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We compile new and previously published lichenometric and cosmogenic 10Be moraine ages to summarize the timing of Holocene glacier expansions in the Brooks Range, Arctic Alaska. Foundational lichenometric studies suggested that glaciers likely grew to their Holocene maxima as early as the middle Holocene, followed by several episodes of moraine building prior to, and throughout, the last millennium. Previously published 10Be ages on Holocene moraine boulders from the north-central Brooks Range constrain the culmination of maximum Holocene glacier advances between 4.6 ka and 2.6 ka. New 10Be ages of moraine boulders from two different valleys in the central Brooks Range published here show that maximum Holocene glacial extents in these valleys were reached by 3.5 ka and ca. 2.6 ka, supporting previous studies showing that Holocene maximum, or near-maximum, glacial extents in the Brooks Range occurred prior to the Little Ice Age. However, in-depth reconciliations between glacier extent and local an...

Mani walls, Buddhist sacred walls constructed of carved blocks, are common in Langtang Valley, Nepal Himalaya. Fieldwork in 2009–2015 documented all 80 mani walls, including all occurrences of the lichen Rhizocarpon geographicum. According to local informants, the mani walls were constructed 400–600 years ago, and the original mani wall was in the village of Ghoratabela. Based on the indirect method, the oldest lichen on a mani wall dated only to 1942, which, within modeling error, was concurrent with the 1934 earthquake, the last major earthquake in Nepal prior to the Gorkha earthquake of 25 April 2015. In November 2015 it was found that 15% of mani walls could not be located and 20% were severely damaged. The original mani wall had apparently been reconstructed 170 m from its previous location. In two severely damaged and three fully intact mani walls, large lichens (12–49 mm) with unhealthy appearance were found that were not previously present. The most likely explanation was that the three i...

Buddhist sacred walls, called mani walls, are common between Langtang Village and Kyanjin Gompa in Langtang Valley, Nepal Himalaya. The objective of this study was to interview local informants about the mani wall traditions and to use lichenometry to resolve discrepancies regarding the maintenance of the mani walls. The maximum diameters of the lichen Rhizocarpon geographicum were measured on each of 24 mani walls. An apparent lichen growth curve was developed using five sources of indirect data, including the foundation of one stupa (sacred monument) and two locations of former ice cover, for which ages were obtained from local informants, and two debris ridges that had been dated by 10Be. The direct method was pursued by measuring the maximum diameters of 20 lichens in remote locations in both 2009 and 2014. Based on the indirect method, the mani walls are cleaned on a geometric mean cycle time of 13 years. The direct and indirect methods yield equivalent ages when the minimum direct growth ra...

Directly measured growth rates of two lichens (Pseudephebe minuscula and Rhizocarpon sections Rhizocarpon and Superficiale) from Svalbard made over a two-decade interval (1984–2007) are presented. Growth rates were determined by measuring the change in area of the lichen thalli from digital images and converting area to diameter. Pseudephebe diameter growth rates ranged from 0.2 to 1.5 mm yr−1 and Rhizocarpon grew 0.05 to 0.30 mm yr−1. Growth rates of both are a function of thalli size—growth rates increase with increasing thallus size up to 70 mm diameter for Pseudephebe and 30 mm diameter for Rhizocarpon. While these directly measured growth rate results are consistent with other recent directly measured lichen growth studies, they are not consistent with indirectly determined age-size curves that show a negative correlation between size and growth rate (i.e., rapid “great growth” followed by slower “linear growth”). We explore several reasons to explain the apparent discrepancy between directl...

We mapped Little Ice Age (LIA) moraines in the Brooks Range to estimate former equilibrium-line altitudes (ELAs), and combined this information with available proxy temperature estimates to infer precipitation trends because little is known about precipitation changes associated with centennial-scale climate variability in the Arctic during the late Holocene. The Brooks Range, northern Alaska (68°N), hosts hundreds of extant glaciers that exhibit geomorphic evidence for multiple fluctuations in ice extent during the past millennium. Our lichenometric age estimates for LIA moraines in the forefields of five cirque glaciers in the Sagavinerktok River valley and Oolah Valley suggest two intervals of LIA moraine formation centered around a.d. 1250 and 1650. The outermost LIA moraine was mapped on aerial photographs for 114 relatively large (1.2 ± 0.5 km) and geographically simple glaciers along a 700-km-long transect following the range crest. At their maximum extent during the LIA, these glaciers we...

A complex sequence of sawtooth moraines occurs on the proglacial foreland at Lambatungnajokull, southeast Iceland. These features reflect the pattern of deglaciation of a highly crevassed ice margin. The whole sequence documents a period of overall glacier recession exceeding 450 m. Dates have been interpolated for the formation of these moraines through the examination of aerial photographs and the application of lichenometry. The moraines formed annually between AD ∼1932 and 1950. Retreat rates were greatest between 1933 and 1939 and slowest between 1942 and 1944, as reflected by the spacing of annual moraine ridges. Differences in glacier recession rate from year to year are related to variations in mean summer air temperature. A rise in mean summer temperature of 1°C results in a retreat rate of ∼30 m yr−1. It is shown that annual moraine spacings are a suitable geomorphological proxy for annual net glacier balance and a potentially valuable source of paleoclimatic information.

A selective review of lichenometry as used to date Holocene moraines in five diverse regions of Alaska and in southeastern Kamchatka suggests that growth curves for this North Pacific area may be improved by attention to several factors. These included lichen identification, control point number and distribution, radiocarbon calibration, alternative curve models, and compatibility of lichen growth rate with climate. Support for control points presented for Kamchatka and published for Alaska areas will benefit from supplementary control at and beyond the break from the great growth curve segments of the last centuries. With regard to alternative—linear, logarithmic, and composite curve—models drawn for the published lichenometric data, the composite (logarithmic and linear composite models) appear the best fit for the Brooks Range and Wrangell–St. Elias areas of slow growth and continental interior climates. Calibration of 14C ages make minor changes in well-controlled curves, but differences may ...

This paper presents the results of a lichenometric and dendrochronological study of the recent retreat history of Glaciar Nef, an eastern outlet glacier of the Hielo Patag6nico Norte. A 600-yr tree regeneration time, based on maximum tree age in the ancient forest, suggests that the forest-clad lateral moraines in the valley, southeast of the 19th century terminal moraine system, were formed some time before A.D. 1370. Dating estimates suggest that retreat from a 19th century maximum began around 1863, a decade or two earlier than the date established for other glaciers in the region, with glacier thinning near the ice front averaging 1.11 m yr- between 1863-1881. After 1884, retreat seems to have slowed, with glacier thinning averaging 0.09 m yr-~. Lichen and tree dating suggests that the glacier had retreated approximately 500 m by 1938; this estimate is supported by an aerial photograph showing a proglacial lake just beginning to form in 1944. Recent glacier movements around the Hielo Patagonico Norte are discussed and it is concluded that the general trend of glacier retreat around the icefield, beginning in the 1860s to 1870s, is consistent with Northern Hemisphere trends.

Image analysis software was used to obtain various measures of thalli in crustose lichen communities. Lichens growing on flat-faced quartzite boulders in two glacier forefields were photographed an...

Dendrochronology, lichenometry, and analysis of aerial photographs taken in 1944, 1979, and 1983 were used to date the 19th- and 20th-century fluctuations of the Arco, Colonia, and Arenales glacier...