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Science and technology
科學技術
The Arctic
北極
Tequila sunset
龍舌蘭日落
Global warming may make the northernmost ocean less productive, not more so
全球變暖可能降低最北部海域的活力，而不是使之更有生命力。
ON SEPTEMBER 16th 2012, at the height of the summer melt, the Arctic Ocean's ice sheet had shrunk to an area of 3.41m square kilometres, half what it was in 1979.
2012年9月16日當天已經達到了夏季海洋冰面融化的溫度，北冰洋的冰蓋縮小到了341萬平方公里，這個數字只有1979年冰蓋面積的一半。
And its volume had shrunk faster still, to a quarter of what it was in 1979, for the sheet is getting thinner as well as smaller.
而且，冰蓋的面積仍舊以越來越快的速度在減少，將來的面積僅僅只有1979年總面積的四分之一。
One culprit is global warming, which is fiercer at the poles than elsewhere.
造成這種情況的原因之一就是全球變暖，全球變暖的后果在兩極地區更為明顯。因為冰蓋正在越來越薄，也越來越小。
The world's average temperature in 2012 was nearly 0.5°C above the average for 1951-80.
2012年全球的平均溫度比1951-1980年的平均溫度高了約0.5°C。
In the Arctic, it was up almost 2°C.
而在北極，平均溫度則高了近2°C。
This sudden warming is like the peeling back of a lid to reveal a new ocean underneath.
突然的變暖像一個被剝離的蓋子一樣，給人們呈現了一個新的海底世界。
That prospect is spreading alarm and excitement.
這種情形正在向周圍發出警報，也讓全世界興奮不已。
Though most of the excitement has been about oil and gas, and the opening of sea routes between the Atlantic and the Pacific, some people hope for a fishing bonanza, too, as warmth and light bring ecological renewal to what is now an icy desert.
雖然，最讓人興奮的是發現了石油和天然氣，還有大西洋和太平洋之間海上航線的開通，但是還是有一些人希望，在人們通過溫暖和光明對現在這個冰冷沙漠進行生態重建時，也能帶來漁業的發展機會。
But they may be disappointed.
但是他們可能要失望了。
At the moment, the waters around the Arctic account for a fifth of the world's catch.
目前，北極附近海域的捕獲量占世界總和的五分之一。
There are few fish, however, under the ice itself.
然而，在北極冰面下很少有魚。
A fishing bonanza would require big ecological change.
漁業的發展機遇將需要極大的生態改革。
Arctic Frontiers, a conference organised at the University of Tromso in January, looked at how warming will change the ecology, to estimate whether it will bring one about.
今年一月，由特羅姆瑟大學主辦的北極前沿會議上，討論了全球變暖將會對北極生態產生的變化，以預測是否有利于漁業的發展。
The consensus was that it won't—not because the Arctic will change too little, but because it will change too much.
達成的共識是—不，不是因為北極幾乎沒什么變化，而是因為北極的變化太大。
Change and decay
改革和衰退
At first sight, this is counterintuitive.
乍看之下，這簡直違背常理。
As the ice melts, more light can reach the water, and that means more photosynthesis by marine algae.
當冰塊融化時，水中將會有更多的光線，那就意味著海藻可能進行更多的光合作用。
In the past, algae began to grow under the ice sheet in May and continued to do so until late September.
過去，當五月來臨時，冰下的海藻開始生長，整個生長期會持續到九月末。
Now, such growth starts in mid-March and continues until October.
現在，海藻在三月中旬就開始生長，生長期會持續到十月。
These ice algae, attached to the sheet itself, account for half the mass of living things in Arctic waters.
這些依附于冰蓋生長的冰藻數量占了北極海域生物中的一半。
Much of the rest is unattached algae, known as phytoplankton, and tiny animals, known as zooplankton.
而其它大多數是獨立生長的海藻，被稱為浮游植物，還有被稱為浮游動物的小動物。
Both sorts of plankton support, directly or indirectly, the fish and mammals that live in the Arctic Ocean.
同時，這兩種浮游生物都直接或間接地供養了生活在北冰洋的魚類和哺乳類動物。
And the plankton, too, are flourishing thanks to global warming.
而且，由于全球變暖也讓這些浮游生物大量繁殖。
The Arctic phytoplankton bloom, which used to run from June to September, now runs from April to September.
以前，北極浮游生物的大量繁殖期是六月到九月，而現在繁殖期則早在四月就開始了，直到九月才結束。
The upshot is more plankton, farther north.
結果是越往北，浮游生物越多。
That attracts more fish.
于是就吸引了更多的魚類。
In 2000 Atlantic cod were caught throughout the Barents Sea.
2000年，在巴比倫海域捕獲了大西洋鱘魚。
By 2012 their distribution was skewed towards the northern part of that sea.
到2012年，這些浮游生物的影響更傾向于北極海域的北部地區。
Stocks of capelin used to be concentrated south of Svalbard, at latitude 75°N.
以前，大量的毛鱗魚—是鱘魚的食物—集中于北緯75度的斯瓦爾巴群島南部。
In 2012 this had moved to 78°N. Some found their way as far up as 80°N.
而2012年，發現它們已經遷移到了北緯78度。還有些人甚至發現它們已經遠移至北緯80度。
Which all sounds most promising.
這些似乎讓大多數人看到了希望。
But many researchers think it will not continue.
但是，許多研究者認為，這種情況不會再持續下去。
First, the central Arctic is too deep for some important species, such as the polar cod.
首先，對某些重要物種來說，比如，極地鱘魚北極中心的海域太深。
Young polar cod are pelagic, meaning they live at or near the surface.
年幼的極地鱘魚是海洋生物，也就是說他們生活在或者接近海平面。
Those one or more years old are benthic, meaning they live near the bottom. In the Beaufort that bottom is 200 metres down.
那些一歲或者以上的鱘魚是深海生物，他們生活的區域接近海底。
In the central Arctic it descends to about 4,000 metres, which is too deep for polar cod to survive.
在博福爾，最深處就是200米以下。而北極中心的海底是約4,000米以下，那里對鱘魚來說太深了無法生存。
A second reason why there may be no bonanza is acidification of the ocean.
漁業沒有發展前途的第二個原因是海洋的酸化。
When water absorbs carbon dioxide, it produces carbonic acid.
當水吸收二氧化碳時會產生碳酸。
More CO2 means oceans everywhere are becoming more acidic, but the phenomenon is particularly marked at high latitudes because cold water absorbs CO2 more readily than warm water does.
更多的二氧化碳意味著海洋的各個地方都會變得更加酸化，但是這種現象在高緯度地區特別明顯，因為寒冷的水會更易于吸收二氧化碳。
The retreat of the ice also exposes ever more sea to do the absorbing.
加上冰塊的融化也暴露了更多的海水，加速了對二氧化碳的吸收。
Cruises by the United States Geological Survey and the University of South Florida over the past three years have found rising carbonic-acid levels north of Alaska.
美國地質調查局和美國南佛羅里達大學在過去三年里的巡查發現，阿拉斯加北部海水的酸化程度在上升。
They have also discovered that the shells of many organisms in the area are short of aragonite, a form of calcium carbonate that gives them strength, but whose formation acid discourages.
他們也發現，這里許多生物的外殼缺少文石—一種讓這些生物產生力量的碳酸鈣形式—但是，它們體內的酸性形式阻礙了這種物質的合成。
Weaker shells means fewer shelled organisms and less food for fish.
不夠強硬的外殼就表示帶殼生物和供魚類食用的生物越來越少。
The most important reason, though, for thinking that global warming will not produce an Arctic feeding frenzy is that it may increase ocean stratification.
但是，認為全球變暖不會使北極成為巨大“經濟資源”最重要的原因是，它可能會加劇海洋的分層化。
This is the tendency of seawater to separate into layers, because fresh water is lighter than salt and cold water heavier than warm. The more stratified water is, the less nutrients in it move around.
這是一種海水分層的趨勢，因為新鮮水比又咸又冷的水輕，而又比溫暖的水重。海水分層程度越高，那么它的營養成分流動得就越少。
Most free-swimming sea creatures are pelagic.
大多數自由移動的海洋生物都是海面生物。
Algae need light, so must live near the surface—as must the zooplankton and other animals that need the phytoplankton.
海藻需要光線，所以必須生活在接近海面的區域—還有需要浮游植物的浮游動物和其它動物也同樣如此。
When they die, all these organisms sink to the bottom, where they become food for benthic creatures.
當它們死亡時，所有這些生物都會下沉到海底，在那里它們會成為底棲生物的食物。
Once they have been consumed their component molecules, including nutrients such as nitrates, phosphates and iron, are stuck in Davy Jones's locker.
一旦它們消耗掉這些成份分子，包括硝酸鹽，磷酸鹽和鐵等營養成份，就會成為戴維-瓊斯小柜子的裝飾了。
For the surface to be productive, the locker must be opened and the nutrients lifted back up, so that they can feed the growth of phytoplankton.
因為要保持海面的多樣性，小柜子必須要打開，滋養物會重新恢復生機，因此它們能夠給浮游植物提供養份。
Walking the plankton
移動的浮游生物
One of the most important ways this happens is by upwellings of water from the bottom—great churning columns caused by the collision of cold and temperate waters.
產生這種情況最重要的一種方式是通過海底水的上升流—通過寒冷和溫和水域的碰撞產生巨大的水柱。
Two of the most important are in the Arctic: south of Greenland on the Atlantic side and south of the Bering Strait on the Pacific side.
還有兩種最重要方式的實現就在北極：大西洋岸格陵蘭島南部和太平洋一側白令海峽南部。
Nitrates are abundant at the surface in both places, which is why they are among the world's richest fishing grounds.
這兩個地區的海面都有豐富的硝酸鹽，這也是為什么這兩處是世界上最大漁場的原因。
There are few upwellings in the tropics, which are thus nutrient-poor.
熱帶地區很少有上升流，因此缺乏硝酸鹽。
Stratification threatens this recycling system by suppressing the vertical movement of water.
而海水分層會抵制水的垂直流動，從而威脅著這種再循環系統。
And global warming encourages stratification because it turns the ice into a layer of fresh water that sits on the surface.
而全球變暖卻推動了海水分層，因為變暖會讓冰融化成為覆蓋著海面的新鮮水層。
Imagine the ocean as a Tequila sunrise sitting on a warm bar.
可以把海洋想象為坐落在一個溫馨酒巴上的龍舌蘭日出。
The ice cubes at the top are melting away and the orange juice is sinking to the bottom.
頂部的冰柱正在融化，桔汁慢慢滑到底部。
At the conference, a paper by Jean-eric Tremblay and Marcel Babin of Laval University, in Quebec, described the effect by reporting the density difference of water at the surface and at a depth of 100 metres in different oceans.
在這次會議上，魁北克拉瓦爾大學的讓-埃里克-特倫布萊和馬塞爾-巴賓提交的報告中，通過報告不同海洋海平面和100米深處不同的水密度，描述了這種效應。
This density difference is an index of ocean stratification.
這種水密度差就是海洋分層的標志。
Parts of the Arctic seem to be getting badly stratified.
北極部分地區的分層現象正越來越嚴重。
In winter, there is almost no density difference in the North Atlantic and the Barents Sea—as you would expect given the upwelling there.
北大西洋和巴倫支海在冬天幾乎不會出現水密度差—鑒于那里的上涌現象，人們會有所期待。
But in summer, the northern part of the Barents Sea is even more stratified than the tropical Atlantic and Pacific.
但是在夏天，巴倫支海的北部比大西洋和太平洋熱帶區域的分層程度還嚴重。
And the Beaufort Sea's stratification is high in both summer and winter.
波弗特海在夏冬兩季的分層都很活躍。
Dr Tremblay concludes that the replenishment of nutrients is already limited by stratification, especially at high latitudes, and that global warming will make things worse.
特倫布博士的結論是，養份的補充已經被分層抵制，特別是在高緯度地區，加上全球變暖會讓這種現象更加嚴重。
For Arctic productivity, the consequences are likely to be dire.
考慮到北極地區的生產力，這種后果可能更加可怕。
Paul Wassmann of the University of Tromso looked at the production of organic matter by algae in different parts of the European Arctic, and used a climate model to predict the future.
特羅姆瑟大學的保羅-威薩曼仔細研究了歐洲北極不同地區藻類產生有機物的過程，使用一種氣候模型以預測未來的形式。
The area is divided into five economic zones.
這個區域會被區分為五個經濟區。
By 2050, according to the model, primary production is likely to have fallen in three of them, to be flat in one and to rise only in the Russian zone.
根據這個模式，到2050年，其中三個經濟區的初級生產量會下降，第四個會持平，只有俄羅斯經濟區的初級生產量會上升。
Primary production is measured as the weight of carbon fixed by photosynthesis per square metre of the Earth's surface.
初級生產量是衡量地球表面每平米光合作用固定的碳重量的指標。
At the moment, in the most productive area of the Arctic, the Norwegian Sea, that figure is 142 grams a square metre a year.
目前，在北極最有生產力的區域-挪威海，這個數字為每平米年均142克。
The model predicts this will fall to 128 grams.
而根據模式預測，這個數字會跌至128克。
And by 2100, according to the model, things will be worse.
到2100年，情況會變得更糟。
By then, four of the five zones will have experienced a loss in primary production. Only Russia will benefit.
到那時，五個經濟區的四個會發生初級生產量大幅減少的現象。屆時，只有俄羅斯還會從中受益。
A warming Arctic will not, in other words, be full of fish.
換句話說，變暖的北極不會滿眼是魚。
It will simply be an ice-free version of the desert it already is.
它將還是現在看到的北方沙漠，不同的是浮在海面上的冰消失了。
