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Steven M Bohaty - One of the best experts on this subject based on the ideXlab platform.

  • southern ocean warming and wilkes land ice sheet retreat during the mid miocene
    Nature Communications, 2018
    Co-Authors: Francesca Sangiorgi, Peter K Bijl, Sandra Passchier, Ulrich Salzmann, Stefan Schouten, Robert M Mckay, Rosemary Cody, Jorg Pross, Tina Van De Flierdt, Steven M Bohaty
    Abstract:

    Observations and model experiments highlight the importance of ocean heat in forcing ice sheet retreat during the present and geological past, but past ocean temperature data are virtually missing in ice sheet proximal locations. Here we document paleoceanographic conditions and the (in)stability of the Wilkes Land subglacial basin (East Antarctica) during the mid-Miocene (~17-13.4 million years ago) by studying sediment cores from offshore Adelie Coast. Inland retreat of the ice sheet, temperate vegetation, and warm oligotrophic waters characterise the mid-Miocene Climatic Optimum (MCO; 17-14.8 Ma). After the MCO, expansion of a marine-based ice sheet occurs, but remains sensitive to melting upon episodic warm water incursions. Our results suggest that the mid-Miocene latitudinal temperature gradient across the Southern Ocean never resembled that of the present day. We demonstrate that a strong coupling of Oceanic Climate and Antarctic continental conditions existed and that the East Antarctic subglacial basins were highly sensitive to ocean warming.

Magdalena Hajdukiewicz - One of the best experts on this subject based on the ideXlab platform.

Francesca Sangiorgi - One of the best experts on this subject based on the ideXlab platform.

  • southern ocean warming and wilkes land ice sheet retreat during the mid miocene
    Nature Communications, 2018
    Co-Authors: Francesca Sangiorgi, Peter K Bijl, Sandra Passchier, Ulrich Salzmann, Stefan Schouten, Robert M Mckay, Rosemary Cody, Jorg Pross, Tina Van De Flierdt, Steven M Bohaty
    Abstract:

    Observations and model experiments highlight the importance of ocean heat in forcing ice sheet retreat during the present and geological past, but past ocean temperature data are virtually missing in ice sheet proximal locations. Here we document paleoceanographic conditions and the (in)stability of the Wilkes Land subglacial basin (East Antarctica) during the mid-Miocene (~17-13.4 million years ago) by studying sediment cores from offshore Adelie Coast. Inland retreat of the ice sheet, temperate vegetation, and warm oligotrophic waters characterise the mid-Miocene Climatic Optimum (MCO; 17-14.8 Ma). After the MCO, expansion of a marine-based ice sheet occurs, but remains sensitive to melting upon episodic warm water incursions. Our results suggest that the mid-Miocene latitudinal temperature gradient across the Southern Ocean never resembled that of the present day. We demonstrate that a strong coupling of Oceanic Climate and Antarctic continental conditions existed and that the East Antarctic subglacial basins were highly sensitive to ocean warming.

Edward Hanna - One of the best experts on this subject based on the ideXlab platform.

  • a century of variation in the dependence of greenland iceberg calving on ice sheet surface mass balance and regional Climate change
    Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2014
    Co-Authors: Grant R Bigg, Hualiang Wei, David J Wilton, Yifan Zhao, S A Billings, Edward Hanna, Visakan Kadirkamanathan
    Abstract:

    Iceberg calving is a major component of the total mass balance of the Greenland ice sheet (GrIS). A century-long record of Greenland icebergs comes from the International Ice Patrol's record of icebergs (I48N) passing latitude 48° N, off Newfoundland. I48N exhibits strong interannual variability, with a significant increase in amplitude over recent decades. In this study, we show, through a combination of nonlinear system identification and coupled ocean–iceberg modelling, that I48N's variability is predominantly caused by fluctuation in GrIS calving discharge rather than open ocean iceberg melting. We also demonstrate that the episodic variation in iceberg discharge is strongly linked to a nonlinear combination of recent changes in the surface mass balance (SMB) of the GrIS and regional atmospheric and Oceanic Climate variability, on the scale of the previous 1–3 years, with the dominant causal mechanism shifting between glaciological (SMB) and climatic (ocean temperature) over time. We suggest that this is a change in whether glacial run-off or under-ice melting is dominant, respectively. We also suggest that GrIS calving discharge is episodic on at least a regional scale and has recently been increasing significantly, largely as a result of west Greenland sources.

  • atmospheric and Oceanic Climate forcing of the exceptional greenland ice sheet surface melt in summer 2012
    International Journal of Climatology, 2014
    Co-Authors: Edward Hanna, Xavier Fettweis, Sebastian H Mernild, John Cappelen, Mads H Ribergaard, C A Shuman, Konrad Steffen, Len Wood
    Abstract:

    The NASA announcement of record surface melting of the Greenland ice sheet in July 2012 led us to examine the atmospheric and Oceanic climatic anomalies that are likely to have contributed to these exceptional conditions and also to ask the question of how unusual these anomalies were compared to available records. Our analysis allows us to assess the relative contributions of these two key influences to both the extreme melt event and ongoing Climate change. In 2012, as in recent warm summers since 2007, a blocking high pressure feature, associated with negative NAO conditions, was present in the mid-troposphere over Greenland for much of the summer. This circulation pattern advected relatively warm southerly winds over the western flank of the ice sheet, forming a heat dome' over Greenland that led to the widespread surface melting. Both sea-surface temperature and sea-ice cover anomalies seem to have played a minimal role in this record melt, relative to atmospheric circulation. Two representative coastal climatological station averages and several individual stations in south, west and north-west Greenland set new surface air temperature records for May, June, July and the whole (JJA) summer. The unusually warm summer 2012 conditions extended to the top of the ice sheet at Summit, where our reanalysed (1994-2012) DMI Summit weather station summer (JJA) temperature series set new record high mean and extreme temperatures in 2012; 3-hourly instantaneous 2-m temperatures reached an exceptional value of 2.2 degrees C at Summit on 11 July 2012. These conditions translated into the record observed ice-sheet wide melt during summer 2012. However, 2012 seems not to be climatically representative of future average' summers projected this century.

P Moran - One of the best experts on this subject based on the ideXlab platform.