Golledge Nicholas

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Last Name
Golledge
First Name
Nicholas
ORCID
0000-0001-7676-8970

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  • Article
    Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat
    (European Geosciences Union, 2021-01-05) Ashley, Kate E. ; McKay, Robert ; Etourneau, Johan ; Jimenez-Espejo, Francisco J. ; Condron, Alan ; Albot, Anna ; Crosta, Xavier ; Riesselman, Christina ; Seki, Osamu ; Massé, Guillaume ; Golledge, Nicholas ; Gasson, Edward ; Lowry, Daniel P. ; Barrand, Nicholas E. ; Johnson, Katelyn ; Bertler, Nancy ; Escutia, Carlota ; Dunbar, Robert B. ; Bendle, James A.
    Over recent decades Antarctic sea-ice extent has increased, alongside widespread ice shelf thinning and freshening of waters along the Antarctic margin. In contrast, Earth system models generally simulate a decrease in sea ice. Circulation of water masses beneath large-cavity ice shelves is not included in current Earth System models and may be a driver of this phenomena. We examine a Holocene sediment core off East Antarctica that records the Neoglacial transition, the last major baseline shift of Antarctic sea ice, and part of a late-Holocene global cooling trend. We provide a multi-proxy record of Holocene glacial meltwater input, sediment transport, and sea-ice variability. Our record, supported by high-resolution ocean modelling, shows that a rapid Antarctic sea-ice increase during the mid-Holocene (∼ 4.5 ka) occurred against a backdrop of increasing glacial meltwater input and gradual climate warming. We suggest that mid-Holocene ice shelf cavity expansion led to cooling of surface waters and sea-ice growth that slowed basal ice shelf melting. Incorporating this feedback mechanism into global climate models will be important for future projections of Antarctic changes.
  • Article
    Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
    (Nature Publishing Group, 2017-09-12) Turney, Christian S. M. ; Jones, Richard ; Phipps, Steven J. ; Thomas, Zoë ; Hogg, Alan ; Kershaw, Peter ; Fogwill, Christopher J. ; Palmer, Jonathan G. ; Bronk Ramsey, Christopher ; Adolphi, Florian ; Muscheler, Raimund ; Hughen, Konrad A. ; Staff, Richard A. ; Grosvenor, Mark ; Golledge, Nicholas ; Rasmussen, Sune O. ; Hutchinson, David K. ; Haberle, Simon ; Lorrey, Andrew ; Boswijk, Gretel ; Cooper, Alan
    Contrasting Greenland and Antarctic temperatures during the last glacial period (115,000 to 11,650 years ago) are thought to have been driven by imbalances in the rates of formation of North Atlantic and Antarctic Deep Water (the ‘bipolar seesaw’). Here we exploit a bidecadally resolved 14C data set obtained from New Zealand kauri (Agathis australis) to undertake high-precision alignment of key climate data sets spanning iceberg-rafted debris event Heinrich 3 and Greenland Interstadial (GI) 5.1 in the North Atlantic (~30,400 to 28,400 years ago). We observe no divergence between the kauri and Atlantic marine sediment 14C data sets, implying limited changes in deep water formation. However, a Southern Ocean (Atlantic-sector) iceberg rafted debris event appears to have occurred synchronously with GI-5.1 warming and decreased precipitation over the western equatorial Pacific and Atlantic. An ensemble of transient meltwater simulations shows that Antarctic-sourced salinity anomalies can generate climate changes that are propagated globally via an atmospheric Rossby wave train.