Pass it on: Popular Science

This City In Alaska Is Warming So Fast, Algorithms Removed The Data Because It Seemed Unreal

Last week, scientists were pulling together the latest data for the National Oceanic and Atmospheric Administration’s monthly report on the climate when they noticed something strange: One of their key climate monitoring stations had fallen off the map.

All of the data for Barrow, Alaska — the northernmost city in the United States — was missing.

No, Barrow hadn’t literally been vanquished by the pounding waves of the Arctic Sea (although it does sit precipitously close).




The missing station was just the result of rapid, man-made climate change, with a runaway effect on the Arctic.

The temperature in Barrow had been warming so fast this year, the data was automatically flagged as unreal and removed from the climate database.

It was done by algorithms that were put in place to ensure that only the best data gets included in NOAA’s reports.

They’re handy to keep the data sets clean, but this kind of quality-control algorithm is good only in “average” situations, with no outliers. The situation in Barrow, however, is anything but average.

If climate change is a fiery coal-mine disaster, then Barrow is our canary. The Arctic is warming faster than any other place on Earth, and Barrow is in the thick of it.

With less and less sea ice to reflect sunlight, the temperature around the North Pole is speeding upward.

The missing data obviously confused meteorologists and researchers, since it’s a record they’ve been watching closely, according to Deke Arndt, the chief of NOAA’s Climate Monitoring Branch.

He described it as “an ironic exclamation point to swift regional climate change in and near the Arctic.

Just this week, scientists reported that the Arctic had its second-warmest year — behind 2016 — with the lowest sea ice ever recorded.

The announcement came at the annual meeting of the American Geophysical Union, and the report is topped with an alarming headline: “Arctic shows no sign of returning to reliably frozen region of recent past decades.

Changes in the Arctic extend beyond sea ice. Vast expanses of former permafrost have been reduced to mud. Nonnative species of plants, types that grow only in warmer climates, are spreading into what used to be the tundra.

Nowhere is this greening of the Arctic happening faster than the North Slope of Alaska, observable with high-resolution clarity on NOAA satellite imagery.

The current observed rate of sea ice decline and warming temperatures are higher than at any other time in the last 1,500 years, and likely longer than that,” the NOAA report says.

At no place is this more blatantly obvious than Barrow itself, which recently changed its name to the traditional native Alaskan name Utqiagvik.

In just the 17 years since 2000, the average October temperature in Barrow has climbed 7.8 degrees. The November temperature is up 6.9 degrees.

The December average has warmed 4.7 degrees. No wonder the data was flagged.

The Barrow temperatures are now safely back in the climate-monitoring data sets. Statisticians will have to come up with a new algorithm to prevent legitimate temperatures from being removed in the future.

New algorithms for a new normal.

Please like, share and tweet this article.

Pass it on: Popular Science