On the Irish island of Inishboffin, we are fishermen from father to son.
So,
when a new European Union regulation deprives John O' Brien of his
ancestral way of life, he takes the lead in a crusade to assert the
simple right of indigenous people to live off their traditional
resources.
Joining together NGOs, fishermen from all over Europe and ordinary citizens, John braved industrial lobbies for 8 years and proved, from the Donegal coast to the corridors of Brussels, that another Europe is possible.
ESA’s CryoSat and the Copernicus Sentinel-1 missions have been used to measure subtle changes in the elevation and flow of ice shelves that, in turn, reveals how huge canyons are forming underneath. Warm bottom ocean water is entering the cavity under Antarctica’s Dotson ice shelf and is stirred by Earth’s rotation.
This is causing one side of the ice shelf to melt.
The canyon, which has formed over 25 years, is now 200 m deep in places and the ice just above it is heavily crevassed, affecting the shelf’s future ability to buttress the ice on land.
We are all aware that Antarctica’s ice shelves are thinning, but recently scientists have also discovered huge canyons cutting through the underbelly of these shelves, potentially making them even more fragile. Thanks to the CryoSat and Sentinel-1 missions, new light is being shed on this hidden world.
Antarctica is surrounded by ice shelves, which are thick bands of ice that extend from the ice sheet and float on the coastal waters.
They play an important role in buttressing the ice sheet on land, effectively slowing the sheet’s flow as it creeps seaward.
Some fast-thinning glaciers drain into the Amundsen Sea
(Pine island, Twaites, Haynes & Pope, Smith, Kohler and Dotson Ice shelf in the Admunden Sea)
The ice sheet that covers Antarctica is, by its very nature, dynamic and constantly on the move. Recently, however, there has been a worrying number of reports about its floating shelves thinning and even collapsing, allowing the grounded ice inland to flow faster to the ocean and add to sea-level rise.
While scientists continue to study the changing face of Antarctica, monitor cracks in the surface of the ice that might signal the demise of a shelf and learn how these changes are affecting the biology of coastal waters, they are also aware of dramatic changes taking place below the surface, hidden from view.
Ice shelf appears flat
There are huge inverted canyons in the underside of ice shelves, but little is known about how they form and how they affect the stability of the ice sheet.
One type is thought to be caused by subglacial water that drains from beneath the ice sheet and runs into the ocean.
In this region, the ocean water is stratified, with the warmer water at the bottom.
However, as the colder meltwater pours down into the ocean it then rises because it is less dense than the seawater – but as it rises it drags up the warm bottom water which causes the underbelly of the floating ice shelf to melt.
Another type is thought to be caused by the way ocean water circulates under the shelf.
Scientists have been using ESA’s CryoSat to study changes in the surface of the ice shelf and the Copernicus Sentinel-1 mission to study how shelves flow to learn more about what’s going on hidden from view.
Their focus has been on the Dotson ice shelf in West Antarctica.
Dotson ice shelf from Sentinel-1
Noel Gourmelen from the University of Edinburgh said “We have found subtle changes in both surface elevation data from CryoSat and ice velocity from Sentinel-1 which shows that melting is not uniform, but has centred on a 5 km-wide channel that runs 60 km along the underside of the shelf.
“Unlike most recent observations, we think that the channel under Dotson is eroded by warm water, about 1°C, as it circulates under the shelf, stirred clockwise and upward by Earth’s rotation.
“Revisiting older satellite data, we think that this melt pattern has been taking place for at least the entire 25 years that Earth observation satellites have been recording changes in Antarctica.
“Over time, the melt has calved in a broad channel-like feature up to 200 m deep and 15 km across that runs the entire length of the underside of Dotson ice shelf.
“We can see that this canyon is deepening by about 7 m a year and that the ice above is heavily crevassed.
A figure showing Dotson Ice Shelf and the Amundsen Sea Sector of West Antarctica.
Colors show ice flow of grounded ice across the grounding line (white line) feeding floating ice shelves (DIS and Crosson Ice Shelf (CIS)), as well as ocean regions of high annual primary productivity (APP) (Arrigo et al., 2015).
(Image credit: Noel Gourmelen)
“Melt from Dotson ice shelf results in 40 billion tonnes of freshwater being poured into the Southern Ocean every year, and this canyon alone is responsible for the release of four billion tonnes – a significant proportion.
”The strength of an ice shelf depends on how thick it is. Since shelves are already suffering from thinning, these deepening canyons mean that fractures are likely to develop and the grounded ice upstream will flow faster than would be the case otherwise.
“It is the first time that we’ve been able to see this process in the making and we will now expand our area of interest to the shelves all around Antarctica to see how they are responding. We couldn’t do this without CryoSat and the European Commission’s Copernicus Sentinel missions,” added Dr Gourmelen.
New research published on Monday finds there is so much wind energy potential over oceans that it could theoretically be used to generate “civilization scale power” — assuming, that is, that we are willing to cover enormous stretches of the sea with turbines, and can come up with ways to install and maintain them in often extreme ocean environments.
It’s very unlikely that we would ever build out open ocean turbines on anything like that scale — indeed, doing so could even alter the planet’s climate, the research finds.
But the more modest message is that wind energy over the open oceans has large potential — reinforcing the idea that floating wind farms, over very deep waters, could be the next major step for wind energy technology.
“I would look at this as kind of a greenlight for that industry from a geophysical point of view,” said Ken Caldeira of the Carnegie Institution for Science in Stanford, Calif.
The study, in the Proceedings of the National Academy of Sciences, was led by Carnegie researcher Anna Possner, who worked in collaboration with Caldeira.
An offshore wind farm stands in the water near the Danish island of Samso, May 19, 2008. Reuters/Bob Strong
The study takes, as its outset, prior research that has found that there’s probably an upper limit to the amount of energy that can be generated by a wind farm that’s located on land.
The limit arises both because natural and human structures on land create friction that slows down the wind speed, but also because each individual wind turbine extracts some of the energy of the wind and transforms it into power that we can use — leaving less wind energy for other turbines to collect.
“If each turbine removes something like half the energy flowing through it, by the time you get to the second row, you’ve only got a quarter of the energy, and so on,” explained Caldeira.
The ocean is different.
First, wind speeds can be as much as 70 percent higher than on land.
But a bigger deal is what you might call wind replenishment.
The new research found that over the mid-latitude oceans, storms regularly transfer powerful wind energy down to the surface from higher altitudes, meaning that the upper limit here for how much energy you can capture with turbines is considerably higher.
“Over land, the turbines are just sort of scraping the kinetic energy out of the lowest part of the atmosphere, whereas over the ocean, it’s depleting the kinetic energy out of most of the troposphere, or the lower part of the atmosphere,” said Caldeira.
Wind farms offshore British coast with the GeoGarage platform (UKHO ENCs)
The study compares a theoretical wind farm of nearly 2 million square kilometers located either over the U.S. (centered on Kansas) or in the open Atlantic.
And it finds that covering much of the central U.S. with wind farms would still be insufficient to power the U.S. and China, which would require a generating capacity of some 7 terawatts annually (a terawatt is equivalent to a trillion watts).
But the North Atlantic could theoretically power those two countries and then some.
The potential energy that can be extracted over the ocean, given the same area, is “at least three times as high.”
It would take an even larger, 3 million square kilometer wind installation over the ocean to provide humanity’s current power needs, or 18 terawatts, the study found.
That’s an area even larger than Greenland.
Hence, the study concludes that “on an annual mean basis, the wind power available in the North Atlantic could be sufficient to power the world.”
It is not just utility companies racing to respond to the rise of renewable energy.
Oil and gas giant Statoil is building on four decades of offshore experience to erect its first floating wind farm.
But it’s critical to emphasize that these are purely theoretical calculations.
They are thwarted by many practical factors, including the fact that the winds aren’t equally strong in all seasons, and that the technologies to capture their energy at such a scale, much less transfer it to shore, do not currently exist.
Oh, and then there’s another large problem: Modeling simulations performed in the study suggest that extracting this much wind energy from nature would have planetary-scale effects, including cooling down parts of the Arctic by as much as 13 degrees Celsius.
“Trying to get civilization scale power out of wind is a bit asking for trouble,” Caldeira said.
But he said the climate effect would be smaller if the amount of energy being tapped was reduced down from these extremely high numbers, and if the wind farms were more spaced out across the globe."
“I think it lends itself to the idea that we’re going to want to use a portfolio of technologies, and not rely on this only,” said Caldeira.
Energy gurus have long said that among renewable sources, solar energy has the greatest potential to scale up and generate terawatt-scale power, enough to satisfy large parts of human energy demand.
Caldeira doesn’t dispute that.
But his study suggests that at least if open ocean wind becomes accessible someday, it may have considerable potential too.
Wind farms projects in Europe
blue : authorized / green : operational / grey : planned /
brown : production / red : under construction
source : EMODNET
Alexander Slocum, an MIT mechanical engineering professor who has focused on offshore wind and its potential, and who was not involved in the research, said he considered the paper a “very good study” and that it didn’t seem biased.
“The conclusion implied by the paper that open ocean wind energy farms can provide most of our energy needs is also supported history: as a technology gets becomes constrained (e.g., horse drawn carriages) or monopolized (OPEC), a motivation arises to look around for alternatives,” Slocum continued by email.
“The automobile did it to horses, the U.S. did it to OPEC with fracking, and now renewables are doing it to the hydrocarbon industry.”
“The authors do acknowledge that considerable technical challenges come into play in actually harvesting energy from these far off-shore sites, but I appreciate their focus on the magnitude of the resource,” added Julie Lundquist, a wind energy researcher at the University of Colorado, Boulder.
“I hope this work will stimulate further interest in deep water wind energy.”
Underscoring the theoretical nature of the calculations, Lundquist added by email that “current and foreseeable wind turbine deployments both on- and off-shore are much smaller than would be required to reach the atmospheric energy limitations that this work and others are concerned with.”
The research points to a kind of third act for wind energy.
On land, turbines are very well established and more are being installed every year.
Offshore, meanwhile, coastal areas are now also seeing more and more turbine installations, but still in relatively shallow waters.
But to get out over the open ocean, where the sea is often well over a mile deep, is expected to require yet another technology — likely a floating turbine that extends above the water and sits atop some kind of very large submerged floating structure, accompanied by cables that anchor the entire turbine to the seafloor.
Each wind turbine is taller than Big Ben and the farm can power 20,000 homes.
Experimentation with the technology is already happening: Statoil is moving to build a large floating wind farm off the coast of Scotland, which will be located in waters around 100 meters deep and have 15 megawatts (million watts) of electricity generating capacity.
The turbines are 253 meters tall, but 78 meters of that length refers to the floating part below the sea surface.
“The things that we’re describing are likely not going to be economic today, but once you have an industry that’s starting in that direction, should provide incentive for that industry to develop,” said Caldeira.
The Mercator projection creates increasing distortions of size as you move away from the equator.
As you get closer to the poles the distortion becomes severe.
Cartographers refer to the inability to compare size on a Mercator projection as "the Greenland Problem."
Greenland appears to be the same size as Africa, yet Africa's land mass is actually fourteen times larger (see figure below right).
The nineteen largest islands in the world in a to-scale
Because the Mercator distorts size so much at the poles it is common to crop Antarctica off the map. This practice results in the Northern Hemisphere appearing much larger than it really is.
Typically, the cropping technique results in a map showing the equator about 60% of the way down the map, diminishing the size and importance of the developing countries. (from Peter's Map)
Many large countries seem to be as tall as Greenland
Whether you realize it or not, you're probably pretty familiar with the
Mercator projection.
It's the chosen map of Google, and often displayed
in classrooms around the country.
