http://hdl.handle.net/1842/1632 2013-05-20T14:46:06Z 2013-05-20T14:46:06Z Marino, Armando Cloude, Shane R. Woodhouse, Iain H. http://hdl.handle.net/1842/3723 2010-09-24T13:53:19Z 2010-05-01T00:00:00Z

Title: A Polarimetric Target Detector Using the Huynen Fork Authors: Marino, Armando; Cloude, Shane R.; Woodhouse, Iain H. Abstract: The contribution of synthetic aperture radar polarimetry in target detection is described and found to add valuable information. A new target detection methodology that makes novel use of the polarization fork of the target is described. The detector is based on a correlation procedure in the target space, and other target representations (e.g., Huynen parameters or a angle) can be employed. The mathematical formulation is general and can be applied to any kind of single target; however, in this paper, the detection is optimized for the odd and even bounces (the first two elements of the Pauli scattering vector) and for the oriented dipoles. Validation against real data shows significant agreement with the expected results based on the theoretical description.

2010-05-01T00:00:00Z Stuart, Finlay M Lass-Evans, Solveigh Fitton, J Godfrey Ellam, Robert M http://hdl.handle.net/1842/718 2005-04-19T12:30:02Z 2003-07-03T00:00:00Z

Title: High 3He/4He ratios in picritic basalts from Baffin Island and the role of a mixed reservoir in mantle plumes Authors: Stuart, Finlay M; Lass-Evans, Solveigh; Fitton, J Godfrey; Ellam, Robert M Abstract: The high 3He/4He ratio of volcanic rocks thought to be derived from mantle plumes is taken as evidence for the existence of a mantle reservoir that has remained largely undegassed since the Earth’s accretion1–3. The helium isotope composition of this reservoir places constraints on the origin of volatiles within the Earth and on the evolution and structure of the Earth’s mantle. Here we show that olivine phenocrysts in picritic basalts presumably derived from the proto-Iceland plume at Baffin Island, Canada, have the highest magmatic 3He/4He ratios yet recorded.

2003-07-03T00:00:00Z Peeters, Frank JC Acheson, Ruth Brummer, Geert-Jan A de Ruijter, Wilhelmus P. M Schneider, Ralph R Ganssen, Gerald M Ufkes, Els Kroon, Dick http://hdl.handle.net/1842/681 2005-04-19T12:30:02Z 2004-08-05T00:00:00Z

Title: Vigorous exchange between the Indian and Atlantic oceans at the end of the past five glacial periods Authors: Peeters, Frank JC; Acheson, Ruth; Brummer, Geert-Jan A; de Ruijter, Wilhelmus P. M; Schneider, Ralph R; Ganssen, Gerald M; Ufkes, Els; Kroon, Dick Abstract: The magnitude of heat and salt transfer between the Indian and Atlantic oceans through ‘Agulhas leakage’ is considered important for balancing the global thermohaline circulation1–3. Increases or reductions of this leakage lead to strengthening or weakening of the Atlantic meridional overturning and associated variation of North Atlantic Deep Water formation4–6. Here we show that modern Agulhas waters, which migrate into the south Atlantic Ocean in the form of an Agulhas ring, contain a characteristic assemblage of planktic foraminifera. We use this assemblage as a modern analogue to investigate the Agulhas leakage history over the past 550,000 years from a sediment record in the Cape basin. Our reconstruction indicates that Indian–Atlantic water exchange was highly variable: enhanced during present and past interglacials and largely reduced during glacial intervals. Coherent variability of Agulhas leakage with northern summer insolation suggests a teleconnection to the monsoon system. The onset of increased Agulhas leakage during late glacial conditions took place when glacial ice volume was maximal, suggesting a crucial role for Agulhas leakage in glacial terminations, timing of interhemispheric climate change7 and the resulting resumption of the Atlantic meridional overturning circulation6.

2004-08-05T00:00:00Z Bauch, D Darling, K Simstich, J Bauch, HA Erlenkeuser, H Kroon, Dick http://hdl.handle.net/1842/680 2005-07-27T09:15:15Z 2003-07-17T00:00:00Z

Title: Palaeoceanographic implications of genetic variation in living North Atlantic Neogloboquadrina pachyderma Authors: Bauch, D; Darling, K; Simstich, J; Bauch, HA; Erlenkeuser, H; Kroon, Dick Abstract: The shells of the planktonic foraminifer Neogloboquadrina pachyderma have become a classical tool for reconstructing glacial–interglacial climate conditions in the North Atlantic Ocean1–3. Palaeoceanographers utilize its left- and right-coiling variants, which exhibit a distinctive reciprocal temperature and water mass related shift in faunal abundance both at present and in late Quaternary sediments1,2,4,5. Recently discovered cryptic genetic diversity in planktonic foraminifers6–8 now poses signifi- cant questions for these studies. Here we report genetic evidence demonstrating that the apparent ‘single species’ shell-based records of right-coiling N. pachyderma used in palaeoceanographic reconstructions contain an alternation in species as environmental factors change. This is reflected in a speciesdependent incremental shift in right-coiling N. pachyderma shell calcite d 18O between the Last Glacial Maximum and full Holocene conditions. Guided by the percentage dextral coiling ratio, our findings enhance the use of d 18O records of rightcoiling N. pachyderma for future study. They also highlight the need to genetically investigate other important morphospecies to refine their accuracy and reliability as palaeoceanographic proxies.

2003-07-17T00:00:00Z