A mosphe ic and Clima e Sciences, 2016, 6, 367-374
Published Online July 2016 in SciRes. h p://www.sci p.o g/jou nal/acs
h p://dx.doi.o g/10.4236/acs.2016.63030
How o ci e his pape : Lindholm, M., Jalkanen, R. and Ogu so , M.G. (2016) Cu en Ne wo ks o Long P oxies o Building
Recons uc ion Models o he A lan ic Mul idecadal Oscilla ion. A mosphe ic and Clima e Sciences, 6, 367-374.
h p://dx.doi.o g/10.4236/acs.2016.63030
Cu en Ne wo ks o Long P oxies o
Building Recons uc ion Models o he
A lan ic Mul idecadal Oscilla ion
Ma kus Lindholm1, Ris o Jalkanen1, Maxim G. Ogu so 2
1Luke, Ro aniemi Resea ch Uni , Ro aniemi, Finland
2A.F. Io e Physico-Technical Ins i u e, S . Pe e sbu g, Russia
Recei ed 10 Decembe 2015; accep ed 20 May 2016; published 23 May 2016
Copy igh © 2016 by au ho s and Scien i ic Resea ch Publishing Inc.
This wo k is licensed unde he C ea i e Commons A ibu ion In e na ional License (CC BY).
h p://c ea i ecommons.o g/licenses/by/4.0/
Abs ac
Cu en ly a ailable p oxies we e s udied as ne wo ks o building econs uc ion models o he
A lan ic Mul idecadal Oscilla ion (AMO). Only p oxies ha would double he cu en eco d leng h
(backwa ds in ime om AD 1564) we e included. We p esen wo p oxy ne wo ks and co es-
ponding econs uc ion ( ans e ) models, one o ee-g ow h based p oxies only and ano he o
mul ip oxies. Bo h o hem show a use ul ma ch in iming as well as ampli ude wi h he AMO.
These model s uc u es demons a ed easonable model pe o mance (o e all 2 = 0.45 - 0.36).
The ime s abili y o p oxy-AMO ela ionships was also alida ed. The new models p oduced ac-
cep able esul s in c oss-calib a ion- e i ica ion ( educ ion o e o and coe icien o e iciency
s a is ics in 1856-1921 and 1922-1990 a y be ween 0.41 and 0.21). The spa ial dis ibu ion o
hese da a se ies indica e ha p oxies espond o an AMO-like clima ic oscilla ion o e much o
he No he n Hemisphe e.
Keywo ds
P oxies, A lan ic Mul idecadal Oscilla ion, T ee G ow h, Clima e Change, T ans e Models
1. In oduc ion
No h A lan ic sea-su ace empe a u es (SSTs) a e known o a y p ominen ly on mul idecadal imescales.
These a ia ions a e domina ed by he al e na ion be ween wa m and cold SST anomalies on an oscilla ing
imescale o 60 - 80 yea s. The AMO has been iden i ied in he ins umen al eco d as a cohe en , basin-wide
pa e n o oscilla o y changes in SST [1]-[3]. On Hemisphe ic scale, i also seems likely ha an a mosphe ic
M. Lindholm e al.
368
b idge con eys he in luence o he A lan ic Ocean o he Paci ic modula ing he El Niño-Sou he n Oscilla ion
(ENSO) and Paci ic Decadal Oscilla ion (PDO) [4] [5].
The o cing mechanism pacing he AMO emains subjec o conside able deba e. On one hand, he AMO is
hough o be d i en by in e nal ocean a iabili y and is ela ed o mul idecadal luc ua ions in he A lan ic Me-
idional O e u ning Ci cula ion [1] [6] [7]. On he o he hand, a combina ion o ex e nal o cing due o sola
a iabili y, e.g. olcanic e up ions, may ha e de e mined he pace and phasing o he AMO [8] [9]. A majo
sho coming in assessing he ue na u e o he AMO as well as he unde lying o cing mechanisms has been he
sho ness o he ins umen al eco d ( om 1856 o he p esen ). P oxy econs uc ions a e i eplaceable ools in
o e coming his p oblem.
We ocused he e on building ne wo ks o long p oxies a ailable om open a chi es as well as s udying hei
po en ial in modeling he AMO. The well-known econs uc ion o he AMO since AD 1567 by G ay e al. [10]
based on wel e o al- ing-wid h eco ds was used as an example. We now included only p oxies ha ex ended
back o he 11 h cen u y and hus would double he leng h o he cu en eco d, 423 yea s om 1567 o 1990 by
G ay e al. [10] o exceed 900 yea s. Limi ing he analyses only o p oxies ha co e he en i e ime in e al is a
easonable expec a ion since he numbe o a ailable da a is inc easing and he a chi es o e.g. he In e na ional
T ee-Ring Da a Bank (ITRDB) a e being ac i ely upda ed. Secondly, we aimed o include no only ee- ing da-
a bu also o he ypes o clima e p oxies wi h esolu ions co esponding o hose o he a ge (e.g. lake and
sea- loo sedimen s as well as iso opic analyses om speleo hems and ice). Because o po en ially wo ldwide
clima e impac s [7], we s udied an AMO signal in p oxy ne wo ks om he whole No he n hemisphe e and
a ailable da a we e hus no geog aphically limi ed o he A lan ic im. Thi dly, we wan ed o enhance cu en
p ocedu es o building ans e models o he AMO by applying c oss-pe iod alida ion o assessing he ime
s abili y o de i ed ans e unc ions.
2. Ma e ials and Me hods
P oxy da a se ies om 0˚ - 90˚N co e ing he pe iod 1100-1990 we e ob ained om he paleoclima e a chi es
hos ed by Na ional Oceanic and A mosphe ic Adminis a ion (NOAA) and In e na ional T ee-Ring Da a Bank
(ITRDB) (h ps://www.ncdc.noaa.go /da a-access/paleoclima ology-da a/da ase s). Candida e da a se ies we e
sc eened mainly o empe a u e o p ecipi a ion, bu hey we e also accep ed i hey we e known o show some
sensi i i y o ela ed clima ological pa ame e s.
I aw ee- ing measu emen s we e a ailable hey we e s anda dized using wo me hods ha p ese e me-
dium and low- equency a iabili y: 1) he conse a i e nega i e exponen ial o lines o ze o o nega i e slope
(NE) [10] [11] and 2) mo e lexible 180-yea splines (Sp180) [12]-[15]. Thus o each da a se wo ch onologies
we e p oduced and compa ed. The ch onologies p oducing be e co ela ion wi h he a ge (see below) was se-
lec ed o u he analyses. I only a mean ch onology (buil using a known s anda diza ion me hod) was a aila-
ble i was used as such. Co espondingly he o he (non-dend o) p oxies we e used as p o ided by he da a-
banks. Common low-pass il e s in AMO-s udies—10-yea mo ing a e ages [4] [10]—we e used.
All he p oxies mee ing he ini ial equi emen s (minimum eco d leng h and clima e sensi i i y) we e co e-
la ed wi h annual No h A lan ic SST in 1856-1990 [16]. The se ies exceeding h eshold alue ( ≤ −0.25 o
≥0.25) we e combined o a ec angula ma ix and subjec ed o p incipal componen s analysis (PCA), which o -
hogonalized he da a o p incipal componen sco es (PCs). The numbe o PCs was hen limi ed in a wo-s age
p ocedu e. Highe -o de PCs we e i s ejec ed based on he cumula i e p oduc o eigen alues and he emain-
ing PCs we e u he limi ed by he - alue o pai ed co ela ion, which should ha e an absolu e alue equal o
g ea e han 1.0 [10] [17]-[19]. The PCs we e hen en e ed in o linea eg ession o p oduce ans e unc ions
and p oxy models o he annual AMO.
Empi ically de i ed equa ions which link p oxies o changes in ac ual clima ic ime se ies mus be alida ed
o e i ied on independen da a ( o e.g. assess he ime s abili y o he equa ions). To allow o compa ison we
used he same pe iods o calib a ion and e i ica ion (1922-1990, 1856-1921) as G ay e al. [10]. P e ious
AMO s udies ha e used only one pe iod o calib a ion and one o e i ica ion. Indi idual models we e now
es ed u he in spli pe iod calib a ion- e i ica ion, whe e each pe iod was es ed sepa a ely and independen ly.
The wo sub-pe iods (1856-1921, 1922-1990), used o calib a ion du ing one pe iod and e i ica ion du ing he
o he a e e e ed o as ea ly calib a ion-la e e i ica ion and la e calib a ion-ea ly e i ica ion (EC-LV and
LC-EV, espec i ely). Bo h sub-pe iods should now p oduce posi i e alues o educ ion o e o (RE) [11] [17]
M. Lindholm e al.
369
[18] and coe icien o e iciency (CE) [17] [20]. RE and CE a e cen al s a is ics in clima e econs uc ion ec-
ommended by e.g. Na ional Resea ch Council [20]. Thei alues may a y om +1 o −∞. The models we e also
compa ed using co ela ion ( ) and explained a iance o coe icien o de e mina ion ( 2).
3. Resul s
The sea ch o sui able p oxies p oduced a ne wo k o 16 long se ies (Table 1). They include da a o bo h an-
nual and decadal esolu ion, which mee he ini ial c i e ion o co ela ion (indi idual p oxies s annual AMO
index wi h g ea e han |0.25|). The sp ead o he ne wo k and he esponse o hese se ies o he AMO a e
shown in Figu e 1. Nicoa Ca e se ies (speleo hem, se ies 3, Table 1, Figu e 1) had he highes and he Finnish
ee- ing (MXD) se ies he lowes co ela ion ( = 0.49 and 0.25 espec i ely). Th ee o he p oxies a e speleo-
hem se ies and one a lake sedimen se ies. The emaining 12 a e dend och onological da a. Fi e o hese
eached highe - alues using he NE me hod and six wi h he SP180 me hod. One ee- ing wid h da a se
(Taimy Peninsula, Russia, se ies 5, Table 1) was only a ailable as egional cu e s anda dized (RCS) ch onol-
ogy and was included as such.
The da a se o 16 se ies we e ans o med o PCs, he numbe o which was i s limi ed o 12 and hen o i e.
These PCs (1, 2, 3, 4 and 8 wi h cumula i e a iance explained = 65%) we e e ained o use in building he e-
cons uc ion models. In c oss-calib a ion- e i ica ion he model o i e PCs p oduced posi i e alues o RE
(>0.37) and CE (>0.36) in bo h EC_LV and LC_EV pe iods (Table 2(a)). The ea ly and la e calib a ed econ-
s uc ion models we e able o explain 37% - 42% o he a iance in e i ica ion pe iod AMO wi h high con i-
dence (Table 2(a)). Thus a ull model using he en i e 135-ya calib a ion pe iod (1856-1990) could be d awn
wi h 2 = 0.45 (Figu e 2(a)):
a)
0.0176 0.0474* 1 0.0119* 2 0.0359* 3 0.0257* 4 0.0197* 8y PC PC PC PC PC=−+ + − + −
The ne wo k o 16 se ies includes 12 ee-g ow h based ch onologies (11 ee- ing wid h and one maximum-
la ewood densi y se ies). The abo e p ocedu e was now epea ed especially o hese dend och onological se ies.
Table 1. Name, loca ion and ype o p oxy se ies 1 - 16 co e ing he 900 yea s pe iod 1090-1990. Re e ence o p incipal
in es iga o named in he da a-bases o la es pape by he au ho s.
P oxy loca ion Longi ude La i ude P oxy ype Re e ence
Non-dend ose ies:
1) Dongge Ca e, Sou h China 108.5 25.17 Sp Wang e al. 2005
2) Soco a Island, Indian Ocean 50 12,5 Sp Bu ns e al. 2003
3) Nicoa Ca e, Nicoya, Cos a Rica −85.3 10.2 Sp Mann e al. 2008
4) Lake Chichancanab, Yaca an, Mexico −88.9 19.8 Is Hodell e al. 1995, 2005
Dend ose ies:
5) Taimy Peninsula, Russia 105 70.3 - 73 TRW Nau zbae e al. 2002
6) To ne äsk, No h Sweden 19.43 68.13 TRW G udd e al. 2002
7) Laanila, No h Finland 27.30 68.50 MXD McCa oll e al. 2013
8) Kola Peninsula, Russia 33.15 67.41 TRW Konono e al. 2009
9) Hen ii Moun ains, Mongolia 107.28 48.21 TRW Cook e al. 2010
10) Whi lpool Poin , Albe a, Canada −116.27 52 TRW Sauchyn e al. 2011
11) No h Fo k Ridge, Mon ana, USA −111.2 45.18 TRW John C. King
12) Pin le s, Mon ana, USA −113.22 46.01 TRW Pede son e al. 2011
13) Flin C eek Range, Mon ana, USA −113.09 46.17 TRW Hughes, M.K., Woodhouse, C.A., B own, P.M.
14) Yellow Moun ain Ridge 2, Mon ana, USA −111.19 45.18 TRW G aumlich e al. 2002
15) Pea l Peak upda e, Ne ada, USA −115.32 40.14 TRW Salze e al. 2009
16) Sheep Moun ain upda e, Cali o nia, USA −118.12 37.31 TRW Salze e al. 2009
M. Lindholm e al.
370
Figu e 1. The ne wo k includes 16 ee-g ow h based ( iangles) and o he ypes o p oxies (s a s).
Co ela ion wi h he AMO (1856-1990) in b acke s: 1, Dongge Ca e (−0.43); 2, Soco a Island
(−0.39); 3, Nicoa Ca e (0.49); 4, Lake Chichancanab (0.26); 5, Taimy Peninsula (0.35); 6, To ne äsk
(0.32); 7, Laanila (0.25); 8, Kola Peninsula (0.35); 9, Hen ii Moun ains (0.28); 10, Whi lpool Poin
(−0.25); 11, No h Fo k Ridge (0.25); 12, Pin le s (0.31); 13, Flin C eek Range (0.36); 14, Yellow
Moun ain Ridge 2 (−0.25); 15, Pea l Peak upda e (0.29); and 16, Sheep Moun ain upda e (0.28).
Figu e 2. Ac ual s. es ima ed alues: wo model s uc u es p oduced using ei he 16 mixed p oxies (a)
and 12 ee-g ow h based p oxies (b). Do ed line is he a ge annual AMO index. Ve ical line (dash)
di ides he a ailable calib a ion and e i ica ion pe iods.
Among hem he se ies om Flin C eek Range (Mon ana, USA) has he highes co ela ion wi h he AMO ( =
0.36, Figu e 1). The 12 se ies we e now subjec ed o PCA and sc eening o PCs. Fou PCs (1, 3, 5 and 8 wi h
cumula i e a iance explained ~54%) now passed he sc eenings and we e used in calib a ion wi h he AMO. In
e i ica ion bo h EC_LV and LC_EV models had posi i e alues o RE and CE (Table 2(b)). In espec i e e i-
ica ion pe iods hese wo econs uc ions explain 24% - 35% o he AMO a iance (Table 2(b)). All a ailable
da a (1856-1990) we e again ecalib a ed o build a ull model wi h 2 = 0.36 (Figu e 2(b)):
b)
0.0176 0.05* 1 0.0154* 3 0.0374* 5 0.0236* 8y PC PC PC PC
=−+ − + −
The F-s a is ic o inal models A and B a e 25.64 and 17.88 espec i ely–bo h highly signi ican . I is e y
unlikely o ge F- a ios as la ge as hese by chance alone i he slope o o e all eg ession line we e ze o (H0: no
M. Lindholm e al.
371
Table 2. Calib a ion and e i ica ion pe iod s a is ics o he wo ypes o econs uc ion
models ((a) and (b)). The ea ly calib a ion (1856-1921) igu es a e e i ied o e he 1922-
1990 pe iod and he la e calib a ion (1922-1990) igu es a e e i ied on he 1856-1921 da a.
(a) Mul ip oxy om 16 se ies
Ea ly calib a ion La e calib a ion
Calib a ion 2 0.42 0.50
Ve i ica ion 2 0.42 0.37
Signi icance le el (p) 1.6 × 10−9 7 × 10−8
RE 0.41 0.37
CE 0.41 0.36
(b) P oxy om 12 dend och onological se ies
Calib a ion 2 0.35 0.42
Ve i ica ion 2 0.35 0.24
Signi icance le el (p) 8.8 × 10−8 2.6 × 10−5
RE 0.31 0.21
CE 0.31 0.21
dependence o y on x).
Co ela ion be ween he annual AMO index and he econs uc ions du ing he ull (135-yea ) calib a ion pe-
iod is 0.67 o model A and 0.60 o model B (Table 3). These esul s show highly signi ican associa ions
since he null hypo hesis can be ejec ed wi h easonable con idence (p ≤ 2.5 × 10−14). Using il e ed da a co e-
la ions ise o 0.92 and 0.87 o models A and B espec i ely and he ela ionship become e en mo e e iden
(Figu e 3(a), Figu e 3(b)). Despi e an ob ious o e all esemblance, in de ail model B i s somewha unde es-
ima es he AMO in la e 19 h cen u y and hen o e es ima es i in ea ly 1900s up o a ound 1940 (Figu e 3(b)).
Model A pe o ms mo e e enly in his espec (Figu e 3(a)).
Addi ional e i ica ion was achie ed by compa isons o ou p oxy models and he econs uc ion by G ay e
al. [10], which p oduced = 0.53 o model A and = 0.54 o model B in 1856-1990 (Table 3). Pai ed se ies
- es alue anges espec i ely om 7.3 o 7.7. In compa ison using 10-yea mo ing a e ages, co ela ion ises
o 0.79 o model A and 0.85 o model B (Table 3, Figu e 3).
4. Discussion
A 16-se ies mul ip oxy as well as a 12-se ies ee-g ow h based eco d p oduced easible econs uc ion models
o he AMO. These ne wo ks o nea ly millennial se ies likely double he leng h o he exis ing 450-yea p oxy
AMO back o he 11 h cen u y. Bo h o he new models a e s a is ically highly signi ican , indica ing s ong li-
nea (s a is ical) ela ionships. Al hough he 16-se ies mul ip oxy is supe io in model pe o mance (measu ed as
2), bo h o ou wo models gene ally wo k a leas as well as he one by G ay e al. [10]. Acco ding o hese au-
ho s [10] he co ela ion be ween hei econs uc ion and he annual obse ed AMO is 0.64 wi hou il e ing
and 0.84 a e il e ing. In addi ion, he new models a e nea ly independen om he old model. They ha e only
one pa ly common componen se ies, i.e. some da a sha ed by he p e ious and upda ed e sions o he To -
ne äsk ee- ing ch onology om no he n Sweden.
G ay e al. [10] epo ed ha he ou pu om hei model has RE = 0.25 (LC_EV). Ou models A and B wi h
RE = 0.37 and 0.21 espec i ely compa e well wi h his. Only he LC_EV e i ica ion was applied by G ay e al.
[10]. We ha e now enhanced he p ocedu e using wo spli pe iods o c oss- alida ion in addi ion o applying
he mo e sea ching CE s a is ic (no used p e iously in AMO- econs uc ions). Bo h pe iods he e pe o m well
allowing easible independen e i ica ion.
The wo calib a ion and e i ica ion pe iods show ha he AMO swi ch be ween nega i e and posi i e shi s
(wa m and cool phases) in 1920s do no al e he ime s abili y o hese equa ions (i.e. simila calib a ion and e-
i ica ion s a is ics in EC_LV and LC_EV). RE and CE a e cen al ools in dend oclima ology assessing he

M. Lindholm e al.
372
Figu e 3. 10-yea mo ing a e ages (1860-1985) o ac ual (do ed line) and es ima ed alues:
he 16 se ies mul ip oxy (a), 12 se ies ee-g ow h based p oxy (b) and in (c) model A se ies
(do ed) s he one buil by G ay e al. [10].
Table 3. Co ela ion and S uden s -s a is ic be ween he AMO and ou models A, B and he
econs uc ion by G ay e al. [10] du ing 1856-1990 using bo h il e ed and un il e ed alues.
The la e is also compa ed wi h he new models A and B.
- alue
Model A s AMO
Un il e ed 0.67 10.45
Fil e ed 0.92 25.64
Model B s AMO
Un il e ed 0.60 8.55
Fil e ed 0.87 19.29
The model by G ay e al. s ou model A
Un il e ed 0.53 7.3
Fil e ed 0.79 14.34
The model by G ay e al. s ou model B
Un il e ed 0.54 7.7
Fil e ed 0.85 17.71
gene al easibili y o a model, wi h ze o indica ing ha he econs uc ion model pe o ms no be e as a p edic-
o han he mean alue o he calib a ion (RE) o e i ica ion (CE) pe iod. The la e calib a ions o bo h models
A and B a e sligh ly be e han he ea ly ones. The mul idecadal scale is enhanced using 10-yea unning means,
which e ec i ely emo es any high equency cha ac e is ics in he da a. Co ela ion o especially il e ed se-
ies—AMO s ou models A and B—compa es e y a ou ably wi h he new models.
The geog aphical dis ibu ion o hese da a indica e ha an AMO-like oscilla ion is mo e widely sp ead o e
M. Lindholm e al.
373
he No he n Hemisphe e han was e iden in he p e ious mo e basin-wide da a o G ay e al. [10], he ocus o
which was close o he No h A lan ic im. The imp o ed s a is ics o he new models u he suppo he idea
ha a s ong mul idecadal scale a iabili y (wi h a easonable ma ch wi h he AMO) is no limi ed o egions
bo de ing he No h A lan ic. In addi ion he AMO-signal e iden ly does no weaken om he A lan ic owa ds
he ou e inges o his ne wo k. In he pas he AMO index has been linked o a ious p oxy empe a u es and
ain all o e much o he No he n Hemisphe e as well as o a wide ange o o he clima e pa ame e s. Simila
pe iodici y has been ound in e.g. A lan ic A c ic sea ice [21], win e empe a u es in Eu ope, A ican d ough
equency [21] [22], Asian summe monsoons [23] [24] and clima e pa ame e s om No heas e n Asia [24] as
well as Sou h Ame ican ain all [25].
Some o he ypes o s udies wi h dense ne wo ks gi e suppo o he possibili y o an AMO signa u e on
global mul idecadal clima e a iabili y [7] [24] [26]. Al hough pa o he speleo hem and sedimen da a in ou
analyses come om ma i ime egions, he majo i y o p oxy se ies o igina e om e es ial (con inen al) e-
gions. Thus acco ding o hese da a he mul idecadal clima ic signal is pe sis en in he p oxy ne wo k om he
bulk o he No he n Hemisphe e. This con i ms p e ious s udies showing AMO-links om a -away egions [5]
[21] [22] [24]-[26]. Fo example A c ic ai empe a u e and p essu e ha e been shown o display s ong mul-
i-decadal a iabili y on simila ime scales [27]. Acco ding o Schlesinge and Ramanku y [1] he su ace em-
pe a u e eco ds o 11 geog aphical egions shows ha a 65 - 70-yea oscilla ion is he s a is ical esul o 50 -
88-yea oscilla ions o he No h A lan ic Ocean and i ’s bounding No he n Hemisphe e con inen s. In addi ion,
also Delwo h and Mann [6] ex ac ed a mul idecadal signal om global su ace- empe a u e econs uc ions.
5. Conclusions
This pape was de o ed o he calib a ion o p oxies agains he AMO, i.e. ex ac ing an AMO signal. The wo
ne wo ks o p oxy da a p o ided new and well eplica ed ans e models o he AMO. Despi e using nea ly
millennium-long eco ds, he models pe o m e y well, in pa icula he mul ip oxy op ion. In addi ion, bo h
models now easily passed igo ous c oss-calib a ion- e i ica ion es s. We used spli pe iods and also he CE
s a is ic, i.e. compa ison o econs uc ion also o he mean o e i ica ion pe iod and no jus o ha o he cali-
b a ion pe iod as in p e ious s udies.
These p oxies will help o ex end he cu en AMO eco d backwa ds in ime om AD 1567 o exceed 900
yea s in eco d leng h. Wo k con inues on analyses o he ac ual long- e m p oxy econs uc ion in a ious e-
quency anges du ing he pas cen u ies. Such a long ime-se ies is needed in u u e compa isons o he 20 h
cen u y modes o a iabili y o hose o he pas as well as o highe equency a mosphe ic modes, e.g. No h
A lan ic Oscilla ion and A c ic Oscilla ion.
Somewha su p isingly he new ne wo ks showed a meaning ul esponse o he AMO in a mo e ex ensi e
spa ial dis ibu ion o he phenomenon in p oxies han he p e ious model o G ay e al. [10]. Gene ally he wo
ee-g ow h-based models—old model o G ay e al. [10] and ou new model B a e ob iously somewha mo e
alike han he new mul ip oxy model A, which howe e has he bes i o he obse ed AMO in bo h annual and
decadal scales.
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