Deep ocean floor can focus tsunami waves

credit NASA

From OurAmazingPlanet

As the waves of a tsunami approach a coastline, the topography of the seafloor near the coast plays a major role in determining how large those waves become and what places get hit harder than others.


For example, when the waves of the massive tsunami generated by last year's magnitude 9.0 Japan earthquake crossed the Pacific Ocean and reached the U.S. West Coast, they hit Crescent City, Calif., particularly hard because of two features of the seafloor off the coast: a piece of the ocean floor raised by tectonic activity that runs directly toward the city and the position and shape of the city's harbor.

Scientists had suspected that the same phenomenon might also take place in the deep ocean, where underwater mountains, called seamounts, chasms and even islands could deflect tsunami waves in some places and amplify them in others.

But measurements taken by satellites passing over the waves of last year's tsunami have confirmed that this happens, even at large distances from a quake's epicenter.

Researchers from NASA's Jet Propulsion Laboratory and Ohio State University used satellite altimeters, which can measure sea level changes in very fine detail, to observe "merging tsunamis" — a phenomenon where smaller waves merge to form one bigger wave.
These waves can travel hundreds to thousands of miles without losing power.

The measurements showed that the March 2011 tsunami doubled in intensity when passing over rugged ocean ridges and around islands in the middle of the Pacific.

The team used a computer-based model to translate the measurements into images and animations, which shows how the waves can refract, bend and merge as they propagate.
The peaks of waves are colored red-brown, while depressions in sea surface appear blue-green. Grayscale outlines show the location of mid-ocean ridges, peaks and islands.

The measurements came from the Jason-1, Jason-2, and Envisat satellites, which each flew over the tsunami at a different location.
"It was a one in 10 million chance that we were able to observe this double wave with satellites," said Tony Song, principal investigator of the study and a scientist at JPL.
"Researchers have suspected for decades that such ‘merging tsunamis’ might have been responsible for the 1960 Chilean tsunami that killed about 200 people in Japan and Hawaii, but nobody had definitively observed a merging tsunami until now. It was like looking for a ghost," Song said. "Jason happened to be in the right place at the right time to capture the double wave."

A census of the ocean

Oceanographer Paul Snelgrove shares the results of a ten-year project with one goal: to take a census of all the life in the oceans.
He shares amazing photos of some of the surprising finds of the Census of Marine Life.

"We can only sense that in the deep and turbulent recesses of the sea are hidden mysteries far greater than any we have solved."

~ Rachel Carson, 1907-1964.

From TheGuardian

Oceans cover more than 70% of the surface of Earth, and contain a large portion of Earth's biodiversity, much of it still unknown.
Further, we know more about the surface of the Moon and Mars than we know about the floor of the world's oceans.
To remedy this knowledge deficit, the Census of Marine Life programme was initiated to catalogue and study the distribution, diversity and abundance of life in the oceans.
The census revealed how diverse, surprising, still vastly unknown, and tenacious life is in the oceans.

Screen grab

In this disturbing and fascinating video, oceanographer Paul Snelgrove shares some of the results of this ten-year project.
Professor Snelgrove, who compiled the data collected by this decade long marine census into a book, tells how shifting baselines have obscured our view of the loss that oceans have suffered as a result of human over-exploitation and shows us some of the amazing tools used to investigate oceanic habitats.
So far, more than 6,000 potential new species have been discovered, so Dr Snelgrove shares photographs of a few of his favourite newly discovered species.

First map of entire Titanic wreck site sheds new light on disaster

A collaboration between various partners, the 2010 expedition to the Titanic wreck site produced the first comprehensive map of the 15-square-mile debris field.
AUVs (autonomous underwater vehicles) and an ROV (remote operated vehicle) were used in conjunction to harness cutting-edge 2-D, 3-D and sonar technology.

From Discovery

The first comprehensive map of the Titanic wreck site has been created as researchers pieced together some 130,000 photos taken by underwater robots in the depths of the North Atlantic Ocean.

Resembling the moon's surface, the map shows debris and parts of the ship scattered across a 15 square-mile patch of ocean floor.

The detailed images might provide new clues about what happened after the "unsinkable" luxury liner hit an iceberg and sank on April 15, 1912, killing more than 1,500 of the 2,200 passengers and crew on board.

ANALYSIS: Did the Moon Conspire To Bring Down Titanic?

"If we are going to do our best to manage the Titanic wreck site as a testament to those that sailed on her, we need to understand the disposition and physical state of what's there," Titanic expedition co-leader David Gallo, director of special projects at Woods Hole Oceanographic Institution in Falmouth, Mass., told Discovery News.

"In addition, we need to put Titanic in context of it is natural setting on the deep Atlantic seafloor," Gallo said.

Detail of the bow of the Titanic taken from a comprehensive map of the 3-by-5 mile debris field.
When Titanic sank in the early hours of April 15, 1912, its stern and bow sections separated.
The two pieces came to rest roughly 2,000 feet apart from one another on the ocean floor, 2.3 miles below the surface of the North Atlantic.
Credit:RMS Titanic Inc.

It's not the first time that the Titanic wreck site has been mapped.
The first attempts began soon after the doomed liner was discovered in 1985.
Explorers used photos taken with cameras aboard remotely controlled vehicles, which did not hazard too far from the bow and stern.

Therefore, all the maps are incomplete, covering only fragmented portions of the wreck area.
"As much as 40 percent of the wreck site has not been fully studied and documented, including multiple hull sections," RSM Titanic Inc, the legal custodian of the wreck, said on its website.

ANALYSIS: Steering Error Sank The Titanic, Says Author

The comprehensive survey map of the wreck site took place in the summer of 2010 as part of a project aimed at "virtually raising Titanic and preserving her legacy for all time."

The expedition to the wreck was led by RMS Titanic Inc., the Woods Hole Oceanographic Institution and the Waitt Institute of La Jolla, California.
They were joined by other groups, such as the National Oceanographic and Atmospheric Administration (NOAA), and cable TV's History channel.

During the expedition, torpedo-shaped AUVs (autonomous underwater vehicles) surveyed the entire search area with high-resolution side-scan sonar.
Pinpointed by the AUVs, the debris-rich sites were then explored by a ROV (remote operated vehicle) fitted with cameras.

The resulting 130,000 high resolution photos were pieced together on a computer to provide a detailed photomosaic map of Titanic and the surrounding sea floor.

"We are still processing some of the data but the elements of a 3D map are there," Gallo said.

"The images are staggering. There you are on the bottom of the ocean, transported to the sea floor. It's mindboggling; even veterans who have been to Titanic numerous times are slack-jawed," he added.

NEWS: Titanic Being Eaten by Destructive Bacteria

The wreck of the Titanic was found on Sept. 1, 1985 about 13 miles from the last position recorded before the ship sank on her maiden voyage from Southampton, England, to New York City and became a legend.

A deep canyon carved out of the ocean floor lies some 3.5 nautical miles west of the wreck site -- had the ship landed there, she might never have been found.

Because of the way the ship broke apart -- the stern and bow face opposite directions and are 1,970 feet apart from each other -- some areas in the 3-by-5-mile wreck field have a larger debris concentration.

Debris abound in the so-called "hell's kitchen," an area of the seabed scattered with broken china, pots, pans other cooking tools.
Another debris rich area is the "coal fields," which features a large quantity of the black combustible.
Indeed, the Titanic left England carrying 6,000 tons of coal .

According to RSM Titanic Inc, the "coal concentration in one area is believed to be due to both the coal's weight and how the ship broke apart."

ANALYSIS: Titanic's 'Unknown Child' Identified

Other features on the mapped wreck site include a pile of rubble identified as "deckhouse debris," a 60-foott long chunk of the side of the ship, five of the ship's huge boilers, and pieces of the ship's bottom.

"You really begin to understand how violently the ship tore itself apart when it went down and landed all over this enormous footprint on the bottom of the ocean," said David Alberg, Sanctuary superintendent for NOAA’s Monitor National Marine Sanctuary.

The layout of the wreck site, where the pieces ended and how they are arranged and oriented on the ground, might help solve some of the remaining mysteries on how the Titanic broke apart and sank.

For example, marks on the ocean floor to the west of the stern, with debris concentrated to the east, indicated that the stern rotated.

The new findings will be detailed during a two-hour History channel documentary on April 15, exactly 100 years after the Titanic settled at the bottom of the North Atlantic.

During the show, computer simulations will re-enact the sinking in reverse, bringing pieces of Titanic’s wreckage back to the surface and reassembling the ship in a virtual hangar.

Links :

• TheTelegraph :Digital 'map' of the Titanic to be released for 100-year anniversary
• History : First map of entire Titanic wreck site sheds new light on disaster
  

What Fukushima accident did to the ocean

Fukushima guilty of world's worst sea contamination

From CNN

One year ago, a series of events began with an earthquake off the cost of Japan that culminated in the largest accidental release of radioactivity into the ocean in history.

We have to be careful and say "accidental" because in the late 1950s and early 1960s, 50 to 100 times more radioactivity was released worldwide as fallout from the intentional testing of nuclear weapons.

Wave on Fukushima (March 11, 2011)
photos / video
>>> geolocalization with the Marine GeoGarage <<<

The word "ocean" is also important, since Chernobyl in 1986 was hundreds of miles inland, so it had a smaller impact on the concentrations of radionuclides in the sea than was measured directly off Japan in 2011.
One year later, we have to ask, what do we know about Fukushima's impact on the ocean and levels of radioactive contaminants in water and fish?

In many ways we were fortunate that impacts were largely confined to the ocean.
Certainly, the Japanese people continue to feel devastating effects of so large a release within their country, and many people may never be able to return to their homes.
But in general the winds during the height of the accident at the Fukushima Daiichi nuclear power plant were blowing offshore.
As a result, more than three-quarters of the radioactivity fell on the ocean.
This is important, as any that lands on soil remains in place, resulting in the potential for greater human exposure and increased chances of contamination to food supplies and property.

In the Pacific, however, the strong Kuroshio Current (similar to the Atlantic Gulf Stream) helped move any contamination quickly away from shore and diluted it by mixing it into deeper water.
This allowed us to report that by June 2011, even when we sampled within sight of the nuclear power plants, levels of cesium-137 and cesium-134 in the ocean, two primary products of nuclear fission, were elevated, but still below those considered of concern for exposure to humans.
They were also well below biological thresholds of concern to the small fish and plankton we sampled, even if these were consumed by humans.
Several other groups have now confirmed our findings about levels of radioactivity up to 400 miles offshore.

Other measurements show trends that are more worrisome.
Levels of radioactivity found in fish are not decreasing and there appear to be hot spots on the seafloor that are not well mapped.
There is also little agreement on exactly how much radioactivity was released or even whether the fires and explosions at the power plant resulted in more radioactive fallout to the ocean than did direct releases of radioactivity caused by dumping water on the reactors to keep them cool.

Japan is taking what some think of as a precautionary measure by lowering the limits of radioactive contaminants in drinking water and food supplies, including seafood, on April 1.
The new level for fish will be one-tenth of the acceptable level in the United States.
Will Japan's new limits build consumer confidence or raise fears and questions about why more fish are considered unsafe for consumption?
And why were fish caught last year considered safe, but now are not?

Despite the announcement in December that operators of the power plant had achieved cold shut down, we know they are still using tons of water to cool the reactors and that not all the water has been collected or treated.
As a result, the ground around the site is like a dirty sponge, saturated with contaminated water that is leaking into the ocean.

Marine sediments are also collecting radioactive contaminants, exposing bottom-dwelling fish, shellfish and other organisms on the sea floor to higher levels of contaminants than those in the waters above.
Little is known, however, about the level of contamination in the groundwater and on the seafloor and whether these will be a source of contaminants long after levels in the ocean have become diluted to the point that only the most sensitive instruments can detect them.
We do know that we can detect cesium at very dilute levels, well below those considered harmful.

Using these sensitive techniques we can track the Fukushima contaminants as ocean currents carry the peak releases across the Pacific where they are expected to reach the U.S. West Coast in 2013-2014 at levels that are much lower than we measured off Japan in 2011 and thus not of concern to human health.

Two weeks ago, we held the largest international gathering of marine scientists studying radioactive substances in the ocean originating from Fukushima.
Although we shared freely what each of us has learned in the last year, what we need today is also what we needed on March 11, 2011 — greater international coordination of long-term studies of the fate and consequences of the radiation.
We've done the initial assessments.
Now we need to begin answering the tougher questions, building public confidence in scientific studies by having multiple, independent groups at work, and ensuring we have the resources to build comprehensive, long-term studies.

As a scientist and a marine radiochemist, I (Ken Buesseler, Senior Scientist at the Woods Hole Oceanographic Institution who has studied marine radioactivity since Chernobyl in 1986 and led an international research cruise off Japan in June 2011) am trained to provide answers about radioactivity in the ocean—how much is out there, where it is, and what its fate is likely to be in the future.
Today, we haven't gone very far beyond the first question, which was key on March 11, 2011, but hardly seems sufficient one year later.

Links :

• TheGuardian : UK nuclear sites at risk of flooding, report shows
• Discovery : Mix seawater, nuclear fuel: result is still an unknown
  

30 dolphins stranding and incredibly saved

About 30 dolphins stranded and saved by local people at Arraial do Cabo (Brazil)

in the morning at 8:00 AM on March 5th 2012.

>>> geolocalization with the Marine GeoGarage <<<
The whole episode was captured by Gerd Traue in a video (above),
which has racked up over a million views online.
They were apparently caught in a strong ocean current.

From NewScientist

It was just another day on the beach for holidaymakers off the coast of Rio de Janeiro, Brazil, when a pod of about 30 dolphins swam ashore on Monday.
Beachgoers quickly came to the rescue, rushing into the sea and dragging the dolphins by their fins and tails into deeper water.

What can experts learn from the footage?
The species involved, for one.
These are common dolphins (Delphinus delphis), which typically live a long way off shore, says Mark Simmonds of the Whale and Dolphin Conservation Society, a global charity.

However the video does not reveal what caused the stranding – fishing boats or sonar are two possibilities.

Had experts rescued the dolphins, says Simmonds, they may have examined the individuals for damage, such as net marks, that may have provided clues.
But he says the dolphins in the video appear to be healthy.

Out of their depth

The topography of the coastline may have disoriented the dolphins, says Michael Moore of the Wood's Hole Oceanographic Institution in Massachusetts.
It would not be surprising if offshore dolphins like these had trouble navigating the sandbars and silty seabeds found in shallow waters.

Nor is it surprising that such a large number of dolphins would head for land together.
Dolphins are social creatures, so it would take only one member of the pod to go astray – say, if it was diseased – and the others would follow.

This social behaviour is what makes mass strandings of cetaceans so common.
In the last month, for example, an unusually high number of dolphins – reportedly 179 – has been stranded in Cape Cod, Massachusetts.

Call in the experts

Understanding what's going on in such cases is especially hard because scientists must rely largely on postmortem evidence.
Moore and others are trying to develop early warning systems to get to the dolphins while they're still alive.

Sensors deployed in regions where strandings are common, for example, could detect the sounds of the cetaceans nearing shore and send a text message warning officials of an imminent stranding.

The Brazilian video has widely been greeted as a good news story.
But Simmonds is uneasy about this.
"There's a clock ticking, so it's important to respond quickly, but it's also important to move them in the right ways," he says.
Typically it's best not to touch the animals and to call in experts instead, he says.
"Pulling their flippers can dislocate their bones, or even pull a flipper right off."