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Emeritus Woodwardian Professor of Geology I. Nicholas McCave

Emeritus Woodwardian Professor of Geology I. Nicholas McCave

Emeritus Professor

Climate Change and Earth-Ocean-Atmosphere Systems

N298

Office Phone: +44 (0) 1223 333422

Research Interests

The Sediment Record of the Deep-Sea Circulation

Core slabbing on EN539

Slicing multicore at 0.5 cm intervals (<10 years per slice) south of Iceland May 2014, RV Endevour.

My research aims to understand how the modern deep ocean circulation shapes the sea bed and controls the distribution of sediment types, grain-sizes and bedforms. I then apply that understanding to interpretation of the geological record of the changing deep-sea circulation in piston and gravity cores for the late Pleistocene, and Ocean Drilling Project cores for the Neogene and earlier Pleistocene. Insight developed over the last 30 years concerning mechanics of fine sediment erosion, transport, aggregation and deposition shows that sediments become more cohesive, and all form aggregates, below 10 µm grainsize, but above that size they increasingly behave non-cohesively and are sorted by prevailing currents. This 'sortable silt' (10-63 µm) has a mean size that provides a proxy for depositional current speed and allows insight into changes in deep circulation vigour.

The deeper objective is to understand the impact of climate change on the deep sea (and vice versa). Part of the meridional heat flux on earth is carried by warm surface ocean currents with a corresponding cold deep return flow. We look for good monitoring points for these deep flows and have studied the inflow to the North Atlantic south of Iceland, and the deep inflows to the Pacific east of New Zealand and Indian ocean east of Madagascar. Among our recent striking results are the discovery of a Holocene ~1500 year variability in the flow south of Iceland, matching the Mediaeval Warm Period - Little Ice Age climate changes, flow changes at the inception of the Antarctic circum-polar current, and Southern Ocean control of flow in the glacial deep N. Atlantic.

Current work is focussed on records of relatively shallow flows in the sub-Arctic around Greenland and Iceland as well as the Southern Ocean. Here the problem of disentangling the effects of sediment delivery by ice rafting and current-controlled transport and deposition has been a necessary precursor to examination of late Glacial and Holocene sediment data revealing Atlanti and Pacific (Bering throughflow) influences on the E. Greenland and Labrador Currents. 

 

Cartoon of two settings for deposition of ice-rafted and plume-delivered sediment  from McCave & Andrews (2019a): A) Sediment falls out from icbergs into a fast current, fines are removed to downstream locations where they are deposited at a place where the current is slower, forming a drift, while coarse material (medium sand to gravel) falls directly to the bed at the point of release where it remains. B) Sediment falls out into a slow current and all material falls directly to the bed close to the point of release. Fauna show the bi-polar nature of the processes.

 

SS normalised calibration data

Normalised sortable silt mean size versus normalised mean flow speed U; Sensitivity is 1.36 ± 0.19 cm s-1/μm which allows us to specify the magnitude of flow speed changes on climatic transitions from millions to a few tens of years ago.

Key Publications

Rong Hu, Bostock H.C., Greaves, M., Piotrowski A.M., McCave, I.N., 2020. Coupled evolution of stable carbon isotopes between the Southern Ocean and the atmosphere over the last 260 ka. Earth and Planetary Science Letters, 588, #116215, 9pp. doi: 10.1016/j.epsl.2020.11621

McCave, I.N. & Andrews, J.T., 2019b. distinguishing current effects in sediments delivered to the ocean by ice. II. Glacial to Holocene changes in high latitude North Atlantic upper ocean flows. Quaternary Science Reviews, 223, no. 105902, 21pp. doi: 10.1016/j.quascirev.2019.105902

McCave I.N. & Andrews, J.T., 2019a. distinguishing current effects in sediments delivered to the ocean by ice. I. Principles, methods and examples. Quaternary Science Reviews 212, 92-107. doi: 10.1016/j.quascirev.2019.03.03

Yu, J.,  L. Menviel, L., Jin, Z., Thornalley, D.J.R., Foster, G.L, Rohling, E.J., McCave, I.N., McManus, J.F., Ren, H., Sigman, D.M., Feng He, Zhang, F., Pujiao Chen, Roberts, A., 2019. More efficient North Atlantic carbon pump during the Last Glacial Maximum. Nature Communications 10, Art. No. 2170. doi: 10.1038/s41467-019-10028-z

McCave I.N, 2019. Nepheloid Layers. In: Cochran, J.K., Bokuniewicz, J.H., Yager, L.P. (eds.) Encyclopedia of Ocean Sciences, 3rd Ed., v. 4, 170-183. Oxford, Elsevier. doi:10.1016/B978-0-12-409548-9.11207-2

McCave I.N., 2018. Nepheloid layers, in; Reference Module in Earth Systems and Environmental Sciences, Elsevier.

McCave, I.N., Thornalley, D.J.R., & Hall, I.R., 2017. Relation of sortable silt grain size to deep-sea current speeds: Calibration of the ‘Mud Current Meter’ Deep-Sea Research Part I, 127, 1-12. doi: 10.1016/j.dsr.2017.07.003

Roberts, J., I.N. McCave, E.L. McClymont, S. Kender, C.-D. Hillenbrand, R. Matano, D.A. Hodell, and V.L. Peck,  2017. Deglacial changes in flow and frontal structure through the Drake Passage. Earth and Planetary Science Letters, 474, 397-408. doi: 10.1016/j.epsl.2017.07.004

McCave, I.N., 2017. Formation of sediment waves by turbidity currents and geostrophic flows: A discussion. Marine Geology, 390, 89-93. doi: 10.1016/j.margeo.2017.05.003

Parnell-Turner, R.,  N. White, I.N. McCave, T. Henstock, B. Murton, & S. Jones, 2015. Architecture of contourite drifts modified by transient circulation of the Icelandic mantle plume. Geochemistry, Geophysics, Geosystems, 16 (10), 3414-3435,

Hoogakker, B.A.A., Schmiedel, G., Elderfield, H., McCave, I.N. & Rickaby, R.E.M., 2015. Glacial-interglacial changes in bottom water oxygen content on the Portuguese margin. Nature Geoscience, 8, 40-43.

McCave, I.N., Crowhurst, S.C., Kuhn, G., Hillenbrand, C.-D. & Meredith, M.P., 2014.   Minimal change in Antarctic Circumpolar Current flow speed between the last Glacial and Holocene.  Nature Geoscience, 7, 113-116.  doi:10.1038/ngeo2037.

Roberts, N.L., McManus, J.F., Piotrowski, A.M. & McCave, I.N., 2014.  Advection and scavenging controls of Pa/Th in the northern NE Atlantic.  Paleoceanography, 20, 668-679,  doi: 10.1002/2014PA0026332015

Elderfield, H., Ferretti, P., Greaves, M., Crowhurst, S.J., McCave, I.N., Hodell, D.A. & Piotrowski, A., 2012. Evolution of deep ocean temperature and ice volume through the Mid Pleistocene climate transition. Science, 337, 704-709.

Thornalley, D.J.R., M. Blaschek, F.J. Davies, S. Praetorius, D.W. Oppo, J.F. McManus, I.R. Hall, H. Kleiven, H. Renssen & I.N. McCave, 2013. Long-term variations in Iceland-Scotland overflow strength during the Holocene. Climate of the Past, 9, 2073–2084, www.clim-past.net/9/2073/2013/

McCave, I.N. & Elderfield, H.,  2011. Sir Nicholas John Shackleton. 23 June 1937 -- 24 January 2006. Biographical Memoirs of Fellows of the Royal Society,  57, 435-462.   doi: 10.1098/rsbm.2011.0005. Bibliography;  http://rsbm.royalsocietypublishing.org /content/suppl/2011/06/24/rsbm.2011.0005.DC1/rsbm20110005supp1.pdf

Kleiven, H.F., Hall, I.R., McCave, I.N., Knorr, G., & Jansen, E., 2011. Deep-water formation and climate change in the North Atlantic during the Mid-Pleistocene. Geology, 39, 343–346; doi: 10.1130/G31651.1, supp.inf. www.geosociety.org/pubs/ft2011.htm

Thornalley, D.J.R., S. Barker, W.S. Broecker, H. Elderfield & I.N. McCave,  2011. The deglacial evolution of North Atlantic deep convection.  Science, 331, 202-205.

Thornalley, D.J.R., Elderfield H., & McCave I.N., 2009. Holocene oscillations in the temperature and salinity of the surface subpolar North Atlantic.  Nature, 457, 711-4.

 

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