Arctic warming amplified by near-surfaceinfrared radiation feedbacks

R. BintanjaR. G. Graversen

W. Hazeleger

Royal Netherlands Meteorological Institute (KNMI)The Netherlands

GISS

Surface temperature analyses

Arctic warming in observations

Arctic warming in ERA-int

DJF MAM

JJA SON

Screen and Simmonds (2010)

Arctic amplification in models

Holland & Bitz, 2003

1

1.5

2

2.5

3

3.5

4

4.5

30 40 50 60 70 80 90Latitude

EC-Earth (IFS, NEMO, LIM)

Feedbacks/processes that governArctic amplification (AA)

– Ice-albedo feedback (snow, sea ice)

– Longwave cooling (related to near-surface inversion)

– Horizontal transport of (latent) heat

– Evaporation

– Clouds

– Vegetation

– …

The amplifying effect of longwave cooling

TOA

Warming Warming

LW-cooling

LW-cooling is due to the temperature profile(among other things)

Where does OLR come from?

A 1-D radiative transfer model

Climatological inversion strength

-4

-2

0

2

4

6

50 55 60 65 70 75 80 85 90

ERA inversion strength (1990-2010)

DJFMAMJJASON

Latitude

Inversion

Does the presence of the Arctic inversion amplifysurface warming through infrared trapping?

OLR

Surface

Atmosphere

OLR = Surface part + Atmospheric part = (1 – e) Ls + Latm

(1 – e) Ls Latm

Fits of OLR against Ls…

…provide the slope (1-e) and the axis intercept (Latm)

EC-Earth– 1 x CO2 control– 2 x CO2 (instantaneous)

70-80N80-90N

1 x CO2

2 x CO2

T2

m (

glo

ba

l)

44 years

LW components (DJF)

ERA & NCEPDifference between1990-1999 and 2000-2009

Atmospheric cooling efficiency

LAup

LAdown

= LAup

LAup + LAdown

30 40 50 60 70 80 90

-0.06-0.05-0.04-0.03-0.02-0.01

0

-6 -4 -2 0 2 4

Change in

(° )Inversion strength C

R2=0.94

Inversion strength (K)

Ch

an

ge

in

Concluding remarks

– Arctic LW cooling ‘hampered’ by near-surface inversion

– Inversion layer ‘traps’ longwave radiation, amplifying surface warming

– LW-inversion feedback is positive

– Inversion will change due to surface warming, altering the feedback strength

Thank you for your attention