HR: 1020h
AN: PP52A-0655    [Abstracts]
TI: Past Surface Temperature Variations in North West England From Borehole Temperature Data.
AU: * Hopcroft, P O
EM: peter.hopcroft@imperial.ac.uk
AF: Dept. of Earth Science and Engineering, Imperial College London Prince Consort Road South Kensington , London, SW7 2AS United Kingdom
AU: Gallagher, K
EM: kerry@imperial.ac.uk
AF: Dept. of Earth Science and Engineering, Imperial College London Prince Consort Road South Kensington , London, SW7 2AS United Kingdom
AU: Pain, C C
EM: c.pain@imperial.ac.uk
AF: Dept. of Earth Science and Engineering, Imperial College London Prince Consort Road South Kensington , London, SW7 2AS United Kingdom
AB: Determination of past climate is important for placing recent warming in the long term context. Surface air temperatures (SAT) are a standard measure of the climate variation, but SAT instrumental records are of limited extent. This project is aimed at reconstructing SAT variations in the U.K. in order to examine variability which predates the industrial age. This is to be achieved by inversion of underground temperature-depth profiles which show perturbations due to long-term surface temperature trends. The project relies on a suite of high-quality underground data, acquired by Nirex during a study for a proposed nuclear waste repository in Cumbria, U.K. The data-set includes 5 closely spaced boreholes ranging in depth from 1.0 km to 1.6 km. As such the boreholes provide an excellent opportunity for climate reconstruction. The depth of the boreholes allows reconstructions going back hundreds of years to be derived, whilst their proximity allows simultaneous inversion to extract the common climatic signal. Initially underground temperatures are simulated using a 1D finite element heat transfer model which incorporates conduction between the ground surface and the air with a surface air temperature transient boundary condition. The inversion is achieved by non-linear conjugate gradients for which the gradient is calculated by the adjoint method. This has the advantage of being both efficient and exact. Initial results of individual and simultaneous inversions show evidence for a warm period centred around AD 1200, cooling to AD 1800 with subsequent warming to the present day.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1637 Regional climate change
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005