Implications for the Earth System of a melted Greenland ice-sheet

1
Implications for the Earth System of a melted
Greenland ice-sheet
Dan Lunt (1) , Nathalie de Noblet (2) , Sylvie
Charbit (2)

1. Bristol Research Initiative for the Dynamic
   Global Environment (BRIDGE), University of
   Bristol, UK.
2. LSCE, Gif-sur Yvette, France

• Motivation
• Experiment aims and setup
• Results
• surface physics and atmospheric dynamics
• vegetation
• ice-sheet re-growth
• 4) Conclusions and future work

d.j.lunt_at_bristol.ac.uk
2
EXPERIMENT AIMS

• If Greenland ice sheet melts.
• How will climate (local and remote) be affected
• thermodynamics.
• dynamics.
• vegetation.
• Will the ice sheet regrow?
• given a return to lower greenhouse gas
  concentrations.

3
MOTIVATION (previous work by Marie-France
Loutre) Model LLN 2-D Forcing CO2 emission
scenario (relatively high) Results Greenland
ice melted by 2000 years.
4
EXPERIMENTAL SETUP
2 GCM experiments (IPSLCM4_D, 74x45x19)
CONTROL present day control NOICE
Greenland ice sheet removed Bedrock
(rebounded) gives orography Tundra
vegetation FOLLOWED BY 1) Forcing of ORCHIDEE
vegetation model offline 2) Forcing of
GREMLINS ice-sheet model offline
5
GCM RESULTS (1) surface temperature change in GCM
JJA
DJF
Winter agrees v. well with lapse-rate
calculation, and low-ice simulation. Summer
lapse rate albedo effect.
6
GCM RESULTS (2) circulation changes time mean.
Increase in geopotential height to west of
Greenland. Presence of Greenland causes blocking
of air masses to west of Greenland. Radiative
cooling. Circulation more zonal.
DJF 500mbar geopotential height
7
GCM RESULTS (3) circulation changes - eddies
Storm tracks weaken south of Greenland. Decrease
in meridional temperature gradient. Storm tracks
more zonal.
DJF 500mbar band-pass (3-5 day) variance
8
GCM RESULTS (4) sea-ice and circulation changes
Decreased heat transport over Barents Sea when
Greenland is not present sea ice build up.
9
GCM RESULTS (5) Precipitation change (annual
mean)
Orographic-induced precipitation on west coast
when Greenland is present.
10
VEGETATION MODEL RESULTS
11
RESULTS (7) Regrowth of the ice sheet
12
(No Transcript)
13
(No Transcript)
14

• CONCLUSIONS
• If Greenland melts, the local surface
  temperatures will increase, but there will also
  be surface cooling in the Barents and Berings
  Sea, linked to circulation changes. There will
  be a decrease in N. Atlantic storminess, linked
  to the decreased N-S temperature gradient.
• Vegetation is likely to grow on a deglaciated
  Greenland, with boreal forests in the south.
• Given a return to present day greenhouse gas
  concentrations, the Greenland ice sheet will
  regrow, triggered by high altitude eastern
  mountains and relatively high precipitation over
  central-eastern Greenland.

Effects of a melted Greenland ice sheet on
climate, vegetation, and the cryosphere, Lunt,
de Noblet, and Charbit, submitted to Climate
Dynamics.
15

• FUTURE WORK
• Asynchronous coupling with GCM.
• What about fully coupled ice-sheet/vegetation/clim
  ate simulations? IGCM/Glimmer a good tool.
• What about other CO2 concentrations. Is there a
  threshold for the regrowth of the ice-sheet?
• Role of the ocean. Freshwater flux.