Longest-lived animals reveal climate change secrets
Activities at the School of Ocean Science's stand at GwyddonLe at the Urdd Eisteddfod last week explain to children and adults what scientist can learn from the growth rings of the shells of our longest-lived animal.Researchers at 天天吃瓜 have used some of the world鈥檚 longest-lived animals to look at how the North Atlantic Ocean has affected our climate over the past 1,000 years.
By looking in great detail at the shell of a species of clam that can live for at least 500 years, they have shown that a weakening of the Gulf Stream 鈥� the current that brings warm water from the Caribbean to northwest Europe - may have contributed to exceptionally cold conditions in Europe from the 15th to the 19th centuries. This is the period known as the Little Ice Age, and it was a time of bitter cold, poor harvests, famines and revolutions, but also of spectacular ice fairs on the frozen River Thames.
鈥淚f the Gulf Stream is weaker, then less heat is being transported north, so that temperatures in northwest Europe became more like temperatures at the same latitude in Canada鈥�, said Dr Paul Butler of at 天天吃瓜.
Arctica islandica Clam shells, which can live to a great age.The research, published in the leading journal , uses radiocarbon analysis of the shells 鈥� which come from animals that lived north of Iceland - to work out the source of the water in which the clams were living. 鈥淭he radiocarbon tells us how long it has been since the last time the water was at the surface,鈥� said Dr. Butler. 鈥淚f the water is 鈥榦ld鈥�, we know that it originated deep within the Arctic Ocean. On the other hand, Atlantic sourced water, like the Gulf Stream, was at the surface more recently, so it is expressed in the shells as 鈥榶oung鈥�. During the Little Ice Age, the older Arctic water seems to have been dominant north of Iceland, and there was less Atlantic-sourced water. We interpret this as meaning that the Gulf Stream was weaker. Before the 15th century 鈥� in what we call the Medieval Warm Period 鈥� the situation was reversed.鈥�
The announcement by 天天吃瓜scientists in October 2007 of the remarkable lifespan of these clams generated worldwide interest and achieved a place in Time magazine鈥檚 ten most significant scientific discoveries of the year. The latest results show how this field of research can be used in the study of the marine environment of the past.
The banding on the shells seen under a microscope. These can reveal secrets about the climate.鈥淭he nice thing about these shells is that they have distinct annual growth lines, so we can accurately date the shell material鈥�, said Dr Butler. 鈥淲hat makes them even more useful is that the lines have the same patterns throughout the population, so by comparing patterns in dead shells with patterns in shells from live animals, we can work out the dates of the dead shells. That鈥檚 just the same as what archaeologists do when they use tree rings in dead wood to work out the dates of old buildings.鈥�
Publication date: 12 June 2012