On the spectral characteristics of the Atlantic multidecadal variability in an ensemble of multi-century simulations

The Atlantic multidecadal variability (AMV) is a coherent pattern of variability of the North Atlantic sea surface temperature
field affecting several components of the climate system in the Atlantic region and the surrounding areas. The relatively
short observational record severely limits our understanding of the physical mechanisms leading to the AMV. The present
study shows that the spatial and temporal characteristics of the AMV, as assessed from the historical records, should also
be considered as highly uncertain. Using 11 multi-century preindustrial climate simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) database, we show that the AMV characteristics are not constant along the simulation
when assessed from different 200-year-long periods to match the observed period length. An objective method is proposed to
test whether the variations of the AMV characteristics are consistent with stochastic internal variability. For 7 out of the 11
models analysed, the results indicate a non-stationary behaviour for the AMV time series. However, the possibility that the
non-stationarity arises from sampling errors can be excluded with high confidence only for one of the 7 models. Therefore,
longer time series are needed to robustly assess the AMV characteristics. In addition to any changes imposed to the AMV
by external forcings, the detected dependence on the time interval identified in most models suggests that the character of
the observed AMV may undergo significant changes in the future.

Ba J, Keenlyside NS, Latif M, Park W, Ding H, Lohmann K et al (2014)
A multi-model comparison of Atlantic multidecadal variability.
Clim Dyn 43(9–10):2333–2348
Bellucci A, Mariotti A, Gualdi S (2017) The role of forcings in the 20th
century North Atlantic multi-decadal variability: the 1940–1975
North Atlantic cooling case study. J Clim 30:7317–7337 Booth BBB, Dunstone NJ, Halloran PR, Andrews T, Bellouin N (2012)
Aerosols implicated as a prime driver of twentieth-century North
Atlantic climate variability. Nature 484:228–232
Brockwell PJ, Davis RA (1991) Time series: theory and methods.
Springer, New York
DelSole T, Tippett MK, Shukla J (2011) A significant component of
unforced multidecadal variability in the recent acceleration of
global warming. J Clim 24:909–926
Delworth TL, Mann ME (2000) Observed and simulated multidecadal
variability in the Northern Hemisphere. Clim Dyn 16:661–676
Deser C, Blackmon ML (1993) Surface climate variations over the North
Atlantic Ocean during winter: 1900–1989. J Clim 6:1743–1753
Deshayes J, Curry R, Msadek R (2014) CMIP5 model intercomparison
of freshwater budget and circulation in the North Atlantic. J Clim
27:3298–3317
Ebisuzaki W (1997) A method to estimate the statistical significance
of a correlation when the data are serially correlated. J Clim
10:2147–2153
Enfield DB, Mestas-Nuñez AM, Trimble PJ (2001) The Atlantic multidecadal oscillation and its relation to rainfall and river flows in the
continental US. Geophys Res Lett 28(10):2077–2080
Frankcombe LM, von der Heydt A, Dijkstra HA (2010) North Atlantic multidecadal climate variability: an investigation of dominant
time scales and processes. J Clim 23(13):3626–3638
Goldenberg SB, Landsea CW, Mestas-Nuñez AM, Gray WM (2001)
The recent increase in atlantic hurricane activity: causes and
implications. Science 293:474
Gray ST, Graumlich LJ, Betancourtv JL, Pederson GT (2004) A treering based reconstruction of the Atlantic Multidecadal Oscillation
since 1567 A.D. Geophys Res Lett 31:L12205
Hasselmann K (1976) Stochastic climate models, Part I. Theory. Tellus 28:473–485
Huang J, Higuchi K, Shabbar A (1998) The relationship between the
North Atlantic oscillation and El Niño-Southern oscillation. Geophys Res Lett 25:2707–2710
Hurrell JW, Van Loon H (1997) Decadal variations in climate associated with the North Atlantic oscillation. Clim Change 36:301–326
Kilbourne KH, Alexander MA, Nye JA (2014) A low latitude paleoclimate perspective on Atlantic multidecadal variability. J Mar
Syst 133:4–13
Knight JR, Allan RJ, Folland CK, Vellinga M, Mann ME (2005) A
signature of persistent natural thermohaline circulation cycles in
observed climate. Geophys Res Lett 32:L20708
Knight JR, Folland CK, Scaife AA (2006) Climate impacts of the
Atlantic multidecadal oscillation. Geophys Res Lett 33:L17706
Kushnir Y (1994) Interdecadal variations in North Atlantic Sea surface temperature and associated atmospheric conditions. J Clim
7:141–157
Latif M, Collins M, Pohlmann H, Keenlyside NS (2006) A review of
predictability studies of Atlantic sector climate on decadal time
scales. J Clim 19:5971–5987
Latif M, Keenlyside NS (2011) A perspective on decadal climate variability and predictability. Deep Sea Res. Part II
58(17–18):1880–1894
Mariotti A, Dell’Aquila A (2012) Decadal climate variability in the
Mediterranean region: roles of large-scale forcings and regional
processes. Clim Dyn 38:1129–1145
Marullo S, Artale V, Santoleri R (2011) The SST multidecadal variability in the Atlantic–Mediterranean region and its relation to
AMO. J Clim 24:4385–4401
Medhaug I, Furevik T (2011) North Atlantic 20th century multidecadal
variability in coupled climate models: sea surface temperature and
ocean overturning circulation. Ocean Sci 7:389–404
Menary MB, Hodson DLR, Robson JI, Sutton RT, Wood RA, Hunt
JA (2015) Exploring the impact of CMIP5 model biases on the
simulation of North Atlantic decadal variability. Geophys Res Lett
42:5926–5934
Otterå OH, Bentsen M, Drange H, Suo L (2010) External forcing as
a metronome for Atlantic multidecadal variability. Nat Geosci
3:688–694
Rayner NA, Parker DE, Horton EB, Folland CK, Alexander LV,
Rowell DP, Kent EC, Kaplan A (2003) Global analyses of sea
surface temperature, sea ice, and night marine air temperature
since the late nineteenth century. J Geophys Res 108:4407
Rotstayn LD, Lohmann U (2002) Tropical rainfall trends and the
indirect aerosol effect. J Clim 15:2103–2116
Saenger C, Cohen AL, Oppo DW, Halley RB, Carilli JE (2009) Surface-temperature trends and variability in the low-latitude North
Atlantic since 1552. Nat Geosci 2:492–495
Schlesinger ME, Ramankutty N (1994) An oscillation in the global
climate system of period 65–70 years. Nature 367:723–726
Sutton RT, Dong B (2012) Atlantic Ocean influence on a shift in
European climate in the 1990s. Nat Geosci 5:788–792
Sutton RT, Hodson DLR (2005) Atlantic Ocean forcing of North
American and European summer climate. Science 309:115
Swingedouw D, Mignot J, Labetoulle S, Gilardi E, Madec G (2013)
Initialisation and predictability of the AMOC over the last 50
years in a climate model. Clim Dyn 40:23981–23990
Taylor KE, Stouffer RJ, Meehl GA (2012) An overview of CMIP5
and the experiment design. Bull Am Meteorol Soc 93:485–498
Terray L (2012) Evidence for multiple drivers of North Atlantic
multi-decadal climate variability. Geophys Res Lett 39:L19712
Thomson DJ (1982) Spectrum estimation and harmonic analysis.
Proc IEEE 70(9):1055–1096
Ting M, Kushnir Y, Seager R, Li C (2009) Forced and internal
twentieth-century SST trends in the North Atlantic. J Clim
22:1469–1481
Ting M, Kushnir Y, Seager R, Li C (2011) Robust features of Atlantic multi-decadal variability and its climate impacts. Geophys
Res Lett 38:L17705
Ting M, Kushnir Y, Li C (2014) North Atlantic multidecadal SST
oscillation: external forcing versus internal variability. J Mar
Syst 133:27–38
Trenberth KE, Shea DJ (2006) Atlantic hurricanes and natural variability in 2005. Geophys Res Lett 33:L12704
Wittenberg AT (2009) Are historical records sufficient to constrain
ENSO simulations? Geophys Res Lett 36:L12702
Zanchettin D, Rubino A, Jungclaus JH (2010) Intermittent multidecadal-to-centennial fluctuations dominate global temperature evolution over the last millennium. Geophys Res Lett 37:L14702
Zanchettin D, Bothe O, Müller W, Bader J, Jungclaus JH (2014) Different flavors of the Atlantic multidecadal variability. Clim Dyn
42(1–2):381–399
Zhang R (2008) Coherent surface-subsurface fingerprint of the Atlantic
meridional overturning circulation. Geophys Res Lett 35:L20705
Zhang R, Delworth TL (2006) Impact of Atlantic multidecadal oscillations on India/Sahel rainfall and Atlantic hurricanes. Geophys
Res Lett 33:L17712
Zhang L, Wang C (2013) Multidecadal North Atlantic sea surface
temperature and Atlantic meridional overturning circulation variability in CMIP5 historical simulations. J Geophys Res Oceans
118(10):5772–5791