Dendroglaciological investigations of mid- to late-Holocene glacial activity in the Mt. Waddington area, British Columbia Coast Mountains, Canada

Abstract

Dendroglaciological investigations near Mt. Waddington in the central British Columbia Coast Mountains provide an enhanced perspective of Holocene glacial activity. Field investigations at Confederation, Franklin, and Jambeau glaciers led to the discovery of subfossil wood mats encased in glacial deposits and glacially sheared stumps buried beneath till. Radiocarbon-dated wood collected from valley-bottom and lateral moraine sites at Confederation Glacier suggest that an early-Holocene advance occurred at c. 5665 cal. yr BP, followed by succeeding intervals of glacier expansion at c. 3700 and 3500 cal. yr BP. At Jambeau Glacier detrital wood mats buried close to the contemporary lateral moraine crests document glacier expansion at c. 3000 cal. yr BP. Detrital subfossil wood buried in lateral moraines at the confluence of Confederation and Franklin glaciers records distinct episodes of 'Little Ice Age' glacier expansion as early as c. 1212 cal. yr ad, and suggests the glacier surface continued to thicken until at least c. 1330-1410 cal. yr ad. An interval of downwasting and retreat followed, before late 'Little Ice Age' advances such as those at Jambeau Glacier were overwhelming valley-bottom forests by c. 1740 cal. yr ad. With the exception of the previously unrecognized advance of Confederation Glacier at c. 3700 cal. yr BP, our dendroglaciological findings corroborate the emerging record of Holocene glacier activity in the British Columbia Coast Mountains.

Holocene glacier fluctuations

“…The 8 ka advance corresponds to the 8.2 ka event and is consistent with chironomid records from western Canada (Chase et al, 2008;Bunbury and Gajewski, 2009). An update of glacial histories include the papers by Osborn et al (2012), Hoffman and Smith (2013), Clague et al (2010), Coulthard et al (2013), Harvey et al (2012), Koch and Clague (2011), and Koehler and Smith (2011). These studies have recognized an additional period of ice expansion in the Mount Waddington area at 5.8 ka, consistent with other proxy records from palynology, from a marine core along the coast (Galloway et al, 2011) and interior records from lakes (Gavin et al, 2011) that all show decreased summer temperatures.…”

A 4000-year record of hydrologic variability from the Olympic Mountains, Washington, USA

“…In contrast to the MCA, the LIA brought cooler temps and possibly wetter conditions to the Pacific Northwest, and was also a time marked by a low degree of fire disturbance (e.g. Coulthard et al, 2013; Gavin and Brubaker, 2015; Lewis and Smith, 2004; Lucas and Lacourse, 2013; Mann et al, 2009). Just as increased fire disturbance may have increased sediment availability during the MCA, decreased fire may have led to the opposite effect during the LIA and may partly explain the dip in grain size and extreme storm events between 300 and 400 years ago.…”

Glacier fluctuations during the past 2000 years

“…Evidence for glacier advances during the first millennium CE is widespread in the western Cordillera of North America outside of Alaska (Luckman, 2000;Reyes and Clague, 2004;Allen and Smith, 2007;Koch et al, 2007a;Jackson et al, 2008;Menounos et al, 2009;Clague et al, 2010;Samolczyk et al, 2010;Bowerman and Clark, 2011;Craig et al, 2011;Johnson and Smith, 2012;Maurer et al, 2012;Coulthard et al, 2012;Munro et al, 2012;Osborn et al, 2012;Craig and Smith, 2013;Hoffman and Smith, 2013;Mood and Smith, 2015), but glacier extent generally appears to have been smaller than during advances of the past millennium. Some glaciers were likely smaller before CE 500 than in the late 20 th century (Allen and Smith, 2007;Clague et al, 2010), even though other glaciers seem to have advanced during that same period (Jackson et al, 2008;Samolczyk et al, 2010;Maurer et al, 2012;Osborn et al, 2012;Hoffman and Smith, 2013).…”