IRELAND

According to Renken, one the most effective ways to make sense of these
developments, to improve future predictability and fill gaps in the
existing knowledge, is to look at variations in ocean and climate conditions
in the past – the very distant past. Renken deals in time-blocs of millennia
and her territory of interest is the North Atlantic region, where she
believes that a study of the evolution and demise of what was once the
British-Irish Ice Sheet can unlock information on the responses of marinebased
ice-sheets in a warming world. Quite clearly, this is no
straightforward task and marine geoscience of this kind has been
traditionally constrained by issues of time, technology and finance. It is a
time-demanding and expensive exercise, but one also dependant on
good weather to be effective.
When Renken and her fellow crew members set off on their cruise, the
weather was anything but good: strong winds and poor visibility made
work almost impossible and the Celtic Explorer, all sixty-five metres of it,
was steered into Bantry Bay for shelter before the first day was complete.
This was only a temporary setback for a venture for which preparations
had begun months earlier, when all the future crew members were
required both to undertake safety training and identify those points
along the Irish coast from which they wished to draw their sample.
There is a good reason why Renken selected an area of the Irish shelf
known as the Porcupine Bank as the focus of her research work. Situated
about 200 kilometres off the west coast of Ireland and with a raised
seabed that - at its height - reaches 200 metres below the sea’s surface,
the Porcupine Bank is ‘a block of continental crust that became separated
from the rest of the European continent by a failed rift during the opening
phase of the North Atlantic, which began about 250 million years ago.’
Owing its name to its discovery by a British survey ship in the late
nineteenth century, the HMS Porcupine, it is a well-known area of scientific
interest and research already undertaken has identified evidence of socalled
Heinrich events, the phenomenon by which large icebergs broke
from glaciers and crossed the North Atlantic. To put it another way, this
climatically sensitive region has a ‘proven potential for furnishing
palaeoceaonographic records of ice sheet and ocean circulation change.’
In all, Renken identified eight sites to be ‘cored’ in the Porcupine Bank,
four of them in what were regarded as shallow waters that still ran to a
depth of 1,000 metres, and four in deep water that plunged to around
3,000 metres. The sites were chosen in the hope that ‘optimal thickness
and undisturbed layers of the last glacier’ could be recovered using an
800 kilogram ‘gravity corer’ - a long pipe, in effect - which settles into the
ocean floor and draws out the sediment.
This is precisely how it worked out. With the researchers on board the
Celtic Explorer divided into two teams, one working by day, the other by
night, Renken found herself operating mostly under the cover of
darkness. Up on deck, the core materials were extracted, recorded,
labelled and the timings of each stage of the process were documented.
Renken stepped off the cruise ship with 12 ‘cores’ and these have provided
the focus for her subsequent laboratory-based research. X-ray technology
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