Rapid climate change in ice cores

Transcription

1 Rapid climate change in ice cores Liz Thomas British Antarctic Survey

2 Overview Introduction to ice cores Evidence of rapid climate change in the Greenland ice cores DO events Younger Dryas 8.2 kyr cold event Evidence of rapid climate change in Antarctic ice cores 20 th century changes in temperature and snowfall

3 Snowflakes fall to Earth and leave a message. Henri Bader ( ) Chief Scientist of the U.S. Army Snow, Ice and Permafrost Research Establishment

4 Norwegian British Swedish Antarctic Expedition (NBSAE) Camp century, Greenland. First deep ice core drilled to bedrock 1966 Camp century isotope record

5 Ice cores contains environmental information in several ways: Ratio of heavy to light molecules of water = temperature Chemicals within the ice = volcanic eruptions, dustiness, wind strength/direction, sea ice and biological activity Bubbles of air trapped within the ice = composition of the atmosphere

6 Temperature proxy 18 O (per mil) Holocene Glacial Greenland 0 C Warmer CO C Colder NGRIP community members, 2004

7 Temperature proxy 18 O (per mil) Temperature proxy D (per mil) Antarctica Holocene Glacial Jouzel et al, 2007 CO Greenland C Warmer C Colder NGRIP community members, 2004

8 Causes of DO events? Atlantic Meridional Overturning Circulation (AMOC) Freshwater release from ice sheets slow down of AMOC cold conditions Heinrich events ice rafted debris across north Atlantic precede the largest DO events Renewed convection warm conditions Causes of the warming not well constrained 8

9 Rapid warming in Greenland Holocene Glacial Dansgaard-Oeschger Events Present 9

10 DO-8 Warmer Dustier More sea salts? Wetter Thomas et al, JGR

11 Warmer and wetter Source change Low-latitude change? DO-8 Warmer Dustier More sea salts? Wetter Thomas et al, JGR

12 Deglaciation in Greenland MWP-1B ~11.3 ka MWP-1A ~14 ka Holocene Glacial Bolling-Allerod Younger Dryas Present 12

13 Terrestrial sources low latitude Asian deserts δ 18 O ~ 10 K warming d ~3 K cooling of marine moisture source Steffensen et al.,

14 Younger Dryas cooling 12.9 ka δ 18 O ~ 10 K warming Steffensen et al.,

15 Rapid climate change during the Glacial Greenland ice core records reveal atmospheric circulation can shift very rapidly 1-3 years shift in d-excess Sequence of events similar for DO-8, 14.7 ka and 11.7 ka despite different stages of deglaciation? Changes originating in the lower latitudes leading to ocean and atmospheric circulation changes

16 Rapid cooling in Greenland Holocene Glacial Present 16

17 Rapid cooling in Greenland 9.3 kyr 8.2 kyr 17

18 RAPID Paleoclimate records Peat bogs Ocean cores Ice cores Lake cores Speleothems Volcanic ash Greenland Estonia Newfoundland British Isles Spain 18 Rapid Climate Change End of Programme Event Royal Society 26 June 2008

19 Newfoundland Atlantic Ocean Greenland Europe Outburst Lake Agassiz / Ojibway Daley, Thomas et al., Rapid Climate Change End of Programme Event Royal Society 26 June 2008

20 Causes of the 8.2 kyr event? Freshwater flux to North Atlantic from proglacial lake flooding Led to slow down of North Atlantic Conveyor Cold, dry conditions 163,000 km 2 ~8,470 years ago [Barber et al., 1999; Teller et al., 2002] 20

21 Causes of the 8.2 kyr event? Outburst flood only 1 yr flux of 2.5 Sv climate perturbation that recovers quickly Need additional sources of freshwater to sustain the cooling for years? Two stage freshwater forcing New drainage pathways Accelerated melt from Laurentide ice sheet 21

22 Causes of the 8.2 kyr event? Ice saddle collapse connecting Labrador and Baffin domes over Hudson Bay 100-year freshwater input through Hudson strait Matero et al., EPSL, 2017 Gregoire et al. Nature (2012) 22

23 The 8.2 kyr event GReenland Ice core Project (GRIP) North Greenland Ice core Project (NGRIP) Greenland Ice Sheet Project 2 (GISP2) Dye 3 Composite record Thomas et al.,

24 The 8.2 kyr event 160 yrs 69 yrs Thomas et al.,

25 The 8.2 kyr event Maselli et al., 2017 Thomas et al.,

26 The 8.2 kyr event Maselli et al., 2017 Thomas et al.,

27 The 8.2 kyr event Ice saddle collapse increased SSTs reduced sea ice (more open water) more marine species to ice core Matero et al., EPSL,

28 Summary Highlighted rapid climate change in Greenland during the last Glacial period, the deglaciation and the Holocene Ice cores provide: accurate dating and durations records of climate, atmospheric circulation and marine conditions phasing of parameters and mechanisms of change (theories) constraints for the modelling community to investigate causes of rapid climate change

29 Rapid climate change in Antarctica Stenni et al., Climate of the Past 2017

30 Rapid climate change in Antarctica Thomas et al., Climate of the Past 2017

31 Rapid climate change in Antarctica Thomas et al., Climate of the Past 2017