Atlantic multi-decade oscillation

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AMO between 1856 and 2013.
The course of the ACE from 1850 to 2007 correlates very well with the course of the AMO over this period

The Atlantic multi-decade oscillation (abbreviation AMO; English atlantic multidecadal oscillation ) is the name for a cyclical fluctuation in the circulation of the ocean currents in the North Atlantic . It brings about a change in sea ​​surface temperatures throughout the North Atlantic basin, which affects the atmosphere.

Explanation

The AMO has a period of 50 to 70 years and has “warm” and “cold” phases. From 1900 to 1925 and from 1965 to 1995 it was in a cold phase, from 1925 to 1965 and since the mid-1990s in a warm phase. With the help of tree ring proxies , the phases of the AMO up to 1567 could be reconstructed. However, indications of phase position and change can also be found in ice cores and corals. Since this pronounced fluctuation in the surface temperature of the Atlantic has existed for at least almost 500 years, it can be assumed that it will also play an essential role in the future climate development of the northern hemisphere.

The temperature fluctuations are caused by changing ocean currents and swelling deep water. The majority of scientists are of the opinion that the AMO is driven by a changed speed of the thermohaline circulation , which in turn is caused by a natural fluctuation in the climate system. An accelerated circulation leads to a positive phase of the AMO, more heat is transported from the tropics to the North Atlantic. Similarly, a slowed down circulation leads to a negative phase.

The effects of the warm phase of the AMO are droughts in the American Midwest and Southwest. In Florida and the northwestern United States, as well as in Europe, more precipitation falls overall, with the changes taking place primarily in summer. More severe hurricanes are developing . The intensity of the Indian monsoons and the amount of precipitation in the Sahel zone are increased; the mean sea ice cover in the Arctic Ocean is lower than in times with a negative index.

A phase change of the AMO causes the inflow to Lake Okeechobee in Florida to vary by 40%, while the Mississippi outflow varies by only 5–10% and the amount of precipitation in Europe by 5–15%.

Due to the long cycle duration of approx. 60 years and the comparatively short period over which reliable climate records exist (approx. 150 years), statements about the climate-determining influences of the AMO can only be checked over a few cycles and therefore show great uncertainties. Climate proxies extend the data space to a few hundred years, but are less accurate. A precise qualitative and quantitative understanding of the share of this natural variability of the climate system allows natural and anthropogenic climate influences to be separated and the accuracy of statements about the expected short-term development to be improved. Therefore, an attempt was made to understand the assumed climatic effects of the AMO in various climate models (GFDL, HadCM3) taking into account direct climate recordings and climate proxies; it was found that the models confirmed almost all of the phenomena actually observed.

See also

literature

Web links

Commons : Atlantic Multi-Decade Oscillation  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d Henk A. Dijkstra, et al. : On the physics of the Atlantic Multidecadal Oscillation . In: Ocean Dynamics . tape 56 , no. 1 , 2005, p. 36–50 , doi : 10.1007 / s10236-005-0043-0 ( knmi.nl [PDF; 830 kB ]). PDF file; 830 KB ( Memento of the original from April 3, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.knmi.nl
  2. ↑ Stephen T. Gray, et al. : A tree-ring based reconstruction of the Atlantic Multidecadal Oscillation since 1567 AD In: Geophysical Research Letters . tape 31 , no. 12 , 2004, p. L12205 , doi : 10.1029 / 2004GL019932 ( nrmsc.usgs.gov [PDF; 170 kB ]). PDF; 170 KB ( Memento of the original from April 8, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.nrmsc.usgs.gov
  3. ^ Richard A. Kerr: A North Atlantic climate pacemaker for the centuries . In: Science . tape 288 , no. 5473 , 2000, pp. 1984–1986 , doi : 10.1126 / science.288.5473.1984 .
  4. ↑ Steffen Hetzinger, et al. : Caribbean coral tracks Atlantic Multidecadal Oscillation and past hurricane activity . In: Geology . tape 36 , no. 1 , 2008, p. 11–14 , doi : 10.1130 / G24321A.1 ( eprints.uni-kiel.de [PDF; 415 kB ]). PDF file; 415 KB ( Memento of the original from November 27, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / eprints.uni-kiel.de
  5. ^ Fred Pearce , Michael Le Page: Climate change: the next ten years . In: New Scientist . No. 2669 , 2008, p. 26–30 ( excerpt from article [accessed May 23, 2013]). Article excerpt ( memento of the original from October 22, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / environment.newscientist.com
  6. ↑ Jeff R. Knight, et al. : A signature of persistent natural thermohaline circulation cycles in observed climate . In: Geophysical Research Letters . tape 32 , no. 20 , 2005, pp. L20708 , doi : 10.1029 / 2005GL024233 ( lightning.sbs.ohio-state.edu [PDF; 836 kB ]). PDF file; 836 KB ( Memento of the original from August 10, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / lightning.sbs.ohio-state.edu
  7. ↑ Gregory J. McCabe, Michael A. Palecki, Julio L. Betancourt: Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States . In: Proceedings of the National Academy of Sciences of the United States of America . tape 101 , no. 12 , 2004, p. 4136-4141 , doi : 10.1073 / pnas.0306738101 ( wwwpaztcn.wr.usgs.gov [PDF; 1000 kB ]). PDF file; 1 MB ( Memento of the original from February 23, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / wwwpaztcn.wr.usgs.gov
  8. ↑ Stanley B. Goldenberg, et al. : The recent increase in Atlantic hurricane activity: Causes and implications . In: Science . tape 293 , no. 5529 , 2001, pp. 474–479 , doi : 10.1126 / science.1060040 ( aoml.noaa.gov [PDF; 812 kB ]).
  9. ^ Rong Zhang, Thomas L. Delworth: Impact of Atlantic multidecadal oscillations on India / Sahel rainfall and Atlantic hurricanes . In: Geophysical Research Letters . tape 33 , no. 17 , 2006, p. L17712 , doi : 10.1029 / 2006GL026267 ( gfdl.noaa.gov [PDF; 385 kB ; accessed on May 23, 2013]).
  10. ↑ David B. Enfield, Alberto M. Mestas-Nuñez, Paul J. Trimble: The Atlantic Multidecadal Oscillation and its relationship to rainfall and river flows in the continental US In: Geophysical Research Letters . tape 28 , no. 10 , 2001, p. 2077-2080 , doi : 10.1029 / 2000GL012745 ( aoml.noaa.gov [PDF; 1.1 MB ]).
  11. ↑ Jeff R. Knight, Chris K. Folland, Adam A. Scaife: Climate impacts of the Atlantic Multidecadal Oscillation . In: Geophysical Research Letters . tape 33 , no. 17 , 2006, p. L17706 , doi : 10.1029 / 2006GL026242 ( deas.harvard.edu [PDF; 917 kB ]).
  12. ↑ Thomas L. Delworth, Michael E. Mann : Observed and simulated multidecadal variability in the Northern Hemisphere . In: Climate Dynamics . tape 16 , no. 9 , 2000, pp. 661–676 , doi : 10.1007 / s003820000075 ( gfdl.noaa.gov [PDF; 1.7 MB ]).