permafrost-2016 – global-cryosphere-watch

Permafrost and Frozen Ground Assessments

The Recent State of Permafrost, 2016

Aaron Letterly

11 May 2017, updated 14 July 2017

Alaskan Active Layer Thickness Trends

In 2016, active layer thicknesses (ALT) at multiple sites in the Arctic slightly increased relative to 2015, and ended the melt season higher than their respective long-term averages. The Alaskan North Slope region has a high density of ALT measurement sites, allowing the effects of hotter summers and shorter, less-cold winters on the underlying soil to be closely monitored. Figure 1 shows annual end-of-season thicknesses by site, revealing a slow increase in thaw depths for most locations. 2016 ALTs in many sites did not show a large amount of change from their 2015 values. The largest recorded North Slope increase took place in Happy Valley, where thaw depths increased from 42 to 46 cm.

Figure 1: Time series of thaw depths measured in Alaska’s North Slope and Brooks Range regions. All sites are located in the continuous permafrost zone. Data are from the Circumpolar Active Layer Monitoring (CALM) website.

Active Layer Thickness Changes by Region

Figure 2 shows the location and trends of ALT changes over the last ten years. Measurement sites are shown in three panels: Alaskan, Siberian, and Russian/European. The fourth panel displays all sites worldwide. Circles indicate the location of sites, where the color of the circle depicts the ten-year trend of ALTs at that location. Sites that did not post measurements in 2016 are omitted. In all regions there is an overwhelming majority of positive ALT trends, responding to increasing surface temperatures at high latitudes (e.g., Smith et al. 2009, Popova and Shmakin, 2009). It is important to note, however, that permafrost changes may occur on time scales ranging from shorter than ten years to longer than fifteen years (Christiansen et al. 2010, Burn and Kokelj 2009, Romanovsky et al., 2014,Streletskiy et al. 2008).

Figure 2: Ten-year trends of ALT changes. Each circle represents a CALM site reporting in 2016; the circle’s color indicates the trend. Only 87 out of 2036 CALM reported values in 2016.

In the last fifteen years, Arctic-wide measurement sites have shown agreement on an increasing ALT trend (Figure 3). Thaw depth observations at individual sites are significantly forced by surface air temperatures and can experience a substantial amount of inter-annual variability. In 2016, however, regional average thaw depths in all 7 zones were above their 25-year average. In both Alaskan regions and Greenland, the 2016 ALT averages are among the deepest active layers locally recorded. Similarly changing active layers are expected for Canada, but ALT changes have not been posted since 2014. European and Siberian ALT averages were similar to their 2015 values, increasing by 2-6 centimeters in all three regions. Over the last 25 years, the ALTs in Siberia have increased, but have not experienced significant deviations from average since 2014.

Figure 3: Percent change in active layer thicknesses (ALT) relative to the 1991-2015 average for 7 different Arctic regions. The legend in the lower left details the number of observation sites in a region that were used to make the corresponding time series.

Anarctic Permafrost

Measurements at the Johann Gregor Mendel site (James Ross Island, Eastern Antarctic Peninsula, 63.8S, 57.866E) show that mean annual ground temperatures at 5 and 75 m depths have increased over the last five years, and increased significantly in 2016 (Figure 4). The active layer thickness has seen a general increase, or deepening, over the last five years (Figure 5), but did not increase significantly in 2016. This is in contrast to the increase in the annual mean ground temperature, probably indicating that the temperature increase occurred in the non-thawing time portion of the year.

Figure 4: Mean annual temperatures at depths of 5 and 75 cm measured at the Johann Gregor Mendel site.

Figure 5: Active layer thickness (left axis, blue line) and the thawing degree days (red bars) at the Johann Gregor Mendel site.

References

Burn C. R. and S. V. Kokelj. 2009. The environment and permafrost of the Mackenzie Delta area. Permafr. Periglac. Process., 20(2), 83-105, doi: 10.1002/ppp.655.

Christiansen, H. H., B. Etzelmüller, K. Isaksen, H. Juliussen, H. Farbrot, O. Humlum, M. Johansson, T. Ingeman-Nielsen, L. Kristensen, J. Hjort, P. Holmlund, A. B. K. Sannel, C. Sigsgaard, H. J. Åkerman, N. Foged, L. H. Blikra, M. A. Pernosky and R. Ødegård. 2010. The Thermal State of Permafrost in the Nordic area during the International Polar Year. Permafr. Periglac. Process., 21, 156-181, doi: 10.1002/ppp.687.

Hrbáček F., Láska, K., Engel, Z., 2016. Effect of Snow Cover on the Active-Layer Thermal Regime – A Case Study from James Ross Island, Antarctic Peninsula. Permafrost and Periglacial Processes, 27, 307–315.

Hrbáček, F., Kňažková, M., Nývlt, D., Láska, K., Mueller, C.W., Ondruch, J., 2017. Active layer monitoring at CALM-S site near J.G.Mendel Station, James Ross Island, Eastern Antarctic Peninsula. Science of Total Environment. 601–602, 987–997.

Popova, V. V. and A. B. Shmakin. 2009. The influence of seasonal climatic parameters on the permafrost thermal regime, West Siberia, Russia. Permafr. Periglac. Process., 20, 41-56, doi:10.1002/ppp.640.

Romanovsky, V.E., W.L. Cable, A.L.Kholodov, S.S. Marchenko, S.K. Panda, N.I. Shiklomanov, and Walker, D.A., 2014, Changes in permafrost and active-layer thickness due to climate in Prudhoe Bayregion and North Slope, AK. (http://www.geobotany.uaf.edu/library/posters/Romanovsky2014_OttawaAC2014_pos20141205.pdf)

Smith, S. L., S. A. Wolfe, D. W. Riseborough and F. M. Nixon. 2009. Active-layer characteristics and summer climatic indices, Mackenzie Valley, Northwest Territories, Canada. Permafr. Periglac. Process., 20, 201-220, doi:10.1002/ppp.651.

Streletskiy D. A, N. I. Shiklomanov, F. E. Nelson and A. E. Klene. 2008. 13 years of observations at Alaskan CALM sites: Long-term active layer and ground surface temperature trends. Proceedings of the 9th International Conference on Permafrost, D. L. Kane and K. M. Hinkel (eds.), June 29-July 3, Fairbanks, Alaska, Institute of Northern Engineering, University of Alaska Fairbanks, vol. 2, 1727-1732.

Global Cryosphere Watch