Dan J. Smith

Interdecadal climate variability and regime‐scale shifts in Pacific North America

A transect of climate sensitive tree ring-width chronologies from coastal western North America provides a useful proxy index of North Pacic ocean-atmosphere variability since 1600 AD. Here we use this high-resolution record to identify intervals of an enhanced interdecadal cli- mate signal in the North Pacic, and to assess the timing and magnitude of abrupt shifts in this system. In the con- textofthisrecord,thestep-likeclimateshiftthatoccurredin 1976-1977 is not a unique event, with similar events having occurredfrequentlyduringthepast400years. Furthermore, most of the pre-instrumental portion of this record is char- acterized by pronounced interdecadal variability, while the secularportionismorestronglyinterannualinnature. Ifthe 1976-1977 event marks a return to this mode of variability there may be signicant consequences for natural resources management in the North Pacic Sector.

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

Radiocarbon ages and lichen-dated moraines from 17 glaciers in coastal and near- coastal 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 ;2000 km transect of the Pacific North American cordillera overrode forests, impounded lakes, and deposited moraines. The synchroneity of this glacier ad- vance and inferred cooling over a large area suggest a regional climate forcing and, to- gether with other proxy evidence for late Holocene environmental change during the Me- dieval Warm Period and Little Ice Age, provide support for millennial-scale climate variability in the North Pacific region.

Dendrochronological Mass Balance Reconstruction, Strathcona Provincial Park, Vancouver Island, British Columbia, Canada

Abstract A long-term proxy record of glacier mass balance was developed for Colonel Foster and Septimus glaciers on Vancouver Island, British Columbia, Canada. This was accomplished by analyzing the radial growth characteristics of climatically-sensitive mountain hemlock trees (Tsuga mertensiana), and by comparing this response with mass balance records from four glaciers in the Pacific Northwest. A strong (negative) relationship between the two records for the period 1966–1994 provides the basis for a mass balance reconstruction extending back to 1600. The reconstruction is in general agreement with information derived from dated moraine sequences at the two glaciers on Vancouver Island, and it has potential applicability to glaciers in adjacent areas of coastal Pacific North America. Our results highlight the likely influence of the Pacific Decadal Oscillation (PDO) on glacier dynamics during the mid- to late-Little Ice Age (LIA) and provide the groundwork for long-term glaciohydrologic studies.

Dendroglaciological Evidence For A Neoglacial Advance Of the Saskatchewan Glacier, Banff National Park, Canadian Rocky Mountains

Seventeen glacially sheared stumps in growth position and abundant detrital wood fragments were exposed by stream avulsion at the terminus of the Saskatchewan Glacier in 1999. The stumps lay buried beneath the glacier and over 5 m of glacial sediment until historical recession and stream incision exposed the 225- to 262-year-old stand of subalpine fir, Englemann spruce and whitebark pine trees. Crossdating and construction of two radiocarbon-controlled floating tree-ring chronologies showed that all the subfossil stumps and boles exposed at this location were killed during a Neoglacial advance of the Saskatchewan Glacier 2,910 ±60 to 2,730 ±60 14C years B.P. These findings support the Peyto Advance as a regional glaciological response to changing mass balance conditions.

Snow-avalanche impact pools in the Canadian Rocky Mountains

Snow-avalanche impact pits (Corner, 1980) are large circular to semicircular erosional hollows located at the foot of long, steep avalanche slopes (e.g., Fitzharris and Owens, 1984; Nyberg, 1985). They are especially conspicuous where they intercept the local water table and are transformed into water-filled pools (e.g., Davis, 1962; Liest0l, 1974). Most avalanche pit/pool sites are bordered by arcuate debris accumulations up to several meters in height on the downpath side (e.g., Schytt, 1965; Corner, 1980). These deposits consist of rock, soil, and organic debris that is almost certainly the product of avalanche-induced transportation (Peev, 1966; Ballantyne, 1989; Luckman et al., 1994) although some authors have suggested a protalus (Fitzharris and Owens, 1984) or even meteoritic origin (Corer, 1975, 1980). Avalanche impact landforms have received scant attention in the North American cordillera (Luckman, 1977), and no detailed studies have been reported from Canada. This paper describes the morphology and recent history of three avalanche impact pools in the Canadian Rocky Mountains. Observations of the geomorphic effects of avalanche impact are presented for each site and the origin of these features discussed with respect to the magnitude/frequency of the events responsible for their formation.

Radial-growth forecasts for five high-elevation conifer species on Vancouver Island, British Columbia

Biologically-based deterministic multiple regression models are developed to investigate the consequences of future climates on the radial-growth response of five high-elevation conifer species on Vancouver Island. Historical climate data and tree-ring chronologies are used to establish robust relationships between climate and radial growth. Coupled general circulation modeled (CGCM) outputs are then used to provide monthly predictions of future climates from 2000 to 2100 A.D. The established historical relationships are projected into the future using the CGCM data to predict radial growth. Results indicate that each species will react individually to predicted changes in climate, with no one dominant radial-growth trend established. The most radical changes in the radial-growth behavior occur within mountain hemlock (Tsuga mertensiana) trees that have adapted to survive in deep snowpack environments, a condition that future predictions highlight as the most susceptible to change. # 2003 Elsevier Science B.V. All rights reserved.

Frost-heave activity in the Mount Rae area, Canadian Rocky Mountains.

The activity of frost-heaving processes is described for two alpine sites in the Front Range of the Canadian Rocky Mountains over the period 1980 to 1983. The two sites recording frostheave frames demonstrated heaving resulting from both diurnal and seasonal mechanisms. Diurnal heaving was related to the nocturnal growth of needle ice and resulted in an average heave of 10 mm. Averaging only 20 events per year, its geomorphic significance appeared limited. Seasonal heaving resulted in between 23 to 45 mm yr-1 of surface displacement. These relatively low values appear to correspond to limited soil moisture in the fall freeze-up period. Comparison of the magnitude of potential downslope creep generated by seasonal heaving with the actual amount of mass wasting at 120 points revealed that actual frost creep was less than 36 to 630%7o of the computed values.

Dendrogeomorphological assessment of movement at Hilda rock glacier, Banff National Park, Canadian Rocky Mountains

Abstract The results of this dendrogeomorphological study provide evidence of the active movement of Hilda rock glacier, a tongue‐shaped rock glacier in the Columbia Icefield region of Banff National Park. Cross‐sectional samples were cut from 44 detrital subalpine fir (Abies Iasiocarpa (Hook.) Nutt.) and Engelmann spruce (Picea engelmannii Parry) boles killed and buried by debris spilling off the steep distal slope of the rock glacier. The samples were crossdated using locally and regionally developed tree‐ring chronologies, and were shown to have been killed between 1576 and 1999. Our results show that Hilda rock glacier has advanced at an average rate of 1.6 cm/year since the late 1790s, with limited evidence of similar rates of activity extending back to the mid‐1570s. This rock glacier activity is believed to be linked to persistent periglacial processes that appear to be independent of the climatic forcing mechanisms known to influence glacier mass balances over the same interval.

GEOMORPHIC EFFECTS OF GROUND SQUIRRELS IN THE MOUNT RAE AREA, CANADIAN ROCKY MOUNTAINS

The geomorphic effects of ground squirrels (Spermophilus columbianus c.) are described for two study plots in the Front Ranges of the Canadian Rocky Mountains over the period 1977 to 1980. At the two plots, the average rates of sediment transport to the ground surface were 1.36 and 1.12 t ha-1 yr-1. These values are considerably less than has been noted in previous studies of burrowing mammals. The geomorphic work conducted by ground squirrels at the study site amounts to 6.587 x 104 J yr-1 km-2 which is several orders of magnitude less than the work done by rockfalls, snow avalanches, solution, streams, and solifluction and soil creep. The indirect geomorphic effects of burrowing (e.g., subsequent transport of sediment raised to the surface) are not examined.

GLACIOLOGICAL STUDIES AT RAE GLACIER, CANADIAN ROCKY MOUNTAINS

Rae Glacier is a small cirque glacier located in the front ranges of the Canadian Rocky Mountains. In 1990 and 1991 field research was completed to describe the physical glaciology of Rae Glacier and to characterize historical glaciological trends at the site. Ablation and surface movement rates were measured using a network of stakes drilled into the glacier and radio-echo sounding was used to describe local ice depths. Rae Glacier has experienced a significant loss in size and mass during the historical period, owing to a lengthy interval of negative mass-balance conditions. The glacier has decreased in surface area by over 50% and now contains less than 24% of the ice it did at the end of the last century. Surface-ice velocity varied between 1.4 and 5.4 m from 1990 to 1991. Rates of ice ablation proved to be highly variable, with steeper areas showing up to 50% more ablation. Combined with data on the emergent flow component of the glacier, the ablation data suggest that the glacier presently is unable...