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Summary: The development of terrestrial ecosystems depends greatly on plant mutualists such as mycorrhizal fungi. The global retreat of glaciers exposes nutrient‐poor substrates in extreme environments and provides a unique opportunity to study early successions of mycorrhizal fungi by assessing their dynamics and drivers.We combined environmental DNA metabarcoding and measurements of local conditions to assess the succession of mycorrhizal communities during soil development in 46 glacier forelands around the globe, testing whether dynamics and drivers differ between mycorrhizal types.Mycorrhizal fungi colonized deglaciated areas very quickly (< 10 yr), with arbuscular mycorrhizal fungi tending to become more diverse through time compared to ectomycorrhizal fungi. Both alpha‐ and beta‐diversity of arbuscular mycorrhizal fungi were significantly related to time since glacier retreat and plant communities, while microclimate and primary productivity were more important for ectomycorrhizal fungi. The richness and composition of mycorrhizal communities were also significantly explained by soil chemistry, highlighting the importance of microhabitat for community dynamics.The acceleration of ice melt and the modifications of microclimate forecasted by climate change scenarios are expected to impact the diversity of mycorrhizal partners. These changes could alter the interactions underlying biotic colonization and belowground–aboveground linkages, with multifaceted impacts on soil development and associated ecological processes. [ABSTRACT FROM AUTHOR]

Large stratovolcanoes in the Cascade Range have high equilibrium-line altitudes that support glaciers whose Holocene and latest Pleistocene advances are amenable to dating. Glacier advances produced datable stratigraphic sequences in lateral moraines, which complement dating of end moraines. New mapping of glacial deposits on Mount Rainier using LIDAR and field observations supports a single latest Pleistocene or early Holocene advance. Rainier R tephra overlies deposits from this advance and could be as old as >11.6 ka; the advance could be of Younger Dryas age. Radiocarbon ages on wood interbedded between tills in the lateral moraines of Nisqually, Carbon, and Emmons glaciers and the South Tahoma glacier forefield suggest glacier advances between 200 and 550 CE, correlative with the First Millennium Advance in western Canada, and during the Little Ice Age (LIA) beginning as early as 1300 CE. These results resolve previous contradictory interpretations of Mount Rainier's glacial history and indicate that the original proposal of a single pre-Neoglacial cirque advance is correct, in contrast to a later interpretation of two advances of pre- and post-Younger Dryas age, respectively. Meanwhile, the occurrence of the pre-LIA Burroughs Mountain Advance, interpreted in previous work as occurring 3–2.5 ka, is questionable based on inherently ambiguous interpretations of tephra distribution. [ABSTRACT FROM AUTHOR]

The worldwide retreat of glaciers is causing a faster than ever increase in ice‐free areas that are leading to the emergence of new ecosystems. Understanding the dynamics of these environments is critical to predicting the consequences of climate change on mountains and at high latitudes. Climatic differences between regions of the world could modulate the emergence of biodiversity and functionality after glacier retreat, yet global tests of this hypothesis are lacking. Nematodes are the most abundant soil animals, with keystone roles in ecosystem functioning, but the lack of global‐scale studies limits our understanding of how the taxonomic and functional diversity of nematodes changes during the colonization of proglacial landscapes. We used environmental DNA metabarcoding to characterize nematode communities of 48 glacier forelands from five continents. We assessed how different facets of biodiversity change with the age of deglaciated terrains and tested the hypothesis that colonization patterns are different across forelands with different climatic conditions. Nematodes colonized ice‐free areas almost immediately. Both taxonomic and functional richness quickly increased over time, but the increase in nematode diversity was modulated by climate, so that colonization started earlier in forelands with mild summer temperatures. Colder forelands initially hosted poor communities, but the colonization rate then accelerated, eventually leveling biodiversity differences between climatic regimes in the long term. Immediately after glacier retreat, communities were dominated by colonizer taxa with short generation time and r‐ecological strategy but community composition shifted through time, with increased frequency of more persister taxa with K‐ecological strategy. These changes mostly occurred through the addition of new traits instead of their replacement during succession. The effects of local climate on nematode colonization led to heterogeneous but predictable patterns around the world that likely affect soil communities and overall ecosystem development. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Since the last glacial maximum, soil formation related to ice‐cover shrinkage has been one major sink of carbon accumulating as soil organic matter (SOM), a phenomenon accelerated by the ongoing global warming. In recently deglacierized forelands, processes of SOM accumulation, including those that control carbon and nitrogen sequestration rates and biogeochemical stability of newly sequestered carbon, remain poorly understood. Here, we investigate the build‐up of SOM during the initial stages (up to 410 years) of topsoil development in 10 glacier forelands distributed on four continents. We test whether the net accumulation of SOM on glacier forelands (i) depends on the time since deglacierization and local climatic conditions (temperature and precipitation); (ii) is accompanied by a decrease in its stability and (iii) is mostly due to an increasing contribution of organic matter from plant origin. We measured total SOM concentration (carbon, nitrogen), its relative hydrogen/oxygen enrichment, stable isotopic (13C, 15N) and carbon functional groups (C‐H, C=O, C=C) compositions, and its distribution in carbon pools of different thermal stability. We show that SOM content increases with time and is faster on forelands experiencing warmer climates. The build‐up of SOM pools shows consistent trends across the studied soil chronosequences. During the first decades of soil development, the low amount of SOM is dominated by a thermally stable carbon pool with a small and highly thermolabile pool. The stability of SOM decreases with soil age at all sites, indicating that SOM storage is dominated by the accumulation of labile SOM during the first centuries of soil development, and suggesting plant carbon inputs to soil (SOM depleted in nitrogen, enriched in hydrogen and in aromatic carbon). Our findings highlight the potential vulnerability of SOM stocks from proglacial areas to decomposition and suggest that their durability largely depends on the relative contribution of carbon inputs from plants. [ABSTRACT FROM AUTHOR]

Some lateral moraines contain a rich record of Holocene glacial expansion. Previous workers have used such evidence to document glacial fluctuations in western Canada, Alaska, and the U.S. Pacific Northwest, but similar studies in Patagonia are uncommon. Here we report on the late Holocene behavior of Stoppani Glacier, a 75 km2 glacier sourced in the Cordillera Darwin, southernmost Patagonia. Based on radiocarbon-dated wood and organic material contained in the glacier's northeast lateral moraine, we infer that Stoppani Glacier advanced shortly before 3.8–3.6, at 3.2–2.8, 2.3–2.1, and 0.3–0.2, and possibly sometime before 1.4–1.3 and 0.8–0.7 cal ka BP. These advances culminated at 0.3–0.2 cal ka BP, when the glacier constructed a prominent end moraine, marking its greatest extent of the past 4000 years. Although the timing of several of the advances overlap with the age range of glacial expansion recognized elsewhere in Patagonia, some do not. Asynchronous behavior observed in the glacial record may arise from the type of evidence (e.g., lateral stratigraphy vs. end moraine) used to document glacial fluctuations or variations in climate or glacial response times. A significant difference between the Stoppani record and some other Patagonian records is that the former indicates general expansion of ice over the last 4000 years, whereas the latter indicate a net decrease in extent over that period. [ABSTRACT FROM AUTHOR]

Two adjacent glaciers in the Chugach Mountains of south-central Alaska have markedly different histories on decadal to perhaps centennial timescales. Sheridan Glacier has advanced and retreated hundreds of metres during the latest Holocene. Its recent fluctuations have markedly altered local base level of Sherman River, which drains Sherman Glacier and flows into Sheridan Lake. Sheridan Glacier advanced to its greatest extent during the Little Ice Age, raising base level of Sherman River and inducing aggradation there of up to 17 m of sediment. Retreat of Sheridan Glacier formed a series of lakes that have coalesced. As lower lake outlets have become available, base level of Sherman River has dropped, resulting in the evacuation of substantial volumes of sediment from Sherman River valley. In about 2000, the terminus of Sheridan Glacier began to disintegrate; retreat accelerated dramatically in 2010. By 2016, the glacier had retreated an average of 600 m from its 2010 terminus, although some areas retreated up to 1.9 km and others did not retreat at all. Meanwhile, Sherman Glacier continued a slow advance initiated by a rock avalanche that blanketed much of its ablation area in the 1964 Alaska earthquake. [ABSTRACT FROM AUTHOR]

In 2010, the south flank of Mount Meager failed catastrophically, generating the largest (53 ± 3.8 × 106 m3) landslide in Canadian history. We document the slow deformation of the edifice prior to failure using archival historic aerial photographs spanning the period 1948-2006. All photos were processed using Structure from Motion (SfM) photogrammetry. We used the SfM products to produce pre-and post-failure geomorphic maps that document changes in the volcanic edifice and Capricorn Glacier at its base. The photographic dataset shows that the Capricorn Glacier re-advanced from a retracted position in the 1980s then rapidly retreated in the lead-up to the 2010 failure. The dataset also documents 60 years of progressive development of faults, toe bulging, and precursory failures in 1998 and 2009. The 2010 collapse was conditioned by glacial retreat and triggered by hot summer weather that caused ice and snow to melt. Meltwater increased pore water pressures in colluvium and fractured rocks at the base of the slope, causing those materials to mobilize, which in turn triggered several secondary failures structurally controlled by lithology and faults. The landslide retrogressed from the base of the slope to near the peak of Mount Meager involving basement rock and the overlying volcanic sequence. Elsewhere on the flanks of Mount Meager, large fractures have developed in recently deglaciated areas, conditioning these slopes for future collapse. Potential failures in these areas have larger volumes than the 2010 landslide. Anticipated atmospheric warming over the next several decades will cause further loss of snow and glacier ice, likely producing additional slope instability. Satellite- and ground-based monitoring of these slopes can provide advanced warning of future landslides to help reduce risk in populated regions downstream. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Our study combines new geological and paleoecological information to reconstruct the glacial history and terrestrial paleoenvironments on Haida Gwaii during the advance phase of the Fraser glaciation (Marine Isotope Stage 2). At Cape Ball on eastern Graham Island, five accelerator mass spectrometry radiocarbon ages ranging from 23,200±280 to 26,650±390 14C yr BP (ca. 27,000–31,400 cal yr BP) record the earliest approach of mainland glaciers to Haida Gwaii. Abundant marine dinoflagellate cysts indicate isostatic depression by glacial ice in Hecate Strait to the east. At Mary Point on the north coast of Graham Island, similar outwash of a piedmont lobe advancing westward along Dixon Entrance preserves plant remains dated from 19,270±360 to 23,740±300 14C yr BP (22,500–28,600 cal yr BP). These sediments also contain marine indicators. Plant macrofossils, pollen, and invertebrates support the geological evidence of a proglacial environment under a colder-than-present macroclimate. Although some trees were likely present on Graham Island at this time, tundra-like plant communities dominated low-lying areas. A large area that appears to have been ice-free during this time is a portion of the continental shelf off the east coast of Moresby Island, referred to provisionally as the “Hecate Refugium.” [ABSTRACT FROM PUBLISHER]

Abstract: Glacier-dammed lakes and their associated jökulhlaups cause severe flooding in downstream areas and substantially influence glacier dynamics. Brady Glacier in southeast Alaska is well suited for a study of these phenomena because it presently dams 10 large (>1km2) lakes. Our objectives are to demonstrate how Brady Glacier and its lakes have co-evolved in the past and to apply this knowledge to predict how the glacier and its lakes will likely evolve in the future. To accomplish these objectives, we georeferenced a variety of maps, airphotos, and optical satellite imagery to characterize the evolution of the glacier and lakes. We also collected bathymetry data and created bathymetric maps of select lakes. Despite small advances and retreats, the main terminus of Brady Glacier has changed little since 1880. However, it downwasted at rates of 2–3m/y between 1948 and 2000, more than the regional average. The most dramatic retreat (2km) and downwasting (120m) have occurred adjacent to glacier-dammed lakes and are primarily the result of calving. Brady Glacier is a former tidewater glacier. With continued downwasting, Brady Glacier may return to a tidewater regime and enter into a phase of catastrophic retreat. The situation at Brady Glacier is not unique, and the lessons learned here can be applied elsewhere to identify future glacier-dammed lakes, jökulhlaups, and glacier instability. [Copyright &y& Elsevier]

Abstract: Most glaciers in western North America with reliable age control achieved their maximum Holocene extents during final advances of the Little Ice Age. Tiedemann Glacier, a large alpine glacier in western Canada, is an enigma because the glacier constructed lateral moraines that are up to 90 m higher, and extend 1.8 km farther downvalley, than those constructed during the Little Ice Age. Our data show that the activity of the glacier is more complex than originally documented and that the glacier advanced many times during the past six thousand years. Surface exposure dating and radiocarbon ages of stumps beneath till demonstrate that the glacier achieved its maximum Holocene extent at about 2.7 ka. We hypothesize that one or more rock avalanches delivered surface debris to the glacier and caused the 2.7 ka glacier advance to be much larger than can be explained by climate forcing. To test our hypothesis, we developed and used a surface debris advection routine coupled to an ice dynamics model. Our results show that even a moderately sized rock avalanche ( ) delivered to the top of the ablation zone could cause the glacier to thicken and advance far beyond its Little Ice Age limit. [Copyright &y& Elsevier]

Glaciers are an important element of the Earth system. Glaciers provide numerous, though poorly appreciated, ecological and economic benefits. However, glacial processes can also be hazards. Local glacial hazards include catastrophic floods from lakes impounded by glaciers and their moraines, landslides and debris flows induced by glacier thinning and retreat and permafrost thaw, and enhanced seismicity and volcanism due to large-scale deglaciation. Regionally, rivers can be affected by changes in sediment supply from glacier forefields. Perhaps the greatest hazard that glaciers pose on a global scale of coastal erosion and flooding caused by sea-level rise. If Earth's climate continues to warm, as scientists forecast, the rate of sea-level rise will increase and some low-lying coastal areas will be flooded by the end of this century. [ABSTRACT FROM AUTHOR]

ABSTRACT Climate change, manifested by an increase in mean, minimum, and maximum temperatures and by more intense rainstorms, is becoming more evident in many regions. An important consequence of these changes may be an increase in landslides in high mountains. More research, however, is necessary to detect changes in landslide magnitude and frequency related to contemporary climate, particularly in alpine regions hosting glaciers, permafrost, and snow. These regions not only are sensitive to changes in both temperature and precipitation, but are also areas in which landslides are ubiquitous even under a stable climate. We analyze a series of catastrophic slope failures that occurred in the mountains of Europe, the Americas, and the Caucasus since the end of the 1990s. We distinguish between rock and ice avalanches, debris flows from de-glaciated areas, and landslides that involve dynamic interactions with glacial and river processes. Analysis of these events indicates several important controls on slope stability in high mountains, including: the non-linear response of firn and ice to warming; three-dimensional warming of subsurface bedrock and its relation to site geology; de-glaciation accompanied by exposure of new sediment; and combined short-term effects of precipitation and temperature. Based on several case studies, we propose that the following mechanisms can significantly alter landslide magnitude and frequency, and thus hazard, under warming conditions: (1) positive feedbacks acting on mass movement processes that after an initial climatic stimulus may evolve independently of climate change; (2) threshold behavior and tipping points in geomorphic systems; (3) storage of sediment and ice involving important lag-time effects. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This article describes and compares the deposits of four large landslides on two glaciers in Alaska using field mapping and remote sensing. Digital image analysis is used to compare the sedimentological characteristics of nearly 200 000 individual surface blocks deposited by three landslides at Black Rapids Glacier in 2002. The debris sheets of one of the three landslides on Black Rapids Glacier and a landslide emplaced on Sherman Glacier in 1964 are also investigated. The three landslides on Black Rapids Glacier have undergone little post-depositional modification by glacier flow, whereas the Sherman Glacier landslide has been transported supraglacially up to ca 1 km over the past 46 years. The three debris sheets on Black Rapids Glacier have coarse blocky rims at their distal edges, and all four debris sheets have longitudinal flowbands characterized by differences in texture and produced by shearing within the moving debris. Elongated blocks are parallel to flow, except at the perimeter of the debris sheets, where they are aligned more perpendicular to flow. Blocks on the Sherman Glacier debris sheet have been reoriented by glacier flow. The matrix shows no systematic differences with depth or distance from the source. However, it appears to become coarser over a time scale of decades due to weathering. [ABSTRACT FROM AUTHOR]

The Medieval Warm Period is an interval of purportedly warm climate during the early part of the past millennium. The duration, areal extent, and even existence of the Medieval Warm Period have been debated; in some areas the climate of this interval appears to have been affected more by changes in precipitation than in temperature. Here, we provide new evidence showing that several glaciers in western North America advanced during Medieval time and that some glaciers achieved extents similar to those at the peak of the Little Ice Age, many hundred years later. The advances cannot be reconciled with a climate similar to that of the twentieth century, which has been argued to be an analog, and likely were the result of increased winter precipitation due to prolonged La Niña-like conditions that, in turn, may be linked to elevated solar activity. Changes in solar output may initiate a response in the tropical Pacific that directly impacts the El Niño/Southern Oscillation and associated North Pacific teleconnections. [ABSTRACT FROM AUTHOR]

We utilized dendrochronology and precise elevation-constrained mapping to date glacially overridden and drowned trees at the margin of Brady Glacier in southeast Alaska. This technique allowed determination of the timing of the former tidewater glacier’s last advance and consequent formation and filling of two marginal lakes. The subfossil tree-ring chronology spans the interval from AD 1370 to 1861. Brady Glacier impounded Spur Lake to an elevation of 83 m a.s.l. around 1830 and 121 m a.s.l. around 1839. Soon after, Spur Lake reached 125 m a.s.l. and began to overflow a stable bedrock sill. The glacier continued to advance, thickening by at least 77 m between c. 1844 and 1859 at a site down-glacier of Spur Lake on the opposite glacier margin. Farther down-glacier, North Trick Lake began to form by 1861 and reached its highest elevation at approximately 130 m a.s.l. when Brady Glacier reached its maximum extent around 1880. Our findings add precision to the chronology of the last advance of Brady Glacier and provide insight into the evolution of glacier-dammed lakes and calving glaciers. [ABSTRACT FROM AUTHOR]

The article discusses a study on identifying and characterizing alpine subglacial lakes dammed by Brady Glacier in Alaska using inteferometric synthetic aperture radar (InSAR). Based on ice-penetrating measurements, the bed of Brady Glacier is at least 200 meters (m) below sea level. Four ascending and six descending European Remote-Sensing Satellite-1/-2 (ERS-1/-2) image pairs of Brady Glacier served as the bases of InSAR measurements. Downstream ice flow is blamed for a distortion in the so-called bull's-eye patterns of the glacier. ERS-1/-2 has reportedly enabled the researchers to isolate vertical displacements over dynamic alpine subglacial lakes.

The article presents a study on the use of the dendroclimatological data in the reconstruction of the discharge history of Chilko River in British Columbia. The study intends to determine the hdyrological influences of the meltwater streams to the downstream flow regimes of tributaries of the Fraser and Homathko rivers which affects Southern British Columbia. The meltwater streams have been viewed important in understanding the climate change and glacier recession.

The article describes a novel differential, repeat-pass interferometric (D-InSAR) process for constructing an accurate digital elevations model (DEM) of a glacier surface and apply it to Black Rapids Glacier, Alaska. The topographic phase from three differential interferograms of Black Rapids Glacier and its surrounding was compared between the 1949 U.S. Geological Survey (USGS) DEM and 1995 European Remote-sensing Satellite (ERS) DEM elevations. The 1995 DEM assessed the accuracy of topographic datasets and evaluated errors in the 1949 DEM.

Radiocarbon and dendrochronological dating of glacially overridden stumps and detrital wood indicates that two outlet glaciers of the Juneau Icefield advanced shortly before the 'Little Ice Age'. Tulsequah Glacier advanced to within 2.4 km of its all-time Holocene limit between ad 865 and ad 940. Llewellyn Glacier, one of the largest glaciers in British Columbia, advanced sometime between ad 300 and ad 500, and reached to within 400 m of its Holocene limit between ad 1035 and ad 1210, well before the climactic, 'classical' 'Little Ice Age' advances of the past several centuries. Our data show that some glaciers in western North America were extensive and expanding at times when alpine glaciers have, in the past, been assumed to be restricted. The evidence raises questions about how to define the time of the beginning of the 'Little Ice Age' and, perhaps more importantly, about the utility of the term. [ABSTRACT FROM AUTHOR]

Abstract: Twenty-two new radiocarbon ages from Skagit valley provide a detailed chronology of alpine glaciation during the Evans Creek stade of the Fraser Glaciation (early marine oxygen isotope stage (MIS) 2) in the Cascade Range, Washington State. Sediments at sites near Concrete, Washington, record two advances of the Baker valley glacier between ca. 30.3 and 19.5 cal ka BP, with an intervening period of glacier recession about 24.9 cal ka BP. The Baker valley glacier dammed lower Skagit valley, creating glacial Lake Concrete, which discharged around the ice dam along Finney Creek, or south into the Sauk valley. Sediments along the shores of Ross Lake in upper Skagit valley accumulated in glacial Lake Skymo after ca. 28.7 cal ka BP behind a glacier flowing out of Big Beaver valley. Horizontally laminated silt and bedded sand and gravel up to 20 m thick record as much as 8000 yr of deposition in these glacially dammed lakes. The data indicate that alpine glaciers in Skagit valley were far less extensive than previously thought. Alpine glaciers remained in advanced positions for much of the Evans Creek stade, which may have ended as early as 20.8 cal ka BP. [Copyright &y& Elsevier]

Abstract: We recovered sediment cores from Cheakamus Lake in the southern Coast Mountains, southwest British Columbia, to reconstruct late Holocene environmental conditions in the watershed. The cored sediments are inorganic, rhythmically laminated clayey silt. Radiocarbon ages and correlation of lamina thickness with the magnitude of the annual flood recorded at a nearby gauging station indicate that the laminae are varves. We discriminate seven types of varves on the basis of couplet thickness and internal structure, and compare them to annual hydrographs over the period of record. The seven varve types record summer snowmelt floods, autumn floods, mid-season floods, years with two major floods, years with three major floods, years with more than three major floods, and periods of sustained glacier runoff. Varves attributed to autumn storms and glacier runoff are dominant, exhibit serial dependence, and are most common during six periods: AD 1300–1320, 1380–1410, 1470–1500, 1710–1730, 1880–1906, and 1916–1945. In contrast, varves attributed to summer snowmelt floods are randomly distributed through time. Thickest varves occur during the decades AD 1090–1110, 1120–1170, 1210–1250, 1310–1330, 1390–1450, 1720–1780, 1860–1900, and 1920–1945. The relation between Little Ice Age glacier activity and lake sedimentation is complex, but the thickest varves coincide with times of rapid glacier retreat and periods when air temperatures were warmer than average. The results confirm the importance of sediment transfers during the summer and autumn runoff season in the British Columbia Coast Mountains. [Copyright &y& Elsevier]

Abstract: Sharp-crested moraines, up to 120 m high and 9 km beyond Little Ice Age glacier limits, record a late Pleistocene advance of alpine glaciers in the Finlay River area in northern British Columbia. The moraines are regional in extent and record climatic deterioration near the end of the last glaciation. Several lateral moraines are crosscut by meltwater channels that record downwasting of trunk valley ice of the northern Cordilleran ice sheet. Other lateral moraines merge with ice-stagnation deposits in trunk valleys. These relationships confirm the interaction of advancing alpine glaciers with the regionally decaying Cordilleran ice sheet and verify a late-glacial age for the moraines. Sediment cores were collected from eight lakes dammed by the moraines. Two tephras occur in basal sediments of five lakes, demonstrating that the moraines are the same age. Plant macrofossils from sediment cores provide a minimum limiting age of 10,550–10,250 cal yr BP (9230±50 14C yr BP) for abandonment of the moraines. The advance that left the moraines may date to the Younger Dryas period. The Finlay moraines demonstrate that the timing and style of regional deglaciation was important in determining the magnitude of late-glacial glacier advances. [Copyright &y& Elsevier]

Holocene glacier fluctuations prior to the 'Little Ice Age' in Garibaldi Provincial Park in the British Columbia Coast Mountains were reconstructed from geomorphic mapping and radiocarbon ages on 37 samples of growth-position and detrital wood from glacier forefields. Glaciers in Garibaldi Park were smaller than at present in the early Holocene, although some evidence exists for minor, short-lived advances at this time. The first well-documented advance dates to 7700-7300 14C yr BP. Subsequent advances date to 6400-5100, 4300, 4100-2900 and 1600-1100 14C yr BP. Some glaciers approached their maximum Holocene limits several times during the past 10 000 years. Periods of advance in Garibaldi Park are broadly synchronous with advances elsewhere in the Canadian Cordillera, suggesting a common climatic cause. The Garibaldi Park glacier record is also broadly synchronous with the record of Holocene sunspot numbers, supporting previous research that suggests solar activity may be an important climate forcing mechanism. [ABSTRACT FROM AUTHOR]

The Little Ice Age glacier history in Garibaldi Provincial Park (southern Coast Mountains, British Columbia) was reconstructed using geomorphic mapping, radiocarbon ages on fossil wood in glacier forefields, dendrochronology, and lichenometry. The Little Ice Age began in the 11th century. Glaciers reached their first maximum of the past millennium in the 12th century. They were only slightly more extensive than today in the 13th century, but advanced at least twice in the 14th and 15th centuries to near their maximum Little Ice Age positions. Glaciers probably fluctuated around these advanced positions from the 15th century to the beginning of the 18th century. They achieved their greatest extent between A.D. 1690 and 1720. Moraines were deposited at positions beyond present-day ice limits throughout the 19th and early 20th centuries. Glacier fluctuations appear to be synchronous throughout Garibaldi Park. This chronology agrees well with similar records from other mountain ranges and with reconstructed Northern Hemisphere temperature series, indicating global forcing of glacier fluctuations in the past millennium. It also corresponds with sunspot minima, indicating that solar irradiance plays an important role in late Holocene climate change. [ABSTRACT FROM AUTHOR]

Moraine Bog lies just outside the outermost lateral moraine of Tiedemann Glacier in the southern Coast Mountains of British Columbia. A sediment core taken from the wetland was analyzed for pollen, magnetic susceptibility, and loss on ignition to reconstruct changes in vegetation and climate during the late Holocene. Vegetation changed little between about 3500 and 2400 14C years BP. A period of local disturbance marked by deposition of a silty clay bed and increases in Alnus pollen, likely reflecting cooler moister conditions, coincides with an extensive Holocene advance of Tiedemann Glacier about 2400 14C years BP. Warm dry conditions between about 1900 and 1500 14C years BP are suggested by peak values of Pseudotsuga pollen and increasing Nuphar sclereids; the latter suggests lowered water levels. This period coincides with a time of drought and increased fire frequency in the southernmost Coast Mountains. About 1300 14C years BP, the forest became more coastal in composition with abundant Tsuga heterophylla and Abies. An increase in Tsuga mertensiana pollen suggests the onset of cool and wet conditions by ca. 500 14C years BP, coincident with the Little Ice Age. The record of inferred climate change at Moraine Bog is broadly synchronous with other paleoclimate records from the Coast Mountains and, at the centennial scale, with records elsewhere in the world. [ABSTRACT FROM AUTHOR]

Cores of annually laminated sediments (varves) from five lakes in the southern Coast Mountains of British Columbia, Canada, document clastic sediment response to climate and geomorphic change over the past 120 years. Interannual varve thickness correlates with annual flood magnitude. Interdecadal trends in varve thickness are influenced by other environmental factors such as glacier recession. Despite major differences in the lakes and their contributing watersheds, substantial concordance is observed among the records. A pronounced change in the nature of lake sedimentation, accompanied by higher interannual variability, occurred in 1980. The change coincides with an increase in the magnitude of autumn flooding and major re-organization of the North Pacific climate system. These results highlight new directions for palaeoenvironmental research using varved sediment records, specifically to study the magnitude and spatial extent of past hydro-climatic events. [ABSTRACT FROM AUTHOR]

Jökulhlaups from lakes dammed by Tulsequah Glacier in northwestern British Columbia have occurred regularly since the early twentieth century. The floods commenced after decades of downwasting and retreat of the glacier from its Holocene maximum position, which it achieved in the nineteenth century. Hydrometric data and other records are used to reconstruct the times and peak discharges of floods from two glacier-dammed lakes. Tulsequah Lake formed in the early 1900s when a tributary glacier separated from Tulsequah Glacier, creating an ice-free embayment between the two. The lake grew rapidly in surface area and volume in the first half of the twentieth century, but later, with continued glacier retreat, it decreased in size. The first jökulhlaups from Tulsequah Lake were the largest. Peak and total discharges decreased as the lake became smaller. Today, Tulsequah Lake is small, and it will disappear completely if Tulsequah Glacier retreats any further. A second lake (Lake No Lake), however, has formed and grown in size as Tulsequah Lake has diminished. Lake No Lake developed from a subglacial water body in a tributary valley, 7 km upglacier from Tulsequah Lake. Like Tulsequah Lake, Lake No Lake rapidly grew in area and volume during its youth, and in the 1970s it began to generate its own jökulhlaups. Lake No Lake appears to be following the same evolutionary path as Tulsequah Lake – its volume is now decreasing due to downwasting of Tulsequah Glacier, and its jökulhlaups are beginning to diminish. As Tulsequah Glacier continues to shrink in response to climatic warming, additional glacier-dammed lakes may form, renewing the cycle of outburst flood activity. Such behaviour can be expected in other high mountains because most alpine glaciers are retreating in response to global warming. [ABSTRACT FROM AUTHOR]

Holocene lateral moraines in the Coast Mountains of British Columbia are commonly composed of multiple drift units related to several glacier advances. In this paper, we document lateral moraine stratigraphy at Lillooet Glacier in the southern Coast Mountains. Five tills, separated by laterally extensive paleosols and layers of large woody debris, were found in three cross-sectional exposures through the northeast lateral moraine and two shallow gullies incised into its steep proximal face. Eighteen new radiocarbon ages constrain the timing of five separate advances of Lillooet Glacier: (1) prior to 3000 14C years BP; (2) ~3000 14C years BP; (3) ~2500 14C years BP; (4) ~1700 to 1400 14C years BP; and (5) during the Little Ice Age (LIA), after 470 14C years BP. The Lillooet Glacier chronology is broadly synchronous with other glacier records from the Coast Mountains. These records collectively demonstrate climate variability at higher frequencies during the late Holocene than is apparent from many paleoecological reconstructions. Reconstructions of glacier fluctuations are often hampered by poor preservation of landforms that predate the extensive LIA advances of the latest Holocene. Our results highlight the potential of lateral moraine stratigraphy for reconstructing these earlier events. [ABSTRACT FROM AUTHOR]

Rivers flowing from glacier-clad Quaternary volcanoes in southwestern British Columbia have high sediment loads and anabranching and braided planforms. Their floodplains aggrade in response to recurrent large landslides on the volcanoes and to advance of glaciers during periods of climate cooling. In this paper, we document channel instability and aggradation during the last 200 years in lower Cheakamus River valley. Cheakamus River derives much of its flow and nearly all of its sediment from the Mount Garibaldi massif, which includes a number of volcanic centres dominated by Mount Garibaldi volcano. Stratigraphic analysis and radiocarbon and dendrochronological dating of recent floodplain sediments at North Vancouver Outdoor School in Cheakamus Valley show that Cheakamus River aggraded its floodplain about 1–2 m and buried a valley-floor forest in the early or mid 1800s. The aggradation was probably caused by a large (ca. 15–25×106 m3) landslide from the flank of Mount Garibaldi, 15 km north of our study site, in 1855 or 1856. Examination of historical aerial photographs dating back to 1947 indicates that channel instability triggered by this event persisted until the river was dyked in the late 1950s. Our observations are consistent with data from many other mountain areas that suggest rivers with large, but highly variable sediment loads may rapidly aggrade their floodplains following a large spike in sediment supply. Channel instability may persist for decades to centuries after the triggering event. [Copyright &y& Elsevier]

Stratigraphy and landforms in the Brohm Creek basin and lowermost Mamquam River valley provide evidence for a readvance of a valley glacier in the southern Coast Mountains of British Columbia during the Younger Dryas interval. At Brohm Creek, till containing wood 10,500 and 10,700 14C yr old (ca 12,500–12,900 cal yr old), overlies an ice-contact terrace that is correlative with similar terraces at the mouth of Mamquam River, 11 km to the south and 900 m lower in elevation. A line linking the two sites has a slope of 5°, which is similar to slopes of termini of present-day valley glaciers in the southern Coast Mountains. We used these observations to reconstruct the Younger Dryas glacier in Squamish valley at the head of Howe Sound. The glacier deflected landslide debris, derived from steep slopes at the head of Cheekye River basin on the west flank of Mt. Garibaldi, southward to an ice-marginal lake at the mouth of Mamquam River. Foreset-bedded sediments in the core of a large fan at the mouth of Cheekye River indicate the glacier terminus had retreated up Squamish valley beyond Cheekye and Mamquam rivers by 10,200 14C yr BP (11,900 cal yr old). Radiocarbon ages on the oldest postglacial sediments in a kettle on the landslide debris show that stagnant ice in the study area had melted before 10,000 14C yr BP (11,500 cal yr BP). The readvance of the Squamish valley glacier during the Younger Dryas Chronozone was probably driven by a regional climate reversal. [Copyright &y& Elsevier]

Near the Pleistocene Termination, a glacier-dammed lake in central British Columbia suddenly drained to the south along the Fraser River valley. Floodwater travelled 330 km down the valley to Hope, British Columbia, and from there to the west into the Salish Sea near Vancouver. The flood was caused by the failure of an ice dam formed by the terminus of glaciers flowing from the central Coast Mountains across the British Columbia Interior Plateau. The ice dam impounded several hundred cubic kilometres of water to a maximum elevation of about 810 m asl (above sea level); at its maximum, the lake at the ice dam was over 250 m deep. Geomorphic and sedimentary evidence for the flood includes streamlined boulder-strewn bars, gravel dune fields, and terraces sloping up Fraser and lowermost Thompson valleys, opposite the present direction of river flow. The gravel bars and flood terraces are underlain by sheets of massive to poorly sorted gravel containing large boulders and rip-up clasts of silt and till. Shortly after the flood, a landslide near the northern margin of the former glacier dam impounded water to an elevation of about 550 m asl. This lake emptied due to overflow and incision of the landslide dam. The outburst flood from glacial Lake Fraser and the subsequent draining of the landslide-dammed lake deeply incised the older sediment fill in Fraser Valley and transported much of this sediment into the proto-Salish Sea west of Vancouver, British Columbia and Bellingham, Washington. TCN ages on flood-transported boulders at three localities along the flood path agree with radiocarbon ages on inferred flood layers in ODP cores collected from Saanich Inlet, a fiord on southern Vancouver Island, 80 km south-southwest of Vancouver. [ABSTRACT FROM AUTHOR]

At least seven late Pliocene tills cap plateaus (mesetas) south of Lago Viedma, just east of the Andes in Argentine Patagonia. Chronologic constraints on the tills are provided by 40Ar/39Ar ages and magnetic polarities on associated basalt flows and sediments. The tills were deposited by piedmont glaciers that reached at least 80 km east of the crest of the Andes and flowed on a low-relief surface sloping gently downward in that direction. The oldest of the tills is about 3.6 Ma old. Glacial deposits dating to the Pliocene-Pleistocene transition are present at least 40 km beyond the east limit of the Pliocene tills at Lago Viedma, and tills of similar age occur at Condor Cliff in the Río Santa Cruz valley to the southeast. A sequence of at least seven Early Pleistocene (2.1–1.1 Ma) tills is present between basalt flows in the Cerro del Fraile meseta south of Lago Argentino. The glaciers that deposited these Early Pleistocene tills reached far beyond the Marine Isotope Stage 2 limit in the Río Santa Cruz valley. Based on positions, extents, and ages of the un-deformed, basalt-capped mesetas flanking Lago Viedma, we conclude that the topography in this area was profoundly changed during the Pleistocene – the low to moderate relief Pliocene surface was deeply incised by glaciers that became increasingly confined to, and flowed within, troughs. The valley floors today are up to 1350 m below the late Pliocene surface. • The Patagonian Ice Sheet advanced over the western Argentine steppe many times during the late Pliocene. • The steppe east of the southern Andes during the late Pliocene was an elevated surface of low to moderate relief. • The late Pliocene steppe was elevated and slightly tilted during the Quaternary, but not otherwise deformed. • Pleistocene glaciers deeply incised the Pliocene land surface, forming the deep valleys of the present landscape. [ABSTRACT FROM AUTHOR]

Abstract: Fluctuations of glaciers during the 20th century in Garibaldi Provincial Park, in the southern Coast Mountains of British Columbia, were reconstructed from historical documents, aerial photographs, and fieldwork. Over 505 km2, or 26%, of the park, was covered by glacier ice at the beginning of the 18th century. Ice cover decreased to 297 km2 by 1987–1988 and to 245 km2 (49% of the early 18th century value) by 2005. Glacier recession was greatest between the 1920s and 1950s, with typical frontal retreat rates of 30 m/a. Many glaciers advanced between the 1960s and 1970s, but all glaciers retreated over the last 20 years. Times of glacier recession coincide with warm and relatively dry periods, whereas advances occurred during relatively cold periods. Rapid recession between 1925 and 1946, and since 1977, coincided with the positive phase of the Pacific Decadal Oscillation (PDO), whereas glaciers advanced during its negative phase (1890–1924 and 1947–1976). The record of 20th century glacier fluctuations in Garibaldi Park is similar to that in southern Europe, South America, and New Zealand, suggesting a common, global climatic cause. We conclude that global temperature change in the 20th century explains much of the behaviour of glaciers in Garibaldi Park and elsewhere. [Copyright &y& Elsevier]

Abstract: Castle Creek Glacier in the Cariboo Mountains of British Columbia remained close to its Little Ice Age limit for most of the past 1500 years, without significant recession until the 20th century. This conclusion is based on radiocarbon-dated detrital and in-situ plant material overrun by the glacier, and the sedimentary record from informally named On–off Lake, which received clastic sediments only when Castle Creek Glacier crossed a hydrologic divide 330 m upvalley of the Little Ice Age limit. Plant macrofossils recovered from the transition between basal inorganic silt and overlying organic silty clay in a sediment core from the lake indicate that the glacier first retreated behind the divide ca. 10.92–9.70 ka. Ages of 8.97–8.61 and 5.58–5.53 ka on detrital wood from the glacier''s forefield may record earlier advances, but the first unequivocal evidence of glacier expansion is from an overridden stump with an age of 4.96–4.45 ka. Continuous accumulation of gyttja within On–off Lake, however, indicates that Castle Creek Glacier did not cross the hydrologic divide at any time during the first half of the Holocene. Glacigenic sediments began to accumulate in the lake between 2.73 and 2.49 ka, indicating that Castle Creek Glacier expanded beyond the hydrologic divide at that time. A coincident advance is also recorded in the northern Rocky Mountains of British Columbia at Kwadacha Glacier, which overran a vegetated surface at 2.69–2.36 ka. Clastic sedimentation in On–off Lake ceased soon after the Bridge River volcanic eruption (2.70–2.35 ka), indicating that Castle Creek glacier retreat to a position upvalley of the divide at that time. Sedimentation resumed before 1.87–1.72 ka when the glacier advanced again past the hydrologic divide. Following a second retreat, Castle Creek Glacier advanced across the divide a final time at ca. 1.54–1.42 ka. The snout of the glacier remained less than 330 m upvalley of the Little Ice Age moraine until the early twentieth century when annual moraines indicate rapid frontal recession to a position upvalley of the hydrologic divide. These data collectively indicate that glaciers in the Cariboo Mountains of British Columbia nearly achieved their all-time Holocene limits as early as 2.73–2.49 ka and climatic conditions in the early 20th century abruptly ended a 1500-year period favoring glacier expansion. [Copyright &y& Elsevier]

Abstract: Glaciers on stratovolcanoes of the Pacific Northwest of North America offer opportunities for dating late Pleistocene and Holocene glacier advances because tephra and fossil wood are common in lateral moraines and in glacier forefields. We capitalize on this opportunity by examining the Holocene glacial record at Mount Baker, an active stratovolcano in northwest Washington. Earlier workers concluded that glaciers on Mount Baker during the early Holocene were more extensive than during the Little Ice Age and hypothesized that the explanation lay in unusual climatic or hypsometric effects peculiar to large volcanoes. We show that the main argument for an early Holocene glacier advance on Mount Baker, namely the absence of ca 10,000-year-old tephra on part of the south flank of the mountain, is incorrect. Moreover, a lake-sediment core indicates that a small cirque moraine previously thought be of early Holocene age is also likely older than the tephra and consequently of late Pleistocene age. Lateral and end moraines and wood mats ca 2 km downvalley of the present snout of Deming Glacier indicate that an advance during the Younger Dryas interval was little more extensive than the climactic Little Ice Age advance. Tephra and wood between tills in the left lateral moraine of Easton Glacier suggest that ice on Mount Baker was restricted in the early Holocene and that Neoglaciation began ca 6 ka. A series of progressively more extensive Neoglacial advances, dated to about 2.2, 1.6, 0.9, and 0.4 ka, are recorded by stacked tills in the right lateral moraine of Deming Glacier. Intervening retreats were long enough to allow establishment of forests on the moraine. Wood mats in moraines of Coleman and Easton glaciers indicate that Little Ice Age expansion began before 0.7 ka and was followed by retreat and a readvance ca 0.5 ka. Tree-ring and lichen data indicate glaciers on the south side of the mountain reached their maximum extents in the mid-1800s. The similarity between glacier fluctuations at Mount Baker and those elsewhere in the Cascades and in British Columbia suggests a coherent history of Holocene climate change over a broad area of the western Cordillera. We found no evidence that glaciers on stratovolcanoes behave differently than glaciers elsewhere. [Copyright &y& Elsevier]

Abstract: Forty-eight new and previously published radiocarbon ages constrain deglacial and postglacial sea levels on southern Vancouver Island, British Columbia. Sea level fell rapidly from its high stand of about +75m elevation just before 14 000cal BP (12 000 radiocarbon yrs BP) to below the present shoreline by 13 200cal BP (11 400 radiocarbon years BP). The sea fell below its present level 1000 years later in the central Strait of Georgia and 2000 years later in the northern Strait of Georgia, reflecting regional differences in ice sheet retreat and downwasting. Direct observations only constrain the low stand to be below −11m and above −40m. Analysis of the crustal isostatic depression with equations utilizing exponential decay functions appropriate to the Cascadia subduction zone, however, places the low stand at −30±5m at about 11 200cal BP (9800 BP). The inferred low stand for southern Vancouver Island, when compared to the sea-level curve previously derived for the central Strait of Georgia to the northwest, generates differential isostatic depression that is consistent with the expected crustal response between the two regions. Morphologic and sub-bottom features previously interpreted to indicate a low stand of −50 to −65m are re-evaluated and found to be consistent with a low stand of −30±5m. Submarine banks in eastern Juan de Fuca Strait were emergent at the time of the low stand, but marine passages persisted between southern Vancouver Island and the mainland. The crustal uplift presently occurring in response to the Late Pleistocene collapse of the southwestern sector of the Cordilleran Ice Sheet amounts to about 0.1mm/yr. The small glacial isostatic adjustment rate is a consequence of low-viscosity mantle in this tectonically active region. [Copyright &y& Elsevier]

There is disagreement in the Quaternary research community in how much of the marine δ 18 O signal is driven by change in ice volume. Here, we examine this topic by bringing together empirical and modelling work for Marine Isotope Stage 3 (MIS 3; 57 ka to 29 ka), a time when the marine δ18O record indicates moderate continental glaciation and a global mean sea level between −60 m and −90 m. We compile and interpret geological data dating to MIS 3 to constrain the extent of major Northern Hemisphere ice sheets (Eurasian, Laurentide, Cordilleran). Many key data, especially published in the past ~15 years, argue for an ice-free core of the formerly glaciated regions that is inconsistent with inferences from the marine δ 18 O record. We compile results from prior studies of glacial isostatic adjustment to show the volume of ice inferred from the marine δ18O record is unable to fit within the plausible footprint of Northern Hemisphere ice sheets during MIS 3. Instead, a global mean sea level between −30 m and − 50 m is inferred from geological constraints and glacial isostatic modelling. Furthermore, limited North American ice volumes during MIS 3 are consistent with most sea-level bounds through that interval. We can find no concrete evidence of large-scale glaciation during MIS 3 that could account for the missing ~30 m of sea-level equivalent during that time, which suggests that changes in the marine δ 18 O record are driven by other variables, including water temperature. This work urges caution regarding the reliance of the marine δ 18 O record as a de facto indicator of continental ice when few geological constraints are available, which underpins many Quaternary studies. • Establishes a footprint of Northern Hemisphere ice sheets during MIS 3. • Geological data suggest an ice-free core of the formerly glaciated regions during MIS 3. • Explores inconsistencies between geological data and the marine δ 18 O record. • Identifies a ~ 30 m discrepancy in sea-level equivalent during MIS 3. • Results suggest rapid glacier growth in response to climate variability. [ABSTRACT FROM AUTHOR]

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 ∼2000 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. [ABSTRACT FROM AUTHOR]

Terrestrial and lake sediment records from several sites in the southern Coast Mountains, British Columbia, provide evidence for an advance of alpine glaciers during the early Holocene. Silty intervals within organic sediments recovered from two proglacial lakes are bracketed by AMS 14C-dated terrestrial macrofossils and Mazama tephra to 8780–6730 and 7940–6730 14C yr BP [10,150–7510 and 8990–7510 cal yr BP]. Radiocarbon ages ranging from 7720 to 7380 14C yr BP [8630–8020 cal yr BP] were obtained from detrital wood in recently deglaciated forefields of Sphinx and Sentinel glaciers. These data, together with previously published data from proglacial lakes in the Canadian Rockies, imply that glaciers in western Canada advanced during the early Holocene. The advance coincides with the well-documented 8200-yr cold event identified in climate proxy data sets in the North Atlantic region and elsewhere. [Copyright &y& Elsevier]

Combined use of radiocarbon-dated subfossil wood within lateral moraines and surface exposure ages on moraine boulders provides an approach to better constrain times of glacier advance and onset of retreat. We test this method at Gilbert Glacier in the southern Coast Mountains of British Columbia where units of sediments associated with glacier expansion date to 4.8–4.6, 4.5–4.3, 4.0–3.9, 3.8–3.6, 3.4, 3.2–2.9, 2.7, and 0.5–0.3 kilo calendar years BP (ka; 2-sigma age range). Surface exposure (10Be) ages reveal times of moraine stabilization at 1.83–1.78, 1.38–1.28, 0.85–0.76, and 0.13–0.06 ka (interquartile range). Analysis of both datasets, as well as previously published regional advance records, narrows the age range of four late Holocene advances to 2.0–1.8, ∼1.5–1.3, ∼0.9–0.8, and 0.4–0.1 ka. We advocate for widespread use of our tandem approach at other sites throughout Earth's high mountains to narrow the uncertainties associated with glacier expansion and better understand how glaciers respond to climate change. [ABSTRACT FROM AUTHOR]