Tree-ring dates on two pre-Little Ice Age advances in Glacier Bay National Park and Preserve, Alaska, USA

Abstract

Two interstadial tree ring-width chronologies from Geikie Inlet, Glacier Bay Southeast, Alaska were built from 40 logs. One of these chronologies has been calendar dated to AD 224–999 (775 yr) crossdating with a living ring-width chronology from Prince William Sound, Alaska. Trees in this chronology were likely killed through inundation by sediments and meltwater from the advancing Geikie Glacier and its tributaries ca. AD 850. The earlier tree-ring chronology spans 545 yr and is a floating ring-width series tied to radiocarbon ages of about 3000 cal yr BP. This tree-ring work indicates two intervals of glacial expansion by the Geikie Glacier system toward the main trunk glacier in Glacier Bay between 3400 and 3000 cal yr BP and again about AD 850. The timing of both expansions is consistent with patterns of ice advance at tidewater glaciers in other parts of Alaska and British Columbia about the same time, and with a relative sea-level history from just outside Glacier Bay in Icy Strait. This emerging tree-ring dated history builds on previous radiocarbon-based glacial histories and is the first study to use tree-ring dating to assign calendar dates to glacial activity for Glacier Bay.

Testing the consistency between changes in simulated climate and Alpine glacier length over the past millennium

“…The modern observations can be complemented by historical sources including old maps, painting, drawing and early photographs as well as written documents (Grove, 2004;Nussbaumer and Zumbühl, 2012;Purdie et al, 2014;Zumbühl and Nussbaumer, 2018). Additional evidence is obtained by dating the position of moraines indicating the position of the glacier at specific times or from the trees that have been overridden by the advance of a glacier (Masiokas et al, 2009;Ivy-Ochs et al, 2009;Wiles et al, 2011;Schimmelpfennig et al, 2014;Le Roy et al, 2015;Moran et al, 2017).…”

Tree Ring—Dated Glacial History for the First Millennium c.e., Casement Glacier and Adams Inlet, Glacier Bay, Alaska, U.S.A.

“…Dating was done visually and supported and checked statistically using the CO-FECHA routine (Holmes, 1983;Grissino-Mayer, 2001) to produce floating chronologies. These floating series were then compared with calendar-dated ring-width records from across the Gulf of Alaska (Barclay et al, 2009a(Barclay et al, , 2013Wiles et al, 2008Wiles et al, , 2011 that, combined, begin in 114 c.e. The dating among floating chronologies from the first millennium c.e.…”

“…. During the Holocene, ice advanced and retreated several times in both the East and West Arms; closely following retreats, forest regrowth occurred, from which interstadial stumps and logs were often preserved by subsequent ice expansions (Muir, 1895;Cooper, 1937;Goldthwait, 1963Goldthwait, , 1966Haselton, 1966;McKenzie and Goldthwait, 1971;Lawson et al, 2007;Connor et al, 2009;Wiles et al, 2011).…”

“…This work is part of an ongoing project building the tree-ring record for a portion of the Holocene (Lawson et al, 2007;Capps et al, 2011;Wiles et al, 2011). To date, tree rings have been used to calendar-date Little Ice Age advances at Brady Glacier and two pre-LIA advances in the Geikie Glacier drainage (Fig.…”

“…These records and this present study allow for comparisons of glacier histories across the Gulf of Alaska. The calendar-dated landterminating glacial histories based on dendrochronology from the Gulf of Alaska (Barclay et al, 2013;Wiles et al, 2011) can also be used to infer times of cooling based on glacier expansion, and thereby help to identify potential climate forcings.…”