The role of snow albedo feedback in Earths

The role of snow albedo feedback in Earth’s climate Tao Wang Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 1

Background Recent temperature change relative to 1961 -1990 Source UNEP 2012, Keeping Track of our Changing Environment, original source of data – NASA Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 2

Background Feedback regulates speed of global warming Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 3

Background Feedback regulates speed of global warming Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 4

Background Some large amplifying feedbacks Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 5

Background Some large amplifying feedbacks Snow albedo feedback Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 6

Albedo What is Albedo? Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 7

Albedo Snow has a high albedo Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 8

Albedo Different snow types Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 9

Albedo Different snow types Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 10

Direction and magnitude of snow albedo feedback in extratropical land Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 11

Snow albedo feedback to climate Snow cover/snow mass Temperature albedo Positive feedback Perturbation absorbed radiation Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 12

Snow albedo feedback to climate Ø Northern hemisphere insolation incident upon snowpack peaks during March-May Snow cover/snow mass Temperature Ø Boreal spring is time of maximum snow -albedo feedback strength albedo Positive feedback Perturbation absorbed radiation Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 13

How to quantify snow albedo feedback (W m-2 K-1) Propogation of albedo change to net shortwave flux Impact of a change in T upon albedo (% K-1) Ø Observation-based albedo (satellite) Temperature (e. g. CRU, reanalysis products) Ø Model-based GCMs with an interactive albedo and temperature feedback Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 14

How to quantify snow albedo feedback (W m-2 K-1) Propogation of albedo change to net shortwave flux Impact of a change in T upon albedo (% K-1) Ø Determined at seasonal cycle April vs. July Ø Determined at interannual, decadal and century-scale Linear regression between surface temperature and albedo integrated over spring (extratropical land) or summer (Antarctic) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 15

How to quantify snow albedo feedback (W m-2 K-1) Propogation of albedo change to net shortwave flux Impact of a change in T upon albedo (% K-1) Ø Determined at seasonal cycle April vs. July Ø Determined at interannual, decadal and century-scale Linear regression between surface temperature and albedo integrated over spring (extratropical land) or summer (Antarctic) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 16

How to quantify snow albedo feedback (W m-2 K-1) Propogation of albedo change to net shortwave flux Impact of a change in T upon albedo (% K-1) Ø Determined at seasonal cycle April vs. July Ø Determined at interannual, decadal and century-scale Linear regression between surface temperature and albedo integrated over spring (extratropical land) or summer (Antarctic) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 17

Present SAF strength satellite observation (% K-1) determined at seasonal cycle Fernandes et al. (2009) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 18

Impacts of SAF strength on surface warming Xu and Hall (2013) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 19

Vegetation controls on SAF strength Tree cover impacts on albedo Loranty et al. (2014) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 20

Vegetation controls on SAF strength Tree cover impacts on seasonal SAF Loranty et al. (2014) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 21

How about future SAF strength There is a large model spread in SAF Hall and Xu (2007) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 22

How about future SAF strength Linking SAF from seasonal cycle to that from climate change Xu and Hall (2013) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 23

How about future SAF strength Linking SAF from seasonal cycle to that from climate change Is this really unbiased? Xu and Hall (2013) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 24

Factors affecting future SAF strength Ø Expansion of tree Ø Disturbance Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 25

Expansion of tree Predicted changes in Vegetation class (circumpolar region) Observed 2050 s scenario Pearson et al. (2013) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 26

Expansion of tree Predicted changes in Vegetation class (circumpolar region) Observed 2050 s scenario Tree expansion Pearson et al. (2013) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 27

Expansion of tree Predicted changes in Vegetation class (circumpolar region) Observed 2050 s scenario Tree expansion Pearson et al. (2013) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 28

Factors affecting future SAF strength Ø Expansion of tree Ø Disturbance Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 29

Fire occurrence (e. g. West Canada) Jin et al. (2012) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 30

Impacts of Fire disturbance Chapin III et al. (2008) Randerson et al. (2005) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 31

Impacts of Fire disturbance amplify the albedo contrast Chapin III et al. (2008) Randerson et al. (2005) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 32

Impacts of Fire disturbance amplify the albedo contrast Post-fire albedo trajectory !! Chapin III et al. (2008) Randerson et al. (2005) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 33

Impacts of Fire disturbance Impacts of burn severity in albedo change Beck et al. (2011) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 34

Factors affecting future SAF strength Ø Expansion of tree Ø Disturbance Ø Other factors (Soot, forest infilling, change in forest statue) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 35

Future directions in earth system models Ø Masking effects of snow albedo by trees Ø Parameterisation of post-fire albedo trajectory Ø Impacts of soot, aerosols and black carbon on albedo Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 36

Direction and magnitude of snow albedo feedback on ice sheet Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 37

Snow albedo feedback to climate Snow on ice sheet (Antarctic/greenland) Snow grain size Temperature albedo Positive feedback Perturbation absorbed radiation Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 38

Snow albedo feedback to climate Snow grain size Snow on ice sheet (Antarctic/greenland) Snow grain size snowfall Temperature albedo Negative feedback Positive feedback Perturbation absorbed radiation Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 39

Snow albedo feedback to climate Snow grain size Snow on ice sheet (Antarctic/greenland) Snow grain size snowfall Temperature albedo Which loop is more efficient? Negative feedback albedo Positive feedback Perturbation absorbed radiation Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 40

Present SAF on Antarctic Picard et al. (2013) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 41

Present SAF on Antarctic Positive SAF was significantly compensated by negative SAF Picard et al. (2013) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 42

Present SAF on Greenland Box et al. (2012) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 43

How about future SAF for Antarctic Picard et al. (2013) Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 44

Conclusions Ø Snow albedo feedback - recent warming and vegetation controls on its magnitude Ø Potential Inhibition of Snow albedo feedback by increased snowfall Ø Future directions in well representing Snow-albedo feedback in models Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 45

Thanks a lot for your attention! Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 46

How Fire influences albedo • Stand replacing fire increased albedo in Alaskan boreal forests. • Recovery to pre-fire albedo ~ 55 years • Albedo had a larger impact on radiative forcing than did fire emissions (CO 2, aerosols, etc. ) Randerson et al. (2006) Winter Summer Sino-French institute for earth system sciences (SOFIE) May. 12 -17 2014 47