fresh water
; ice
; surface water
; article
; atmosphere
; climate change
; cold air
; cooling
; feedback system
; Greenland
; heat exchange
; Little Ice Age
; melting point
; ocean current
; oscillation
; positive feedback
; pressure
; priority journal
; salinity
; sea ice
; sea level
; sea surface temperature
; thermodynamics
; time series analysis
; white noise
; climate modeling
; Great Salinity Anomaly
; thermohaline circulation
; Atmosphere
; Climate Change
; Computer Simulation
; Fresh Water
; Ice Cover
; Models, Theoretical
; Oceans and Seas
; Salinity
; Time Factors
; Water Movements
英文摘要:
Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a highresolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70 °N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change.
Drijfhout, S., Department of Climate Research, Royal Netherlands Meteorological Institute, 3730AE, De Bilt, Netherlands, School of Ocean and Earth Sciences, National Oceanography Centre, Southampton SO14 3TB, United Kingdom; Gleeson, E., Research, Environment and Applications Division, Met Éireann, Dublin 9, Ireland; Dijkstra, H.A., Institute for Marine and Atmospheric Research Utrecht, Utrecht University, 3584 CC Utrecht, Netherlands; Livina, V., National Physical Laboratory, Teddington TW11 0LW, United Kingdom
Recommended Citation:
Drijfhout S.,Gleeson E.,Dijkstra H.A.,et al. Spontaneous abrupt climate change due to an atmospheric blocking-Sea-Ice-Ocean feedback in an unforced climate model simulation[J]. Proceedings of the National Academy of Sciences of the United States of America,2013-01-01,110(49)