Timing and Potential Causes of 19th-Century Glacier Advances in Coastal Alaska Based on Tree-Ring Dating and Historical Accounts

Abstract

The Little Ice Age (LIA), ca. CE 1250-1850, was a cold period of global extent, with the nature and timing of reduced temperatures varying by region. The Gulf of Alaska (GOA) is a key location to study the climatic drivers of glacier fluctuations during the LIA because dendrochronological techniques can provide precise ages of ice advances and retreats. Here, we use dendrochronology to date the most recent advance of La Perouse Glacier in the Fairweather Range of Southeast Alaska. After maintaining a relatively contracted state since at least CE 1200, La Perouse advanced to its maximum LIA position between CE 1850 and 1895. Like many other glaciers bordering the GOA, the La Perouse Glacier reached this maximum position relatively late in the LIA compared with glaciers in other regions. This is curious because reconstructions of paleoclimate in the GOA region indicate the 19th century was not the coldest period of the LIA. Using newly available paleoclimate data, we hypothesize that a combination of moderately cool summers accompanying the Dalton Solar Minimum and exceptionally snowy winters associated with a strengthened Aleutian Low could have caused these relatively late LIA advances. Such a scenario implies that winter climate processes, which are heavily influenced by ocean-atmospheric variability in the North Pacific region, have modulated these coastal glaciers' sensitivity to shifts in summer temperatures.

Historical Landscape Use of Migratory Caribou: New Insights From Old Antlers

“…While antler 87 Sr/ 86 Sr for the Central and Eastern Coastal Plain portrays a degree of ecological consistency across relatively recent history, antique antlers (grown prior to 1900 CE) from this region have comparatively small 87 Sr/ 86 Sr (Figures 4, 6 stars). Our small datasets preclude a full evaluation, but there are two potential reasons why antique Central and Eastern Coastal Plain antlers could have small 87 Sr/ 86 Sr: (1) diagenetic alternation, or (2) different patterns of landscape use during the Little Ice Age (1250 to as late as 1900 CE; Solomina et al, 2015;Gaglioti et al, 2019).…”

Late Pleistocene and early Holocene sea-level history and glacial retreat interpreted from shell-bearing marine deposits of southeastern Alaska, USA

“…Today, within the bounds of the study area, spanning the United States and Canadian Coast Range, the Tongass National Forest, and Glacier Bay National Park, glaciers cover >28,000 km 2 (RGI Consortium, 2017). Baranof Island, in the western portion of the archipelago, hosts small glaciers that are likely remnants of Little Ice Age (1250-1850 CE) glacial advance (Gaglioti et al, 2019). Many areas throughout southeastern Alaska are still rebounding as the result of post-Little Ice Age melting, with uplift rates varying from 10 to 32 mm yr −1 (Larsen et al, 2004(Larsen et al, , 2005.…”

Is the modern-day dieback of yellow-cedar unprecedented?

“…Previous cross-dating of these trees indicates that they were overrun by outwash gravels D r a f t aggrading in front of the advancing La Perouse Glacier ca. CE 1862 (Gaglioti et al 2019a). Wood and sometimes bark are well-preserved in this ghost forest, which allows tree identification to the genus level.…”

“…The US Forest Service has been responsible for mapping YC dieback in the last 35 years, and, using these field observations, they now consider the La Perouse forests as the northernmost known YC stand exhibiting evidence of past dieback (Fig. 1a, 3b-c (Gaglioti et al, 2019a). Note person in bottom right for scale.…”