Swimming stars : dolphins vs humans

From Richard Hammond's Invisible Worlds

In the high speed world, water becomes thick, dense - an alien environment that we struggle to get through.

Over time a strong swimmer can manage about 2 miles an hour.
But that’s nothing compared to other mammals like the dolphin, that can reach speeds 5 times faster.
But it's only in slow motion that we can see why the dolphin is so much at home here, and why we aren't.
Water is 800 times thicker than air - so thick that it pulls and distorts our soft bodies as we swim, causing drag which holds us back.
The water doesn't distort the dolphin's body at all, passing smoothly over it.
The dolphin has much thicker skin, like rubber, that stops his blubber from flapping.

So while we struggle to make headway, the dolphin is barely trying, and when they need to go faster, they can make it look effortless.

Using state-of-the-art technologies, Richard Hammond goes beyond the limits of the naked eye and explores the hidden secrets of the invisible world around us.

Human vision is pretty miraculous, but our eyes aren’t quite as powerful as you might imagine. What we can see is stuff that reflects or emits light with wavelengths in a very narrow band (since you ask, from about 750 to 400 nanometres).
What we can’t see is the rest.
That’s all matter that reflects or emits light over the other 99.99% percent of the spectrum.
In fact, we’re almost blind.

Fixing incorrect information in Google Maps

We got a couple of emails from users that would like to report incorrect information regarding Google Maps info.
Perhaps a misspelled marina name, incorrect building name in some harbor, etc.

Fortunately, Google makes it very easy to report problems like that.
You can read all of your options on this help page, but in most cases you'll simply want to use the "Report a Problem" link in Google Maps.

The item will usually be corrected in Google Maps within a month, and then corrected in Google Earth at some point after that.

Note : that is for Google Maps.
Regarding nautical charts and Marine GeoGarage overlays, don't hesitate to contact us directly and we will redirect the info to the Hydrographic Service concerned by the issue.

What freediving does to the body

Two and a half minutes on one breath.
Filmed underwater in real-time for Human Planet, Bajau fisherman, Sulbin,
freedives on one breath to 20 metres to catch a fish.

From BBCNews

With sea levels rising, can humans adapt to a more watery world?
The Bajau people of South-East Asia live in stilt houses and fish underwater for up to five minutes on one breath.
What does this do to the body?

Take a deep breath in - how long until the urge to gasp for air becomes too much?
Perhaps it comes after 30 or 40 seconds.
But the bodies of habitual freedivers, who hold their breath for minutes at a time, can change to be better adapted to the water.

The Bajau people, sometimes known as the sea gypsies of Malaysia and Indonesia, are renowned natural freedivers.
Traditionally, they are born, live and die at sea, and fish by diving 20m (more than 65ft) underwater for minutes at a time on one breath.
At this depth, water pressure is almost three times what it is on the surface, squeezing lungs already deprived of oxygen.

Filmed underwater in real time for the BBC's Human Planet (see exclusive series trailer), Bajau fisherman Sulbin demonstrates his techniques off the east coast of Sabah, Borneo.
Wearing hand-made wooden goggles and armed with a spear, he first prepares himself mentally.
"I focus my mind on breathing. I only dive once I'm totally relaxed," says Sulbin, who goes into a trance-like state before entering the water.

This degree of mind control is crucial, says freediving instructor Emma Farrell, the author of One Breath, A Reflection on Freediving.
"You have to be warm and relaxed - you don't want to hyperventilate before taking your last breath."

A Bajau stilt village, built on a coral reef - some settlements are far off shore
The mammalian dive reflex - seen in aquatic animals such as dolphins and otters, and in humans to a lesser extent - helps, says Farrell.
"It's a series of automatic adjustments we make when submerged in cold water. It reduces the heart rate and metabolism to slow the rate you use oxygen."

During breath-holding, oxygen stores reduce and the body starts diverting blood from hands and feet to the vital organs.
Our bodies have a way to compensate.
Underwater pressure constricts the spleen, squeezing out extra haemoglobin, the protein in red corpuscles that carry oxygen around the body.

"Not enough research has been done to know if it wears off when you're not diving," says Farrell. "But I know people who do a lot of deep training - as Sulbin does - whose blood is like that of people living at high altitude."
In high altitudes, there is less oxygen and so the amount of haemoglobin in blood increases.

Seeing underwater

For most of their history, the Bajau have lived on houseboats, or in stilt houses built on coral reefs - some far from shore.
Many report feeling "landsick" on the rare occasions they spend time on dry land.

Thanks to time spent in the water as children when the eyes are developing, the Bajau, in common with other coastal dwelling people, have unusually strong underwater vision.
Their eye muscles have adapted to constrict the pupils more, and to change the lens shape to increase light refraction.

This makes their underwater eyesight twice as strong, according to Anna Gislen, of Sweden's Lund University, who from 2003 has compared the water vision of sea gypsy children of Thailand and Burma with that of European children.
A gap that can narrow with training.

One part of the Bajau body that hasn't fared well is the eardrum, which ruptures at a young age, says Human Planet director Tom Hugh-Jones.
"Sulbin's hearing is shot because he doesn't equalise the pressure in his ears as he dives. He's never had formal dive training. He was taught by his father to hold his breath."

There are evolutionary theories - not widely accepted, he adds - that an early ancestor of modern humans had to adapt to a partially aquatic environment.
The aquatic ape theory suggests this is why humans are largely hairless and have a subcutaneous layer of fat for underwater insulation, and so are better adapted to swimming than near relations such as the great ape.

Bajau children's underwater vision is less blurred than landlubbers of the same age.
But Sulbin and other Bajau divers have little body fat.
The wiry frame of these subsistence fisherman may actually help.

A lean physique is more efficient at using oxygen.
And having little body fat makes Sulbin less buoyant, able to walk across the reef bed with ease.
"This type of freediving - repeatedly diving to depths of 10 to 20m - carries the greatest risk of decompression sickness," says Farrell.
"But you are less likely to get the bends if you are lean, or very well hydrated."

Some Bajau die of the bends from diving - also a risk for compression divers in the Philippines encountered by the Human Planet team.
"Anyone who thinks this is an example of what a non-smoker's lungs can do will be disappointed," says Hugh-Jones.
"Sulbin smokes like a chimney. He says it relaxes his chest."

Links :

• YouTube : Pa-aling divers, one of the most dangerous fishing methods of all. A 100 strong crew in the Philippines dive to 40 metres, breathing air pumped through makeshift tangled tubes by a rusty compressor.
• TheGuardian : Unsustainable sea-farers, the last Bajau sea nomads
  

Under pressure: stormy weather sensor for hurricane forecasting

Hurricane Bill nears Cuba in 2009.
A vertical profile from the Cloud-Aerosol Lidar and Infrared Pathfinder satellite (CALIPSO) is overlaid on an image from the Moderate-resolution Imaging Spectroradiometer (MODIS). Credit: NASA

From NASA

It’s hard to believe that, in this day and age, we don’t have a way to measure sea-level air pressure during hurricanes.
NASA researchers, however, are working on a system that will improve forecasting of severe ocean weather by doing just that.
The device measures sea-level air pressure, a critical component of hurricane formation – and one that has been extremely difficult to capture.

The Differential Absorption Barometric Radar (DIABAR) prototype is scheduled to make its second flight early this year.

DIABAR remotely senses barometric pressure at sea level, which is important in the prediction and forecasting of severe weather, especially hurricanes, over oceans.

But the ability to measure sea-level air pressure is a major missing link in storm observation, says Dr. Bing Lin, an atmospheric scientist at NASA Langley Research Center in Hampton, Va.

“Air pressure is a driving force of weather systems, especially under severe weather conditions like hurricanes,” he said.
“For severe storms, the forecasts of the intensity and track can be significantly improved by pressure measurements.”

A Hurricane’s Life

A hurricane begins as a tropical wave, a westward-moving area of low air pressure.
As warm, moist air over the ocean rises in the low air-pressure area, surrounding air replaces it, and circulation forms.
This produces strong gusty winds, heavy rain and thunderclouds – a tropical disturbance.

As air pressure drops and winds sustain at 38 mph or more, the disturbance becomes a tropical depression, then a tropical storm, and finally a hurricane with sustained winds of over 73 mph.

Lin hopes eventually to be able to measure sea-level air pressure from aircraft flyovers and space-based satellites.
The local coverage provide by flyovers, combined with a broad perspective from space, will provide enough information to significantly improve the ability of forecasters to determine how intense a hurricane is and where it’s headed.

“Large and frequent sea surface measurements are critically needed,” he said.
“These measurements cannot be made from buoys and aircraft dropsondes. The only hope is from remote sensing using aircraft, unmanned aerial vehicles, and satellites.”

An effort to remotely sense barometric pressure at sea-surface level using microwaves was undertaken at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., in the 1980s.
“JPL has extensive experience on spaceborne microwave sensors,” said Lin.

First Flight

DIABAR was first deployed on a Navy MH-60S helicopter in 2009 at Naval Air Station Patuxent River in Maryland.

“We flew it, got the results, and it looks great,” said Lin.

The next step is testing this year on a blimp called the Bullet™ Class 580, the world’s largest airship. E-Green Technologies Inc. in Alabama makes the aircraft.

The 235-foot long, 65-foot diameter lighter-than-air vehicle is designed to fly on algae-based biofuel at speeds up to 74 mph and altitudes up to 20,000 feet.
It will be stationed in a hanger at Moffett Federal Airfield at NASA Ames Research Center in California.

DIABAR is a partnership between NASA Langley, Old Dominion University in Norfolk, Va., and the State University of New York at Albany.

Links :

• NASA's Hurricane ressource page
  

Mountain glacier melt to contribute 12 centimetres to world sea-level increases by 2100

Icebergs along Princess Ragnhild Coast, Antarctica (NASA)

From UniversityBritishColumbiaScience

Melt off from small mountain glaciers and ice caps will contribute about 12 centimetres to world sea-level increases by 2100, according to UBC research published this week in Nature GeoScience (Regionally differentiated contribution of mountain glaciers and ice caps to future sea-level rise).

The largest contributors to projected global sea-level increases are glaciers in Arctic Canada, Alaska and landmass bound glaciers in the Antarctic.
Glaciers in the European Alps, New Zealand, the Caucasus, Western Canada and the Western United Sates--though small absolute contributors to global sea-level increases--are projected to lose more than 50 per cent of their current ice volume.

The study modelled volume loss and melt off from 120,000 mountain glaciers and ice caps, and is one of the first to provide detailed projections by region.
Currently, melt from smaller mountain glaciers and ice caps is responsible for a disproportionally large portion of sea level increases, even though they contain less than one per cent of all water on Earth bound in glacier ice.

“There is a lot of focus on the large ice sheets but very few global scale studies quantifying how much melt to expect from these smaller glaciers that make up about 40 percent of the entire sea-level rise that we observe right now,” says Valentina Radic, a postdoctoral researcher with the Department of Earth and Ocean Sciences and lead author of the study.

Increases in sea levels caused by the melting of the Greenland and Antarctic ice sheets, and the thermal expansion of water, are excluded from the results.

Radic and colleague Regine Hock at the University of Alaska, Fairbanks, modelled future glacier melt based on temperature and precipitation projections from 10 global climate models used by the Intergovernmental Panel on Climate Change (IPCC).

“While the overall sea level increase projections in our study are on par with IPCC studies, our results are more detailed and regionally resolved,” says Radic.
“This allows us to get a better picture of projected regional ice volume change and potential impacts on local water supplies, and changes in glacier size distribution.”

Global projections of sea level rises from mountain glacier and ice cap melt from the IPCC range between seven and 17 centimetres by the end of 2100.

Radic’s projections are only slightly higher, in the range of seven to 18 centimetres.

Radic’s projections don’t include glacier calving--the production of icebergs.
Calving of tide-water glaciers may account for 30 per cent to 40 per cent of their total mass loss.

“Incorporating calving into the models of glacier mass changes on regional and global scale is still a challenge and a major task for future work,” says Radic.

However, the new projections include detailed projection of melt off from small glaciers surrounding the Greenland and Antarctic ice sheets, which have so far been excluded from, or only estimated in, global assessments.

Links :

• OurAmazingPlanet : Melt of small glaciers could have outsize effect on sea level