Expansion of alpine glaciers in Pacific North America in the first millennium A.D.

Abstract

Radiocarbon ages and lichen-dated moraines from 17 glaciers in coastal and nearcoastal British Columbia and Alaska document a widespread glacier advance during the first millennium A.D. Glaciers at several sites began advancing ca. A.D. 200-300 based on radiocarbon-dated overridden forests. The advance is centered on A.D. 400-700, when glaciers along an ϳ2000 km transect of the Pacific North American cordillera overrode forests, impounded lakes, and deposited moraines. The synchroneity of this glacier advance and inferred cooling over a large area suggest a regional climate forcing and, together with other proxy evidence for late Holocene environmental change during the Medieval Warm Period and Little Ice Age, provide support for millennial-scale climate variability in the North Pacific region.

Late nineteenth to early twenty-first century behavior of Alaskan glaciers as indicators of changing regional climate

“…A study of 17 coastal and near-coastal Alaskan and British Columbian glaciers (Reyes et al, 2006) documents a widespread glacier advance during the first millennium A.D. Glaciers at several sites began advancing about 200 A.D.-300 A.D., based on radiocarbon-dated overridden forests. They report that the advance was centered on 400 A.D.-700 A.D., when glaciers along a 2000 km transect of the Pacific North American cordillera overrode forests, impounded lakes, and deposited moraines.…”

Holocene climate inferred from glacier extent, lake sediment and tree rings at Goat Lake, Kenai Mountains, Alaska, USA

“…On the other hand, the inferred warmer temperature during medieval times (Calkin et al, 2001;Wiles and Calkin, 1994;Wiles et al, 2008) is not apparent in the Goat Lake productivity signal. Nor does Goat Lake sediment document the well-known cooling and glacier advance during the first millennium AD, centred around AD 600 (Reyes et al, 2006). It does, however, demonstrate that the NGG reached its Holocene maximum extent in the 17th century, late during the LIA.…”

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

“…This is due, in part, because the evidence for it was generally destroyed or obscured by the more extensive, subsequent LIA advances. A summary of radiocarbon-dated glacier expansions by Reyes et al (2006) and Wiles et al (2004Wiles et al ( , 2008 and, more recently, tree-ring dates Barclay et al, 2013) document widespread advance of glaciers across coastal and near-coastal British Columbia and Alaska during the first millennium c.e. These glacier advances have been attributed to a general cooling and multidecadal periods of low solar activity (Solomina et al, 2015).…”