STUDI Land Surface Change & Arctic Land Warming Department of Geography Jianmin Wang The Ohio State University 04/06/2015 1

Two papers 2

Background: Arctic summer warming Fig. 1 The Arctic- -a test bed to evaluate the consequences of regional system dynamics. -a trend of arctic summer warming. -a large impact on the rates of water- dependent processes. Goals: -estimate recent and potential future changes in atmosphere heating in arctic Alaska. -figure out the causes. Data: -surface temperature records -satellite-based estimates of cloud cover and energy exchange -ground-based measurements of albedo and energy exchange -field observations of changes in snow cover and vegetation 3 Fig. 1

The causes? changes in atmospheric circulation: the Pacific North American Teleconnection, the Pacific Decadal Oscillation, El Nino Southern Oscillation Loss of the extent of summer sea ice Increase of summer cloud cover Fig. 2 4

The causes? Increase of summer cloud cover Fig. 3 5 decrease in downwelling SW > increase in downwelling LW

The causes? changes in atmospheric circulation: the Pacific North American Teleconnection, the Pacific Decadal Oscillation, El Nino Southern Oscillation Loss of the extent of summer sea ice Increase of summer cloud cover Lengthening of the snowfree season Fig. 2 6

The causes? Lengthening of the snowfree season Snowmelt advance of 2.5 days decade Wm -2 more energy absorbed or transferred = A doubling of atmospheric CO 2 7

The causes? changes in atmospheric circulation: the Pacific North American Teleconnection, the Pacific Decadal Oscillation, El Nino Southern Oscillation Loss of the extent of summer sea ice Increase of summer cloud cover Lengthening of the snowfree season Expansion of shrubs and forests Fig. 2 8

The causes? Since 1950, the cover of tall shrubs within Alaska’s North Slope tundra has increased 1.2% decade ,600 km 2 (2.3% of the treeless area) has been converted from tundra to forest in the past 50 years. Expansion of shrubs and forests (Sturm et al. 2001) (Van Bogaert et al. 2011) 9

The causes? Table. 1 10

Conclusions The longer snow-free season has contributed more strongly than vegetation changes to present summer land warming in the Alaska Improved understanding of the controls over rates of vegetation expansion would reduce the likelihood of unexpected surprises regarding the magnitude of high- latitude amplification of summer warming. 11

Two papers 12

Background: Arctic Sea Ice Loss From NSIDC Rapid sea ice loss events (RILEs) 9 Rapid Sea Ice Events (RILEs) are indentified in 21 st century from the Community Climate System Model (CCSM3) 21st century A1B simulations Goals: 1.The potential consequences for adjacent land climate. 2.The impact on permafrost of the timing of RILEs. Methods: Community Land Model (CLM) 13

Arctic Land Temperature Trends During Rapid Sea Ice Loss Events Fig. 1 Composites are formed by averaging nine RILEs. Increased warming rate during RILEs The signal of enhanced warming can extend 1500 km inland the warming trend during RILEs is 3.5 times greater than outside these periods 0.46 ℃ decade ℃ decade-1 14 Sep Sea ice extent OND arctic land air temperature

Arctic Land Temperature Trends During Rapid Sea Ice Loss Events Warming over land is a response to sea ice loss Inputs: 1. Sea ice conditions- 1980–1999 and 2080–2099 sea-ice conditions from CCSM3 A1B. 2. SST – the same observed data. Two 60-yr simulations with the CAM3 coupled to CLM3 Fig. 2 15

Impact of Accelerated Warming on Permafrost Fig. 3 Main parameter: 1. Period 50 years 2. Timing of warming ： yrs 6–15 EARLY yrs 21–30 MID yrs 36–45 LATE None LINEAR 3. initial permafrost states ： -0.3 ℃, -1.5 ℃, -5.8 ℃ Permafrost: a thick subsurface layer of soil that remains frozen throughout the year, occurring chiefly in polar regions. 16

Impact of Accelerated Warming on Permafrost -0.3 ℃ -1.5 ℃ -5.8 ℃ DPT: Depth to permafrost table SHC: Soil heat content 17

Conclusions Rapid sea ice loss forces a strong acceleration of Arctic land warming in CCSM3 (3.5-fold increase) Arctic land warming can trigger rapid degradation of currently warm permafrost. rapid sea ice loss Arctic land warming Degradation of permafrost 18

Future work The rate of shrub and forest expansion? The impact of Arctic land warming on the sea ice loss? 19

References Lawrence, D. M., Slater, A. G., Tomas, R. A., Holland, M. M., & Deser, C. (2008). Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss. Geophysical Research Letters, 35(11). Chapin, F. S., Sturm, M., Serreze, M. C., McFadden, J. P., Key, J. R., Lloyd, A. H.,... & Welker, J. M. (2005). Role of land-surface changes in Arctic summer warming. science, 310(5748), Sturm, M., Racine, C., & Tape, K. (2001). Climate change: Increasing shrub abundance in the Arctic. Nature, 411(6837), Van Bogaert, R., Haneca, K., Hoogesteger, J., Jonasson, C., De Dapper, M., & Callaghan, T. V. (2011). A century of tree line changes in sub-Arctic Sweden shows local and regional variability and only a minor influence of 20th century climate warming. Journal of Biogeography, 38(5),

Thank you Any questions? 21