Giant ocean vortex linked to monsoon

The edge of the Great Whirl, shown by high chlorophyll concentrations along its flank.
Credit: IOCCG

From OurAmazingPlanet

One of the ocean's weirdest currents is the Great Whirl, a giant clockwise eddy that emerges every summer off the coast of Somalia.
The swirling waters shift sea-surface temperatures, influencing moisture carried to Asia by monsoon winds.

For more than 100 years, sailors have known the Great Whirl arrived with the onset of monsoon winds in early June and disappeared about one month after the winds died down in August.
Monsoon winds are some of the strongest on the planet, blowing at a constant 30 mph (48 km/h).

Because the massive vortex has a powerful impact on local climate, including the monsoon winds, scientists are studying how and why the Great Whirl appears.

It turns out the Great Whirl is even more closely linked to the monsoon than previously thought, but through the ocean, not through the atmosphere.
A new study reveals the clockwise current spins up nearly two months before the winds arrive.

"[Oceanic] Rossby waves are bringing in energy well before the wind forcing sets in," said Lisa Beal, an oceanographer at the University of Miami in Florida.
"We've got this precursor even before the monsoon hits it. That was rather surprising," she told OurAmazingPlanet.

The results were published online the week of Jan. 28 in the Journal of Geophysical Research.

Arabian sea's massive eddy

The Great Whirl is a humongous anti-cyclone: 185 miles (300 kilometers) across and about 3,280 feet (1,000 meters) deep.
Its waters move clockwise, with the surface current (the fastest part) clipping along at a speedy 4.5 mph (7 km/h).

The annual arrival of oceanic Rossby waves in April triggers the clockwise circulation, nearly two months before the monsoon winds start, found Beal and co-author Kathleen Donahue of the University of Rhode Island.
Rossby waves are slow-moving ocean waves, only 2 inches (5 cm) high, that travel from east to west. In the Indian Ocean, these waves are linked to the previous year's monsoon, Beal said.

"The waves themselves are disturbances caused by the previous monsoon winds, which is really neat. It's kind of a feedback from one monsoon to the next via these planetary wave processes," Beal said.
However, the current relies on the monsoon winds for its power.
"The monsoon winds don't initiate it, but it wouldn't be there if there wasn't monsoon winds," she said.

No predictable pattern

The researchers analyzed the Great Whirl's habits by combining 18 years of satellite records with data collected from a research cruise in 1995.
There have been very few research cruises through the Arabian Sea since 1995 because of Somali piracy, Beal said.

The vortex lasts for roughly 166 days each year, but the team found no predictable pattern to its location and orientation.

Over the years, the Great Whirl's wanderings were caused by its own mini-cyclones, the researchers discovered.
As the current spins, it creates two to three flanking cyclones along its edge.
(Cyclones rotate counter-clockwise, opposite to the Great Whirl.)
The interaction between the smaller cyclones and the "mother current" makes the Great Whirl move and shift around in response.

"The Great Whirls spins up these flanking cyclones because it has such high velocity shear along its edge. The water is basically rotating these cyclones clockwise around its flank, and it's causing a kind of turbulence. It's like a mutual eddy advection," Beal said.

Flip-flopping currents

The Great Whirl is not the only strange phenomenon in the Arabian Sea.
The basin is the only place in the world where the ocean's currents reverse direction every year.

"The entire circulation of the basin switches direction from summer to winter, which is really crazy.
It doesn't happen anywhere else in the world's oceans," Beal said.
Understanding how the region's currents respond to the monsoon winds is important because the circulation is directly linked to sea surface temperature, Beal said.
As with the Pacific Ocean's El Niño, sea surface temperature is the No. 1 effect on rainfall, she said.

Because the Great Whirl brings up warm water in its core, but cold water in its smaller flanking cyclones, the current has a complex effect on climate and moisture content in the monsoon winds.

Beal plans to further explore the link between the Great Whirl and Rossby waves.
"If there is some feedback between the previous monsoon and how the Great Whirl is initiated, that could give us some predictability on what the strength of the monsoon will be, and also some predictability about the rainfall, which will be important to people who live in southern Asia."

The high seas are too precious to be left to plunderers and polluters

The 'endangered' bluefin tuna: 'Many high seas fisheries have little or no protection.' 

Photograph: Brian J. Skerry/Getty Images/National Geographic

From TheGuardian

Only now with the launch of the Global Ocean Commission are we finally addressing the ravages of the oceans

The oceans are changing faster today and in more ways than at any time in human history.
We are the cause.
Which is why I welcome the launch of the Global Ocean Commission, dedicated to ending the neglect, in international affairs, of the high seas.
These seas lie far beyond the horizon – 200 nautical miles offshore to be precise – and begin where sovereign national waters give way to the global commons, owned by none, shared by all.

There was a time when foreign travel gave many people a familiarity with the high seas.
Rather than a few hours in a plane, "long haul" often meant days or weeks spent staring at an endless canvas of sea and sky.
Today, few of us know much about what happens beyond the horizon and still fewer care.
Like all common spaces, the high seas are vulnerable to misuse and abuse.
Our indifference is costing the world dear for the high seas are being plundered.

For most of our maritime history, the open oceans have been seen as dangerous places to be traversed as quickly as possible.
Remote and enduring, they were home to giant fish and whales; seabirds wandered their featureless expanses and ancient corals grew in the eternal darkness of the abyss.

Despite an increased awareness of overfishing, the majority of people still know very little about the scale of the destruction being wrought on the oceans.

This film presents an unquestionable case for why overfishing needs to end and shows that there is still an opportunity for change.

Whalers were first to spot the high seas' potential as a source of wealth, slaughtering their way through the 19th and 20th centuries until the great whales were a few breaths from extinction. Ocean-going seabirds such as albatross and petrels were also early victims of exploitation due to the vulnerability of coastal nesting sites.
But commercial fishing was a relative latecomer.
Fishing began in earnest in the 1950s as long-line and drift-net fleets sought profit in open ocean species such as tuna, swordfish, marlin and shark.
By the 1980s, they were everywhere.
The huge collateral damage done by these fisheries soon caused alarm.
Drift nets spread lethal curtains tens of miles long killing indiscriminately, taking turtles, whales and dolphins alongside the target fish.
They were banned by the UN in 1992 but long lines studded with tens of thousands of hooks continue the massacre.
Enough long lines are set every night to wrap around the globe 500 times.

In a separate development, from the 1960s, Soviet and European vessels began to probe deeper in response to the decline of their shallow water fish stocks.
They found riches on the Atlantic frontier, where continental shelves fall away into the deep, and around the summits of submerged offshore mountains.
But these fisheries have proved highly vulnerable to overexploitation.
Within the space of a few decades, species such as the roundnose grenadier and orange roughy have become so depleted they are considered threatened with extinction.
Deep sea fisheries carry another high cost in loss of coral forests and sponge groves.
Life is glacial in the frigid inkiness of the deep, so these habitats have developed over thousands of years, sustained by table scraps sinking from a narrow surface layer where sunlight fuels plant growth.
The bottom trawls that are used to catch fish cut down animals that are hundreds or even thousands of years old.

Without ever making a conscious decision to do it, we are losing unseen habitats whose equals on land would include the giant redwood glades of North America, the baobabs of Madagascar and Amazon rainforest.
Where are the regulators in all of this?
Many high seas fisheries have little or no protection.
Regional fisheries management organisations, where they exist, have been charged by the United Nations with management of fish stocks such as tuna.
The best of them are sleeping on the job; the worst, as with the "management" of the endangered Atlantic bluefin tuna, make decisions in the full knowledge that what they are doing is destroying what they are supposed to protect.

Captain Charles Moore - Plastic Ocean

Fishing is not the only problem.
Remote as they seem, the high seas are no further than anywhere else from the inescapable influence of climate change, nor are they beyond the reach of pollution.
Mercury and industrial emissions from power plants and industry shed their toxic loads far out to sea. Chemicals concentrate in the surface layer that separates air from water and can quickly leapfrog across thousands of miles of ocean in wind-whipped aerosols.
Circulating currents gather the floating refuse of modern society into enormous regions that have been dubbed the "great ocean garbage patches".
Over the years, drifting plastics fragment into ever-smaller particles that pick up and concentrate chemical pollutants such as mercury and DDT.
Small fish mistake plastics for food and pass chemicals up the food chain until they reach the flesh of animals we eat, like tuna and sharks.
What goes around comes around.

This video features David Roberts of Grist
promoting general awareness of the science of climate change.

If this were all we had to fix, it would be challenge enough.
But there is more.
Climate change is enlarging the deserts of the sea as surely as it is doing so on land.
Surface waters of the open ocean have all the light but few nutrients, which severely limits productivity.
Most of the time, upward mixing of nutrients is inhibited by a density barrier between the warm and light surface layer and cold, dense water below.
Global warming is heating the surface ocean, making it even harder to cross between these layers. This in turn is starving deeper waters of oxygen that has to mix downwards from the atmosphere and surface plants.
The living space in the oceans is shrinking.

Ever wondered what impacts all that carbon dioxide we emit is having on the ocean and what consequences this could have for the future?

This Google Earth Tour, narrated by Dan Laffoley from the International Union for Conservation of Nature (IUCN), who is Chair of Europe's Ocean Acidification Reference User Group, takes us on a global journey to understand what impact carbon dioxide has on ocean chemistry.

It explores the phenomenon of ocean acidification and explains why even small changes to ocean chemistry could have profound implications for marine life and future economic activities.

There is one final blow to the integrity of the oceans that may yet prove the heaviest of all.
Carbon dioxide from fossil fuels is building up in the sea as well as the atmosphere.
There, it forms carbonic acid (as in fizzy drinks).
Acid is the nemesis of carbonate, the basic ingredient of chalk and a fundamental building block of ocean life, including shellfish, corals and plankton.
If we do nothing to curtail emissions, ocean acidity will soar by the century's end toward levels not experienced for 55 million years in a period of runaway global warming.
It is difficult to predict the exact outcome, but let's just say that last time around, corals and chalky plankton suffered badly.

We carry on today much as we have done for thousands of years, using natural resources as if they were endless.
But population growth changes everything.
We must get to grips with the consequences of our planetary dominance, otherwise the consequences will master us.
Out of sight and out of mind they may be, but the high seas are vital to everyone.
By virtue of their sheer size they play a dominant role in the processes that keep our world habitable. They are too big for us to let them fail.
The Global Oceans Commission has urgent work to do.

Links :

• TheGuardian : David Miliband to head global fight to prevent eco-disaster in oceans 
• NYT : Europe adopts sweeping changes to fishing policy

Dolphins trick fish with mud "nets"

Shipwreck lifeboat washes up in Australia, after about 6,000 miles of drift

In a surprising find, a fisherman has stumbled across a ship wreck lifeboat along The Coorong, almost two years after it was lost at sea.

From ABCNews

The location of the Nightingale Islands (left point) in comparison to the Coorong, South Australia (right point), where the lifeboat was found :

difficult to imagine the real directions between the two locations

during this long drift with the prevailing currents.

A study of these prevailing currents show that, having drifted south of the Cape of Good Hope, it would be likely that the lifeboat would have drifted southwards, before either heading towards Southern Australia, or being sucked into the anti-clockwise current circulation in the Southern Indian Ocean. Theoretically it could have floated around this system more than once.
Others may argue that, like the Wandering Albatrosses, the lifeboat may have tracked further south, and continued beyond the south of New Zealand, into the Pacific, following an almost continuous easterly drift of ocean currents around the Southern Ocean, eventually passing Cape Horn, back into the Atlantic, passing South of the Cape of Good Hope again...and hence to South Australia.
Any other ideas?

 

A lifeboat has washed ashore in Australia from a ship that ran aground in the middle of the South Atlantic Ocean almost two years ago.
The lifeboat from the bulk carrier Oliva floated about 12,000 kilometres from Nightingale Island to a beach at the Coorong wetlands near the mouth of the Murray in South Australia.

The ship's crew of more than 20 was rescued after the maritime accident in March 2011, which caused a big oil spill.
The Oliva had been sailing from Brazil to China.
It broke up two days after the accident, the forward section drifting off.
The aft section of the bulk carrier capsized and sank. (see video)

Nick Balmer, from Victor Harbor, just west of the Coorong, spotted the lifeboat when he went fishing and said it was in good condition considering its long journey.
"The seats inside are torn up so, you know, the chances are it's probably been sitting on other beaches around the world maybe, you know, and people have sort of trashed it inside a bit," he said.
"The lifejacket was out on the beach down the Coorong there so we're not the first person to find it."

The South Australian Transport Department said it was unsure what to do with the 6.8-metre lifeboat.
Official Joe Rositano said departmental staff were travelling to the beach near Salt Creek and planned to ensure the boat could not wash back out to sea.
"What we're going to make sure is that it actually doesn't become a navigation hazard again," he said.
"What we're going to look at doing is perhaps anchoring it initially because the thing weighs, without the water in it it's a couple of tonnes, so it's not an easy thing to move."

Storm force - Scotland experiences the highest seas in the world

Tuesday's swell chart indicated that the previous day's high seas continued off Scotland

From BBC

Scotland and Ireland experienced the highest seas anywhere in the world earlier this week, according to swell models.
But what is a swell model and how do they work?

Far off the Western Isles in the North Atlantic a buoy called K5 gathers data on the movement of the sea.

situation for the 4th of February

The information is monitored by the National Oceanic and Atmospheric Administration and other organisations such as the Met Office.
The data is also among resources surfers' website Magicseaweed.com in Kingsbridge, South Devon, uses to create swell models - forecasts of wave sizes out to sea and their size close to shore.

Wild Weather! more info: fair-isle.blogspot.co.uk- Fair Isle, Shetland, Scotland, the South Lighthouse received wave damage today Feb. 4, 2013. The south west corner wall was washed down onto the football pitch, window smashed in the NLB engine room, etc.

On Monday, K5 - also known as station 64045 - was relaying some big numbers.
Wave heights of 14.3m (46.90ft) were recorded during Monday to create the highest seas anywhere in the world on that day, according to Magicseaweed.com's modelling.
Significant conditions continued on into Tuesday.

Forecaster Ben Freeston said:
"It's been an active winter in the Northern Atlantic with several large storms already.
"Typically a swell in this sort of size range occurs about once per winter approaching Scotland, which is uniquely placed globally for such an event.
"The storm of 4 February pushed waves averaging almost 47ft past a wave buoy some 200 miles west of the coast of Scotland with waves of an average 30ft recorded on the lee side of the Shetlands.
"While this is extremely large by any standard it's not actually unusual in range for Scotland in the winter."

 The swell chart produced for Monday - reds, pinks and black indicate the highest waves

- courtesy of magicseaweed -

As well K5, Magicseaweed draws on other meteorological information that is being shared across the world by trained observers and air and sea traffic and being sent from automated weather stations and satellites.

The modelling done in Kingsbridge results in colour-coded swell charts.
Bright pinks, deep reds and black signify the highest waves.

Mr Freeston said:
"At Magicseaweed we use a long range numeric modelling system to predict and track these storms and the swells and surf they create.
"As a big storm like this starts to appear in our system - sometimes almost a fortnight in advance - we'll talk simultaneously to big wave surfers and surf contest organisers in Ireland, France, Spain and Portugal who are attempting to ensure they can find the right location at the right time for the largest possible waves and best possible wind conditions."

 Water mountain: Coastal areas including this harbour on the North Sea are likely to suffer the most today

But the prime conditions surfers are seeking begin as something to be avoided, storms in northern and southern latitudes where cold polar air meets warmer tropical air.

Mr Freeston said that for "truly extreme" wave conditions in the Northern Hemisphere there were just two key regions: Scotland/Ireland and Alaska/Western Canada.
He said: "By comparison an Alaskan wave buoy at a similar latitude tops out over the same period at a maximum significant height of just 33ft. A height exceeded almost every winter in Scotland."

Among the chief reasons for this, he added, was a phenomena known as the Greenland Tip Jet.
The forecaster said that as storms pass to the north of Greenland the large, prominent land mass acts almost like an aircraft wing, creating an area of higher speed winds flowing to the east around the tip. This wind pattern builds energy into swells and points itself directly at Scotland.

Nic von Rupp’s tow-in trial by fire on a chilly Irish slab (January 30, 2013)

Frame grab: Divine Intervention / José Pedro Gomes

Mr Freeston said: "Despite these enormous waves the issue for surfing in Scotland or Ireland is that the same storms that create these colossal swells tend to march over the land as the waves arrive, so a typical swell is accompanied by extremely strong winds that make surfing dangerous or impossible in all but the most sheltered locations.
"For this reason it's probably accurate to say that Scotland has some of the largest waves on Earth - but is far less likely to see them ridden at this size than other locations a little further removed from the storm's path."

 Rubble: Scottish islanders are cleaning up after the 'storm of a lifetime' saw 80ft waves destroy lighthouse sea defense walls which had stood for 122 years on Fair Isle, off the north coast

Dave Wheeler, a photographer and local weather forecaster on Fair Isle, in Shetland, was monitoring Monday's swell charts.
He said the high seas were among the worst in living memory on the remote island.
Waves presented as bright colours on the charts caused actual damage on Fair Isle, with the sea smashing a wall at the 120-year-old South Lighthouse and washing the debris several hundred metres inland.
Mr Wheeler said: "No-one can remember damage to this extent at the lighthouse.
"Monday's sea conditions have been described as phenomenal."

Links :

• MagicSeaWeed : Huge Surf at Mullaghmore