Rounding Cape Horn | Volvo Ocean Race 2014-15

On Monday, the Volvo Ocean Race fleet will round the infamous Cape Horn

 courtesy of Jean-Arnold (Volodiaja) 29/12/2015 12:40

 Cabo de Hornos with the Marine GeoGarage

I met my husband in the middle of the sea

I Met My Husband in the Middle of the Sea from olivia wyatt

For the Moken people of Southeast Asia, the sea provides nearly everything a person might need.
It offers food to eat, a comfortable place to live (assuming one owns the appropriate vessel), and, sometimes, love.
Members of this ocean-faring ethnic group – often called “Sea Gypsies” – roam the Andaman Sea off the coasts of Thailand and Myanmar.

The Moken travel on small, handcrafted wooden boats called kabangs, from which they skillfully procure fresh meals of fish, scallops, and clams, using nothing more complicated than a simple spear and a remarkable ability to hold their breath.
To see the full story: junglesinparis.com/stories/49

This film was edited exclusively for Jungles in Paris using footage from the feature "Sailing a Sinking Sea"(2015), which premieres at SXSW March 2015..
Feature film website: cargocollective.com/sailingasinkingsea

Links :

• GeoGarage blog : What freediving does to the body

 

Antarctic ice shelves are melting dramatically, study finds

A new study published by Science and led by Scripps Institution of Oceanography at UC San Diego researchers has revealed that the thickness of Antarctica’s floating ice shelves has recently decreased by as much as 18 percent in certain areas over nearly two decades, providing new insights on how the Antarctic ice sheet is responding to climate change.
Data from nearly two decades of satellite missions have shown that the ice volume decline is accelerating.

From The Guardian by Karl Mathiesen

Melting of floating ice shelves around the continent is accelerating, potentially unlocking extra sea level rise from larger ice sheets jammed behind them

The ice around the edge of Antarctica is melting faster than previously thought, potentially unlocking metres of sea-level rise in the long-term, researchers have warned.

A team of US scientists looked at 18 years’ worth of satellite data and found the floating ice shelves that skirt the continent are losing 310km³ of ice every year.

One shelf lost 18% of its thickness during the period.

The loss of ice shelves does not contribute much directly to sea level rise.

But they act like a cork in a bottle at the point where glaciers meet the sea – jamming the flow of ice from the massive ice sheets of east and west Antarctica.

 Satellite view of a large iceberg separating from Antarctica’s Pine Island Glacier, where ice loss has doubled in speed over the last 20 years.

Photograph: MODIS/Aqua/NASA

Professor Andrew Shepherd, director of the Centre for Polar Observation and Modelling at the University of Leeds, said the rates of ice loss were unsustainable and could cause a major collapse.

This is already occurring at the massive Pine Island glacier, where ice loss has doubled in speed over the last 20 years as its blocking ice shelf has melted.

“This is a real concern, because such high rates of thinning cannot be sustained for much longer, and because in the places where Antarctic ice shelves have already collapsed this has triggered rapid increases in the rate of ice loss from glaciers above ground, causing global sea levels to rise,” he said. 

 Changes to the thickness and volume of Antarctica's ice shelves between 1994 and 2012.

Credit: Paolo, et al./Science

The new research, published in the journal Science on Thursday, discovered for the first time that ice shelf melt is accelerating.

Dr Paul Holland, a climate scientist at the British Antarctic Survey (BAS), said the loss of the shelves would speed the complete collapse of the west Antarctic ice sheet, which would eventually cause up to 3.5m of sea level rise.

But he said it was highly unlikely this would occur this century.

He said the “worst case scenario” for 2100 was that ice sheets would contribute an additional 70cm to the sea level rise caused by the warming of the ocean.

 Antarctica's Brunt Ice Shelf.

Credit: Michael Studinger/NASA.

The UN’s climate science body has not previously included the ice sheets of Antarctica and Greenland in its predictions for future sea level rise because scientists are not certain how fast they will slide into the ocean.

 Pine Island Glacier on Sentinel-1A’s radar

This image combining two scans by Sentinel-1A’s radar shows that parts of the Pine Island glacier flowed about 100 m (in pink) between 3 March and 15 March 2015.

Light blue represents stable ice on either side of the stream.
Pine Island is the largest glacier in the West Antarctic Ice Sheet and one of the fastest ice streams on the continent, with an average of over 4 km per year.

About a tenth of the ice sheet drains out to the sea by way of this glacier.
With its all-weather, day and night radar vision, the Sentinel-1 mission is an important tool for monitoring polar regions and the effects that climate change has on ice.

Holland said: “What humanity needs to know is what’s the sea level rise in 2100 and the biggest source of uncertainty in that is what’s going to happen to the ice sheets.”

Over the past decade the loss of ice shelf volume in Antarctica increased from 25km³ to 310km³ every year.

It is unclear whether the loss of ice is directly related to man-made climate change or a cyclical change in ocean currents.

But the extra sea level rise from ice sheets will exacerbate the rise caused by the expansion of oceans as the world warms.

Professor David Vaughan, director of science at BAS, said the findings would help scientists to make more accurate predictions about future sea level rise.

“The rate of ice loss, especially when considered in terms of the percentage of ice lost in the last two decades, is dramatic. This research is a significant step towards improving our ability to predict the future of the Antarctic ice sheet and its contribution to global sea level rise.”

 Schematic diagram of an Antarctic ice shelf showing the processes causing the volume changes measured by satellites.

Ice is added to the ice shelf by glaciers flowing off the continent and by snowfall that compresses to form ice.

Ice is lost when icebergs break off the ice front, and by melting in some regions as warm water flows into the ocean cavity under the ice shelf.

Under some ice shelves, cold and fresh meltwater rises to a point where it refreezes onto the ice shelf.

Helen Amanda Fricker, Professor, Scripps Institution of Oceanography, UC San Diego, Author provided

The western coast ice shelves contributed the majority of the ice loss.

The rate of loss increased by 70% in the last decade.

Two shelves in this region could completely disappear within a century.

Conversely, there were some areas in east Antarctica where the shelves stayed stable or grew slightly. Vaughan said the regional variations were predicted by previous studies.

Holland said it was important not to confuse floating ice shelves, which can be up to 2km thick, with the much thinner sea ice.

The one metre thick layer of sea ice around Antarctica has been expanding in recent decades, which some scientists think is because of increasing polar winds, which push the ice further out.

Links :

• Climate Central : Antarctica’s Icy ‘Doorstops’ Thin; Rising Seas At Risk
• Scientific America : Antarctica's Ice Shelves Thin, Threaten Significant Sea Level Rise
• Washington Post : Antarctica’s floating ice shelves, the doorstop of the continent, are melting away
• NPR : Big Shelves Of Antarctic Ice Melting Faster Than Scientists Thought
• The Conversation : Shrinking of Antarctic ice shelves is accelerating

France SHOM update with the Marine GeoGarage

new update (17/03/2015) in the France (SHOM) layer

2 charts has been substituted since the last update (October 2014) :

7705   Abords de Mohammadia (replacing chart 6142 Abords de Mohammadia)

7800   Golfe d'Aden et approches (replacing chart 6947 Abords et Partie Est du golfe d'Aden)

All the other charts have been updated according to the new editions :

voir GAN Groupe d'Avis aux Navigateurs en ligne

Today 750 charts including sub-charts from SHOM material are displayed in the Marine GeoGarage.

The iceberg watch

Navigators in stressful icy areas

From VovoOceanRace by Agathe Armand

Icebergs.

Drifting blocks of ice detached from the Antarctic glaciers, frozen cubes of a couple of metres – or even tens of kilometres.
They are a polar symbol, an environmental marker – and a huge hazard for the Volvo Ocean Race teams, sailing across the Southern Ocean from Auckland to Itajaí.

 Abu Dhabi Race Team talk us through the iceberg updates they receive on the boat

and Phil Harmer's less technical approach to iceberg detection.

“So far, we’ve detected about 20 of them for the race,” says Franck Mercier of CLS.
The French company has been contracted by the organisers to deliver ice analysis and data that Alicante Race Control then uses to place the ice limits* for Leg 5.

So how exactly do you find an iceberg?
Well, it’s a tiny bit technical, and CLS has to use a lot of different data and up to four satellites for that.
First, the sea temperature.
The colder the water, the more likely they are to find drifting ice.
Currents have an effect, too, pushing it all around the Southern Ocean.
Secondly, the historical data CLS has gathered these past few years – they’ve been assisting several sailing races including the Vendée Globe and the Barcelona World Race.
And finally, the radar techniques.
Now we’re talking.

The brown and red squares are potential icy areas; the green and blue stars are detected icebergs.

CLS is working with space agencies, using their satellites to scan the sea surface in search of ice. They use altimetry techniques to draft a first exclusion zone, and SAR imagery to target the areas identified as potentially dangerous and scan them thoroughly.
Altimetry only spots the biggest icebergs, that is, ones bigger than 300m.
SAR imagery is much more precise, every standard image covering a 500km x 500km area.
SAR satellite sensors can detect smaller bits of ice – up to 50m in the case of a high-resolution picture. That’s as accurate as it gets, and it’s pretty expensive.
“Remember it’s not an exact science,” adds Franck, a French researcher who knows the icebergs by name.
“We’re contributing to decrease the risks, but we don’t suppress it.
“The idea is to detect the biggest icebergs to anticipate the position of the smaller ones, which are still very dangerous for the boats, all of this part of the ocean dynamic.”
Their biggest catch this time around?
A 1km long iceberg, first spotted because of a cold water plume, then “photographed” three times.
Franck and his colleagues have done the calculations – it’s 150m wide, 300m high, underwater part included, and it weighs 25 millions tons, the equivalent of 50 super tankers.
And the current was pushing it north at 1.1 knot, straight towards the fleet’s predicted position.
So they’ve warned Race Management, who moved the ice limits north.
They can change one of the points of this virtual line no later than 30 degrees of longitude before the first boat reaches it.

“There’s definitely plenty of ice around,” comments Simon Fisher. 
Picture : Guo Chuan / Green Dragon Racing

 
Abu Dhabi Ocean Racing’s navigator is sat at the chart table and looks at a satellite picture of the area, wearing a nervous grin.
His boat is currently 2,000 nautical miles away from land – they simply cannot afford to run into drifting ice.
In 2001-02, News Corp sailed through ice and it's not something the sailors recall fondly.
“All the blue dots are icebergs that have been picked up by the various radars," adds Simon.
"So far they’re doing a good job at keeping us out of it.”

It’s a matter of safety – but it goes way beyond that.
“There is very little scientific literature about Antarctic drifting icebergs.
The existing data only goes back 10 years or so, when sailing races took an interest.
“Because there is no record yet, we cannot really link the ice activity in the area to the global warming theme.
We see more of these icebergs, that’s true, but that’s also due to our improved techniques.
“The icebergs of the northern hemisphere come from the Artic polar icecap and are studied more. They’re directly linked to the climate change - and the quantity of sea ice decreases indeed.
“But in Antarctica, there is little change. In fact, the southern ice field tends to increase in winter… it could be one of the consequences of the global warming that causes an increase in the precipitations. These are only hypotheses.”

(picture courtesy of volodiaja)

* Ice limits: 
A virtual line the fleet must leave to starboard, it can be modified by Race Management depending on the movement of the ice in the southern part of the globe. An imaginary point has been placed every five degrees, drawing a precise contour that can be adapted.

Ice limit changes on March 25:Leg 5 Sailing Instructions Amendment 8 has been posted and communicated to the boats – waypoints 11 and 12 have been moved further north after the detection of a new iceberg close to the ice limit line had been confirmed, between 95 W and 100 W.

Links :

• GeoGarage blog : Vendee Globe : Cape Horn and ice danger / Vendee Globe : stressful areas
• BYU : Current Antarctic large iceberg positions derived from ASCAT
• CLS : Vigisat