Transcript CCSM PaleoClimate Working Group Transient Mid-Holocene Simulation Caspar Ammann Bette Otto-Bliesner Esther Brady Carrie Morrill Fortunat Joos Raimond Mueschler Sam Levis Bob Tomas Noah.

CCSM PaleoClimate Working Group
Transient Mid-Holocene Simulation
Caspar Ammann Bette Otto-Bliesner Esther Brady Carrie Morrill
Fortunat Joos Raimond Mueschler Sam Levis Bob Tomas
Noah Diffenbaugh Zhengyu Liu Matthew Huber Bruce Briegleb
Goal Simulating mid-Holocene natural climate variability
and potential abrupt climate change
Model
CCSM3, fully coupled T31x3 with dynamic vegetation
Forcing
Variable orbital, solar irradiance, ghg and explosive volcanoes
Initialization
Fixed forcing 6000 BP spinup with dynamic vegetation (300 yr)
Years 65-84 (~ 5920 BP)
Compared to Pre-Industrial
+4.5 Wm-2 North Pole
-1.0 Wm-2 Equator
Years 1580-1599 (~ 4410 BP)
Compared to Pre-Industrial
+3.6 Wm-2 North Pole
-0.8 Wm-2 Equator
Transient Mid-Holocene Temperature Trends
6000 BP
4350 BP
Global Mean
Surface Temperature
Ocean Mean
Temperature
Years 65-84 (~5920 BP)
Years 1580-1599 (~4410 BP)
JJA Ts Difference with PI
JJA Precipitation Difference with PI
North African Grasses and Boreal Forests have small
downward trends in percent concentrations
North African Monsoon, 10 to 30 latitude
6000 BP
4200 BP
Boreal, 50 to 90 latitude
6000 BP
4200 BP
JAS years 950-1050 (~5000 BP) minus 150-250 (~5800 BP)
Precip (color, 0.2 mm/day) SLP (contours, 0.2 mb)
1000 mb Wind (vectors, 1 m/sec reference)
mm / day
300
5900 BP
600
900
Years
1200
1500
4400 BP
Transient
Mid-Holocene
Pre-Industrial
Dynamic
Vegetation
6000 BP
Present
Transient Mid-Holocene Simulation
Preliminary Results after 1650 years
Global cooling -0.38 C
Stabilization of ocean temperature
Southward shift in African-Asian monsoons
Some southward shift in boreal forests and
North African grasses
Current Plan
Run forward to present day
At ~10 yrs / day, might finish late summer 2007
Encourage Analysis
Some interesting features noticed already
Will any abrupt changes occur? Stay tuned
Selected data analysis available online at:
http://www.ccsm.ucar.edu/working_groups/Paleo/experiments/b30.108.html
Data available on NCAR Mass Store /CCSM/paleo/b30.108
Transient Holocene Simulation
Players Carrie Morrill, Caspar Ammann, Bette Otto-Bliesner,
Fortunat Joos, Raimond Mueschler, Sam Levis, Bob Tomas,
Noah Diffenbaugh, Zhengyu Liu, Matthew Huber, Bruce Briegleb
Vision
Many paleoclimate proxy records show abrupt shifts in the mid-Holocene. The
Transient Holocene simulation allows us to address:
(1) Are there any abrupt changes simulated by CCSM3 (either regional,
hemispheric or global)?
(2) If yes, how are these transitions similar/different from those observed
in paleoclimate records (i.e. location, speed, direction of climate change)?
(3) If no, what are the limitations of the model and its forcings? What else
might need to be changed for abrupt changes to occur?
Model
CCSM3, T31 x 3
Includes dynamic vegetation
Initialized from 6 kyr ago spinup with dynamic vegetation, 300 years long
Transient Holocene Simulation (cont)
Forcings
Orbital:
Solar:
Parameters updated every four years.
Solar constant from fit to solar modulation estimated
from 14C/10Be ice core data, using satellite observations at
end of record. Peak to peak range 0.12% of mean;
minimal trends.
GHG:
CO2, CH4 and N2O using smooth fits to ice core data.
Volcanic: Statistical occurance from 4050 BC to 850 AD, historical after
850 AD. Maximum monthly tropical volcanic mass equals
Tambora 1815; maximum extratropical equals Laki 1783.
History Files
Monthly means: cam, pop, clm, csim.
Daily means:
T,u,v @ 850, 300 hPa, sea level pressure;
surface temperature and precipitation.
Transient Holocene Simulation (cont)
Current Status
Out 800+ years (i.e. from 4050 BC to 3250 BC)
Progressing approximately 10 years / day
Preliminary Results
Noticeable short term impact of volcanoes.
Slight global cooling trend (-0.1 to -0.2 C)
Southward shift in subtropical Monsoon and vegetation
associated with regional cooling, presumably due to
changes in orbital forcing.
Noticeable modulation of C3 grasses in African Monsoon,
presumably due to drought cycles.
Southward shift in boreal forests, also presumably due to
changes in orbital forcing.
Years 65-84
Orbital forcing has small changes
over several hundred years
Years 680-699
Greenhouse gases have small and
very smooth changes
Summary of Forcings
Orbital
~ 0.5 W m-2 / century mid to high latitudes; long term secular trend
Solar
~ 0.29 W m-2 peak-to-peak over ~2 centuries; no secular trend
GHG
~ +0.0067 W m-2 / century CO2, 4050 BC to ~1000 AD
~ +0.0016 W m-2 / century CH4, 4050 BC to ~ 1500 AD
~ +0.0006 W m-2 / century N2O, 4050 BC to ~ 1000 BC
Volcanic
0 down to -10 W m-2, but short lived (a few years). Estimated
long term (i.e. several hundred years) mean forcing ~ -0.3 W m-2
Top of model fluxes
show volcanic forcings
Global surface
temperature shows
small cooling trend
High northern latitude
snow depth shows
slight upward trend
Years 680-699
Years 65-84
JJA Solar Insolation
JJA Ts
Years 65-84
Years 680-699
JJA Ts
JJA Precipitation
African Grasses and Boreal Forests have small downward
trends in concentrations
African Monsoon, 10 to 30 latitude
Boreal, 50 to 90 latitude
Transient Holocene Simulation
Preliminary Results
Noticeable short term impact of volcanoes.
Slight global cooling trend (-0.1 to -0.2 C)
Southward shift in subtropical Monsoon and vegetation
associated with regional cooling, presumably due to
changes in orbital forcing.
Noticeable modulation of C3 grasses in African Monsoon,
presumably due to drought cycles.
Southward shift in boreal forests, also presumably due to
changes in orbital forcing.
Transient Holocene Simulation
Current Plan
Run out 2400 years, or from 4050 BC to 1650 BC
At approximately 10 years / day, should finish August 2006
Encourage Analysis
Some interesting features noticed already
Will any abrupt changes occur? Stay tuned
Selected data analysis available online at:
http://www.ccsm.ucar.edu/working_groups/Paleo/experiments/b30.108.html
and updated every few days
Data available on NCAR Mass Store /CCSM/paleo/b30.108
Monthly and selected daily data available
Future?
Forcing files continuous up to 2000 AD