2008年06月18日

CARBON CYCLE : Sources, sinks and seasons

CARBON CYCLE
Sources, sinks and seasons

Changes in the phasing of seasonal cycles of carbon dioxide in the atmospher mark the time when a region becomes a source or a sink of Autumn warming.

One study of such changes prompts thought-provoking conclusions.



We are currently getting a 50% discount on the climatic impact of our fossil-fuel emissions.

Since 1957, and the beginning of the Mauna Loa record of atmospheric carbon dioxide, only about half of the CO2 emissions from fossil-fuel combustion have remained in the atmosphere, with the other halfbeing taken up by the land and ocean.

In the face of increasing fossil-fuel emissions, this remarkably stable airborne fraction' has meant that the rate of carbon absorotion by the land and ocean has accelerated over time (Canadell, J. G. et al. Proc. Natl Acad. Sci. USA 104,18866-1870/2007).

Unfortunately, we have no guarantee that the 50% discount will continue, and uf it disappears we will full climatic burnt of our unrelenting emission of CO2 from fossil fuels.

Indeed, climate models that include descriptions of the carbone cycle predict that treestrial uptake of carbone will decrease in the next century as crimate warms (Friedlingstein, P. et al. J. Clim. 19,3337-3353/2006).

As they describe elsewhere in this issue (Nture,7174,1-106/2008, Letter p.49), Piao et al. have used observational data to show that rising temoeratures may already be decreasing the efficiency of terrestrial carbon uptake in the Northern Hemisphere (Piao, S et al. Nature 451,49-52/2008).


Piao et al. looked at changes in the phasing of seasonal cycles of atmospheric CO2 concentratin at ten sites north of about 20゜N. Seasonal cycles of tomospheric CO2 are caused primarily by the terrestrial biosphere moving from being a net souece of carbon to the atmosphere (mainly in winter) to becoming a net sink (mainly in summer), where net carbon uptake or release is determined by the balance betweenphotosynthesis and respiration.

Changs in the phasing therefore reflect changes in the riming of when the land is a net sink or source to the atmosphere.


Piao et al. used a metric for the phasing known as the 'zero-crossing date' (the ZC date, which is when the seasonal cycle crosses the line that delineates the calculated long-term trend in CO2 concentration Fig.1).

They found that higher temperatures led to earlier ZC dates and colder temperatures to later ones, Givin the trend towards warmer autumn temparatures, they also found that the ZC was occurring an average of 0.4 days earlier par year.

In addition, they identified a temperature correlation with the ZC dates and a trend towards earlier ZC in the spring that was similar to a trend evident in a previous analysis of data from between the 1970s and 1990s (Keeling, C. D., Chin, J. F. S. & Whorf, T. P. Nature 382,146-149/1996).

But moust significantly, Piao et al. found that the advancement of the autumn ZC was occurring at nearly the same rate as the advancement of the spring ZC, meaning that gains of carbon uptake during spring were being cancelled out by carbon releases in autumn.


The shrinking autumn-uptake signal seems to contradict earlier satellite-derived 'greening' trends that showed a lengthening of the growing season in both spring and autumn in the Northern Hemisphere.(Myneni, R. B. et al. Nature 386,698-702/1997; Zhou, L. M. et al. j. Geophys. Res. 160,20069-20083/2001)

To better understand this apparent conflict, Piao et al. used a computer model of the terrestrial biosphere to help separate the observed 'bottom line' net carbon fluxes of the atmospheroc observations into atmospheric debits (photosynthesis) and credits (respiration) that are mechanistically relevant.

The model reslts suggest that increased autumn respiration (triggered by warmer temperatures) dominated over the autumn photosynthetic gains that were seen by the satellites as a longer green period.

Moreover, the model also shows that the loss of carbon in autumn seems to largely cancel the uptake gains made by earlier, greener springs, just as the atmospheric data did.


(...to be continue...)


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### DataBace ###
nature Vol 451 | Issue no.7174 | 1-106 | 3 January 2008
Letter p.49 / Net carbon dioxide losses of northern ecosystem in response to autumn warming / CEA-CNRS(仏) S. Piao etal. (update)
News & Views p.26 / CARBON CYCLE : Sources, sinks and seasons / John B. Miller (update)
THIS ISSUE p.xvii / Autumn warming (update)
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posted by 0≠素子(由理政宗) at 01:00| Comment(0) | Climate Change | このブログの読者になる | 更新情報をチェックする

Autumn warming


Autumn warming

An analysis of variation in atmospheric CO2 and ecosystem CO2 fluxes in the Northern Hemisphere shows that warmer autumns have been associated with an earlier autumn-to-winter CO2 build-up in the atnisphere.

This seems counter-intuitive : warm autumns surely imply long growing seasons and a beneficial effect on terrestrial carbon sinks as trees and plants make more biomass.

Anexplanation isprovided by satellite observations and numerical modelling.

Enhanced respiration caused by higher tenperatures causes carbon losses that offest photosynthetic gains, limiting the potetial of these ecosystems to act as carbon sinks.

And CO2 loss due to autumn warming may offset most of the increased CO2 uptake during spring.

If future warming occurs more rapidly in autumn than in spring, the ability of northern ecosystems to sequester carbon may diminish more rapidly than previously predicted.


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### DataBace ###
nature Vol 451 | Issue no.7174 | 1-106 | 3 January 2008
Letter p.49 / Net carbon dioxide losses of northern ecosystem in response to autumn warming / CEA-CNRS(仏) S. Piao etal. (update)
News & Views p.26 / CARBON CYCLE : Sources, sinks and seasons / John B. Miller (update)
THIS ISSUE p.xvii / Autumn warming (update)
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posted by 0≠素子(由理政宗) at 00:00| Comment(0) | Climate Change | このブログの読者になる | 更新情報をチェックする

2008年06月17日

Fisheries Oceanography : A menace of ABASIA

 ABASIA is known as insects causing damage to crops which you should be careful to in surface of the sea culture.

 The wild salmon resources inhabiting the Canada coast area of the sea come under serious influence by infestant flowing out from a nursery. And the part of the salmon population faces a crisis of the extinction because the spread of such a parasitic worm is very strong.

AQUACULTURE
The price of lice

Wild salmon stocks in Canadian coastal waters are being severely affected by parasites from fish farms. So intense are these infestations that some populations of salmon are at risk of extinction.

The global demand for fish is on the rise, and farmed sources are talking much of the strain ― the catch of wild fish has levelled off off, and may well be declining (Watson,R.& Pauly, D. Nture 414,534-536/2001), but aquaculture production is expanding rapidly (Food & Agriculture Organization of the United Nations State of World Aquaculture 2006 Fisheries Tech. Pap. 500 - FAO, Rome, 2006).

The ecological costs of that expansion can be heavy, however, as Krkosek et al. show in Science(Krkosek, M. et al. Science 318,1772-1775/2007).

The message of their paper is that there are some serious issues that cannot be ignored if the expansion of a aquaculuture is to be productive rather than destructive.


Consmers can readlily see the shift to wards aquaculture, particuarly for products such as farmed salmon, which has become a staple of supermarkets and restaurants in Eourope and North America.

Those buying fish will be aware of press reports of overfishing and resource depletion.

Some may even look for eco-labels or carry a little card to guide them towards the purchase of sustainable products.

As my colleague Carl Safina has saud, "Give a man a fish and you have fed him for day. Give a man a seafood choice and card and you have made him impossible to dine with."


But aquaculture products tend to be subject to less public attention, even as issuesranging from habitat destruction to the effects of using wild fish to feed farmed stocks become of greater concern (Naylor, R. L. et al. Issues Ecol. No.8/2001).

The emphasis of aquaculture developent has, not surprisingly, been on increasing production, lowering costs and improving products.

Those needs of the industry have been well served by the science of fish farming.

Unfortunately, however, research pointing out the environmental costs of production has been vewed as an attack on the industry, rather than as a challenge to be tackled and overcome.


(...to be continue...)



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### DataBace ###
nature Vol 451 | Issue no.7174 | 1-106 | 3 January 2008
news and views p.23-24
AQUACULTURE : The price of lice / Andrew A. Rosenberg

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2008年06月16日

Paradox: Whale protection and an earthquake study

Whales sink plans for seismic survey off the Canadian coast


Airgun ban halts seismic tests

 Geologists hoping to study Earth's crust off British Cloumbia have reached an impasse with the Canadian government, delaying their long-planned resarch projects.

Canada has not issed permits for geological work using airguns ― which fire bursts of air into the ocean ― on the basis that it may disturb marine life, including whales.

The dispute is so intense that one long-planned US$2.5-million project is "dead in the water".

A second sutudy, meant to facilitate a Can$100-million(US$99-million) Canadian selfloor observatory system, has been delayed at last three months, if not indefinitely.


The researchers are exasperated, arguing that they have done "everything right" to comply with environmental protection laws.

They say that Canadian agencies have capitulated to environmental organizations.


Canada has a moratorium on oil and gas development, which also involves airguns to locate reserves, along its western coastal waters.

Fears that a scientific airgun cruise could open the waters to oil and gas exploration sunk the research projects' chances, says Lincoln Hollster, a gioscientist at Princeton University in New Jersey.

Hollister has spent more than four years trying to win Canadian approval to use airguns to map the crust beneath the mountains and coastal fjords of Queen Charlotte Sound in northern British Columbia.


In 1994, he led a similar cruise without causing any environmental harm, he says.

The team has footage of humpback whale basking undisturbed in the distant background while airguns ware fired.


Anecdotes aside, there is no definitive data yet available on the effects such seismic tests have on marine animals.

Results from a US study on this conducted in summer 2007 have yet to be piblished.


In March, the Natural Sciences and Engineering Research Council Canada(NSERC)killed plans to provide Can$300,000 for the Canadian members of Hollister's team.

NSERC environmental officer Diane Fraser in Ottawa says that this was done on advice from scientists at the Department of Fisheries and Ocean(DFO).

"There were not enough scientific data to be able to determine one way or another if airguns would be harmful," says Fraser.


Since that rejection, Hollister says he has attempted repeatedly to learn from the DFO and NSERC what could done to remedy the situation, but no one responds.

Adam Silverstein, an environmental-assessment manager at the DFO in Vancouver, denies knowledge of such requests.

Hollister counters that Silverstein was repeatedly copied in on e-mail.

"It is widely recognized that everything was done right to get the permits," Hollister claims.


Margot Venton, a legal consultant for environmental group Ecojustice in Vancouver, acknowledges that the potential for oil and gas exploration was a concern, and say that as Canadian agencies failed to show the acoustic study would not cause harm to animals, it shouldn't proceed.


At the US National Science Foundation(NSF), which funds the US component of Hollister's study, there is dismay notes William Lang, who secures environmental permits for NSF-funded scientists in foreign waters.

"The very high-value proposal didn't get a fair hearing in the public forum," he says.


The airgun issue is also thwarting plans for the Marcus Langseth, a US$20-million research vessel operated by the Lamont-Doherty Earth Observatory at Colunbia University in New York City.

The ship was intended to be in Cabadian waters next July to measure seismic velocities in preparation for the installation of Neptune Canada ― a seafloor observatory ― in the summer of 2009, says Douglas Toomey, a geologist at the University of Oregon in Eugene.

But the US$2-million cruise has now been delayed until at least October.


A Lamont-Doherty spokesman says that US state department officials are seeking "reasonable assurance" that the Toomey project will secure a permit before an expensive Canadian application process is initiatsd.


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### DataBace ###
nature Vol 451 | Issue no.7174 | 1-106 | 3 January 2008
News p.3 / Whales sink plans for seismic survey off the Canadian coast / Rex Dalton

By airguns prohibition laws and ordinances for whale protection, the earthquake study at the Canada coast reached a deadlock.

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