Distribution and biophysical processes of beaded streams in Arctic permafrost landscapes

Abstract

Abstract. Beaded streams are widespread in permafrost regions and are considered a common thermokarst landform. However, little is known about their distribution, how and under what conditions they form, and how their intriguing morphology translates to ecosystem functions and habitat. Here we report on a circum-Arctic survey of beaded streams and a watershed-scale analysis in northern Alaska using remote sensing and field studies. We mapped over 400 channel networks with beaded morphology throughout the continuous permafrost zone of northern Alaska, Canada, and Russia and found the highest abundance associated with medium to high ground-ice content permafrost in moderately sloping terrain. In one Arctic coastal plain watershed, beaded streams accounted for half of the drainage density, occurring primarily as low-order channels initiating from lakes and drained lake basins. Beaded streams predictably transition to alluvial channels with increasing drainage area and decreasing channel slope, although this transition is modified by local controls on water and sediment delivery. The comparisons of one beaded channel using repeat photography between 1948 and 2013 indicate a relatively stable landform, and 14 C dating of basal sediments suggest channel formation may be as early as the Pleistocene-Holocene transition. Contemporary processes, such as deep snow accumulation in riparian zones, effectively insulate channel ice and allows for perennial liquid water below most beaded stream pools. Because of this, mean annual temperatures in pool beds are greater than 2 • C, leading to the development of perennial thaw bulbs or taliks underlying these thermokarst features that range from 0.7 to 1.6 m. In the summer, some pools thermally stratify, which reduces permafrost thaw and maintains cold-water habitats. Snowmelt-generated peak flows decrease rapidly by two or more orders of magnitude to summer low flows with slow reach-scale velocity distributions ranging from 0.01 to 0.1 m s −1 , yet channel runs still move water rapidly between pools. The repeating spatial pattern associated with beaded stream morphology and hydrological dynamics may provide abundant and optimal foraging habitat for fish. Beaded streams may create important ecosystem functions and habitat in many permafrost landscapes and their distribution and dynamics are only beginning to be recognized in Arctic research.

Seasonal cues of Arctic grayling movement in a small Arctic stream: the importance of surface water connectivity

“…Though lacking gravel substrates, Crea Creek, like many other shallow beaded streams, warms rapidly after ice break-up and may provide the earliest spawning opportunities for Arctic grayling which generally begin spawning as temperatures reach 4°C (Northcote 1995). Furthermore, the unique physical aspects of beaded streams, which often include headwater and flow-through lakes, may provide thermal complexity and favorable growing conditions for young grayling (Luecke and MacKinnon 2008;Arp et al 2015). Though beaded streams are generally not regarded as spawning habitat, our results suggest this notion should be re-evaluated.…”

“…Adults and juveniles forage on terrestrial and aquatic invertebrates and smaller fish until winter approaches and fish initiate migration back to winter refugia (Morris 2003). Foraging success during this short (~4 month) period is important for acquiring adequate energy reserves to survive the following winter , and recent research indicates that forage-rich beaded stream habitats (Arp et al 2015) may be commonly used by Arctic grayling for this purpose.…”

“…However, there is a little understanding of these relationships in the Arctic, and furthermore the patterns of seasonal use of beaded stream habitats remains poorly understood. As beaded streams are a widespread and abundant stream type throughout Arctic Alaska and Russia (Arp et al 2015), understanding their ecological role is widely important.…”

Routes of Evolutionary Geography

“…Они широко распространены в верхних звеньях флювиальной сети на равнинах и низменностях криолитозоны и занимают до 50% длины русловой сети речных бассейнов (Arp, 2015).…”

“…Большинство исследователей тундры связывают образование четковидных русел с термокарстом -вытаиванием льда в узлах решетки полигональных трещин (Hopkins, 1955;Arp, 2015;Термоэрозия…, 1982), которое приводит к образованию глубоких (до 3-3,5 м) озеровидных расширений в русле. Действительно, наибольшая протяженность четковидных русел наблюдается в районах распространения высоко-и среднельдистых многолетнемерзлых пород, они часто приурочены к местам развития полигонально-жильных льдов, озеровидные расширения таких русел имеют ритмичное расположение, а их предельные размеры (до 50 м) соответствуют предельным размерам мерзлотных полигонов (Hopkins, 1955;Arp et all., 2015).…”