EPICA ice core Dronning Maud Land: Results from stable isotope EPICA ice core Dronning Maud Land: Results from stable isotope measurements back to the LGM measurements back to the LGM

Age (yr B.P.) d(!¹⁸O)/dt = 0.16±0.06 ^o/oo/ka n=400, r= 0.26

a

0 2000 4000 6000

-47 -46 -45 -44 -43 -42

δ18O (‰)

European Research Conference „Polar Regions and Quaternary Climate“, San Feliu de Guixols, Spain, 4-9 October 2003

layout: hans oerter, 2003

EPICA ice core Dronning Maud Land: Results from stable isotope EPICA ice core Dronning Maud Land: Results from stable isotope

measurements back to the LGM measurements back to the LGM

Hans Oerter, Hanno Meyer, Anja Lambrecht, Sepp Kipfstuhl, Frank Wilhelms

Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven & Potsdam, Germany

Wolfgang Graf

Willibald Stichler,

This work is a contribution to the “European Project for Ice Coring in Antarctica” (EPICA), a joint European Science Foundation/European Commission (EC) scientific programme, funded by the EC under the Environment and Climate Programme and by national contributions from Belgium, Denmark, France, Germany, Italy, The Netherlands, Norway, Sweden, Switzerland, and U.K.. Additional funding by Deutsche Forschungsgemeinschaft (projects Oe130/5-1&

STI207/1-1) is gratefully acknowledged.

hoerter@awi-bremerhaven.de

Introduction Introduction

The European Project for Ice Coring in Antarctica (EPICA) focuses on the drilling of two deep ice cores, the first at Dome C in the Indian/Pacific sector, and the second in Dronning Maud Land in the Atlantic sector of Antarctica. We focus on Dronning Maud Land and the isotope record from the EDMLEDML (EPICA Dronning Maud Land)

(EPICA Dronning Maud Land) ice core drilled there. The drilling of EDML started in the 2001/2002 season at Kohnen station (75º00’S, 0º04’E, 2882 m a.s.l.) and reached in the 2002/03 season a depth of 1564 m recovering approx. 55,000 year old ice.

References:

Fuji, Y. et al. (1999): Thephra layers in the Dome Fuji (Antarctica) deep ice core. Ann. Glac.29, 126-130.

Johnsen S. J. et al. (1997) The ¹⁸O record along the Greenland Ice Core Project deep ice core and the problem of possible Eemian climatic instability. J. Geophys. Res. 102, 26397-26410.

Jouzel, J. et al. (2001) A new 27 ky high resolution East Antarctic climate record. Geophys. Res. Lett. 28, 3199-3202.

Steinhage, D., et al. (2003). Internal structure of the ice sheet between Kohnen Station and Dome Fuji revealed by airborne radio-echo sounding, 7th Intern. Symp. Antarctic Glaciology, 25-29/08/2003, Milano.

Watanabe, O. et al. (2003): Homogenous climate variability across East Antarctica over the past three glacial cycles. Nature, 422, 509-512.

European Project for Ice Coring in Antarctica

(EPICA )

δδ¹⁸¹⁸O and DEP high resolutionO and DEP high resolution

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546.0 545.5 545.0 544.5 544.0

22 21 20 19 18 17 16 15 14

δ18O (‰-SMOW) DEP conductivity (µS/m)

Depth below surface (m) DEP

δ¹⁸O 30.7 a/m or 0,032 m/a

d (o/oo)!18O (o/oo) R (18O - d )

!18O (o/oo)d (o/oo)

1999-2000 year period 1994-1995 year period

month delay [month]

R (18O - d )

0 6121824

0 6121824

0 3 6 9 12 0 3 6 9 12

-50 -48 -46 -44 -42 -40 -38 0 2 4 6 -48 -46 -44 -42 -40 -38 2 4 6 8 10 12

-1.0 -0.5 0.0 0.5 1.0 -1.0 -0.5 0.0 0.5 1.0

Depth (m Firn)

0.0 0.5 1.0 1.5 2.0

0.0 0.5 1.0 1.5 2.0

-48 -44 -40 -36 0 4 8 12 16

d (‰)δ18O (‰)

The near surface snow

The near surface snow andand its isotopic composition its isotopic composition

Times series of

Times series of ¹⁸¹⁸O contents (10-year,O contents (10-year, 300-years means)

300-years means)

Times series of ¹⁸O contents (10-year means) deduced from the ice cores B32 and EDML, which were drilled at slightly different positions and supplement each other. The smoothed curve (thick line) has been calculated using Gaussian low-pass filter over 300 years. Generally, the stable isotope profiles (¹⁸O, ²H) are characterized by Holocene stable climate and show only low variability.

But, in the last 4000 years (based on a preliminary time scale) the δ¹⁸O values decrease continuously and the deuterium excess values d increase in the same time by about 0.5 ‰. Both trends could indicate climate cooling in this part of Antarctica. The depth section of the EDML core (123-173m) for which higher resolution measurements are available is marked by arrows and a yellow bar.

EDMLEDML ice core ice core: : δδ¹⁸¹⁸O 5cm samplesO 5cm samples

ca. 30 a/m

-460 -440 -420 -400 -380

25 20 15 10 Age (kyrs BP)

-52 -50 -48 -46 -44 -42

1200 1000 800 600 Depth (m)

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

25 20 15 10 Age (kyrs BP)

Dome C

J. Jouzel et al. , GRL (2001)

EDML

GRIP

S.J. Johnsen et al., JGR (1997) δ18O (‰-SMOW)δ18O (‰-SMOW)δ2H (‰-SMOW)

? ?

EDML ice core EDML ice core: : δ δ

O and DEP O and DEP

d¹⁸O (‰-SMOW)

-54 -52 -50 -48 -46 -44 -42

1600 1400

1200 1000 800

600 400 200

22

20

18

16

14

12

δ18O (‰-SMOW) DEP conductivity (µS/m)

Depth below surface (m) Dust/ash layer

visible in the core

δ¹⁸O,

10-m running average

δ¹⁸O,

50-cm samples

δ¹⁸O,

Single samples

DEP, 10-m average

296.6 808.2 939.8 1053.9 1292.6 1463.0 1558.9m

transition D/O 8 12 ?

ACR

„8.2 ky“

event decreasing

trend

δ¹⁸O und deuterium excess profiles, plotted against the depth, at the position of the snow pit SS0203, close to the EDML drilling site. The vertical lines indicate the annual layering and mark the austral summer (Dec/Jan).

Cross-correlations between the ¹⁸O content and the d values in the snow cover at SS0203, sampled 18.12.2002. To perform the correlation, the profile data were converted to monthly resolved time series using ¹⁸O stratigraphy for dating and assuming equal accumulation rates throughout the year

-48 -46 -44 -42

570 565 560 555 550 545 540 535 530

Depth (m below surface) -48

-46 -44 -42

160 155 150 145 140 135 130 125 δ18O (‰-SMOW)δ18O (‰-SMOW)

50cm resolution 5 cm resolution Mean ±sdev

50cm resolution 5 cm resolution Mean ±sdev ca. 16 a/m

ca. 30 a/m

„

„8.28.2 kyr kyr““ event event

δ¹⁸O profiles for two core sections (123-164m and 529-569m) where 5cm samples were available. In the upper profile the annual layer thickness corresponds to ca. 6.2cm, in the lower profile to ca. 3.3cm.

The lower profiles originates from the time around the socalled “8.2 kyr” event. An exact dating of the EDML is still missing.

δ¹⁸O and DEP profiles in the centre of the “8.2 kyr” event. The DEP profile (depth resolution 5mm) still shows variations which indicate annual layers (grey lines). The variations of the δ¹⁸O values are in the order of a decade.

Profile of δ¹⁸O values along the EDML core down to the depth of 1564 m: Shown are values measured at 50cm samples (single values grey, 10-m running mean thick red line) and at 4cm samples with a spacing of 10 m (red circles connected by lines).

The blue lines are 10-m averages of DEP measurements, showing good correlation with the isotope values. The dating of the core is still under discussion. The isotope profile available so far shows a decreasing trend from around 270 m to the surface (cf. Figure above), a clear cooling event is indicated around the depth of 545 m (“8.2 kyr” event; cf. Figures left) as well as the Antarctic Cold Reversal (ACR). It looks whether the transition zone is steeper than known from the Dome C, Dome F or Vostok cores (Watanabe et al., 2003) (cf. Figure right). The dust/ash layers which can be seen in the EDML core are indicated by lines. There is indication from air-borne radar survey (Steinhage et al., 2003) that the layers at 939.8m and 1053.9m correspond to visible tephra layers in the Dome F core at a depth of 505.8m and 573.9m (Fuji et al., 1999). According to Watanabe et al.

(2003) those layers in the Dome F core correspond to appr. 19.5 kyr and 24.5 kyr.

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