Greenland ice cores tell tales on the extent of the Greenland Ice Sheet during past warm climate periods

Dorthe Dahl-Jensen

Centre for Ice and Climate Niels Bohr Institute University of Copenhagen Copenhagen Denmark ddj@nbi.ku.dk

Photo: Morrell

The Arctic is warming at three times the global rate ddj@nbi.ku.dk

Annual warming 2010-2014 compared to 1951-1980 (NASA GISS)

Arctic 2 oC Global 0.6 oC

The Greenland Ice Sheet has increasing mass loss 249 Gt /yr Increasing 25 Gt/yr2

(Wouters Nature Geoscience, 2013)

Good questions:

With the accelerating rate of mass loss from Greenland – what will Greenland contribution to sea level rise in year 2100 ?

Back of the envelope calculation: dM/dt = 249 Gt/yr + 25 Gt/yr2 * t M = 249 Gt/yr * 85 yr + 0.5 * 25 Gt/yr2 * 85 yr * 85 yr = 110.000 Gt (0.3 m GMSLR)

0.3 m

(Jevrejeva, IOP, 2014)

Good questions:

With the accelerating rate of mass loss from Greenland – what will Greenland contribution to sea level rise in year 2100?

0.3 m

(Jevrejeva, IOP, 2014)

Good questions:

With the accelerating rate of mass loss from Greenland – what will Greenland contribution to sea level rise in year 2100 ?

(Jevrejeva, IOP, 2014)

Approach: Predict future sea level rise

Fortune teller What happened in earlier warm periods

Wise man

Knowledge from ice cores and ocean sediment cores

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GRIP

DYE3

ODP918

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GISP2 NGRIP

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ODP646

Knowledge from ice cores and ocean sediment cores Climate curve for the last 3 mill years: MIS 5 11 31

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From ocean sediment cores:

Glacial till and ice rafted debris

found at ODP site 918 and is

7 mill years old (Science, Larsen, 1994)

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GRIP

DYE3

ODP918

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GISP2 NGRIP

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ODP site 646 has most pollen in MIS 11

430.000 years ago (Reyers, 2014)

From NEEM

5.3 oC warmer in average over MIS 5e GMSLR from Greenland no more than 2 m (1.5±0.5 m) Happened over 5000 years (in average 150 Gt/yr)

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GRIP

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From CC DYE3 NEEM NGRIP GISP2 GRIP

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GRIP

DYE3

ODP918

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NGRIP

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We find basal material older that MIS5e in ALL the deep ice cores.

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From CC DYE3 NEEM NGRIP GISP2 GRIP

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GRIP

DYE3

ODP918

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GISP2 NGRIP

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ODP646

From DNA and macro fossils: Boreal Forest with no imprint of Tundra

Temperatures 10 oC warmer than the present

From CC DYE3 NEEM NGRIP GISP2 GRIP

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From dating of the basal ice and the embedded basal material:

Temperatures 10 oC warmer than the present

Greenland is resilient

We find MIS 5e ice in ALL ice cores: Greenland was ice covered in MIS 5e 125 ka South Greenland might have been ice free in MIS 11 430 ka Central and North Greenland has been ice covered for more than 1 mill years

Good questions:

With the accelerating rate of mass loss from Greenland – what will Greenland contribution to sea level rise in year 2100?

What do ice cores tell? When Greenland was ice free – probably more than 1 mill years ago – it was 10 oC warmer than at present During MIS 5e – 125 ka – it was 5 oC warmer over Greenland and the ice sheet reduced volume proportional to 2 m GMSL.

Good questions:

With the accelerating rate of mass loss from Greenland – what will Greenland contribution to sea level rise in year 2100?

What do ice cores tell? When Greenland was ice free – probably more than 1 mill years ago – it was 10 oC warmer than at present During MIS 5e – 125 ka – it was 5 oC warmer over Greenland and the ice sheet reduced volume proportional to 2 m GMSL. Where does the missing 3-7 m of the 5-10 m GMSLR in MIS5e come from? West Antarctic Ice Sheet ? When will the accelerating mass loss from Greenland reduce?

The ice streams represent

the largest unknown for predicting future sea level rise

Thanks for your attention