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Abrupt Changes in Atmospheric ∆ 14 C and CO 2 at the Onset of the Bølling/Allerød: the Permafrost Thawing Hypothesis

Peter K¨ ohler

1

, Gregor Knorr

1

, Edouard Bard

2

1: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany, peter.koehler@awi.de

2: CEREGE, Aix Marseille Universit´e, CNRS, Aix-en-Provence, France

One of the most abrupt and yet unexplained CO2rises found in the ice cores (>10 ppmv in two centuries) occurred quasi-synchronous with the abrupt northern hemispheric warming into the Bølling/Allerød around 14,600 years ago. Here we use U/Th dated atmospheric∆14C from Tahiti corals as independent and precise age control for this CO2rise in combination with simulations to show that the release of old nearly14C- free carbon might have caused these changes in CO2and∆14C. The∆14C data also independently constrain the magnitude of the carbon released to about 125 PgC. We suggest, in line with CH4 records and terrigenous biomarkers, that carbon released from thawing permafrost in the high northern latitudes might be the source of the abrupt CO2 rise, partly caused by Siberian shelf flooding during meltwater pulse 1A.

Our findings highlight the potential of the permafrost carbon reservoir to modulate abrupt climate changes via greenhouse-gas feedbacks.

Simulated ∆

14

C and CO

2

160 180 200 220 240 260 280

160 180 200 220 240 260 280

atm14C(o/oo)

Tahiti IntCal13 -4o/oo/100y -10o/oo/100y

sim sim-04o/oo/100y

sim-10o/oo/100y

a

220 225 230 235 240 245 250 255 260

220 225 230 235 240 245 250 255 260

CO2(ppmv)

15.0 14.8 14.6 14.4. 14.2 14.0 Time (kyr BP)

potentially@EDC atm. CO2according to 14C

data (AICC2012)

data (Parrenin2013)

b

0 10 20 30 40 50

0 50 100 150 200 250 300 350 Length of C release (yr)

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0

atm(14C)(o/oo)

c

-50o/oo

-400o/oo

-700o/oo

-1250o/oo

agrees with14C data no trend -4o/oo/century -10

o/oo/century

0 10 20 30 40 50

atm(CO2)(ppmv)

0 50 100 150 200 250 300 350 agrees with CO2data

d

Left: Simulation vs data. Right: Best-guess scenario (125 PgC in 200 yr) against data.

Permafrost thawing

— where?

PMIP3 LGM: ice (dark blue), permafrost (blue), seasonal frozen (light blue), not frozen (red), potential thawing (green).

Termination I 15–14 kyr BP

100 150 200 250 300 350 400 450

atm14C(o/oo) Tahiti

IntCal13 -4o/oo/100y -10o/oo/100y

100 150 200 250 300 350 400 450

atm14C(o/oo)

180 190 200 210 220 230 240 250 260 270

180 190 200 210 220 230 240 250 260 270

EDCCO2(ppmv)

300 350 400 450 500 550 600 650 700 750 800

CH4(ppbv)

300 350 400 450 500 550 600 650 700 750 800

-44 -42 -40 -38 -36 -34 -32 -30

NGRIP18 O(o /oo) -44

-43 -42 -41 -40 -39 -38 -37 -36 -35 -34 -33

WD18O(o/oo)

20 18 16 14 12 10

Time (kyr BP) 14.6 kyr BP

-12 -10 -8 -6 -4 -2 0 2 4

TANT(K)

14.6 kyr BP

220 230 240 250 260

220 230 240 250 260

atmCO2(ppmv)

450 500 550 600 650 700

GreenlandCH4(ppbv) ages aligned

-44 -42 -40 -38 -36 -34

NGRIP18O(o/oo) ages aligned 15.0 14.8 14.6 14.4 14.2 14.0

Time (kyr BP) -39

-38 -37 -36 -35 -34

WD18O(o/oo)

145 yr

-4 -3 -2 -1 0

TANT(K)

Details on Data

∆14C CO2

160 180 200 220 240 260 280

160 180 200 220 240 260 280

atm14C(o/oo) Tahiti Bahamas Hulu Cariaco@Hulu2 Lake Suigetsu

IntCal13 -4o/oo/100y -10o/oo/100y linear model NL model IntCal13 -4o/oo/100y -10o/oo/100y linear model NL model

15.0 14.8 14.6 14.4 14.2 14.0 Time (kyr BP)

220 225 230 235 240 245 250 255 260

220 225 230 235 240 245 250 255 260

CO2(ppmv)

15.0 14.8 14.6 14.4. 14.2 14.0 Time (kyr BP)

potentially@EDC corresponding atm CO2 atm CO2according to 14C EDC @ AICC2012

EDC @ Parrenin2013 age model Taylor Dome @ revised age model Siple Dome @ own age model Byrd @ GICC05

a

latest rise in CO2 due to 14C

15.6 15.4 15.2 15.0 14.8 14.6

SD age (kyr BP)

0 1 2 3 4 5 6

Probability(o /oo)

0 200 400 600 800 1000 Time since exchange with atm (yr)

EB/A@EDC=400 80yr B/A @ EDC f(x)=1/(x sqrt(2 )) e(-1/2 ((ln(x) - )/ ))2)

c

220 230 240 250 260 270

atmosphericCO2(ppmv) 0.0 0.2 0.4 0.6 0.8 1.0

Simulation Time (kyr)

atmosp.:

125 PgC 100 PgC

@ EDC:

125 PgC 100 PgC

d

Scenario: 200 yr release, AMOC weak

Gases in ice co res

10

Be data indicate no change in

14

C production rate

0 10 20 30 40 50 60

0 10 20 30 40 50 60

10Be(103atomsg-1)

GISP2 GRIP

0.0 0.1 0.2 0.3 0.4 0.5 0.6

10Beflux

a

0.0 0.1 0.2 0.3 0.4 0.5 0.6

(106atomscm-2yr-1)

100 150 200 250 300 350 400 450

atm14C(o/oo)

Tahiti IntCal13 -4o/oo/100y -10o/oo/100y

100 150 200 250 300 350 400 450

atm14C(o/oo)

20 18 16 14 12 10

Time (kyr BP)

14.6 kyr BP

b

10 15 20 25 30 35 40 45 50 55

10 15 20 25 30 35 40 45 50 55

10Be(103atomsg-1) 10 15 20 25 30 35 40 45 50 55

10 15 20 25 30 35 40 45 50 55

10Be(103atomsg-1)

GISP2 GRIP

0.0 0.1 0.2 0.3 0.4 0.5 0.6

10Beflux 0.0 0.1 0.2 0.3 0.4 0.5 0.6

(106atomscm-2yr-1)

150 175 200 225 250 275

atm14C(o/oo)

Tahiti IntCal13 -4o/oo/100y -10o/oo/100y

150 175 200 225 250 275

atm14C(o/oo) 15.0 14.8 14.6 14.4 14.2 14.0

Time (kyr BP)

14.6 kyr BP

14

C signature of old soil carbon

-54-52 -50 -48 -46 -44 -42 -40 -38 -36 -34 -32 -30 -28 -26

-54-52 -50 -48 -46 -44 -42 -40 -38 -36 -34 -32 -30 -28 -26

120 80

b

20 25

-54 -52 -50 -48 -46 -44 -42 -40 -38 -36 -34 -32 -30 -28 -26

NGRIPtemperature(o C)

50 40 30 20 10 0

Time (kyr BP)

B/A 1 2 3 8 12

13 kyr 32 kyr

0 100 200 300 400 500 600

0 100 200 300 400 500 600

atm14 C(o /oo)

60 50 40 30 20 10 0

Time (kyr BP)

250o/oo

a

-1300 -1200 -1100 -1000 -900 -800 -700 -600 -500 -400 -300 -200 -100 0

(14 C)(o /oo)

40 30 20 10 0

Age of C released at B/A (kyr)

-1250o/oo

GHG versus AMOC impacts on Antarctic surface temp (∆T

ANT

)

200 220 240 260

N2O(ppbv) GHG forcing experiments

N2O (TALDICE-1 age)

190 200 210 220 230 240 250 260 270

190 200 210 220 230 240 250 260 270

CO2(ppmv)

CO2atm (this study)

400 450 500 550 600 650 700

CH4(ppbv)

CH4Greenland (GICC05-80yr)

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

TANT(K)

0 100 200 300 400 500 600 Simulation time (years)

CO2_ATM - PRE_BA CO2_ATM

200 years

a

200 220 240 260

N2O(ppbv) GHG forcing experiments

N2O (TALDICE-1 age)

190 200 210 220 230 240 250 260 270

190 200 210 220 230 240 250 260 270

CO2(ppmv)

CO2atm (this study)

400 450 500 550 600 650 700

CH4(ppbv)

CH4Greenland (GICC05-80yr)

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

TANT(K)

0 100 200 300 400 500 600 Simulation time (years)

CO2_ATM - PRE_BA CO2_ATM

a

0.0 0.2

Flux(Sv)

Freshwater hosing experiments

0 5 10 15 20 25 30 35 40

AMOCindex(Sv)

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

TANT(K)

0 100 200 300 400 500 600 Simulation time (years)

PI LGM MIS3

200 years

b

weak strong AMOC 0.0 0.2

Flux(Sv)

Freshwater hosing experiments

0 5 10 15 20 25 30 35 40

AMOCindex(Sv)

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

TANT(K)

0 100 200 300 400 500 600 Simulation time (years)

PI LGM MIS3

b

Methods

. Reference for14C data:

Durand, N. et al. Comparison of 14 C and U-Th ages in corals from IODP #310 cores offshore Tahiti. Radiocarbon 55, 19471974 (2013).

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