Centennial-scale Holocene climate variations amplified by Antarctic Ice Sheet discharge

• Published in: Nature (London) 2017-01, Vol.541 (7635), p.72-76
• Main Authors: Bakker, Pepijn, Clark, Peter U., Golledge, Nicholas R., Schmittner, Andreas, Weber, Michael E.
• Format: Article
• Language: English
• Subjects: 704/106/125; 704/106/413; 704/106/694/1108; Anthropogenic factors; Carbon cycle; Climate change; Climate models; Climate variability; Fluctuations; Geographical research; Geological time; Global climate; Holocene; Holocene paleogeography; Humanities and Social Sciences; Ice sheets; Icebergs; letter; multidisciplinary; Ocean temperature; Science
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature20582

Records of iceberg-rafted debris and climate model simulations reveal that fluctuations in Antarctic Ice Sheet discharge may have amplified climate fluctuations during the Holocene. Drivers of climate change during the Holocene During glacial periods, the climate undergoes enormous and abrupt changes. In comparison, the Holocene—the past 12,000 years or so—seems to have been climatically stable. But within this overall stability, the Holocene also experienced extensive climate variability on centennial to millennial timescales. Pepijn Bakker and colleagues combine observational records of iceberg-rafted debris with climate models to show that the climate fluctuations seen during the Holocene may have been driven by small variations in the discharge of freshwater from the Antarctic Ice Sheet, amplified through the climate system. Proxy-based indicators of past climate change show that current global climate models systematically underestimate Holocene-epoch climate variability on centennial to multi-millennial timescales, with the mismatch increasing for longer periods 1 , 2 , 3 , 4 , 5 . Proposed explanations for the discrepancy include ocean–atmosphere coupling that is too weak in models 6 , insufficient energy cascades from smaller to larger spatial and temporal scales 7 , or that global climate models do not consider slow climate feedbacks related to the carbon cycle or interactions between ice sheets and climate 4 . Such interactions, however, are known to have strongly affected centennial- to orbital-scale climate variability during past glaciations 8 , 9 , 10 , 11 , and are likely to be important in future climate change 12 , 13 , 14 . Here we show that fluctuations in Antarctic Ice Sheet discharge caused by relatively small changes in subsurface ocean temperature can amplify multi-centennial climate variability regionally and globally, suggesting that a dynamic Antarctic Ice Sheet may have driven climate fluctuations during the Holocene. We analysed high-temporal-resolution records of iceberg-rafted debris derived from the Antarctic Ice Sheet, and performed both high-spatial-resolution ice-sheet modelling of the Antarctic Ice Sheet and multi-millennial global climate model simulations. Ice-sheet responses to decadal-scale ocean forcing appear to be less important, possibly indicating that the future response of the Antarctic Ice Sheet will be governed more by long-term anthropogenic warming combined with multi-centennial natural variability than by