Monthly Archives: April 2019

Five Decades of Arctic Change

Posted by William Colgan on April 08, 2019
Climate Change, New Research / No Comments

We have just completed a study that assesses indicators of Arctic change since 1971. It is available open-access in the current issue of Environmental Research Letters. We assimilate nine hyper-diverse data types – air temperature, permafrost temperature, precipitation, river discharge, tundra greenness, wildfire area, snowcover duration and, of course, sea ice area and land ice loss – into standardized indices. The motivation of this study is to bring together almost a five-decade time-series of biophysical variables into a common open-data framework.

Figure 1 – Three of the nine types of Arctic indicators compiled in this study over the 1971-2017 period. These three biophysical indicators show that Arctic tundra is becoming greener in response to increasing Arctic temperature and precipitation.

If there is one climate variable to rule them all, it is air temperature. Increasing air temperature leads to an intensification of the hydrologic cycle, which is clearly evident as increases precipitation and river discharge. Increasing temperature also drives increasing land ice loss and decreasing fall sea ice area. Beyond just the physical climate system, changing air temperature is also driving changes in the biological ecosystem. There is a startlingly clear – more than 99.9 % certain – correspondence between air temperature and the greenness of Arctic-wide tundra. This means a warmer Arctic is a greener Arctic.

In addition to assessing the nine types of indicators, we also discuss some of the tremendous number of knock-on effects of these biophysical trends. These knock-on, or biophysical cascade, effects include decreased alignment of flowering and pollinating windows for plant; increased prevalence of wildfire ignition conditions; an acceleration of the CO2 cycle with increased uptake during growing season counterbalanced by increased emissions in spring and fall; conversion between terrestrial and aquatic ecosystems; and shifting animal distribution and demographics. The Arctic biophysical system is now clearly trending away from its 20th Century state and into an unprecedented state, with biophysical implications not only within but beyond the Arctic.

This study was developed within the Arctic Monitoring and Assessment Program (AMAP), with the ambition that high-level Arctic summary statistics are of interest to the forthcoming IPCC Sixth Assessment Report (AR6). Annual time-series of the nine types of Arctic indicators compiled for this study will soon be freely available for download at www.amap.no. For now, you can access them via this GoogleSheet.

Box, J., W. Colgan, T. Christensen, N. Schmidt, M. Lund, F.-J. Parmentier, R. Brown, U. Bhatt, E. Euskirchen, V. Romanovsky, J. Walsh, J. Overland, M. Wang, R. Corell, W. Meier, B. Wouters, S. Mernild, J. Mård, J. Pawlak and M. Olsen. 2018. Key indicators of Arctic climate change: 1971–2017. Environmental Research Letters. 14: doi:10.1088/1748-9326/aafc1b.

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