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Atlantic multidecadal oscillation

August 22, 2023

Not to be confused with North Atlantic oscillation or Atlantic meridional overturning circulation.

The Atlantic Multidecadal Oscillation (AMO), also known as Atlantic Multidecadal Variability (AMV),[1] is the theorized variability of the sea surface temperature (SST) of the North Atlantic Ocean on the timescale of several decades.[2]

Atlantic multidecadal oscillation spatial pattern obtained as the regression of monthly HadISST sea surface temperature anomalies (1870-2013).
Atlantic Multidecadal Oscillation Index according to the methodology proposed by van Oldenborgh et al. 1880-2018.
Atlantic Multidecadal Oscillation index computed as the linearly detrended North Atlantic sea surface temperature anomalies 1856-2022.

While there is some support for this mode in models and in historical observations, controversy exists with regard to its amplitude, and whether it has a typical timescale and can be classified as an oscillation. There is also discussion on the attribution of sea surface temperature change to natural or anthropogenic causes, especially in tropical Atlantic areas important for hurricane development.[3] The Atlantic multidecadal oscillation is also connected with shifts in hurricane activity, rainfall patterns and intensity, and changes in fish populations.[4]

Definition and history

Evidence for a multidecadal climate oscillation centered in the North Atlantic began to emerge in 1980s work by Folland and colleagues, seen in Fig. 2.d.A.[5] That oscillation was the sole focus of Schlesinger and Ramankutty in 1994,[6] but the actual term Atlantic Multidecadal Oscillation (AMO) was coined by Michael Mann in a 2000 telephone interview with Richard Kerr,[7] as recounted by Mann, p. 30 in The Hockey Stick and the Climate Wars: Dispatches from the Front Lines (2012).

The AMO signal is usually defined from the patterns of SST variability in the North Atlantic once any linear trend has been removed. This detrending is intended to remove the influence of greenhouse gas-induced global warming from the analysis. However, if the global warming signal is significantly non-linear in time (i.e. not just a smooth linear increase), variations in the forced signal will leak into the AMO definition. Consequently, correlations with the AMO index may mask effects of global warming, as per Mann, Steinman and Miller,[8] which also provides a more detailed history of the science development.

AMO index

Several methods have been proposed to remove the global trend and El Niño-Southern Oscillation (ENSO) influence over the North Atlantic SST. Trenberth and Shea, assuming that the effect of global forcing over the North Atlantic is similar to the global ocean, subtracted the global (60°N-60°S) mean SST from the North Atlantic SST to derive a revised AMO index.[9]

Ting et al. however argue that the forced SST pattern is not globally uniform; they separated the forced and internally generated variability using signal to noise maximizing EOF analysis.[3]

Van Oldenborgh et al. derived an AMO index as the SST averaged over the extra-tropical North Atlantic (to remove the influence of ENSO that is greater at tropical latitude) minus the regression on global mean temperature.[10]

Guan and Nigam removed the non stationary global trend and Pacific natural variability before applying an EOF analysis to the residual North Atlantic SST.[11]

The linearly detrended index suggests that the North Atlantic SST anomaly at the end of the twentieth century is equally divided between the externally forced component and internally generated variability, and that the current peak is similar to middle twentieth century; by contrast the others methodology suggest that a large portion of the North Atlantic anomaly at the end of the twentieth century is externally forced.[3]

Frajka-Williams et al. 2017 pointed out that recent changes in cooling of the subpolar gyre, warm temperatures in the subtropics and cool anomalies over the tropics, increased the spatial distribution of meridional gradient in sea surface temperatures, which is not captured by the AMO Index.[4]

Mechanisms

See also: Atlantic meridional overturning circulation and Ocean heat content

Based on the about 150-year instrumental record a quasi-periodicity of about 70 years, with a few distinct warmer phases between ca. 1930–1965 and after 1995, and cool between 1900–1930 and 1965–1995 has been identified.[12] In models, AMO-like variability is associated with small changes in the North Atlantic branch of the Thermohaline Circulation.[13] However, historical oceanic observations are not sufficient to associate the derived AMO index to present-day circulation anomalies.[citation needed] Models and observations indicate that changes in atmospheric circulation, which induce changes in clouds, atmospheric dust and surface heat flux, are largely responsible for the tropical portion of the AMO.[14][15]

The Atlantic Multidecadal Oscillation (AMO) is important for how external forcings are linked with North Atlantic SSTs.[16]

Climate impacts worldwide

The AMO is correlated to air temperatures and rainfall over much of the Northern Hemisphere, in particular in the summer climate in North America and Europe.[17][18] Through changes in atmospheric circulation, the AMO can also modulate spring snowfall over the Alps[19] and glaciers' mass variability.[20] Rainfall patterns are affected in North Eastern Brazilian and African Sahel. It is also associated with changes in the frequency of North American droughts and is reflected in the frequency of severe Atlantic hurricane activity.[9]

Recent research suggests that the AMO is related to the past occurrence of major droughts in the US Midwest and the Southwest. When the AMO is in its warm phase, these droughts tend to be more frequent or prolonged. Two of the most severe droughts of the 20th century occurred during the positive AMO between 1925 and 1965: The Dust Bowl of the 1930s and the 1950s drought. Florida and the Pacific Northwest tend to be the opposite—warm AMO, more rainfall.[21]

Climate models suggest that a warm phase of the AMO strengthens the summer rainfall over India and Sahel and the North Atlantic tropical cyclone activity.[22] Paleoclimatologic studies have confirmed this pattern—increased rainfall in AMO warmphase, decreased in cold phase—for the Sahel over the past 3,000 years.[23]

Relation to Atlantic hurricanes

See also: Tropical cyclones and climate change
 
North Atlantic tropical cyclone activity according to the Accumulated Cyclone Energy Index, 1950–2015. For a global ACE graph visit this link[dead link] 2018-11-02 at the Wayback Machine.

A 2008 study correlated the Atlantic Multidecadal Mode (AMM), with HURDAT data (1851–2007), and noted a positive linear trend for minor hurricanes (category 1 and 2), but removed when the authors adjusted their model for undercounted storms, and stated "If there is an increase in hurricane activity connected to a greenhouse gas induced global warming, it is currently obscured by the 60 year quasi-periodic cycle."[24] With full consideration of meteorological science, the number of tropical storms that can mature into severe hurricanes is much greater during warm phases of the AMO than during cool phases, at least twice as many; the AMO is reflected in the frequency of severe Atlantic hurricanes.[21] Based on the typical duration of negative and positive phases of the AMO, the current warm regime is expected to persist at least until 2015 and possibly as late as 2035. Enfield et al. assume a peak around 2020.[25]

However, Mann and Emanuel had found in 2006 that “anthropogenic factors are responsible for long-term trends in tropic Atlantic warmth and tropical cyclone activity” and “There is no apparent role of the AMO.”[26]

In 2014 Mann, Steinman and Miller[8] showed that warming (and therefore any effects on hurricanes) were not caused by the AMO, writing: "certain procedures used in past studies to estimate internal variability, and in particular, an internal multidecadal oscillation termed the “Atlantic Multidecadal Oscillation” or “AMO”, fail to isolate the true internal variability when it is a priori known. Such procedures yield an AMO signal with an inflated amplitude and biased phase, attributing some of the recent NH mean temperature rise to the AMO. The true AMO signal, instead, appears likely to have been in a cooling phase in recent decades, offsetting some of the anthropogenic warming."

Since 1995, there have been ten Atlantic hurricane seasons considered "extremely active" by Accumulated Cyclone Energy - 1995, 1996, 1998, 1999, 2003, 2004, 2005, 2010, 2017, and 2020.[citation needed]

Periodicity and prediction of AMO shifts

There are only about 130–150 years of data based on instrument data, which are too few samples for conventional statistical approaches. With the aid of multi-century proxy reconstruction, a longer period of 424 years was used by Enfield and Cid–Serrano as an illustration of an approach as described in their paper called "The Probabilistic Projection of Climate Risk".[27] Their histogram of zero crossing intervals from a set of five re-sampled and smoothed version of Gray et al. (2004) index together with the maximum likelihood estimate gamma distribution fit to the histogram, showed that the largest frequency of regime interval was around 10–20 year. The cumulative probability for all intervals 20 years or less was about 70%.[citation needed]

There is no demonstrated predictability for when the AMO will switch, in any deterministic sense. Computer models, such as those that predict El Niño, are far from being able to do this. Enfield and colleagues have calculated the probability that a change in the AMO will occur within a given future time frame, assuming that historical variability persists. Probabilistic projections of this kind may prove to be useful for long-term planning in climate sensitive applications, such as water management.

A 2017 study predicts a continued cooling shift beginning 2014, and the authors note, "..unlike the last cold period in the Atlantic, the spatial pattern of sea surface temperature anomalies in the Atlantic is not uniformly cool, but instead has anomalously cold temperatures in the subpolar gyre, warm temperatures in the subtropics and cool anomalies over the tropics. The tripole pattern of anomalies has increased the subpolar to subtropical meridional gradient in SSTs, which are not represented by the AMO index value, but which may lead to increased atmospheric baroclinicity and storminess."[4]

In a 2021 study by Michael Mann, it was shown that the periodicity of the AMO in the last millennium was driven by volcanic eruptions and other external forcings, and therefore that there is no compelling evidence for the AMO being an oscillation or cycle.[28] There was also a lack of oscillatory behaviour in models on time scales longer than El Niño Southern Oscillation; the AMV is indistinguishable from red noise, a typical null hypothesis to test whether there are oscillations in a model.[29]

References

  1. ^ "Multidecadal Climate Changes". Geophysical Fluid Dynamics Laboratory.
  2. ^ Gerard D. McCarthy; Ivan D. Haigh; Joël J.M. Hirschi; Jeremy P. Grist & David A. Smeed (27 May 2015). "Ocean impact on decadal Atlantic climate variability revealed by sea-level observations". Nature. 521 (7553): 508–510. Bibcode:2015Natur.521..508M. doi:10.1038/nature14491. PMID 26017453. S2CID 4399436.
  3. ^ a b c Mingfang, Ting; Yochanan Kushnir; Richard Seager; Cuihua Li (2009). "Forced and Internal Twentieth-Century SST Trends in the North Atlantic". Journal of Climate. 22 (6): 1469–1481. Bibcode:2009JCli...22.1469T. doi:10.1175/2008JCLI2561.1. S2CID 17753758.
  4. ^ a b c Eleanor Frajka-Williams; Claudie Beaulieu; Aurelie Duchez (2017). "Emerging negative Atlantic Multidecadal Oscillation index in spite of warm subtropics". Scientific Reports. 7 (1): 11224. Bibcode:2017NatSR...711224F. doi:10.1038/s41598-017-11046-x. PMC 5593924. PMID 28894211.
  5. ^ Folland, C. K.; Parker, D .E.; Kates, F. E. (1984). "Worldwide marine temperature fluctuations 1856-1981". Nature. 310 (5979): 670–673. Bibcode:1984Natur.310..670F. doi:10.1038/310670a0. S2CID 4246538.
  6. ^ Schlesinger, M. E. (1994). "An oscillation in the global climate system of period 65-70 years". Nature. 367 (6465): 723–726. Bibcode:1994Natur.367..723S. doi:10.1038/367723a0. S2CID 4351411.
  7. ^ Kerr, Richard C. (2000). "A North Atlantic Climate Pacemaker for the Centuries". Science. 288 (5473): 1984–1985. doi:10.1126/science.288.5473.1984. PMID 17835110. S2CID 21968248.
  8. ^ a b Mann, Michael; Byron A. Steinman; Sonya K. Miller (2014). "On forced temperature changes, internal variability, and the AMO". Geophysical Research Letters. 41 (9): 3211–3219. Bibcode:2014GeoRL..41.3211M. doi:10.1002/2014GL059233.
  9. ^ a b Trenberth, Kevin; Dennis J. Shea (2005). "Atlantic hurricanes and natural variability in 2005". Geophysical Research Letters. 33 (12): L12704. Bibcode:2006GeoRL..3312704T. doi:10.1029/2006GL026894.
  10. ^ van Oldenborgh, G. J.; L. A. te Raa; H. A. Dijkstra; S. Y. Philip (2009). "Frequency- or amplitude-dependent effects of the Atlantic meridional overturning on the tropical Pacific Ocean". Ocean Sci. 5 (3): 293–301. Bibcode:2009OcSci...5..293V. doi:10.5194/os-5-293-2009.
  11. ^ Guan, Bin; Sumant Nigam (2009). "Analysis of Atlantic SST Variability Factoring Interbasin Links and the Secular Trend: Clarified Structure of the Atlantic Multidecadal Oscillation". J. Climate. 22 (15): 4228–4240. Bibcode:2009JCli...22.4228G. doi:10.1175/2009JCLI2921.1. S2CID 16792059.
  12. ^ (PDF). IPCC AR5. 2014. Archived from the original (PDF) on 2017-12-07. Retrieved 2017-10-09.
  13. ^ O'Reilly, C. H.; L. M. Huber; T Woollings; L. Zanna (2016). "The signature of low-frequency oceanic forcing in the Atlantic Multidecadal Oscillation". Geophysical Research Letters. 43 (6): 2810–2818. Bibcode:2016GeoRL..43.2810O. doi:10.1002/2016GL067925.
  14. ^ Brown, P. T.; M. S. Lozier; R. Zhang; W. Li (2016). "The necessity of cloud feedback for a basin-scale Atlantic Multidecadal Oscillation". Geophysical Research Letters. 43 (8): 3955–3963. Bibcode:2016GeoRL..43.3955B. doi:10.1002/2016GL068303.
  15. ^ Yuan, T.; L. Oreopoulos; M. Zalinka; H. Yu; J. R. Norris; M. Chin; S. Platnick; K. Meyer (2016). "Positive low cloud and dust feedbacks amplify tropical North Atlantic Multidecadal Oscillation". Geophysical Research Letters. 43 (3): 1349–1356. Bibcode:2016GeoRL..43.1349Y. doi:10.1002/2016GL067679. PMC 7430503. PMID 32818003. S2CID 130079254.
  16. ^ Mads Faurschou Knudsen; Bo Holm Jacobsen; Marit-Solveig Seidenkrantz & Jesper Olsen (25 February 2014). "Evidence for external forcing of the Atlantic Multidecadal Oscillation since termination of the Little Ice Age". Nature. 5: 3323. Bibcode:2014NatCo...5.3323K. doi:10.1038/ncomms4323. PMC 3948066. PMID 24567051.
  17. ^ Ghosh, Rohit; Müller, Wolfgang A.; Baehr, Johanna; Bader, Jürgen (2016-07-28). "Impact of observed North Atlantic multidecadal variations to European summer climate: a linear baroclinic response to surface heating". Climate Dynamics. 48 (11–12): 3547. Bibcode:2017ClDy...48.3547G. doi:10.1007/s00382-016-3283-4. hdl:11858/00-001M-0000-002B-44E2-8. ISSN 0930-7575. S2CID 54020650.
  18. ^ Zampieri, M.; Toreti, A.; Schindler, A.; Scoccimarro, E.; Gualdi, S. (April 2017). "Atlantic multi-decadal oscillation influence on weather regimes over Europe and the Mediterranean in spring and summer". Global and Planetary Change. 151: 92–100. Bibcode:2017GPC...151...92Z. doi:10.1016/j.gloplacha.2016.08.014.
  19. ^ Zampieri, Matteo; Scoccimarro, Enrico; Gualdi, Silvio (2013-01-01). "Atlantic influence on spring snowfall over the Alps in the past 150 years". Environmental Research Letters. 8 (3): 034026. Bibcode:2013ERL.....8c4026Z. doi:10.1088/1748-9326/8/3/034026. ISSN 1748-9326.
  20. ^ Huss, Matthias; Hock, Regine; Bauder, Andreas; Funk, Martin (2010-05-01). "100-year mass changes in the Swiss Alps linked to the Atlantic Multidecadal Oscillation" (PDF). Geophysical Research Letters. 37 (10): L10501. Bibcode:2010GeoRL..3710501H. doi:10.1029/2010GL042616. ISSN 1944-8007.
  21. ^ a b . Archived from the original on 2005-11-26.
  22. ^ Zhang, R.; Delworth, T. L. (2006). "Impact of Atlantic multidecadal oscillations on India/Sahel rainfall and Atlantic hurricanes". Geophys. Res. Lett. 33 (17): L17712. Bibcode:2006GeoRL..3317712Z. doi:10.1029/2006GL026267. S2CID 16588748.
  23. ^ Shanahan, T. M.; et al. (2009). "Atlantic Forcing of Persistent Drought in West Africa". Science. 324 (5925): 377–380. Bibcode:2009Sci...324..377S. CiteSeerX 10.1.1.366.1394. doi:10.1126/science.1166352. PMID 19372429. S2CID 2679216.
  24. ^ Chylek, P. & Lesins, G. (2008). "Multidecadal variability of Atlantic hurricane activity: 1851–2007". Journal of Geophysical Research. 113 (D22): D22106. Bibcode:2008JGRD..11322106C. doi:10.1029/2008JD010036.
  25. ^ Enfield, David B.; Cid-Serrano, Luis (2010). "Secular and multidecadal warmings in the North Atlantic and their relationships with major hurricane activity". International Journal of Climatology. 30 (2): 174–184. doi:10.1002/joc.1881. S2CID 18833210.
  26. ^ Mann, M. E.; Emanuel, K. A. (2006). "Atlantic Hurricane Trends Linked to Climate Change". EOS. 87 (24): 233–244. Bibcode:2006EOSTr..87..233M. doi:10.1029/2006EO240001. S2CID 128633734.
  27. ^ (PDF). Archived from the original (PDF) on 2014-08-26. Retrieved 2014-08-23.{{cite web}}: CS1 maint: archived copy as title (link)
  28. ^ Mann, Michael E.; Steinman, Byron A.; Brouillette, Daniel J.; Miller, Sonya K. (2021-03-05). "Multidecadal climate oscillations during the past millennium driven by volcanic forcing". Science. 371 (6533): 1014–1019. Bibcode:2021Sci...371.1014M. doi:10.1126/science.abc5810. ISSN 0036-8075. PMID 33674487. S2CID 232124643.
  29. ^ Mann, Michael E.; Steinman, Byron A.; Miller, Sonya K. (2020-01-03). "Absence of internal multidecadal and interdecadal oscillations in climate model simulations". Nature Communications. 11 (1): 49. Bibcode:2020NatCo..11...49M. doi:10.1038/s41467-019-13823-w. ISSN 2041-1723. PMC 6941994. PMID 31900412.

Further reading

  • Andronova, N. G.; Schlesinger, M. E. (2000). "Causes of global temperature changes during the 19th and 20th centuries". Geophys. Res. Lett. 27 (14): 2137–2140. Bibcode:2000GeoRL..27.2137A. doi:10.1029/2000GL006109.
  • Delworth, T. L.; Mann, M. E. (2000). "Observed and simulated multidecadal variability in the Northern Hemisphere". Climate Dynamics. 16 (9): 661–676. Bibcode:2000ClDy...16..661D. doi:10.1007/s003820000075. S2CID 7412990.
  • Enfield, D. B.; Mestas-Nunez, A. M.; Trimble, P. J. (2001). "The Atlantic Multidecadal Oscillation and its relationship to rainfall and river flows in the continental U.S." Geophys. Res. Lett. 28 (10): 2077–2080. Bibcode:2001GeoRL..28.2077E. CiteSeerX 10.1.1.594.1411. doi:10.1029/2000GL012745. S2CID 53534572.
  • Goldenberg, S. B. (2001). "The recent increase in Atlantic hurricane activity: Causes and implications". Science. 293 (5529): 474–479. Bibcode:2001Sci...293..474G. doi:10.1126/science.1060040. PMID 11463911.
  • Gray, S. T. (2004). "A tree-ring based reconstruction of the Atlantic Multidecadal Oscillation since 1567 A.D." Geophys. Res. Lett. 31 (12): L12205. Bibcode:2004GeoRL..3112205G. doi:10.1029/2004GL019932.
  • Hetzinger, Steffen (2008). "Caribbean coral tracks Atlantic Multidecadal Oscillation and past hurricane activity". Geology. 36 (1): 11–14. Bibcode:2008Geo....36...11H. doi:10.1130/G24321A.1.
  • Kerr, R. A. (2000). "A North Atlantic climate pacemaker for the centuries". Science. 288 (5473): 1984–1986. doi:10.1126/science.288.5473.1984. PMID 17835110. S2CID 21968248.
  • Kerr, R. A. (2005). "Atlantic climate pacemaker for millennia past, decades hence?". Science. 309 (5731): 41–43. doi:10.1126/science.309.5731.41. PMID 15994503.
  • Knight, J. R. (2005). "A signature of persistent natural thermohaline circulation cycles in observed climate". Geophys. Res. Lett. 32 (20): L20708. Bibcode:2005GeoRL..3220708K. doi:10.1029/2005GL024233. S2CID 16909466.
  • McCabe, G. J.; Palecki, M. A.; Betancourt, J. L. (2004). "Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States". PNAS. 101 (12): 4136–4141. Bibcode:2004PNAS..101.4136M. doi:10.1073/pnas.0306738101. PMC 384707. PMID 15016919.
  • Sutton, R. T.; Hodson, L. R. (2005). "Atlantic forcing of North American and European summer climate". Science. 309 (5731): 115–118. Bibcode:2005Sci...309..115S. doi:10.1126/science.1109496. PMID 15994552.
  • Knight, J. R.; Folland, C. K.; Scaife, A. A. (2006). "Climate impacts of the Atlantic Multidecadal Oscillation". Geophys. Res. Lett. 33 (17): L17706. Bibcode:2006GeoRL..3317706K. doi:10.1029/2006GL026242. S2CID 17217746.
  • Teegavarapu, R. S. V.; Goly, A.; Obeysekera, J. (2013). "Influences of Atlantic Multi-Decadal Oscillation on Regional Precipitation Extremes". Journal of Hydrology. 495: 74–93. Bibcode:2013JHyd..495...74T. doi:10.1016/j.jhydrol.2013.05.003.
  • Goly, Aneesh; Teegavarapu, Ramesh S. V. (2014). "Individual and coupled influences of AMO and ENSO on regional precipitation characteristics and extremes". Water Resources Research. 50 (6): 4686–4709. Bibcode:2014WRR....50.4686G. doi:10.1002/2013WR014540.

External links

 
Wikimedia Commons has media related to Atlantic Multidecadal Oscillation.
  • AMO Data from 1856–present

August 22, 2023
atlantic, multidecadal, oscillation, confused, with, north, atlantic, oscillation, atlantic, meridional, overturning, circulation, atlantic, multidecadal, oscillation, also, known, atlantic, multidecadal, variability, theorized, variability, surface, temperatu. Not to be confused with North Atlantic oscillation or Atlantic meridional overturning circulation The Atlantic Multidecadal Oscillation AMO also known as Atlantic Multidecadal Variability AMV 1 is the theorized variability of the sea surface temperature SST of the North Atlantic Ocean on the timescale of several decades 2 Atlantic multidecadal oscillation spatial pattern obtained as the regression of monthly HadISST sea surface temperature anomalies 1870 2013 Atlantic Multidecadal Oscillation Index according to the methodology proposed by van Oldenborgh et al 1880 2018 Atlantic Multidecadal Oscillation index computed as the linearly detrended North Atlantic sea surface temperature anomalies 1856 2022 While there is some support for this mode in models and in historical observations controversy exists with regard to its amplitude and whether it has a typical timescale and can be classified as an oscillation There is also discussion on the attribution of sea surface temperature change to natural or anthropogenic causes especially in tropical Atlantic areas important for hurricane development 3 The Atlantic multidecadal oscillation is also connected with shifts in hurricane activity rainfall patterns and intensity and changes in fish populations 4 Contents 1 Definition and history 1 1 AMO index 2 Mechanisms 3 Climate impacts worldwide 4 Relation to Atlantic hurricanes 5 Periodicity and prediction of AMO shifts 6 References 7 Further reading 8 External linksDefinition and history EditEvidence for a multidecadal climate oscillation centered in the North Atlantic began to emerge in 1980s work by Folland and colleagues seen in Fig 2 d A 5 That oscillation was the sole focus of Schlesinger and Ramankutty in 1994 6 but the actual term Atlantic Multidecadal Oscillation AMO was coined by Michael Mann in a 2000 telephone interview with Richard Kerr 7 as recounted by Mann p 30 in The Hockey Stick and the Climate Wars Dispatches from the Front Lines 2012 The AMO signal is usually defined from the patterns of SST variability in the North Atlantic once any linear trend has been removed This detrending is intended to remove the influence of greenhouse gas induced global warming from the analysis However if the global warming signal is significantly non linear in time i e not just a smooth linear increase variations in the forced signal will leak into the AMO definition Consequently correlations with the AMO index may mask effects of global warming as per Mann Steinman and Miller 8 which also provides a more detailed history of the science development AMO index Edit Several methods have been proposed to remove the global trend and El Nino Southern Oscillation ENSO influence over the North Atlantic SST Trenberth and Shea assuming that the effect of global forcing over the North Atlantic is similar to the global ocean subtracted the global 60 N 60 S mean SST from the North Atlantic SST to derive a revised AMO index 9 Ting et al however argue that the forced SST pattern is not globally uniform they separated the forced and internally generated variability using signal to noise maximizing EOF analysis 3 Van Oldenborgh et al derived an AMO index as the SST averaged over the extra tropical North Atlantic to remove the influence of ENSO that is greater at tropical latitude minus the regression on global mean temperature 10 Guan and Nigam removed the non stationary global trend and Pacific natural variability before applying an EOF analysis to the residual North Atlantic SST 11 The linearly detrended index suggests that the North Atlantic SST anomaly at the end of the twentieth century is equally divided between the externally forced component and internally generated variability and that the current peak is similar to middle twentieth century by contrast the others methodology suggest that a large portion of the North Atlantic anomaly at the end of the twentieth century is externally forced 3 Frajka Williams et al 2017 pointed out that recent changes in cooling of the subpolar gyre warm temperatures in the subtropics and cool anomalies over the tropics increased the spatial distribution of meridional gradient in sea surface temperatures which is not captured by the AMO Index 4 Mechanisms EditSee also Atlantic meridional overturning circulation and Ocean heat content Based on the about 150 year instrumental record a quasi periodicity of about 70 years with a few distinct warmer phases between ca 1930 1965 and after 1995 and cool between 1900 1930 and 1965 1995 has been identified 12 In models AMO like variability is associated with small changes in the North Atlantic branch of the Thermohaline Circulation 13 However historical oceanic observations are not sufficient to associate the derived AMO index to present day circulation anomalies citation needed Models and observations indicate that changes in atmospheric circulation which induce changes in clouds atmospheric dust and surface heat flux are largely responsible for the tropical portion of the AMO 14 15 The Atlantic Multidecadal Oscillation AMO is important for how external forcings are linked with North Atlantic SSTs 16 Climate impacts worldwide EditThe AMO is correlated to air temperatures and rainfall over much of the Northern Hemisphere in particular in the summer climate in North America and Europe 17 18 Through changes in atmospheric circulation the AMO can also modulate spring snowfall over the Alps 19 and glaciers mass variability 20 Rainfall patterns are affected in North Eastern Brazilian and African Sahel It is also associated with changes in the frequency of North American droughts and is reflected in the frequency of severe Atlantic hurricane activity 9 Recent research suggests that the AMO is related to the past occurrence of major droughts in the US Midwest and the Southwest When the AMO is in its warm phase these droughts tend to be more frequent or prolonged Two of the most severe droughts of the 20th century occurred during the positive AMO between 1925 and 1965 The Dust Bowl of the 1930s and the 1950s drought Florida and the Pacific Northwest tend to be the opposite warm AMO more rainfall 21 Climate models suggest that a warm phase of the AMO strengthens the summer rainfall over India and Sahel and the North Atlantic tropical cyclone activity 22 Paleoclimatologic studies have confirmed this pattern increased rainfall in AMO warmphase decreased in cold phase for the Sahel over the past 3 000 years 23 Relation to Atlantic hurricanes EditSee also Tropical cyclones and climate change North Atlantic tropical cyclone activity according to the Accumulated Cyclone Energy Index 1950 2015 For a global ACE graph visit this link dead link Archived 2018 11 02 at the Wayback Machine A 2008 study correlated the Atlantic Multidecadal Mode AMM with HURDAT data 1851 2007 and noted a positive linear trend for minor hurricanes category 1 and 2 but removed when the authors adjusted their model for undercounted storms and stated If there is an increase in hurricane activity connected to a greenhouse gas induced global warming it is currently obscured by the 60 year quasi periodic cycle 24 With full consideration of meteorological science the number of tropical storms that can mature into severe hurricanes is much greater during warm phases of the AMO than during cool phases at least twice as many the AMO is reflected in the frequency of severe Atlantic hurricanes 21 Based on the typical duration of negative and positive phases of the AMO the current warm regime is expected to persist at least until 2015 and possibly as late as 2035 Enfield et al assume a peak around 2020 25 However Mann and Emanuel had found in 2006 that anthropogenic factors are responsible for long term trends in tropic Atlantic warmth and tropical cyclone activity and There is no apparent role of the AMO 26 In 2014 Mann Steinman and Miller 8 showed that warming and therefore any effects on hurricanes were not caused by the AMO writing certain procedures used in past studies to estimate internal variability and in particular an internal multidecadal oscillation termed the Atlantic Multidecadal Oscillation or AMO fail to isolate the true internal variability when it is a priori known Such procedures yield an AMO signal with an inflated amplitude and biased phase attributing some of the recent NH mean temperature rise to the AMO The true AMO signal instead appears likely to have been in a cooling phase in recent decades offsetting some of the anthropogenic warming Since 1995 there have been ten Atlantic hurricane seasons considered extremely active by Accumulated Cyclone Energy 1995 1996 1998 1999 2003 2004 2005 2010 2017 and 2020 citation needed Periodicity and prediction of AMO shifts EditThere are only about 130 150 years of data based on instrument data which are too few samples for conventional statistical approaches With the aid of multi century proxy reconstruction a longer period of 424 years was used by Enfield and Cid Serrano as an illustration of an approach as described in their paper called The Probabilistic Projection of Climate Risk 27 Their histogram of zero crossing intervals from a set of five re sampled and smoothed version of Gray et al 2004 index together with the maximum likelihood estimate gamma distribution fit to the histogram showed that the largest frequency of regime interval was around 10 20 year The cumulative probability for all intervals 20 years or less was about 70 citation needed There is no demonstrated predictability for when the AMO will switch in any deterministic sense Computer models such as those that predict El Nino are far from being able to do this Enfield and colleagues have calculated the probability that a change in the AMO will occur within a given future time frame assuming that historical variability persists Probabilistic projections of this kind may prove to be useful for long term planning in climate sensitive applications such as water management A 2017 study predicts a continued cooling shift beginning 2014 and the authors note unlike the last cold period in the Atlantic the spatial pattern of sea surface temperature anomalies in the Atlantic is not uniformly cool but instead has anomalously cold temperatures in the subpolar gyre warm temperatures in the subtropics and cool anomalies over the tropics The tripole pattern of anomalies has increased the subpolar to subtropical meridional gradient in SSTs which are not represented by the AMO index value but which may lead to increased atmospheric baroclinicity and storminess 4 In a 2021 study by Michael Mann it was shown that the periodicity of the AMO in the last millennium was driven by volcanic eruptions and other external forcings and therefore that there is no compelling evidence for the AMO being an oscillation or cycle 28 There was also a lack of oscillatory behaviour in models on time scales longer than El Nino Southern Oscillation the AMV is indistinguishable from red noise a typical null hypothesis to test whether there are oscillations in a model 29 References Edit Multidecadal Climate Changes Geophysical Fluid Dynamics Laboratory Gerard D McCarthy Ivan D Haigh Joel J M Hirschi Jeremy P Grist amp David A Smeed 27 May 2015 Ocean impact on decadal Atlantic climate variability revealed by sea level observations Nature 521 7553 508 510 Bibcode 2015Natur 521 508M doi 10 1038 nature14491 PMID 26017453 S2CID 4399436 a b c Mingfang Ting Yochanan Kushnir Richard Seager Cuihua Li 2009 Forced and Internal Twentieth Century SST Trends in the North Atlantic Journal of Climate 22 6 1469 1481 Bibcode 2009JCli 22 1469T doi 10 1175 2008JCLI2561 1 S2CID 17753758 a b c Eleanor Frajka Williams Claudie Beaulieu Aurelie Duchez 2017 Emerging negative Atlantic Multidecadal Oscillation index in spite of warm subtropics Scientific Reports 7 1 11224 Bibcode 2017NatSR 711224F doi 10 1038 s41598 017 11046 x PMC 5593924 PMID 28894211 Folland C K Parker D E Kates F E 1984 Worldwide marine temperature fluctuations 1856 1981 Nature 310 5979 670 673 Bibcode 1984Natur 310 670F doi 10 1038 310670a0 S2CID 4246538 Schlesinger M E 1994 An oscillation in the global climate system of period 65 70 years Nature 367 6465 723 726 Bibcode 1994Natur 367 723S doi 10 1038 367723a0 S2CID 4351411 Kerr Richard C 2000 A North Atlantic Climate Pacemaker for the Centuries Science 288 5473 1984 1985 doi 10 1126 science 288 5473 1984 PMID 17835110 S2CID 21968248 a b Mann Michael Byron A Steinman Sonya K Miller 2014 On forced temperature changes internal variability and the AMO Geophysical Research Letters 41 9 3211 3219 Bibcode 2014GeoRL 41 3211M doi 10 1002 2014GL059233 a b Trenberth Kevin Dennis J Shea 2005 Atlantic hurricanes and natural variability in 2005 Geophysical Research Letters 33 12 L12704 Bibcode 2006GeoRL 3312704T doi 10 1029 2006GL026894 van Oldenborgh G J L A te Raa H A Dijkstra S Y Philip 2009 Frequency or amplitude dependent effects of the Atlantic meridional overturning on the tropical Pacific Ocean Ocean Sci 5 3 293 301 Bibcode 2009OcSci 5 293V doi 10 5194 os 5 293 2009 Guan Bin Sumant Nigam 2009 Analysis of Atlantic SST Variability Factoring Interbasin Links and the Secular Trend Clarified Structure of the Atlantic Multidecadal Oscillation J Climate 22 15 4228 4240 Bibcode 2009JCli 22 4228G doi 10 1175 2009JCLI2921 1 S2CID 16792059 Climate Phenomena and their Relevance for Future Regional Climate Change PDF IPCC AR5 2014 Archived from the original PDF on 2017 12 07 Retrieved 2017 10 09 O Reilly C H L M Huber T Woollings L Zanna 2016 The signature of low frequency oceanic forcing in the Atlantic Multidecadal Oscillation Geophysical Research Letters 43 6 2810 2818 Bibcode 2016GeoRL 43 2810O doi 10 1002 2016GL067925 Brown P T M S Lozier R Zhang W Li 2016 The necessity of cloud feedback for a basin scale Atlantic Multidecadal Oscillation Geophysical Research Letters 43 8 3955 3963 Bibcode 2016GeoRL 43 3955B doi 10 1002 2016GL068303 Yuan T L Oreopoulos M Zalinka H Yu J R Norris M Chin S Platnick K Meyer 2016 Positive low cloud and dust feedbacks amplify tropical North Atlantic Multidecadal Oscillation Geophysical Research Letters 43 3 1349 1356 Bibcode 2016GeoRL 43 1349Y doi 10 1002 2016GL067679 PMC 7430503 PMID 32818003 S2CID 130079254 Mads Faurschou Knudsen Bo Holm Jacobsen Marit Solveig Seidenkrantz amp Jesper Olsen 25 February 2014 Evidence for external forcing of the Atlantic Multidecadal Oscillation since termination of the Little Ice Age Nature 5 3323 Bibcode 2014NatCo 5 3323K doi 10 1038 ncomms4323 PMC 3948066 PMID 24567051 Ghosh Rohit Muller Wolfgang A Baehr Johanna Bader Jurgen 2016 07 28 Impact of observed North Atlantic multidecadal variations to European summer climate a linear baroclinic response to surface heating Climate Dynamics 48 11 12 3547 Bibcode 2017ClDy 48 3547G doi 10 1007 s00382 016 3283 4 hdl 11858 00 001M 0000 002B 44E2 8 ISSN 0930 7575 S2CID 54020650 Zampieri M Toreti A Schindler A Scoccimarro E Gualdi S April 2017 Atlantic multi decadal oscillation influence on weather regimes over Europe and the Mediterranean in spring and summer Global and Planetary Change 151 92 100 Bibcode 2017GPC 151 92Z doi 10 1016 j gloplacha 2016 08 014 Zampieri Matteo Scoccimarro Enrico Gualdi Silvio 2013 01 01 Atlantic influence on spring snowfall over the Alps in the past 150 years Environmental Research Letters 8 3 034026 Bibcode 2013ERL 8c4026Z doi 10 1088 1748 9326 8 3 034026 ISSN 1748 9326 Huss Matthias Hock Regine Bauder Andreas Funk Martin 2010 05 01 100 year mass changes in the Swiss Alps linked to the Atlantic Multidecadal Oscillation PDF Geophysical Research Letters 37 10 L10501 Bibcode 2010GeoRL 3710501H doi 10 1029 2010GL042616 ISSN 1944 8007 a b National Oceanic and Atmospheric Administration Frequently Asked Questions about the Atlantic Multidecadal Oscillation Archived from the original on 2005 11 26 Zhang R Delworth T L 2006 Impact of Atlantic multidecadal oscillations on India Sahel rainfall and Atlantic hurricanes Geophys Res Lett 33 17 L17712 Bibcode 2006GeoRL 3317712Z doi 10 1029 2006GL026267 S2CID 16588748 Shanahan T M et al 2009 Atlantic Forcing of Persistent Drought in West Africa Science 324 5925 377 380 Bibcode 2009Sci 324 377S CiteSeerX 10 1 1 366 1394 doi 10 1126 science 1166352 PMID 19372429 S2CID 2679216 Chylek P amp Lesins G 2008 Multidecadal variability of Atlantic hurricane activity 1851 2007 Journal of Geophysical Research 113 D22 D22106 Bibcode 2008JGRD 11322106C doi 10 1029 2008JD010036 Enfield David B Cid Serrano Luis 2010 Secular and multidecadal warmings in the North Atlantic and their relationships with major hurricane activity International Journal of Climatology 30 2 174 184 doi 10 1002 joc 1881 S2CID 18833210 Mann M E Emanuel K A 2006 Atlantic Hurricane Trends Linked to Climate Change EOS 87 24 233 244 Bibcode 2006EOSTr 87 233M doi 10 1029 2006EO240001 S2CID 128633734 Archived copy PDF Archived from the original PDF on 2014 08 26 Retrieved 2014 08 23 a href Template Cite web html title Template Cite web cite web a CS1 maint archived copy as title link Mann Michael E Steinman Byron A Brouillette Daniel J Miller Sonya K 2021 03 05 Multidecadal climate oscillations during the past millennium driven by volcanic forcing Science 371 6533 1014 1019 Bibcode 2021Sci 371 1014M doi 10 1126 science abc5810 ISSN 0036 8075 PMID 33674487 S2CID 232124643 Mann Michael E Steinman Byron A Miller Sonya K 2020 01 03 Absence of internal multidecadal and interdecadal oscillations in climate model simulations Nature Communications 11 1 49 Bibcode 2020NatCo 11 49M doi 10 1038 s41467 019 13823 w ISSN 2041 1723 PMC 6941994 PMID 31900412 Further reading EditAndronova N G Schlesinger M E 2000 Causes of global temperature changes during the 19th and 20th centuries Geophys Res Lett 27 14 2137 2140 Bibcode 2000GeoRL 27 2137A doi 10 1029 2000GL006109 Delworth T L Mann M E 2000 Observed and simulated multidecadal variability in the Northern Hemisphere Climate Dynamics 16 9 661 676 Bibcode 2000ClDy 16 661D doi 10 1007 s003820000075 S2CID 7412990 Enfield D B Mestas Nunez A M Trimble P J 2001 The Atlantic Multidecadal Oscillation and its relationship to rainfall and river flows in the continental U S Geophys Res Lett 28 10 2077 2080 Bibcode 2001GeoRL 28 2077E CiteSeerX 10 1 1 594 1411 doi 10 1029 2000GL012745 S2CID 53534572 Goldenberg S B 2001 The recent increase in Atlantic hurricane activity Causes and implications Science 293 5529 474 479 Bibcode 2001Sci 293 474G doi 10 1126 science 1060040 PMID 11463911 Gray S T 2004 A tree ring based reconstruction of the Atlantic Multidecadal Oscillation since 1567 A D Geophys Res Lett 31 12 L12205 Bibcode 2004GeoRL 3112205G doi 10 1029 2004GL019932 Hetzinger Steffen 2008 Caribbean coral tracks Atlantic Multidecadal Oscillation and past hurricane activity Geology 36 1 11 14 Bibcode 2008Geo 36 11H doi 10 1130 G24321A 1 Kerr R A 2000 A North Atlantic climate pacemaker for the centuries Science 288 5473 1984 1986 doi 10 1126 science 288 5473 1984 PMID 17835110 S2CID 21968248 Kerr R A 2005 Atlantic climate pacemaker for millennia past decades hence Science 309 5731 41 43 doi 10 1126 science 309 5731 41 PMID 15994503 Knight J R 2005 A signature of persistent natural thermohaline circulation cycles in observed climate Geophys Res Lett 32 20 L20708 Bibcode 2005GeoRL 3220708K doi 10 1029 2005GL024233 S2CID 16909466 McCabe G J Palecki M A Betancourt J L 2004 Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States PNAS 101 12 4136 4141 Bibcode 2004PNAS 101 4136M doi 10 1073 pnas 0306738101 PMC 384707 PMID 15016919 Sutton R T Hodson L R 2005 Atlantic forcing of North American and European summer climate Science 309 5731 115 118 Bibcode 2005Sci 309 115S doi 10 1126 science 1109496 PMID 15994552 Knight J R Folland C K Scaife A A 2006 Climate impacts of the Atlantic Multidecadal Oscillation Geophys Res Lett 33 17 L17706 Bibcode 2006GeoRL 3317706K doi 10 1029 2006GL026242 S2CID 17217746 Teegavarapu R S V Goly A Obeysekera J 2013 Influences of Atlantic Multi Decadal Oscillation on Regional Precipitation Extremes Journal of Hydrology 495 74 93 Bibcode 2013JHyd 495 74T doi 10 1016 j jhydrol 2013 05 003 Goly Aneesh Teegavarapu Ramesh S V 2014 Individual and coupled influences of AMO and ENSO on regional precipitation characteristics and extremes Water Resources Research 50 6 4686 4709 Bibcode 2014WRR 50 4686G doi 10 1002 2013WR014540 External links Edit Wikimedia Commons has media related to Atlantic Multidecadal Oscillation Frequently asked questions about the AMO Probabilistic projection of future AMO regime shifts AMO Data from 1856 present Retrieved from https en wikipedia org w index php title Atlantic multidecadal oscillation amp oldid 1171103137, wikipedia, wiki, book, books, library,

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