30 April 2012

A GLOBAL WARMING REFUGE AT EQUATORIAL ISLANDS

Some islands in the bulls'-eye of climate change may dodge the worst thanks to heretofore unknown dynamics between deep currents, upwelling, and rising temperatures.
⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏
Gilbert Island archipelago in the Pacific island nation of Kiribati. Credit: NASA/Aqua Satellite.
  
A new paper in Nature Climate Change reports on an unexpected refuge of cooler water around the equatorial Gilbert Islands—one of three archipelagos of the Pacific island nation of Kiribati (say: KEER-uh-bus).
  
This is good news at a time when when scientists predict that rising ocean temperatures in the equatorial Pacific will wreak havoc (coral bleaching, coral disease) on coral reef ecosystems by the end of the century
  
The new study shows that climate change could cause ocean currents to operate in a surprising way to mitigate warming near a handful of islands on the equator... which may then become isolated refuges for corals and fish.
    
The three archipelagos of the Pacific island nation of Kiribati straddle the Equator. Map based on: TUBS via Wikimedia Commons.
  
The dynamics of this cooler-water refuge include:
  
  1. Equatorial trade winds pushing a surface current, the Equatorial Countercurrent, from east to west
  2. A swift Equatorial Undercurrent flowing below the Equatorial Countercurrent in the opposite direction, west to east, at 100-200 meters (328-656 feet)

Where the Equatorial Undercurrent encounters an island, its flow is deflected upward on the island's western flank, carrying its cooler nutrient-rich water to the sunlit surface and creating localized areas of greater ocean productivity.

You can see the dynamics of this in the map and graph below showing chlorophyll levels—a marker of phytoplankton and hence marine productivity—across the equatorial Pacific. The red in the map view indicates highest chlorophyll / phytoplankton / marine productivity.

Credit: Kristopher B. Karnauskas and Anne L. Cohen. Nature Climate Change. DOI:10.1038/nclimate1499.
    
Clearly, the most productive waters occur in the eastern tropical Pacific, where the Equatorial Undercurrent drives up against the Galapagos Islands to create huge upwelling.
  
Chlorophyll quantities then dwindle rapidly as you move west... until the anomalous red signature marking the outlines of the Gilbert Islands of Kiribati seen inside the white-dotted rectangle. The islands are not shown in the map view, just their chlorophyll signatures.
  
Co-author Anne Cohen at WHOI says:
  
"Global models predict significant temperature increases in the central tropical Pacific over the next few decades, but in truth conditions can be highly variable across and around a coral reef island. To predict what the coral reef will experience in global climate change, we have to use high-resolution models, not global models."

Coral reef of the equatorial Pacific. Credit: USFWS.

The models predict:
  
  • That as air temperatures rise and equatorial trade winds weaken, the Pacific surface current will also weaken by 15 percent by the end of the century.
  • But the then-weaker surface current will also impose less friction and drag on the EUC, so this deeper current will actually strengthen by 14 percent.
 
The high-resolution models developed by  Kristopher Karnauskas, also at WHOI, and Cohen, suggest the amount of upwelling will actually increase by about 50 percent around the Gilbert Islands, to reduce the rate of warming waters there by about 0.7°C (1.25°F) per century.
  
From the paper:

In the central Pacific, home to one of the largest marine protected areas and fishery regions in the global tropics, sea surface temperatures are projected to increase by 2.8 °C by the end of this century. Of critical concern is that marine protected areas may not provide refuge from the anticipated rate of large-scale warming, which could exceed the evolutionary capacity of coral and their symbionts to adapt. Combining high-resolution satellite measurements, an ensemble of global climate models and an eddy-resolving regional ocean circulation model, we show that warming and productivity decline around select Pacific islands will be mitigated by enhanced upwelling associated with a strengthening of the equatorial undercurrent. Enhanced topographic upwelling will act as a negative feedback, locally mitigating the surface warming. At the Gilbert Islands, the rate of warming will be reduced by 0.7±0.3 °C or 25 ± 9% per century, or an overall cooling effect comparable to the local anomaly for a typical El Niño, by the end of this century. As the equatorial undercurrent is dynamically constrained to the Equator, only a handful of coral reefs stand to benefit from this equatorial island effect. Nevertheless, those that do face a lower rate of warming, conferring a significant advantage over neighbouring reef systems. If realized, these predictions help to identify potential refuges for coral reef communities from anticipated climate changes of the twenty-first century.
  

A bathymetric view of the Phoenix Islands group of the Pacific islands nation of Kiribati. Credit: Phoenix Islands Protected Area.
    
As an interesting aside, in 2006 Kiribati created the Phoenix Islands Protected Area (PIPA) to the east of the Gilbert Islands. In 2008 they doubled its size to make it the world's largest marine protected area. (Since then the Chagos Marine Reserve in the Indian Ocean has surpassed PIPA in size.)

At 
410,500 square kilometers (158,453 square miles), about the size of California, PIPA preserves one of the Earth's last intact oceanic coral archipelago ecosystems, complete with eight coral atolls, two submerged reef systems, underwater sea mounts, and abundant marine and bird life.
 
This is a truly phenomenal accomplishment. 

  
But if the Gilbert Islands are destined to become one of the few places where coral reef biodiversity is able to hang on in the coming century, then maybe we should begin thinking about giving those waters stronger protections too.
 
An atoll of Kiribati. Via Flickr.

The paper:
   

  • Kristopher B. Karnauskas & Anne L. Cohen. Equatorial refuge amid tropical warming. Nature Climate Change (2012) DOI:10.1038/nclimate1499
  

20 April 2012

IT'S TRUE, THE OCEAN REALLY IS GOOD FOR US

Credit: praecepitum via Flickr.

A study from the European Centre for Environment and Human Health 
followed 2,750 people in England over two years and found that most enjoy the seaside better than the countryside or urban parks.

And while all outdoor places are refreshing, the greatest pleasure comes from exercising beside the sea... regardless of a person's age or home environment or who they're travelling with or if they're alone.

The researchers suggest several possibilities (or all of them!):

  • People respond positively to the way light plays on the water or the sounds of the sea
  • We have social or cultural expectations about the benefits of the seaside
  • We have individual associations, like happy childhood memories

H/T the BBC

19 April 2012

THE POWER OF ONE: UPDATE RASA ISLAND

Elegant terns, Rasa Island, Mexico. Credit: © Julia Whitty.
  
I posted here a year ago on my trip back to Rasa Island to catch up with my old friend Enriqueta Velarde and her lifelong efforts to save the birds of Rasa Island in Mexico's Gulf of California. (This amazing place is also the setting of the first third of my book Deep Blue Home.)
  
My article from last year's trip is now out in the May/June issue of Mother Jones. It posted online today, open-access here. Read to the end and you'll learn of some tremendously exciting developments on Rasa, what Enriqueta calls the best news of her career.
  
Enriqueta Velarde, Rasa Island, Mexico. Credit: © Julia Whitty.
  
Accompanying the article is a short sidebar, also online today: Keystone Ladies
  
In ecology-speak, a keystone species is one with a disproportionate effect on its environment relative to its biomass. These six women are keystone humans.
  
Jane Goodall. Credit: World Bank Photo Collection/Flickr.
    
And I've posted a bunch of charts on MoJo Blue Marble to show you the remarkable cumulative effects of many keystone humans working on a radical idea: That nature is not only worth preserving but vital to our own survival too.
  
Credit: World Database on Protected Areas.
  
That revolutionary concept is only 164 years old. But it's already led to more than 120,000 awesomely good works... Check it out.
  
Enriqueta Velarde weighing Heermann's gulls' eggs, the casita where she lives above. Rasa Island, Mexico. Credit: © Julia Whitty.  

12 April 2012

A YEAR IN THE LIFE OF PENGUINS

Time-lapse video of penguin colonies shows challenges of snow and cold.
⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏




Two penguin rookeries in Antarctica appear in time-lapse over the course of a year. The footage was shot by researchers from the Zoological Society of London and the University of Oxford:
  
By adapting existing camera technology and using time-lapse photography, we are trialling the development of a new monitoring array for the southern polar region. By monitoring remotely, we hope to be able to ask new questions about the response of Antarctic penguins to their changing world.  
Cameras capture daily images of the movements of the penguins, allowing us to collect data on the timings of penguin life cycles at different locations, such as their time of arrival to breed and chick fledging. 
 
The first colony on the video is of gentoo penguins at Brown Bluff on the Antarctic Peninsula... Penguins come and go, then mostly go. The whiteout of winter snows buries the camera. The snow melts, penguins return to establish nests as new snow falls and melts.
    
Gentoo penguins with chicks. Credit: Liam Quinn via Wikimedia Commons.

The second colony in the video is of king penguins at the much more populated Salisbury Plain on South Georgia Island, where about 200,000 birds gather to nest... You can see that as winter approaches, and as the parents go off to fish for them, the brown woolly chicks huddle together for warmth in groups known as crèches.
  
King penguins with chicks. Credit: Ben Tubby via Wikimedia Commons.

11 April 2012

ICE VIKINGS

Crazy dudes and dudesses ice-climb icebergs off Newfoundland.
⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏


Ice Vikings from Don Wargowsky on Vimeo.






10 April 2012

THE FATE OF OLD SEA ICE

A few years ago sea ice covered a quarter of the Arctic Ocean. Now: 2 percent.
⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏

Aerial view of the edge of the sea ice in Nunavut, Canada. Credit: Doc Searls via Wikimedia Commons .
  
The latest stats on 2012's sea ice in the Arctic are out from the National Snow and Ice Data Center (NSIDC). The winter of 2012 was not the lowest year since satellite monitoring began 34 years ago—but it was well below the average.
  
And the trend continues downward... as you can see in the graph below showing March sea ice extent since 1979.
  
Credit: National Snow and Ice Data Center.
  
Worse is the fate of old sea ice. 
  
Ice older than four years used to make up about a quarter of the wintertime sea ice cover in the Arctic. It now constitutes only 2 percent. From the NSIDC page:
  
Ice age data this year show that the ice cover remains much thinner than it was in the past, with a high proportion of first-year ice, which is thin and vulnerable to summer melt. After the record low minimum of 2007 the Arctic lost a significant amount of older, thicker ice, both from melting and from movement of ice out of the Arctic the following winter. In the last few years, the melt and export of old ice was less extreme than in 2007 and 2008, and multiyear ice started to re-grow, with second and third-year ice increasing over the last three years.
 
Arctic sea ice. Credit: Pink floyd88 a via Wikimedia Commons.
  
After the near-record summertime melt of 2011 there was a decline in two-year-old ice. And although some thicker three- and four-year-old ice managed to survive, the oldest, thickest ice—the stuff more than four years old—continued to decline. 
   
Credit: National Snow and Ice Data Center courtesy J. Maslanik and M. Tschudi, University of Colorado.
  
In the map above you can see how much of 2012's winter sea ice was new ice—just formed this year (purple). And how there's virtually nothing left of the old sea ice that was born five or more years ago (white).
  
Credit: National Snow and Ice Data Center courtesy J. Maslanik and M. Tschudi, University of Colorado.
  
The graph above shows the trend since 1983... how much old ice there used to be and what an endangered species it is now.

07 April 2012

OYSTER EGGS

And other resurrections...
⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏⸏

Spawning oysters. Via.
Spawning sponge. Via.
Spawning corals. Via.
Spawning horseshoe crabs. Via.
Spawning squid. Via.
Spawning sea star. Via.
Spawning aggregation of devil rays. Via.
Spawning reef fish. Via.


Check out my earlier post Sea Eggs.