Role of land cover changes for atmospheric CO2 increase and climate change during the last 150 years
Impact ofregionallyincreased CO2 concentrationsin coupled … · 2020-02-04 · Seasurfaceheight(m)...
Transcript of Impact ofregionallyincreased CO2 concentrationsin coupled … · 2020-02-04 · Seasurfaceheight(m)...
Impactof regionally increasedCO2concentrations incoupled
climate simulations
TidoSemmler,FelixPithan,ThomasJung
Motivation
Everybody knows: Arctic sea ice has beenstrongly declining over the last 3 to 4 decadesMany studies have investigated the impact ofsuch Arctic sea ice decline on the Northern mid-latitudesBut which influence is stronger: from the Arctic to the Northern mid-latitudes orthe other direction?Novel approach: regionally prescribe 4*CO2 concentrations(recently applied by Stuecker et al., 2018)
• ECHAM 6.3 (from Max Planck Institute) coupled to FESOM 1.4 (AWI ocean model)
• Flexible mesh layout – examples:
Thetool:AWI-CM1.1(CMIP6version)
LR MR
Rackowetal.(2018)
HR
Experiments
control
4*CO2north of 70N4*CO2north ofJanuary ice edge
4*CO2north of 60N
4*CO2south of 60N
4*CO2globally
March
Responseinthe temperature profile4*CO2 north of 60 N for the first 30 years
Winter Spring
Summer Autumn
Warming restricted to near-surface,except for summer
Winter2mtemperature response (K)
4*CO2 north of 70 N for the first 30 years 4*CO2 north ice edge for the first 30 years
4*CO2 north of 60 N for the first 30 yearsNorth America and East Asiacooling without stratosphericwarming
Meridionalatm.energy transport (PW)
Difference to control simulation, first 30 years
Synoptic activity 500hPa(m)4*CO2 north of 60 N, DJF
First30years
Last120years
Less exchange Arctic– extra Arctic
Synoptic activity 500hPa(m)
4*CO2 south of 60 N, DJF
First30years
Redistribution ofincrease/decrease areas
Arctic sea ice volume inMarch
Strong extra-Arctic impact: Even withoutany Arcticforcing (browncurve) half ofthe sea ice ismelted in around 15 years throughatmosphericheat transport. Another sixthdue to oceanicheat transport.
Energy fluxes 70°NMeridional ocean transportsmall andmeridional atmospheretransport large. Howeveranomaliescomparable.
Ocean playsimportant role in redistribution ofenergy whenswitching on extra-Arcticforcing
First30years Surface Meridionalatmosphere
Meridionalocean
control -11.7 102.9 13.8
60N -10.5 98.6 14.6
60Ns -10.6 106.8 17.8
glob -9.7 101.1 18.8
Last30years Surface Meridionalatmosphere
Meridionalocean
control -13.0 101.6 15.2
60N -12.7 96.3 16.2
60Ns -14.8 103.9 20.0
glob -13.2 98.5 19.1
Responseinthe temperature profile4*CO2 south of 60 N for the first 30 years
Winter Spring
Summer Autumn
Arctic amplification without Arctic forcingexcept for summer!
Arctic Amplification Index(AAI)(60°NArctic temperature increase /globaltemperature increase)
Note: AAI = 1: no ArcticAmplification
High AAI forArctic forcingexperiments
60% of ArcticAmplificationdue tonorthwardenergytransport
Sinuosity index (Cattiaux etal.,2016,GRL)
SI = length of isohypse / length of 50°N latitude circleThe chosen isohypse is the area average of Z500 over 30 to 70°N
Sinuosity index NHfirst 30years
Smallersinuosity indexthroughout theyear as a resultof extra-Arcticforcing
Tendency toslightly larger sinuosity indexin winter andspring as a result of Arcticforcing but signal not robust
Sinuosity index NHlast30years
Smallersinuosity indexthroughout theyear as a resultof extra-Arcticforcing
Tendency toslightly larger sinuosity indexin winter andspring as a result of Arcticforcing but signal not robust
Conclusions
Method of regional decomposition of CO2 forcing works (see also Stuecker et al., 2018). Maybe an experiment design to be consideredfor PAMIP?Above 300 hPa cooling rather than warming (expected!) Generally despite strong CO2 forcing in the Arctic relatively littlehappens in the mid-latitudes, especially with increasing simulationlengthThe extra energy in the Arctic forcing experiments largely stays in theArcticIf forcing only outside the Arctic, the energy transport into the Arcticis strongly increased with an increasing role of the ocean over thesimulation timeTherefore, even without any Arctic forcing two thirds of the sea icemelt and Arctic Amplification exists: 60% of Arctic Amplification canbe explained by extra-Arctic forcing!
Winter500hPageopot response (m)
4*CO2 north of 70 N for the first 30 years 4*CO2 north ice edge for the first 30 years
4*CO2 north of 60 N for the first 30 years PNA pattern visible, but small anomalies!
WinterU300response (m/s)
4*CO2 north of 70 N for the first 30 years 4*CO2 north ice edge for the first 30 years
4*CO2 north of 60 N for the first 30 years Positive anomalies stretching fromGulf of Mexico / Florida to Southern Europe – surrounded by negative anomalies. But small anomalies!
Sinuosity index ATfirst 30years
Sinuosity index ATlast30years
Sinuosity index ASfirst 30years
Sinuosity index ASlast30years
Sinuosity index PAfirst 30years
Sinuosity index PAlast30years
Sinuosity index AMfirst 30years
Sinuosity index AMlast30years
Arctic sea ice concentration response (%)
4*CO2north of 60N,last30years,MAM
Arctic sea ice concentration response (%)
4*CO2north of 60N,last30years,SON
Yearly 2mtemperature response
4*CO2 north of 60 N for the last 30 years
Mean sea level pressure (hPa)4*CO2 north of 60 N, DJF
First30years
Last30years
500hPageopotentialheight (m)4*CO2 north of 60 N, DJF
First30years
Last30years
Synoptic activity 500hPa(m)4*CO2 glob, DJF
First30years
Last30years
Ocean mixed layer depth anomaly4*CO2 north of 60 N
First 30 years Last 30 years
1951-1980
Sea surface height (m)
4*CO2 north of 60 N, DJF
First30years
Last30years
Ocean temperature response (K)15m4*CO2 north of 60 N
First30years
Middle 30years
Last30years
Salinity response (psu)15m4*CO2 north of 60 N
First30years
Middle 30years
Last30years