The Nye Lecture, Sponsered by the AGU Cryospheric Focus Group,
was presented by:
Dr. Richard Alley (biography)
We’re All Glaciologists Now: Ice in the Climate System
The cryosphere plays a disproportionately important role in the climate system and in global-change research. Ice cores provide the best histories of climate change, and the most compelling evidence for linkage of atmospheric carbon-dioxide concentration and temperature over long times. Over shorter times, outburst floods and ice-sheet surges triggered abrupt climate changes, flipping the North Atlantic “switch” that controls whether water sinks before it freezes or freezes before it sinks; sea ice provided the main feedbacks, with strong wintertime changes. Cryospheric feedbacks are important in future climate change, and sea-level rise from glacier and ice-sheet melting is probably the clearest and most quantifiable cost of warming. Too much warming will melt ice, and numerous recent events and studies suggest that sufficient warming to melt one or more of the big ice sheets may be reached if available fossil fuels are burned rapidly. Feedbacks on oceanic circulation and other processes are possible, with poorly understood impacts that could be large. The convergence of cryospheric research impresses me greatly. For example, the joint efforts of ice geochemists and glacier-flow dynamicists together develop and calibrate the ice-core records of abrupt climate changes that were forced by ice dynamics and amplified by sea ice and snow cover. Research priorities are clear, exciting and compelling, with much work yet to occur at the interfaces among cryospheric subdisciplines.