Dramatic ocean circulation changes revealed

From CardiffUniversity

The unusually cold weather this winter has been caused by a change in the winds.

Instead of the typical westerly winds warmed by Atlantic surface ocean currents, cold northerly Arctic winds are influencing much of Europe.

However, scientists have long suspected that far more severe and longer-lasting cold intervals have been caused by changes to the circulation of the warm Atlantic ocean currents themselves.

Now new research led by Cardiff University, with scientists in the UK and US, reveals that these ocean circulation changes may have been more dramatic than previously thought.

The findings, published (14 January) in the journal Science, show that as the last Ice Age came to an end (10,000 - 20,000 years ago) the formation of deep water in the North-East Atlantic repeatedly switched on and off.
This caused the climate to warm and cool for centuries at a time.

The circulation of the world’s ocean helps to regulate the global climate.
One way it does this is through the transport of heat carried by vast ocean currents, which together form the ‘Great ocean conveyor’.
Key to this conveyor is the sinking of water in the North-East Atlantic, a process that causes warm tropical waters to flow northwards in order to replace the sinking water.
Europe is kept warmer by this circulation, so that a strong reduction in the rate at which deep water forms can cause widespread cooling of up to 10 degrees Celsius.

Lead author Dr David Thornalley, Cardiff School of Earth and Ocean Sciences, explains how the scientists studied changes in ocean circulation:
"We retrieved ocean sediment cores from the seafloor of the Northeast Atlantic which contained the shells of small organisms. We used these shells to examine the past distribution of radiocarbon in the ocean. Radiocarbon is a radioactive form of carbon that acts like a natural stopwatch, timing how long it has been since water was last at the sea surface. This allows us to determine how quickly deep water was forming in the Northeast Atlantic at different times in the past."

The team of scientists found that each time deep water formation switched off, the Northeast Atlantic did not fill with water that sank locally.
Instead it became inundated with water that had originally formed near Antarctica and then spread rapidly northwards.
The new results suggest that the Atlantic ocean is capable of radical changes in how it circulates on timescales as short as a few decades.

Dr Thornalley said: "These insights highlight just how dynamic and sensitive ocean circulation can be. Whilst the circulation of the modern ocean is probably much more stable than it was at the end of the last Ice Age, and therefore much less likely to undergo such dramatic changes, it is important that we keep developing our understanding of the climate system and how it responds when given a push."

Links :

• YouTube : The great ocean conveyor / Thermohaline circulation
• TheIndependant : Scientists find 'drastic' weather-related Atlantic shifts
  

Climate secrets of Mariana Trench probed

From BBCNews

The climate secrets of the deepest part of the ocean, the Mariana Trench in the western Pacific Ocean, have been probed by scientists.

The international team used a submersible, designed to withstand immense pressures, to study the bottom of the 10.9km-deep underwater canyon.

Their early results reveal that ocean trenches are acting as carbon sinks.
This suggests that they play a larger role in regulating the Earth's chemistry and climate than was thought.

Although two explorers, Jacques Piccard and Don Walsh, reached the deepest part of the Marianas Trench - a point called the Challenger Deep - in 1960, no humans have been back since.

And the handful of scientific missions, including this recent visit to this deepest spot, have been carried out using unmanned underwater vehicles.

Lead researcher Professor Ronnie Glud, from the University of Southern Denmark and the Scottish Association for Marine Science (Sams), said that working at more than 1,000 atmospheres of pressure was challenging, but advances in technology had made it possible.

He told BBC News: "This is the first time we have been able to set down sophisticated instruments at these depths to measure how much carbon is buried there."

Under pressure

Professor Glud, working with scientists from the Japan Agency for Marine Earth Science and Technology (Jamstec) and from the UK and Germany, used a lander equipped with special sensors packed in a titanium cylinder that was able to resist the remarkable pressures.

The lander was launched from a ship and took three hours to free-fall to the sea bottom, where it carried out pre-programmed experiments before releasing its ballast and returning to the surface.
The tests helped the scientists to assess the abundance of carbon at those murky depths.

Professor Glud said: "Basically, we are interested in understanding how much organic material - that is all the material produced by algae or fish in the water above - settles at the sea bed, and is either eaten by bacteria and degraded or is buried.

"The ratio that is either degraded or buried is the ultimate process determining what are the oxygen and carbon dioxide concentrations of the oceans and the atmosphere, and this gives us an overall picture of how efficiently the sea can capture and sequester carbon in the global carbon cycle."

While this has been studied in other parts of the ocean, such as the abyssal plain - the large flat area of the ocean that lies between 4.6km and 5.5km of depth - the role deep sea trenches play in the carbon cycle has until now remained largely unknown.

Professor Glud said: "Although these trenches cover just 2% of the ocean, we thought they might be disproportionately important, because it was likely that they would accumulate much more carbon because they would act as a trap, with more organic matter drifting to the bottom of them than in other parts of the ocean."

He explained that preliminary data from his experiments suggested that this was the case.
He said: "Our results very strongly suggest that the trenches do act as sediment traps. And they also had high activity, meaning that more carbon is turned over by bacteria in the trenches than is turned over at 6,000m of depth in the abyssal plain.
"What it means is that we have carbon storage going on in these trenches that is higher than we thought before, and this really means that we have a carbon dioxide sink in the deep ocean that wasn't recognised before."

The next stage for the team is to quantify their results and work out exactly how much more carbon is stored in deep sea trenches compared with other parts of the sea, and how much carbon turnover by bacteria is being carried out.

This, the researchers said, should help them to better establish the role of the ocean trenches in regulating climate.

Surprising finds

This is not the first time deep sea trenches have surprised scientists.

Recent studies by University of Aberdeen's Oceanlab team have revealed that marine life is much more abundant in this hostile habitat than was previously thought.

In 2008, they filmed the deepest living fish ever to be caught on camera - a 17-strong shoal found at depths of 7.7km in the Japan Trench, and the revealed other animals such as amphipods were present in large numbers even deeper.

Dr Alan Jamieson, from Oceanlab, said the new study was helping researchers to build up a better idea of what happens in the deepest of the deep.

He said: "The trenches continue to amaze us."

And to see an experiment such as this carried out at these extreme depths is a great leap forward in deep-sea science.

"These studies will greatly enhance our understanding of how the deep trenches contribute to carbon cycling in the world's oceans."

Links :

• BBCNews : Meet the creatures that live beyond the abyss
• BBCNews : 'Deepest ever' living fish filmed (YouTube)
• Blog Marine GeoGarage : James Cameron to dive very deep into Pacific Mariana Trench for 'Avatar' sequel
  

Massive Waimea Bay - XXL big wave surfing this week

Big wave surfing at Waimea Bay

The world famous Waimea bay, when it starts breaking in El Niño wintertime, it's the premier big wave spot, you'll find a lot of pro's and big wave legends in the water.

Not the longest wave, or the most perfect. But big.

In winter time it's home for the famous Eddie Aikau Big wave classic on the North Shore of Oahu.
-> location on the Marine GeoGarage

Another solid swell hit the islands Sunday night, and the Bay was firing on Monday morning, January 11th. (video Jan 16th)
Lots of wipe outs, a tow-in ride at first light, heavy barrels.

Links :

• SurferMag : Waimea Bay, a century of change
• NYTimes : As Hawaii’s seas roil, surfers await the big one
• SaveTheSurfers.org : keeping the spirit alive
• YouTube : I / II / III / IV
  

Barrier reef braces for flood impact

Flood water levels based on mapping by Brisbane City Council and computer modeling
by the Australian Bureau of Meteorology.

From BBCNews

As floodwaters in the Queensland capital Brisbane begin to recede, scientists are casting their eyes out to sea and wondering whether the region's greatest natural feature, the Great Barrier Reef, will be scarred by the experience.

-> Position in the Marine GeoGarage

This is the world's largest reef system - in fact, the largest thing on Earth made by living organisms, stretching for 2,600km along the coast.
Its myriad of islands and tendrils teem with fish, also supporting dugongs, dolphins, turtles and shellfish - and because of all that, a tourist trade worth several billion dollars per year.

The flood waters emerging from Brisbane itself are not a major concern, as the reef lies further north.
But northern rivers are also seeing flow rates way above normal.
As the water floods into the seas west of the reef, it inevitably freshens the environment around the reef; which is not good news.

Flood devastation mapped by high-res sky cams from NearMap
View large map

"Freshwater kills corals, and there is nothing we can do about it," says Katharina Fabricius, principal research scientist with the Australian Institute of Marine Science.

Queensland is a heavily agricultural state.
And this means that the floodwater brings with it another threat.
Pesticides, herbicides, fertilizers and sediment - mud - are washed off the farms, into the rivers and then onto the reef.
The fertilizers do in the sea what they do on land - stimulate the growth of plants.

But here, that is a problem, as the marine plants cover growing coral, choking it to death.
The sediment also hurts the reef, blocking sunlight and covering the coral fronds.
This run-off degrades the reef at the best of times; but in flood conditions, it becomes much more serious.
"The young corals are highly sensitive to exposure to organically enriched sediments," Dr Fabricius tells BBC News.
"That retards the ability of reefs to recover from the freshwater damage.
"My own research has also shown that increasing levels of nutrients can lead to more seaweed - up to a five-fold increase - and reduce coral biodiversity, with half of the coral species potentially lost from the exposed sites."

Local issue

The sites at highest risk are reefs close to the shore and close to the mouths of rivers discharging floodwater.
For example, the Keppel group of islands lies about 10km from the shore, in the path of water rushing from the mouth of the Fitzroy River.

Scientists monitoring coral there say they have already seen indications of coral damage, but that is is too early to tell how big the impact is likely to be.

As the floodwater spreads further from land, it dissipates in the seas - but can still have major consequences.
"The waters discharging from the Fitzroy River are moving hundreds of kilometres north and 50-100km offshore," says Michelle Devlin, a coral reef ecologist from James Cook University in Townsville.
"There is the potential for large areas of the reef to experience river plume water, with potentially damaging levels of nutrients, sediments and pesticides."

Recovery hopes

On their own, the floods would not necessarily be a significant threat.
The region has had them regularly down the years (see BOM reports)
1991 saw major damage to inshore coral - but it recovered.
"The 1991 flood was extremely hard for the reef - pretty much most of the corals were wiped out down to about six to eight metres of depth, and it took about 10 years for them to recover," says Alison Jones from Central Queensland University in Rockhampton, through which the Fitzroy flows.
"But they recovered magnificently; we're very spoiled here in terms of the amount of coral and the speed at which it can grow and recover."

However, what concerns scientists most is that this is just one more hit for an ecosystem that is already struggling to cope with many long-term threats.
These include overfishing, climate change, disease, chronic pollution and shipping.
"The problem is that all forms of disturbances, loads of sediments/nutrients/pesticides, as well as bleaching events from warming seawaters, more intense cyclones and more frequent outbreaks of coral predators such as the crown-of-thorns starfish, all increase in frequency and intensity," says Katharine Fabricius.
"This gives the reefs often not enough time to recover before they get hit again."

The crown-of-thorns starfish is a good example of how the various threats interact.
It eats coral polyps, the organisms that actually build reefs.
Overfishing of one of its few predators, the giant triton, allows the starfish population to expand. Meanwhile, in at least one reef system, fertiliser run-off has stimulated the growth of algae, which has provided predators with an alternative food.

Reefs stressed by climatic factors, pollution and disease will be less resilient to attack by the voracious starfish.

Climate of concern

It is likely to be several weeks at least before scientists are able to gauge the true scale of the flood's short-term impacts.
The continuing threat of bad weather means that travel to the reef is constrained.
And it will be some time - the exact period dependend again on weather - before all of the flood's cargo has travelled through the multifarious fronds of the reef system.

The hope is that it will prove to be a one-off hit from which corals, fish and everything else can recover.
The long-term threats, though, remain, despite recent initiatives to reduce agricultural run-off, constrain shipping and fishing, and tackle the crown-of-thorns.

Climate change is likely to hit reefs in the middle of the tropics harder and faster than the Great Barrier Reef.
Neverless, along with ocean acidification also caused by carbon dioxide emissions, it remains the most significant issue for the region, with a 2007 report by the Great Barrier Reef Marine Park Authority concluding:
"Projections of future sea temperatures suggest that coral bleaching could become an annual phenomenon in the course of this century, threatening to undermine the physical and ecological foundations of this diverse and productive ecosystem."

Links :

• NASA : Heavy rains in Queensland
• NASA (2007) : River plumes threaten Great Barrier Reef
  
• ESA : Swamped down under
• GeoSciencesAustralia : Satellite images show flood spread
  
• ABCNews : Great Barrier Reef 'should recover' from flood damage
  

Marine GeoGarage URL generator

http://marine.geogarage.com/api/url

Some webmasters of marine websites asked us how to help them to automatically generate some Marine GeoGarage URL from a list of geographical positions (Lat/Lon).

see also : Sharing Marine GeoGarage places

So, this link is a basic user interface allowing to get a direct access to a geographical position in the Marine GeoGarage.
Notes :

• Latitude/Longitude (WGS84) : in decimal degrees (DD.DDDDD)

e.g. : 37.91 / -122.35 with plus (+) for North/East & minus (-) for South/West

Note : Got coordinates in degree-minute-second degrees and need them in decimal format fast ?

So calculate DD.DDDDD = DD+MM/60+SS.SSS/3600 or DD+MM.MMM/60
or go to Zonums for example

• Chart layer codes :

1. USA (NOAA) : noa
2. Bahamas (WaveyLine) : wl
3. New Zealand (Linz) : nz
4. Brazil (DHN) : dhn
5. Argentina (SHN) : shn
6. UK & misc. (Brit. Adm.) : uk
7. Canada (CHS) : chs
8. Australia (AHS) : ahs
9. ...

• Zoom : maps on Google Maps have an integer "zoom level" which defines the resolution of the current view. Zoom levels between 0 (the lowest zoom level, in which the entire world can be seen on one map) to 21+ (down to individual buildings) are possible within the default roadmap maps view. Google Maps sets zoom level 0 to encompass the entire earth. Each succeeding zoom level doubles the precision in both horizontal and vertical dimensions. Note: not all zoom levels appear at all locations on the earth. Zoom levels vary depending on location, as data in some parts of the globe is more granular than in other locations.

In the case of multiple geographical positions, it's possible to use in a Unix terminal window the following command-line tool. So passing parameters for lat, lon and code :

$ curl -d lat=37.91 -d lon=-122.35 -d z=15 -d code=noa http://marine.geogarage.com/api/url.json

you get the following Marine GeoGarage URL for the corresponding Lat/Lon geographical position (e.g. : 37.91N/122.35W) :

http://marine.geogarage.com/routes?map1=eyJwb3MiOnsieiI6MTUsImxsIjoiMzcuOTEsLTEyMi4zNSJ9LCJvIjp7Im5vYSI6e319fSAg