The Arctic is remote, with often harsh conditions, and its climate is changing rapidly — warming four times faster than the rest of the Earth. This makes studying the Arctic climate both challenging and vital for understanding global climate change.
北極地處偏遠，條件往往惡劣，氣候正迅速變遷中。暖化速度比地球其他地區快四倍。就瞭解全球氣候變遷而言，這使得研究北極氣候，兼具挑戰性及至關重要。
Sandia scientists are using an existing fiber optic cable off Oliktok Point on the North Slope of Alaska to study the conditions of the Arctic seafloor up to 20 miles from shore. Christian Stanciu, project lead, presented their latest findings in December at the American Geophysical Union’s Fall Meeting in San Francisco.
美國桑迪亞國家實驗室的科學家們正使用，阿拉斯加北坡奧利克托克角附近現有的一條光纜，來研究離海岸達20英里的北極海底狀況。計劃領導人， Christian Stanciu於(2023年)12月，在舊金山舉行的美國地球物理聯盟秋季會議上，提出了他們最近的發現。
Their goal is to determine the seismic structure of miles of Arctic seafloor. Using an emerging technique, they can spot areas of the seafloor where sound travels faster than on the rest of the seafloor, typically because of more ice. They have identified several areas with lots of ice, said Christian, a geophysicist.
他們的目標是，確定北極海底數英里的地震結構。利用一種新興技術，他們能發現海底聲音，傳播速度比在海底其他區域快的區域。通常，是因為有較多的冰。地球物理學家，Christian表示，他們已經確定了幾處，具有大量冰的區域。
The scientists also used the cable to determine temperatures over the stretch of seafloor and monitored temperature changes over seasons. These data, unlike any collected before, were inserted into a computer model to infer the distribution of submarine permafrost, said Jennifer Frederick, a computational geoscientist.
此些科學家也使用該光纜，來確定整個海底的溫度，且監測了於四季中的溫度變化。計算地球科學家，Jennifer Frederick表示，此些不像任何先前收集的數據，被載入電腦模型中，來推斷海底永久凍土的分佈。
“One of the innovations of this project is that we can now use a single fiber to get acoustic and temperature data,” Christian said. “We developed a new system to remotely collect both types of data using one fiber strand. We’re getting some interesting results.”
Christian宣稱：「該計劃的創新之一是，目前我們能使用單一光纖，來獲得聲波及溫度的數據。我們開發了一種新系統，來使用一條光纖，從遠端收集這兩類型的數據。我們正在獲得一些令人感興趣的結果。」
Like leftover roast turkey sitting in the back of the freezer since Thanksgiving, Arctic permafrost is a banquet just waiting to be thawed. Specifically, as the once-living matter that was frozen during the last ice age thaws, microbes begin to digest it and produce waste gases such as methane and carbon dioxide, Jennifer said.
Jennifer表示，如同打從感恩節以來，冰箱裡剩下的烤火雞般，北極永凍土是一場，正等待解凍的盛宴。具體地說，當被凍結之曾經有生命的物質，在上一個冰河時期解凍結期間之時，微生物開始消化它，並產生諸如甲烷及二氧化碳等廢氣。
Scientists are studying just how large a microbial banquet lies frozen in the Arctic and how large of an impact those gases could have on the global climate.
科學家正在研究，究竟有多大的微生物盛宴，處於被凍結於北極的狀態，及那些氣體對全球氣候，可能具有多大的影響。
To study permafrost on the Arctic seafloor, the researchers used pulses of laser light shot down a submarine telecommunications fiber optic cable buried off the coast of Alaska, running north from Oliktok Point.
為了研究北極海底上的永久凍土，此些研究人員使用了雷射光的脈衝，投向被埋在阿拉斯加海岸附近，從奧利克托克角向北延伸的海底電信光纖。
Tiny imperfections in the cable caused light to bounce back to a sensor system. By capturing this light at two wavelengths, or colors, and comparing them, the researchers could determine the temperature of the cable every yard, Jennifer said. This is called distributed temperature sensing.
於此光纜中的微小缺陷導致了，光反彈回到一個感測器系統。Jennifer表示，藉由捕捉於兩種波長(也就是顏色)的光，並比較它們。此些研究人員能確定，被稱為分佈式溫度感測之每碼光纜的溫度。
圖1. 一處於美國阿拉斯加北坡，由永凍土層產生的pingo(冰芯山丘)，也就是，“冰丘”。 美國桑迪亞國家實驗室的科學家們，一直使用光纜來研究北極海底的永久凍土，以增進有關全球氣候變遷的瞭解，且在海底下發現了一種類似的結構。
A permafrost-created pingo or “ice pimple” in the North Slope of Alaska. Sandia scientists have been using a fiber optic cable to study permafrost in the Arctic seafloor to improve the understanding of global climate change and found a similar structure under the seafloor.
By looking at light of a different wavelength, the researchers could detect when the cable had been strained by a passing sound wave. This so-called distributed acoustic sensing provided information about the structure of the seafloor to depths of one to three miles, Christian said.
藉由檢視不同波長的光，當光纜已經被經過的聲波拖拉時，此些研究人員能探查出。Christian表示，該種所謂的分佈式聲波感測提供了，有關海底一到三英里深度的結構資訊。
Using this method, the scientists believe they have identified the bottom of the seafloor permafrost at around a quarter of a mile deep. They also found another area with unusually large amounts of ice, possibly consistent with a pingo or “ice pimple,” a domed hill formed by ice pushing upwards, he added.
使用該種方法，此些科學家認為，他們已經確定了，於大約四分之一英里深之海底永久凍土的底部。他附言，他們也發現了另一處，具有異常大量冰，可能與pingo(冰芯山丘)，也就是，“冰丘”一致的區域。這是由冰向上推，形成的圓頂山丘。
The data analysis for the measurements was done principally by Sandia intern Brandon Herr.
此些測量的數據分析，主要由桑迪亞國家實驗室，實習生Brandon Herr完成的。
“The fact that we can monitor the temperature continuously, we can now pick up changes from year to year and season to season,” Jennifer said. “We’re specifically looking for unexplainable warm spots. We think we’ll be able to see areas of seafloor seeps — somewhat like springs coming out of the ground, except on the seafloor. We’re interested in them because they’re carriers of deeper, carbon-rich fluids and are an indication of warming and change.”
Jennifer宣稱：「我們能連續監測溫度的事實，目前我們能獲得逐年及逐季的溫度變化。我們正特別地尋找無法解釋的暖和點。我們認為，我們將能發現海底滲漏的區域。除了於海底上，有點像從地下湧出的泉水。我們對它們感興趣，因為它們是更深、富含碳之流體的載體，且是暖化及變遷的一種指標。」
Sandia has been collecting climate data from northern Alaska for more than 25 years. The current research project started about a year ago and builds off prior work on the same fiber optic cable by Sandia geophysicists Rob Abbott and Michael Baker. This project is funded by Sandia’s Laboratory Directed Research program.
25餘年來，桑迪亞國家實驗室一直在收集，來自阿拉斯加北部的氣候資料。目前的研究計畫，大約一年前開始且以，由桑迪亞國家實驗室地球物理學家，Rob Abbott及Michael Baker之前，在該同一光纖電纜上進行的研究為基礎。該項計劃是由，桑迪亞實驗室定向研究(在教職員的指導下在實驗室或現場環境中進行的研究)計劃所資助。
One recent innovation from Christian’s team is a fully operational system that allows near-real time remote data collection. This minimizes time and cost of travel to Oliktok and the risk of losing data when the system is unattended, Christian said. Acoustic and temperature data cannot be collected at the same time, but one or the other now can be collected continuously.
來自Christian團隊最新的一項創新是一個，容許近乎即時遠端資料收集的全運作系統。Christian表示，這使得到奧利克托克角的時間與成本，及系統無人值守時，漏失資料的風險，減至最小。聲波及溫度數據無法同時被收集，不過現在能連續收集其中之一。
One challenge the team solved during the first year of the project was determining how to calibrate temperature data from the fiber optic cable, Jennifer said. Typically, distributed temperature sensing systems are built with self-check systems such as fiber that doubles back on itself for redundancy or with built-in thermometers.
Jennifer表示，在該項計劃第一年間，該團隊解決的一項挑戰是確定，如何校準來自光纖電纜的溫度數據。通常，分散式溫度感測系統是以，諸如加倍自身以實現冗餘的光纖，或內建溫度計之自檢系統建構的。
However, since the team is using a telecommunications dark fiber, they needed computational models to validate the seasonal temperature changes they detected. The data analysis for this was done principally by Sandia intern Ethan Conley.
然而，由於該團隊是使用電信暗光纖(也通稱為未點燃光纖，是指已鋪設在地下，且光纖股上沒有運作服務或流量的光纜)，因此他們需要諸多運算模型，來證實他們檢測到的季節性溫度變化。此數據分析主要是由，桑迪亞國家實驗室實習生，Ethan Conley所完成。
圖2 桑迪亞國家實驗室研究員，Jennifer Frederick探索了，於阿拉斯加北坡的一條河。研究於北極海底的永凍土，能增進我們有關全球氣候變遷的瞭解。
Sandia researcher Jennifer Frederick explores a river in the North Slope of Alaska. Studying permafrost in the Arctic seafloor can improve our understanding of global climate change.
Jennifer uses the data from the distributed temperature sensing and the results from the distributed acoustic sensing modeling to provide constraints to a geophysical modeling code developed by Sandia. The code models liquids and gases flowing through soils underground.
Jennifer使用來自分佈式溫度感測的數據，及分散式聲波感測模型製作的結果，來為桑迪亞國家實驗室開發的地球物理模型製作碼，提供諸多限制。此製作碼製作了，流經地下土壤的液體及氣體模型。
Jennifer uses this code to model 100,000 years of geologic history for the studied stretch of Arctic seafloor, including the average temperature of the most recent ice age and how much the sea level has risen. The results of the model are maps of the current distribution of submarine permafrost.
Jennifer使用該製作碼，來為該被研究之北極海底區域製作，包括最近冰河時期平均氣溫，及海平面已經上升多少之10萬年地質史的模型。該模型的結果，是當前海底永久凍土的分佈圖。
Limitations of the interrogator system the team uses, including the power of the laser and sensitivity of the sensors, keep the scientists from collecting data more than 18-25 miles offshore, Jennifer said. With improvements to the system, she hopes to push the distance out farther.
Jennifer表示，該團隊使用之詢問器系統的限制，包括雷射的功率及感測器的靈敏度。這阻止了此些科學家，在離岸多於18-25英里處，收集數據。藉由對此系統的諸多改進，她希望將距離外推到更遠處。
“This project has many different pieces,” Jennifer said. “I’m looking at temperature and Christian is looking at acoustics to get a subsurface model. Really you need all of these pieces to say something about the larger picture of the current distribution of permafrost and whether we are seeing changes like seeps and how that plays into the larger greenhouse gas emissions picture. Being able to use new tools and push them to their extreme to see what we can learn is really cool. ”
Jennifer宣稱：「該項目有很多不同的部分。我正在探究溫度，而Christian正在探究聲波，以獲得地下模型。實際上，任何人皆需要所有此些部分，來說明當前永久凍土分佈之更廣泛的狀況，及我們是否正在發現，像滲漏等的變化，及那如何在更大的溫室氣體排放事態中，扮演角色。能使用新工具並將其發揮到極致，來確定我們能獲悉什麼，真的很酷。」
網址：https://www.sandia.gov/labnews/2024/03/07/arctic-fiber-using-fiber-optics-to-study-seafloor-permafrost/
翻譯：許東榮
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