RESEARCH/REVIEW ARTICLE
A ch onology o clima ic down u ns h ough he mid- and la e-
Holocene: acing he dis an e ec s o explosi e e up ions om
palaeoclima ic and his o ical e idence in no he n Eu ope
Samuli Helama,
1
Ja i Holopainen,
2
Ma c Macias-Fau ia,
3
Mau i Timonen
1
& Ka i Mielika
¨inen
4
1
Finnish Fo es Resea ch Ins i u e, No he n Uni , PO Box 16, FI-96301 Ro aniemi, Finland
2
Depa men o Geosciences and Geog aphy, Uni e si y o Helsinki, PO Box 64, FI-00014 Helsinki, Finland
3
Ox o d Long- e m Ecology Labo a o y, Biodi e si y Ins i u e, Depa men o Zoology, Uni e si y o Ox o d, Tinbe gen Building, Sou h Pa ks Road,
Ox o d OX1 3PS, UK
4
Finnish Fo es Resea ch Ins i u e, Sou he n Uni , PO Box 18, FI-01301 Van aa, Finland
Keywo ds
Geoch onology; dend oclima ology;
his o ical ag icul u e; palaeoclima e
olcanism.
Co espondence
Samuli Helama, Finnish Fo es Resea ch
Ins i u e, Ro aniemi Uni , PO Box 16,
FI-96301 Ro aniemi, Finland.
E-mail: [email p o ec ed]
Abs ac
Geoch onological da a o he coni e ee ings in a egion sensi i e o clima ic
e ec s o explosi e e up ions we e analysed o sudden g ow h educ ions in
associa ion wi h ex ao dina ily cool econs uc ed summe empe a u es since
5500 B.C. T ee- ing da a came om he s ems o li ing ees and sub ossil ee
emains collec ed as inc emen co es and discs, espec i ely, om an a ea o
no he nmos Finnish Lapland (70688N o30208E). Calenda yea da es
when he ee- ing signa u es (i.e., g ow h educ ions and econs uc ed
empe a u es) we e concu en we e compa ed wi h sulpha e da a om
G eenland ice co es. P e ious new e idence a e in ag eemen in demons a ing
olcanism behind la e-Holocene e en s in 1601 A.D. and 536 A.D., sugges ing
ha he same causal ela ionship can be implied u he back in ime. Ou da a
show ha ea lie e en s we e ound o ha e occu ed in he yea s 330 B.C.,
874 B.C., 1464 B.C., 1584 B.C., 2564 B.C. and 2850 B.C. In e es ingly, e en s
o lesse magni ude ollowed he h ee majo e en s in 542 A.D., 1453 B.C.
and 1579 B.C. by a ew yea s. Na u al disas e s, and g ain c op ailu es,
occu ed as a esul o hese e en s, as has been documen ed o he summe o
1601 A.D. h ough Finnish his o ical da a and b oadly in he No he n
Hemisphe e. Clima e has su p ised humans du ing his o ic and likely p e-
his o ic imes, causing sudden al e a ions in ag icul u e, ecology and economy,
and may do so in he u u e. We a gue ha he clima e change wi h he mos
magni ied impac s on socie y may be a nega i e empe a u e anomaly ha
ab up ly dec eases esou ce a ailabili y o e wide spa ial scales.
Clima e change may su p ise us wi h unexpec ed phy-
sical changes in he Ea h’s a mosphe e (S ee s & Glan z
2000). Su p ising e en s ha cause he mos damage
o human heal h and p ope y and impac he na u al
en i onmen s a e sudden, discon inuous changes lead-
ing o ex eme wea he and clima e e en s (Eas e ling
e al. 2000; S ee s & Glan z 2000). Obse a ions and
models a e in ag eemen in showing ha s ong clima e
anomalies can esul om he a mosphe ic e ec s
o la ge explosi e olcanic e up ions (Ches e 1988;
Robock 2000; Miles e al. 2004). Indeed, a special
cha ac e is ic o olcanism is ha unusually iolen
e up ions a e known o ollow unusually long pe iods
o quie and ha he e up ion o olcanoes wi h
no his o ic ac i i y may lead o he wo s disas e s
(Simkin 1993). A mul idisciplina y e alua ion is needed
o complemen he his o ical eco d o olcanism.
Di ec and seconda y e idence o he e up ions can be
aced om deep ice co es and long ee- ing se ies,
whe e impu i ies by olcanic ae osols and g ow h
(page numbe no o ci a ion pu pose)
Pola Resea ch 2013. #2013 S. Helama e al. This is an open-access a icle dis ibu ed unde he e ms o he C ea i e Commons A ibu ion-Noncomme cial 3.0
Unpo ed License (h p://c ea i ecommons.o g/licenses/by-nc/3.0/), pe mi ing all non-comme cial use, dis ibu ion, and ep oduc ion in any medium, p o ided he
o iginal wo k is p ope ly ci ed.
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Ci a ion: Pola Resea ch 2013, 32, 15866, h p://dx.doi.o g/10.3402/pola . 32i0.15866
anomalies, espec i ely, a e known o ollow such e up-
ions (Zielinski 2000).
A ecen s udy elucida ed he clima ic esponse in
Eu ope ollowing 15 majo opical e up ions o e he
las hal millennium (Fische e al. 2007) and con i med
he clea pa e n o summe empe a u e cooling du ing
he i s and second pos -e up ion yea s (B adley 1988;
Robock 2000). O hese, he s onges signal o cooling
is ound du ing he yea a e he e up ion. No ably,
Finland lies in he a ea o he mos p onounced summe
cooling (see igu e 1 in Fische e al. 2007). In he same
egion, ee ings and hei summe empe a u e e-
cons uc ions ha e been sugges ed o exhibi olcanic
signa u es as dis an e ec s o explosi e e up ions
(Helama, Lindholm e al. 2005; Salze & Hughes 2007;
Helama, La
¨a
¨nelaid e al. 2010). Simila indica ions ha e
been de ec ed in adjacen a eas o no he n Eu ope
(Ge ais & MacDonald 2001; Salze & Hughes 2007;
Shumilo e al. 2011). By i ue o i s geog aphical
loca ion and he sensi i i y o ee ings as a p oxy o
clima e, ee- ing ma e ial om he egion o no he n
Finland known as Lapland would appea p i ileged o
acing he clima ic e ec s o pas olcanism.
The ongoing ask o explo ing sub ossil wood in
Finnish Lapland o dend oclima ic pu poses has so a
esul ed in a ch onology spanning 7.6 housand yea s
(E onen e al. 1999; E onen e al. 2002; Helama e al.
2008). The ee- ing ch onology o Finnish Lapland has
been used o econs uc he egion’s pas summe
empe a u e a iabili y since 5500 B.C. on annual o
millennial scales (Helama, Macias Fau ia e al. 2010). This
ime ame p o ides an in e glacial window excluding he
ea ly Holocene, du ing which pe u bed olcanism ol-
lowed he deglacia ion isos a ic adjus men o magma
chambe s o he associa ed changes in c us al s esses, as
indica ed by chemical da a yielded by deep ice co es
(Zielinski e al. 1994; Zielinski e al. 1997). Compa ed o
he G eenland ice-co e chemis y (see Table 1), ee- ing
da ing allows o g ea e p ecision in de e mining when
e en s occu ed (Baillie 2008, 2010).
The signa u e yea s o he new palaeoclima ic econ-
s uc ion (Helama, Macias Fau ia e al. 2010) ha e no so
a been sys ema ically examined. To analyse he da a,
we employ obus me hodology based on mul iple lines
o e idence. Fi s , ou analyses a e cons ained by he
knowledge o he e ec s in he egion o explosi e
e up ions ha ake place a away (Fische e al. 2007).
Ensu ing he obus ness o ou dend och onological
analyses, wo di e en ee- ing me hods we e used o
examine he ini ial dend oclima ic da a p oducing he
ch onologies. In addi ion, we combined a p ede e mined
de ini ion o he olcanic signa u e in he dend och o-
nological da a (Ge ais & MacDonald 2001) wi h a
compa ison o he ch onologically cons ained e idence
o he G eenland ice-co e chemis y (Table 1). Fo he
la e-Holocene, i was possible o supe pose he palaeo-
clima e esul s upon he his o ical da a and e iew he
consequences in con ex o human ecology (Holopainen
& Helama 2009). These analyses pa ed he way o ou
new eco d o clima ic down u ns, wi h linkages o he
dis an e ec s o olcanism on no he n Eu ope h ough
he p esen in e glacial.
Ma e ial and me hods
Ini ial ee- ing ch onology
Da a comp ising he se ies o ee ings we e de i ed
om he s ems o li ing ees and unks o sub ossil ee
emains collec ed as inc emen co es and discs, espec-
i ely, om an a ea o no he nmos Finnish Lapland
loca ed a 70688N o30208E (E onen e al. 1999;
E onen e al. 2002; Helama e al. 2008). The wid hs o
he ings we e measu ed unde he mic oscope and he
esul ing ee- ing se ies c oss-da ed using es ablished
dend och onological echniques (Aniol 1983; Holmes
1983; Van Deusen 1990). In his ou ine me hod, he
se ies a e examined o e o s and he in e -co ela i e
sample se ies a e p og essi ely added in o he mean
ch onology (F i s 1976). In addi ion o c oss-da ing
wi hin he ee- ing da a o Finnish Lapland, he ee-
ing ch onologies o o he pa s o Finland (Helama,
Lindholm e al. 2005) and he adjacen a ea in no he n
Sweden (G udd e al. 2002) ha e been success ully
cons uc ed (E onen e al. 2002). The Finnish Lapland
ch onology comp ises 69 li ing and 1249 sub ossil ee-
ing se ies o Sco s pine (Pinus syl es is L.) and he
combined ch onology co e s he in e al om 5633 B.C.
un il he p esen -day (Helama, Macias Fau ia e al. 2010).
T ee- ing sensi i i y
The non-clima ic ends in he ee- ing g ow h we e
emo ed p io o he a ge ed analyses using conse a i e
g ow h end modelling. A modi ied nega i e exponen-
ial cu e (F i s e al. 1969) o linea eg ession wi h
nega i e o ze o slope was i ed o each indi idual ing
wid h se ies. The ee- ing indices we e compu ed as
a ios be ween he measu ed and modelled wid hs. This
me hod o s anda diza ion (F i s 1976) is known o be
well sui ed o Sco s pine ee- ing wid h da a (Lindholm
A ch onology o mid- and la e-Holocene clima ic down u ns S. Helama e al.
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1996; Helama, Lindholm e al. 2004). The mean ch on-
ology was calcula ed using a biweigh obus es ima ion
(Cook e al. 1990). The a iance o he ch onology
was s abilized using he me hod o Osbo n e al.
(1997), using a ime-independen es ima e o mean
in e se ies co ela ion ( 0.344; Helama, Lindholm
e al. 2004). Following he p e iously applied p o ocol
(Ge ais & MacDonald 2001), he ch onology was
Fig. 1 A mid- and la e-Holocene ch onology o clima ic down u ns. (a) T ee- ing sensi i i y (i.e., sudden change in g ow h condi ions). Please no e ha
only nega i e depa u es a e gi en, he alues he e o e indica ing g ow h educ ions. (b) Recons uc ed summe (July) empe a u e a iabili y (black
line) wi h he g een and blue a eas indica ing he 95% and 99% con idence in e als o he econs uc ion. The s udy pe iod was 5500 B.C. h ough 2005
A.D. The yea s discussed in he ex a e shown as ee- ing da ed calenda yea s B.C. and A.D.
S. Helama e al. A ch onology o mid- and la e-Holocene clima ic down u ns
Ci a ion: Pola Resea ch 2013, 32, 15866, h p://dx.doi.o g/10.3402/pola . 32i0.15866 3
(page numbe no o ci a ion pu pose)
cha ac e ized o he ampli ude o he in e -annual
g ow h a ia ions, calcula ed using he sensi i i y (F i s
1976). The sensi i i y was de e mined as (x
x
1
)/
(x
x
1
), whe e x is he mean index o yea (Ge ais
& MacDonald 2001). The ee- ing signa u e o la ge-
scale clima ic e ec s om explosi e e up ions can lag he
ac ual olcanic e en (Jones e al. 1995; B i a e al.
1998). Tha is, he excessi ely nega i e alues in yea
could be expec ed om he explosi e e up ions om he
same yea o he p e ious yea -n, ha is, du ing he
i s and second pos -e up ion yea s (B adley 1988;
Fische e al. 2007).
Indica ions o clima ic cooling
A palaeoclima ic econs uc ion (Helama, Macias Fau ia
e al. 2010) was p oduced using a eg ession o he
egional summe empe a u e on he ee- ing wid h
ch onology. Fi s , an empi ically designed p ocedu e
esembling egional cu e s anda diza ion (B i a e al.
1996) was applied, wi h he excep ion ha he conca i y
o he g ow h end was adjus ed o pas changes in pine
popula ion densi y in he s udy egion (Helama, Timonen
e al. 2005; Helama, Macias Fau ia e al. 2010). Tha is, he
non-clima ic a ia ions we e emo ed om he indi i-
dual ee- ing se ies wi h a modi ied nega i e exponen ial
cu e (F i s e al. 1969) uned o accoun o palaeoeco-
logical in o ma ion abou he non-clima ic changes in he
end shape (Helama, Macias Fau ia e al. 2010). The ee-
ing indices we e de i ed as a ios be ween he obse ed
and e e ence alues, and he ch onology was a e aged
using a biweigh obus mean o p oduce annual index
alues. The a iance o he ch onology was s abilized
using he me hod o Osbo n e al. (1997), using a ime-
independen es ima e o mean in e se ies co ela ion ( 
0.330) (Helama, Lindholm e al. 2004).
Second, he ee- ing ch onology was eg essed agains
ins umen al clima e da a om a wea he s a ion in
Ka asjok, no he n No way (69828?N; 25831?E) o depic
empe a u e a ia ions on a Celsius scale (Helama, Macias
Fau ia e al. 2010). This me hod was used he e as i was
p e iously e alua ed as a obus palaeoclima ic model o
simila da a (Helama e al. 2009). The econs uc ion
accoun s o mo e han 40% o he o al obse ed
a iabili y (R
2
0.43; R
2
ADJ
0.41) o e he ull calib a-
ion pe iod (18772004 A.D.). Mo eo e , ou p e ious
analysis showed ha no only ee ings o li ing pines bu
also he ee- ing ch onology o pu ely sub ossil logs
co ela e posi i ely wi h summe empe a u es (Helama,
Holopainen e al. 2004). Applying he ob ained ans e
unc ion o he ee- ing da a o e he p e-calib a ion
pe iod, he ch onology was ans o med in o yea ly
es ima es o summe empe a u es o 5500 B.C. h ough
2005 A.D. Con idence in e als o he inal econs uc-
ion we e compu ed om he au o eg essi e s uc u e
o he esiduals o he linea associa ion be ween he
econs uc ion and ins umen al da a and he yea s 1877
A.D. and 2004 A.D., based on 1000 Mon e Ca lo simula-
ions (Macias Fau ia e al. 2010; Macias-Fau ia e al.
2012). The ex emely cool summe s ollowing explosi e
olcanic e en s wi h la ge-scale clima ic e ec s we e
iden i ied om he econs uc ion as he mos nega i e
empe a u e depa u es om he long- e m mean o he
econs uc ion.
Resul s
A look a he plo o he ee- ing a iabili y e eals a
cha ac e is ic pauci y o anomalously poo g ow h in
e ms o dend och onological sensi i i y (Fig. 1a). The
mos nega i e yea s o g ow h a e no clus e ed wi hin
a limi ed pe iod bu a e sp ead o e se e al millennia.
Conside ing he la e-Holocene (he e, 12005 A.D.), he
ee- ing eco d shows ex eme d ops in g ow h as
ha ing occu ed in 1601 A.D. and 536 A.D. These yea s
we e econs uc ed as ha ing been excep ionally cool
(Fig. 1b). Fo bo h o hese yea s, he summe empe a-
u es we e econs uc ed o ha e been coole han 108C
on a e age, which is mo e han h ee s anda d de ia ions
om he econs uc ed mean o 138C. The yea 536 A.D.
was ollowed by ano he yea o educed g ow h, in 542
A.D., du ing which he empe a u es a e econs uc ed o
ha e been nea ly as cool as six yea s be o e (Fig. 2).
T ee- ing da a o he B.C. e a indica e ha he e
we e wo yea s o educed g ow h*in 330 B.C. and 2850
B.C.* ha we e compa able o he wo la e-Holocene
e en s desc ibed abo e (Fig. 1a). The yea s 874 B.C.,
1584 B.C. and 2564 B.C. we e also econs uc ed o
be ex emely cool yea s. Howe e , he yea s 874 B.C.
and 1584 B.C. did no show compa able sudden g ow h
supp ession, implying ha he econs uc ed coolness
du ing hese e en s was caused by a p og essi e cooling
Table 1 The G eenland ice co es e e ed o in his s udy.
Ice co e Re e ences
Dye 3 (pa o he G eenland
Ice Shee P ojec )
Clausen e al. (1997), Vin he e al. (2006),
La sen e al. (2008)
G eenland Ice Co e P ojec
(GRIP)
Clausen e al. (1997), Sou hon (2002),
Vin he e al. (2006), La sen e al.
(2008)
No h G eenland Ice Co e
P ojec (NGRIP)
Rasmussen e al. (2006), Vin he e al.
(2006), La sen e al. (2008)
G eenland Ice Shee P ojec
2 (GISP2)
Alley e al. (1993, 1997), Meese e al.
(1997), Zielinski e al. (1994), Sou hon
(2002)
A ch onology o mid- and la e-Holocene clima ic down u ns S. Helama e al.
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o e wo o mo e consecu i e yea s. A quiescence o
he ea lies i s wo-and-a-hal millennia o he eco d
was con as ed wi h an excep ion o g ow h educ ion
in 4866 B.C. (Fig. 1a).
O no e, he e en s o 1464 B.C. and 1584 B.C. we e ol-
lowed by cool yea s 11 and i e yea s la e , espec i ely*
in 1453 B.C. and 1579 B.C. These anomalies b ing o mind
he e en s in 536 A.D. and 542 A.D. (Fig. 2).
Discussion
La e-Holocene e en s
The signa u e yea s o he la e-Holocene occu ed in 1601
A.D. and 536 A.D. A close look a hese e en s is essen ial
as hey allow o he na u al p oxy e idence o be com-
pa ed o his o ical documen a ion. His o ical desc ip ions
om Sweden, No way and Iceland indica e ha he sun
was obscu ed in 1601 A.D. (Kalela-B undin 1997). The
G eenland Ice Co e P ojec (GRIP; Clausen e al. 1997)
and G eenland Ice Shee P ojec 2 (GISP2; Zielinski e al.
1994) ice-co e da a sugges olcanic signa u es in 1601
A.D. and 1604 A.D., espec i ely (Table 2). La e s udies
ha e assigned he coolness o he yea 1601 A.D. o he
e up ion o Huaynapu ina, in Pe u, ha had occu ed he
p e ious yea (B i a e al. 1998; de Sil a & Zielinski 1998).
The geog aphical loca ion o he s udy egion poses
challenges o ag icul u e because o he no he n clima e
(Pa y 1975; Pa y & Ca e 1985), and one would expec
o see clima ic e ec s on pas ag icul u al p oduc ion in
he egion, as p oposed by Solan ie (1997). Documen a y
e idence o ag icul u al success (To nbe g 1989) e eals
ma ked a iabili y o ye and ba ley c ops o e he
in e al o ime in which we a e in e es ed, and seems
o indica e yea s o c op ailu e in sou he n Finland (ca.
608N; 228E) in 1554 A.D., 1577 A.D. and 1601 A.D. (Fig.
3). His o ical ha es s o ye and ba ley ha e been
analysed on he basis o con inuous eco ds be ween
1551 A.D. and 1609 A.D. (Holopainen & Helama 2009).
Recalcula ing hei da a, we ind ha he a e age g ain-
igu e ( a io be ween sown and ha es ed g ain) o he
pe iod o 15921600 A.D. was 5.5, whe eas o he yea o
1601 A.D., i was as low as 2.8 (Fig. 3). A much b oade
spa ial scales, A well (2001) and Ve osub & Lippman
(2008) e iewed e idence om documen a y and na u al
a chi es ha show agg ega ions o anomalously cool
wea he and amine in se e al coun ies and con inen s.
Fig. 2 Recu ing e en s in g ow h and clima e condi ions. The due s occu ed in 536/542 A.D., 1464/1453 B.C. and 1584/1579 B.C., shown he e as
sensi i i ies and econs uc ed empe a u es. Please no e ha only nega i e depa u es a e gi en o sensi i i y. The econs uc ed summe (July)
empe a u e a iabili y (black line) is shown wi h he g een and blue a eas indica ing he 95% and 99% con idence in e als o he econs uc ion.
Table 2 Likely co espondences be ween he ee- ing da es p esen ed
in his s udy and p e iously published e idence om he G eenland
ice co es.
Yea Ice-co e e idence
1601 A.D. 1604 (Zielinski e al. 1994); 1601 (Clausen e al. 1997)
536 A.D. 53354392 (La sen e al. 2008)
330 B.C. 365 (Zielinski e al. 1994)
874 B.C. 864 (Zielinski e al. 1994), 888 (Clausen e al. 1997)
1464 B.C. 1442, 1454, 1459 (Zielinski e al. 1994);
1457, 1463 (Clausen e al. 1997)
1584 B.C. 1577, 1594, 1600 (Zielinski e al. 1994)
2564 B.C. No acidi y peaks a ound his dend och onological da e
2850 B.C. 2815 (Zielinski e al. 1994)
4866 B.C. 4893 (Zielinski e al. 1994)
S. Helama e al. A ch onology o mid- and la e-Holocene clima ic down u ns
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(page numbe no o ci a ion pu pose)

The 536 A.D. e en has long in igued scien is s o
a ious disciplines (S o he s 1984, 1999; B i a e al.
1990; Ze e be g e al. 1994; A ja a 2005; Baillie 2008;
La sen e al. 2008; Woods 2010). The e en wi h he
associa ed e idence in e ed om ee ings has been
p e iously associa ed wi h he Rabaul olcano on he
island o New B i ain, Papua New Guinea (S o he s &
Rampino 1983a, 1983b; S o he s 1984). New e idence
ob ained by adioca bon da ing o cha coal collec ed
om he basal uni s o he local e up ion deposi s has
sugges ed, howe e , ha he Rabaul e up ion occu ed
du ing he 7 h cen u y A.D. (McKee e al. 2011). The
lack o olcanic deposi s in ice co es (Clausen e al. 1997)
has also led o he sugges ion ha a come exploding
in he uppe a mosphe e could esul in he deposi-
ion o deb is in he uppe a mosphe e, which would
educe he pene a ion o sunligh and cause a clima ic
down u n (Rigby e al. 2004). Howe e , he compa ison
o sulpha e om mul iple ice co es*Dye 3 (pa o he
G eenland Ice Shee P ojec ), GRIP and No h G eenland
Ice Co e P ojec (NGRIP)*un eiled a signal consis en
wi h he olcanic hypo hesis o he e en (La sen e al.
2008). The empo al pa e n o sulpha e a ia ions in
he ice co es u he ancho ed he ice-co e and ee-
ing indica ions o olcanic dus and clima ic down-
u ns in he yea s 522 A.D., 532 A.D., 536 A.D., 542
A.D. and 574 A.D. (Baillie 2008). The da a shown he e
suppo ou unde s anding o 536 A.D. and 542 A.D. as
ha ing been among he cooles summe s in he Holocene
(Fig. 2).
Compa isons o e he B.C. e a
E o s o link ee- ing and ice-co e da a become mo e
complex as one looks u he back in ime. Se e al s udies
examining indi idual and mul iple ice co es ha e indi-
ca ed inc easing e o s in laye coun ing wi h olde ice
ma e ials (Clausen e al. 1997; Meese e al. 1997; Sou hon
2002; Rasmussen e al. 2006; Vin he e al. 2006). The
es ima ions ha e shown a maximum da ing e o o 2% in
he Holocene segmen s o he G eenland ice ch onologies
(Meese e al. 1997; Rasmussen e al. 2006). An addi ional
80-yea o se was ound close o 53005400 yea s
ago when compa ing he GRIP and GISP2 ch onolo-
gies (Sou hon 2002). Mo eo e , ou ee- ing esul s
du ing he B.C. e a did no always compa e well
wi h o he ee- ing es ima es (Salze & Hughes 2007).
Wi h espec o di e en ee species and geog aphical
loca ions, he de ia ions can o igina e om co espond-
ingly dissimila ecological ci cums ances. Di e ences
can also esul om disc epancies in me hods (Baillie &
Mun o 1988; Salze & Hughes 2007) o de i e ee- ing
in o ma ion.
An indica ion o he 330 B.C. e en in ou ee- ing
eco ds could be linked wi h a GISP2 sulpha e peak
in 365 B.C. (Zielinski e al. 1994) (Table 2). Though he
appa en di e ence o 35 yea s is la ge, e o s in he ice
ch onology (Meese e al. 1997) may accommoda e i .
B oadly coinciding wi h hese da es, he e up ion o
A acazo occu ed in he Wes e n Co dille a o Ecuado
(Siebe & Simkin 2002). Desc ibed om a geological
pe spec i e by Hidalgo e al. (2008), he e up ions a e
es ima ed o ha e had a la ge explosi e magni ude. The
calib a ed adioca bon da es a e age o 390260 (1-sigma
con idence le el [CI]) and 40023 calib a ed yea s
B.C. (2-sigma CI) (Hidalgo e al. 2008). In addi ion,
ou indica ion o he yea 874 B.C. may ma ch he
sulpha e signal o 864 B.C. shown in he GRIP2 ice
co e (Zielinski e al. 1994) and ha o 888 B.C. in
Fig. 3 Ch onologies o ha es s and clima e a iabili y. (a) Rye and
ba ley g ain- igu es in sou h-wes e n Finland o he pe iod 1549 A.D.
h ough 1619 A.D. shown wi h (b) he econs uc ed summe empe a-
u e a iabili y o his s udy (black line) wi h he g een and blue a eas
indica ing he 95% and 99% con idence in e als o he econs uc ion.
The g ain- igu e da a we e ecalcula ed om he o iginal s udy
(Holopainen & Helama 2009) s abilizing he a iance o he g ain- igu es
using a me hod iden ical o ee- ing analyses (Osbo n e al. 1997).
A ch onology o mid- and la e-Holocene clima ic down u ns S. Helama e al.
6
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he GRIP co e (Clausen e al. 1997). The la e could
poin o a majo olcanic e up ion in he No he n
Hemisphe e as he deposi ed amoun o olcanic acid
was es ima ed o be h ee imes mo e han he mean
annual backg ound acid deposi ion a e (Clausen e al.
1997).
The ad an ages o ancho ing he ee- ing and ice-co e
e idence o olcanism by mul iple ecu ing e en s has
p e iously been demons a ed (Baillie 2008, 2010). In
his ega d, he e is ee- ing e idence o a wo-s age
e en in ol ing he yea s 1464 B.C. (s onge ) and 1453
B.C., wi h an 11-yea in e al. A simila pai o e en s
was obse ed in ee ings in 1584 B.C. (s onge ) and
1579 B.C. The 1584/1579 B.C. e en s would show an
in e es ing co espondence wi h he GISP2 sulpha e
anomalies da ed o 1600 B.C. and 1594 B.C., wi h a
di e ence o six yea s (Zielinski e al. 1994). Ye a single
sulpha e anomaly nea es o he ee- ing da es would
sugges an ice-co e da e o 1577 B.C. (Zielinski e al.
1994). Rega ding he 1464/1453 B.C. e en s, he ee-
ing da a co esponded wi h he GISP2 sulpha e peaks
da ed o 1454 B.C. and 1442 B.C., wi h a 12-yea in e al
(Zielinski e al. 1994). Mo eo e , he Dye 3 ice co e
indica ed chemical signa u es o he yea s o 1463 B.C.
and 1457 B.C. (Clausen e al. 1997). The molumines-
cence da ing o olcanic samples om he island o Yiali
in G eece (dis inguishable om eph as om he mo e
ex ensi ely s udied Medi e anean e up ion o he San-
o ini [The a] olcano) de i ed a mean age o 1460 B.C.
(Li i zis e al. 1996).
Dend och onological da es o 1628 B.C. om Eu opean
oak ee- ing wid hs (Baillie & Mun o 1988), 1627 B.C. as
a os -damaged ing (LaMa che & Hi schboeck 1984),
a g ow h minimum in 1626 B.C. (Salze & Hughes 2007)
om he No h Ame ican b is lecone pine (Pinus longae a
and Pinus a is a a) da a, and he sulpha e e en in 1623
B.C. om GISP2 ice-co e da a (Zielinski e al. 1994) ha e
been sugges ed as aces o he San o ini e up ion. Ou
da a did no indica e anomalous condi ions du ing he
pe iod o 16271623 B.C. The e o e, he pai ed e en s in
1584 and 1579 B.C. ound in his s udy ep esen ye a
new line o e idence o he highly uns able clima e in he
mid-second millennium B.C.
The new e idence o he e en s o po en ially olcanic
o igin in 2564 B.C. did no ha e a po en ial ma ch in
he ice-co e esul s (Table 2). The ee- ing da e o 2850
B.C. appea ed wi hin he unce ain y bounda ies o he
ice-co e e en in 2815 B.C. (Zielinski e al. 1994). The
ea lies ee- ing indica ion o olcanism in 4866 B.C.
could ma ch he GISP2 e idence o high sulpha e alues
in 4893 B.C. (Zielinski e al. 1994).
Geoch onology wi h ecological implica ions
T ee- ing da a sensi i e o summe empe a u e luc ua-
ions we e examined o anomalously nega i e p oxy
depa u es in a egion whe e dis an e ec s o explosi e
e up ions ha e been shown o p oduce a pa e n o
cooling o he i s and second yea s a e he olcanic
e en s (Fische e al. 2007). This was shown o he
yea 1601 A.D., wi h s ong impac s on he ag icul u al
p oduc ion as econs uc ed om his o ical documen s
om sou he n Finland (Fig. 3). The in e annual a ia-
bili y in c op yields in his egion is among he lowes in
Finland (Mukula & Ran anen 1989a, b), which sugges s
ha la ge yea - o-yea a ia ions may ha e been
expe ienced elsewhe e in Finland. The associa ion is
plausible as bo h he ha es s o mode n (Mukula &
Ran anen 1987, 1989a,b) and his o ical (Holopainen &
Helama 2009) ag icul u e a e known o depend on he
g owing season clima e.
Inc eased human mo ali y in he egion in asso-
cia ion wi h he c op ailu es has been documen ed
o he i s yea s o he 17 h cen u y A.D. (Ju ikkala
1958, 2003a, 2003b). We acknowledge ha linking
clima e phenomena wi h pas e up ions in ol es sup-
posi ions (Sadle & G a an 1999), bu we ne e heless
sugges his connec ion o he e en in 1601 A.D. in
no he n Finland. The clima ec op associa ion may ha e
played a ole in he ag icul u e-dependen economic
changes ha occu ed a ound ha ime (Holopainen
e al. 2012) and a ec ed he ep oduc i e success among
he poo amilies li ing in he egion (Ricka d e al.
2010).
The empo al associa ion o ee- ing anomalies wi h
la e-Holocene e up ions is sugges i e o a ela ionship
ha can be ex ended back in ime. In his ega d, pollen
da a indica e spo adic cul i a ion ac i i y in pa s o
Finland since he B onze Age and hus du ing a leas
he pas h ee millennia (Taa i sainen e al. 1998). The
summe empe a u e d i en en i onmen al p oduc i -
i y has also been shown o in luence hun e ga he e
popula ion size luc ua ions in he egion (Talla aa a
e al. 2010; Talla aa a & Seppa
¨2011). A clea pic u e
o his ype was de i ed ia p oxy compa ison be ween
he summed p obabili y dis ibu ion o a chaeological
adioca bon da es (da es-as-da a) and a e hicknesses
o o ganic sedimen laye s om a lake wi hin he s udy
egion (Talla aa a & Seppa
¨2011).
Conclusions
This pape has p esen ed new e idence o ab up
educ ions in clima ic cooling du ing he mid- and la e-
Holocene. The backbone o his s udy was he 7.6
S. Helama e al. A ch onology o mid- and la e-Holocene clima ic down u ns
Ci a ion: Pola Resea ch 2013, 32, 15866, h p://dx.doi.o g/10.3402/pola . 32i0.15866 7
(page numbe no o ci a ion pu pose)
housand yea -long ee- ing ch onology om Finnish
Lapland. P e ious ee- ing and ice-co e s udies, as well
as his o ical documen a y e idence, we e also d awn
upon. The mos se e e o he la e-Holocene e en s (1601
A.D. and 536 A.D.) clea ly illus a ed he dis an e ec s
o explosi e e up ions in he s udy egion o no he n
Eu ope. In pa icula , he e en in 1601 A.D. exempli ied
educed su i al po en ial o his o ic humans when
subjec ed o a olcanic-induced clima ic su p ise. Lack
o cohe ence be ween e en s in e ed om ee- ing da a
and ice-co e sulpha e da a became e iden o e he B.C.
e a. I may be ai o s a e ha hese inconsis encies esul
om inc easing ice-laye coun ing e o s and p oblems
ela ed o annual laye iden i ica ion in he ice co es.
On he o he hand, he ee- ing da a yield mo e accu-
a e da es o cooling e en s bu do no p o e whe he
a olcanic e up ion was he cause. None heless, he
majo i y o he ee- ing da es o e he B.C. e a can be
linked wi h sulpha e peaks in mul iple G eenland ice
co es. O e all, he compa isons p oduced added e idence
o linking he ee- ing and ice-co e signals o olcanism
o e he p esen in e glacial. This pape also suppo s he
idea o analysing and in e p e ing he human ecology
da a in he con ex o geoch onological e idence. Such
analyses will help us o ou line he e ec s ha ou socie y
will encoun e wi h he nex sudden e en o olcanic-
induced la ge-scale cooling.
La ge and explosi e olcanic e up ions ha e occu ed
se e al imes in he pas and i is highly likely he
geological ac i i y o ou plane will p oduce simila
e en s in he u u e, hough he iming o e up ions
and he in ensi y o hei clima ic and en i onmen al
e ec s may again su p ise people (S ee s & Glan z 2000).
Examining iolen clima e changes in he Holocene shows
ha hey ha e low-p obabili y o occu ing in he sho -
e m bu ha he ecu ence o simila new e en s is
una oidable in he long- e m. Socie y is now supposed
o be p epa ing o g adual wa ming as he cu en
clima ic ends a e p edic ed o con inue o e he nex
cen u y (Be gs o
¨m e al. 2011), which could educe ou
abili y o cope when a sudden e en o olcanic-induced
cooling akes place. In he pe spec i e o human ecology,
disas e s occu when he bu e ing capaci y o socie y
is exceeded by na u al e en s (Ka es 1971; McLaughlin
& Die z 2008). Clea ly, he clima e phenomena desc ibed
in his pape ul il he c i e ia o an h opologically-de ined
disas e s, in ol ing a combina ion o na u al and echno-
logical ea u es and a popula ion in a condi ion o ulne -
abili y (Oli e -Smi h 1996). Ou esea ch has indica ed
he ad e se e ec s o ab up nega i e empe a u e anoma-
lies on ood p oduc ion, which has ob ious ecological
and economic implica ions (Holopainen & Helama 2009;
Ricka d e al. 2010; Holopainen e al. 2012). Ou indings
may be seen pa allel wi h a chaeological (Gamble e al.
2005) and palaeon ological (Foley 1994) esea ch which
shows ha clima e changes s ongly dis u b human (and
hominin) popula ions, which espond by con ac ing.
Acknowledgemen s
We hank P o esso Mike Baillie and an anonymous
e e ee o hei c i ical e iew o he manusc ip . This
s udy was suppo ed by he Academy o Finland (g an
no. 251441).
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