今日發表在《科學》(Science)一篇古代海洋溫度的新研究顯示，北大西洋深處的溫度曾經到達20℃，比現在的地中海表面還溫暖。
科學家表示新數據顯了我們急需避免二氧化碳在未來繼續升高的原因。
科學家表示這份涵蓋過去6千萬年的新數據，顯示地質歷史當中二氧化碳濃度升高所造成的巨大衝擊，也強調了我們急需避免二氧化碳在未來繼續升高。
「北大西洋的深海現在都是冰冷的海水，」研究共同作者，聖安德魯斯大學的James
Rae博士表示。「但是在5千萬年前它卻跟現在的地中海一樣溫暖。」
研究團隊包括了挪威、荷蘭、瑞士和美國的科學家。他們從深海泥質岩芯找出微小的化石殼體，利用其中的化學指紋來重建古代的海洋溫度。在當今最為頂尖的實驗室進行測量之後，他們得出了迄今最精確的溫度估計值，顯示北大西洋深處的溫度比之前認為的還要溫暖，變化幅度也更大。
卑爾根大學的教授Nele
Meckler是研究主持人。他解釋：「我們的研究對象是古代殼體中不同碳原子和氧原子的結合方式，在回答殼體形成當時的海水溫度為多少的時候，這是一種非常精確的方法。」
研究共同作者，開放大學的Phil
Sexton博士接著解釋：「由於泥巴和殼體會持續堆積在海床上，因此這些裝在管子裡、最長可以到3公里的泥巴就像是時光膠囊一樣。越往岩芯下方的殼體就越古老，藉著測量它們的化學性質，我們就能得到過去氣候變遷的長期紀錄。」
北大西洋深處的溫度到達20℃發生在始新世，大約是恐龍消失1500萬年之後，當時的大氣二氧化碳濃度是現在的三倍左右。先前的化石指標顯示該時期的特徵為非常高的氣溫，使得棕櫚樹和鱷魚可以生活在北極，而新研究顯示海洋深處也能感受這股極端的高溫。
Rae博士表示：「雖然這些古代的溫室氣候看似離我們相當遙遠，但在幫助我們了解二氧化碳對氣候變遷造成的影響時卻是十分重要。」
他接著說：「二氧化碳曾經改變了地球的樣貌，除非我們盡快限制二氧化碳的排放量，否則同樣的情況勢必會再次發生。」
Depths of North Atlantic ocean once as warm as the
Mediterranean
A new study of ancient ocean
temperatures, published today in Science,
shows that the deep North Atlantic Ocean was once 20℃ – warmer than
the surface of the modern Mediterranean.
Scientists say the new data, spanning the last 60
million years, show the huge impact of higher CO2 levels in the
geological past, and stress the urgent need to avoid continued CO2
rise in the future.
“Today the deep ocean is filled with icy cold
waters,” said Dr James Rae from the University of St Andrews, who co-authored
the study, “but 50 million years ago it was as warm as the Mediterranean is
today.”
The international team, including scientists from
Norway, the Netherlands, Switzerland and the USA, used the chemical
fingerprints of tiny fossil shells from deep-sea mud cores to reconstruct
ancient ocean temperatures. Using state-of-the-art new laboratory measurements,
they were able to obtain the most accurate temperature estimates to date,
showing that temperatures were warmer – and more variable – than previously
thought.
Professor Nele Meckler, of the University of Bergen,
who led the study, explained: “We looked at the way that different atoms of
carbon and oxygen were clumped together in these ancient shells, which turns
out to be a really accurate method of working out the temperature at the time
the shells were formed.”
Dr Phil Sexton, a co-author of the study from the
Open University, added: “Because mud and shells continually pile up on the
seabed, a long tube of this mud – up to 3km long – is like a time capsule. As
you go deeper down the core, the older the fossil shells, and by measuring the
shell chemistry we get a long record of past climate change.”
The temperatures of 20℃
for the deep North Atlantic come from a time called the Eocene, about 15
million years after the end of the dinosaurs, when atmospheric CO2
was around three times higher than today. Previous fossil indicators have shown
that this time was characterised by super warm temperatures, with palm trees
and crocodiles inhabiting the Arctic, and the new study shows that this extreme
warmth was also felt in the depths of the ocean.
Dr Rae said: “These ancient greenhouse climates may
seem a long way removed from today, but they are critical in helping us
understand the impact of CO2 on climate change.”
He added: “Although these super-hot greenhouse
climates occurred a long time ago, they are critical in helping us understand
the impact of CO2 on climate change in the future.
“CO2 has transformed the face of our
planet before, and unless we limit emissions as soon as possible, it will do it
again.”
原始論文：A.
N. Meckler, P. F. Sexton, A. M. Piasecki, T. J. Leutert, J. Marquardt, M.
Ziegler, T. Agterhuis, L. J. Lourens, J. W. B. Rae, J. Barnet, A. Tripati, S.
M. Bernascon. Cenozoic evolution of deep
ocean temperature from clumped isotope thermometry. Science, 2022. DOI: 10.1126/science.abk0604
引用自：University
of St Andrews. “Depths of North Atlantic ocean once as warm as the
Mediterranean.”
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