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The dominant landscape process on the Arctic Coastal Plain of northern Alaska is the formation and drainage of thaw lakes. Lakes and drained thaw-lake basins account for approximately 75% of the modern surface expression of the Barrow Peninsula. The thaw-lake cycle usually obliterates lacustrine or peat sediments from previous cycles, which could otherwise be used for paleoecological reconstruction of long-term landscape and vegetation changes. Several possible erosional remnants of a former topographic surface that predates the formation of the thaw lakes have been tentatively identified. These remnants are characterized by a higher elevation, a thick organic layer with very high ground ice content in the upper permafrost and a plant community somewhat atypical of the region. Ten soil cores were collected from one site, and one core was intensively sampled for soil organic carbon content, pollen analysis and 14C dating. The lowest level of the organic sediments represents the earliest phase of plant growth and dates to ca. 9000 cal BP. Palynological evidence indicates the presence of mesic shrub tundra (including sedge, birch, willow and heath vegetation), and microfossil indicators point to wetter eutrophic conditions during this period. Carbon accumulation was rapid due to high net primary productivity in a relatively nutrient-rich environment. These results are interpreted as the local response to ameliorating climate during the early Holocene. The middle Holocene portion of the record contains an unconformity, indicating that between 8200 and 4200 cal BP sediments were eroded from the site, presumably in response to wind activity during a drier period centered around 4500 cal BP. The modern vegetation community of the erosional remnant was established after 4200 cal BP and peat growth resumed. During the late Holocene, carbon accumulation rates (CARs) were greatly reduced in response to the combined effects of declining productivity associated with climatic cooling, and increased nutrient stress as paludification and permafrost aggradation sequestered mineral nutrients.

Thaw lakes and drained thaw lake basins are ubiquitous on the Arctic Coastal Plain of Alaska. Basins are wet depositional environments, ideally suited for the accumulation and preservation of organic material. Much of this soil organic carbon (SOC) is currently sequestered in the near-surface permafrost but, under a warming scenario, could become mobilized. The relative age of 77 basins on the Barrow Peninsula was estimated using the degree of plant community succession and verified by radiocarbon-dating material collected from the base of the organic layer in 21 basins. Using Landsat-7+ imagery of the region, a neural network classifying algorithm was developed from basin age-dependent spectra and texture. About 22% of the region is covered by 592 lakes (>1 ha), and at least 50% of the land surface is covered by 558 drained lake basins. Analysis of cores collected from basins indicates that (1) organic layer thickness and the degree of organic matter decomposition generally increases with basin ...

Modern and fossil pollen analyses have established the local vegetation succession and landscape evolution along the Meade River near Atqasuk, Alaska. Three data sets were analyzed: (1) a 142-cm-long peat deposit on the exposed river bluff face, (2) a short, 13-cm peat monolith from the near-surface sediment, and (3) a modern data set of surface samples collected along a transect representative of a geomorphic gradient of low-center, transitional, and high-center polygons. Pollen-microfossil assemblages changed significantly along this gradient. Detailed analysis of the short pollen profile shows successional vegetation changes over the last 250 years. The long profile, a 9400-year record of past vegetation, indicates that initially, the site was covered by shallow lakes. Eolian activity had a substantial effect on sediment deposition, but a period of rapid peat growth from 8500 to 5000 14C year B.P. is coincident with increased vegetation cover of mixed grass-shrub tundra. Following this period, peat growth slowed, and shrub vegetation was replaced by tussock-forming sedge vegetation.

A group of ice‐cored frost mounds formed during the winter of 1995–1996 near Barrow, Alaska in a drained thaw‐lake basin. Over 20 mounds, ranging from 5 to 20 m across, were observed in mid‐August ...