MUD FROM the bottom of a Co Clare lake has helped to show that an ice age can take hold in a matter of months, not years as previously thought, writes MARINA MURPHY
It was a chance trip to Ireland in 1997 to find his Irish roots that led Dr Bill Patterson, of the University of Saskatchewan in Canada, to make this unexpected discovery.
Earlier studies using Greenland ice cores suggested that a mini ice age, called the Younger Dryas, which engulfed the northern hemisphere some 12,800 years ago, took a decade or more to develop.
Not so, according to Patterson and his group. Their studies of mud cores taken from Lough Monreagh in Co Clare reveal that the ice age took just months to become established and lasted for around 1,300 years.
“Some global-warming scenarios predict that an increase in temperature could lead to rapid melting of the Greenland ice sheet, forcing a similar Younger Dryas-type ice age – essentially a rapid returning to ice age conditions,” explains Patterson.
“Our results will allow us to better predict future changes in Irish climate and thus help Ireland and the rest of western Europe better prepare for climate change.”
Because Patterson’s group used mud cores, they avoided many of the disadvantages of using ice. “As snow accumulates and is compressed into ice, some of the layers blend from melting and other processes. Thus there is a limit to the resolution of the record,” he says.
By using the mud cores from Lough Monreagh, they were able to look at climate change much more closely than others have before and could see more of the details of climate variability than were visible in other studies.
Lough Monreagh offers just the right conditions for development and preservation of detailed climate records. It has the right lake chemistry, with lots of dissolved calcium and carbonate from limestone. The vegetation in the lake includes large algae called charophytes that use the dissolved limestone to produce crystals. These crystals fall and accumulate as layers of sediment at the bottom of the lake. These layers are not disturbed by fish or animals.
Patterson’s group studied a mud core from the lake, looking at just a fraction of a millimetre at a time. They examined the core for two kinds of stable isotope: carbon and oxygen. The ratio of two naturally occurring forms of carbon (carbon 12 and carbon 13) reveal how productive the lake is, ie how much organic matter there was.
The ratio of two types of oxygen isotope (oxygen 18 and oxygen 16) is determined by temperature and rainfall. By examining changes in carbon and oxygen isotopes through time, it is possible to develop a record of how climate and the vegetation changed in western Ireland over thousands of years.
Patterson has made many trips to Ireland since 1997. “Indeed, we have worked in all 32 counties of Ireland over the years,” he says. The lakes in Ireland are perfect for climate change research because of the prime location of Ireland in the North Atlantic.
He has taken cores from Lough Inchiquin, Lough Corrib and Headford Bog, and he has collaborated with a number of researchers here, including Michael O’Connell of the Palaeoenvironmental Research Unit at NUI Galway and Patrick Wyse-Jackson in the Department of Geology at Trinity College.
“I will likely continue my work in Ireland for the rest of my career. There is a lot of work to be done. I plan to core some lakes in the south-eastern regions of the country and collect some tree samples from Donegal,” he says. “We want to better characterise how climate change is affecting moisture transport over Ireland.”
Patterson says some recent discoveries in Central America indicate a change in the movement of water from the Caribbean to the Pacific Ocean. Because of the Gulf Stream, whatever change in temperature results from this movement will reach the North Atlantic and Ireland.
“What happens in Panama doesn’t stay in Panama, but goes on to affect the climate in Ireland,” Patterson says.