Multi-Decadal Surface Water Dynamics in North American Tundra

Abstract

Abstract:Over the last several decades, warming in the Arctic has outpaced the already impressive increases in global mean temperatures. The impact of these increases in temperature has been observed in a multitude of ecological changes in North American tundra including changes in vegetative cover, depth of active layer, and surface water extent. The low topographic relief and continuous permafrost create an ideal environment for the formation of small water bodies-a definitive feature of tundra surface. In this study, water bodies in Nunavut territory in northern Canada were mapped using a long-term record of remotely sensed observations at 30 m spatial resolution from the Landsat suite of instruments. The temporal trajectories of water extent between 1985 and 2015 were assessed. Over 675,000 water bodies have been identified over the 31-year study period with over 168,000 showing a significant (p < 0.05) trend in surface area. Approximately 55% of water bodies with a significant trend were increasing in size while the remaining 45% were decreasing in size. The overall net trend for water bodies with a significant trend is 0.009 ha year −1 per water body.

Detecting early warning signals of tree mortality in boreal North America using multiscale satellite data

“…Collectively, our results suggest that some component of the browning trends in boreal forests that are not a direct result of land use, fire, or other landscape disturbances Carroll & Loboda, 2017;Goetz et al, 2005;Ju & Masek, 2016;Nitze et al, 2017;Raynolds & Walker, 2016) may be related to droughtand insect-induced tree mortality. We highlight the particular vulnerability of the interior southern boreal, where widespread browning trends (Guay et al, 2014;Ju & Masek, 2016;Sulla-Menashe, Woodcock, & Friedl, 2018) are coupled to recent mortality events, and projections suggest continued drought and potential transitions to open forest or grassland (Abis & Brovkin, 2017;Hogg & Hurdle, 1995;Lenihan & Neilson, 1995;Worrall et al, 2013).…”

The sign, magnitude and potential drivers of change in surface water extent in Canadian tundra

“…Most studies of surface water extent change are performed using a thresholding method to classify an image pair (or a few dates) to get the difference in water extent between those dates (Hinkel et al 2007, Smith et al 2005, Yoshikawa and Hinzman 2003. However, those methods that pick a difference between two arbitrarily selected points in time are likely plagued with considerable uncertainty due to a naturally large inter-annual variability of water extent as demonstrated in Carroll and Loboda (2017). Better approaches focus on multi-temporal assessment of long-term trends in surface water change.…”

“…Lastly a regional study in northern Nunavut (Canada) used the full time series of Landsat to generate annual maps of the nominal surface water extent. These maps were converted to polygons and used to generate a trend in areal extent for each water body (Carroll and Loboda 2017). Unlike the methods from Carroll and Loboda 2017 and Pekel et al 2016, the method from Nitze et al 2017 produces a single output map that shows the classification with change as a class rather than annual maps that are used in a secondary analysis for change.…”

“…In this paper we use an existing surface water change map (Carroll and Loboda 2017) to explore potential Figure 1. Study region in northern Canada, Nunavut territory where multi-decadal trends in surface water extent have been established (Carroll and Loboda 2017). Water bodies in the region show opposite trends of surface water extent.…”

Surface Water Dynamics in the North America Arctic Based on 2000–2016 Landsat Data

“…Images of satellite sensing have been applied extensively to analyze the changes of surface water in the Arctic from the local scale [1][2][3][4][5]. Smith et al [3] reported that lakes in Siberia are disappearing.…”