Calendar dating of tree-ring series from 16 logs sampled near the margin of Casement Glacier combined with tree-ring dates on 36 detrital logs from Adams Inlet, Glacier Bay National Park and Preserve, Alaska, show killing of trees by ice and lake sediments from the mid-sixth through mid-seventh centuries C.E. The dates from the land-terminating Casement Glacier show ice advance into a forest between 560 and 570 C.E. within a few kilometers of the 2011 retreating margin.Advance of the tidewater glacier in Muir Inlet blocked offAdams Inlet forming Lake Adams between 540 and 640 C.E. This glacier and lake history for Glacier Bay is consistent with other land-terminating ice expansions across the Gulf of Alaska that similarly show advance centered on 600 C.E., as well as other proxy records from lakes all suggesting cooling during this interval. The cooling closely follows a series of eruptions in the mid to late sixth century, which may have contributed to the cooling. Radiocarbon ages in Adams Inlet suggest that Lake Adams persisted through 880 cal. yr C.E. and drained by 1170 cal. yr C.E. Ice retreat and this lake drainage are broadly coincident with Medieval warming recognized along the Gulf of Alaska in dendroclimatic reconstructions. Shortly after this retreat, Little Ice Age readvance occurred with Casement Glacier coalescing with glaciers in Adams Inlet and the West Arm, subsequently filling all of Glacier Bay to its Holocene maximum by 1750 C.E.

High-resolution records of the stable isotopic (δ18O and δD) composition of ice within two closed system (hydrostatic) pingos indicate a complex history of ice formation by segregation and injection and pingo growth. Physical properties and internal structure of continuous ice cores in the center of the Weather Pingo near Prudhoe Bay, Alaska, and the Pestsovoye Pingo, in northwestern Siberia, were described and then sub-sampled for analysis of the isotopic composition. Changes in the isotopic signature and physical properties of ice with depth reveal distinct patterns in both pingos indicative of ice growth as permafrost aggraded into the drained lake basin. In the initial stages following active layer deepening and initial freeze back, in-situ water migrating toward the freezing front froze at a relatively rapid rate as revealed by a complex isotopic record and small ice crystal size in the cores of Weather Pingo. Once the water supply became limited, freezing under equilibrium conditions resulted in an isotopic composition consistent with Rayleigh-type fractionation and δ18O and δD values that become more negative with depth. The data for the Pestsovoye Pingo reveal similar trends related to the initial stages of water migration and freezing, followed by isotopic fractionation under equilibrium conditions as unfrozen water available in the talik beneath the pingo became limited. Most of the ice in both pingos (~50%) formed during this final stage of permafrost aggradation. Thus temporal variability in water migration and freezing rate at the base of each pingo created a complex isotopic stratigraphy and ice growth history.

Spatially extensive Arctic stable isotope data are sparse, inhibiting the climatic understanding required to interpret paleoclimate proxy records. To fill this need, we constrained the climatic and physiographic controls on O-18 and D values of stream waters across Alaska and the Yukon to derive interpolated isoscape maps. O-18 is strongly correlated to winter temperature parameters and similarity of the surface water line (H-2=8.0 x O-18+6.4) to the Global Meteoric Water Line suggests stream waters are a proxy for meteoric precipitation. We observe extreme orographic O-18 decreases and a trans-Alaskan continental gradient of -8.3 1000 km(-1). Continental gradients are high in coastal zones and low in the interior. Localized O-18 increases indicate inland air mass penetration via topographic lows. Using observed O-18/temperature gradients, we show that O-18 decreases in a approximate to 24 ka permafrost ice wedge relative to the late Holocene indicate mean annual and coldest quarter temperature reductions of 8.91.7 degrees C and 17.23.2 degrees C, respectively.

The macro‐ and micro‐sedimentology of a supraglacial melt‐out till forming at the Matanuska Glacier was examined in relationship to the properties of the stratified basal zone ice and debris from which it is originating. In situ melting of the basal ice has produced a laminated to bedded diamicton consisting mainly of silt. Macroscopic properties include: discontinuous laminae and beds; lenses of sand, silt aggregates and open‐work gravel; deformed and elongate clasts of clay; widely dispersed pebbles and cobbles, those that are prolate usually with their long axes subparallel to parallel to the bedding. Evidence for deformation is absent except for localized bending of beds over or under rock clasts. Microscopic properties are a unique element of this work and include: discontinuous lineations; silt to granule size laminae; prolate coarse sand and rock fragments commonly with their long axis subparallel to bedding; subangular to subrounded irregular shaped clay clasts often appearing as bands; sorted and unsorted silt to granule size horizons, sometimes disrupted by pore‐water pathways. Limited deformation occurs around rock clasts and thicker parts of lamina. This study shows that in situ melting of debris‐rich basal ice can produce a laminated and bedded diamicton that inherits and thereby preserves stratified basal ice properties. Production and preservation of supraglacial melt‐out till require in situ melting of a stagnant, debris‐rich basal ice source with a low relief surface that becomes buried by a thick, stable, insulating cover of ice‐marginal sediment. Also required are a slow melt rate and adequate drainage to minimize pore‐water pressures in the till and overlying sediment cover to maintain stability and uninterrupted deposition. Many modern and ancient hummocky moraines down glacier of subglacial overdeepenings probably meet these process criteria and their common occurrence suggests that both modern and pre‐modern supraglacial melt‐out tills may be more common than previously thought.

Hubbard Glacier, located in southeast Alaska, is the world's largest nonpolar tidewater glacier. It has been steadily advancing since it was first mapped in 1895; occasionally, the advance creates an ice or sediment dam that blocks a tributary fjord (Russell Fiord). The sustained advance raises the probability of long-term closure in the near future, which will strongly impact the ecosystem of Russell Fiord and the nearby community of Yakutat. Here, we examine a 43 year record of flow speeds and terminus position to understand the large-scale dynamics of Hubbard Glacier. Our long-term record shows that the rate of terminus advance has increased slightly since 1895, with the exception of a slowed advance between approximately 1972 and 1984. The short-lived closure events in 1986 and 2002 were not initiated by perturbations in ice velocity or environmental forcings but were likely due to fluctuations in sedimentation patterns at the terminus. This study points to the significance of a coupled system where short-term velocity fluctuations and morainal shoal development control tidewater glacier terminus position.

For scholars in visual rhetoric, the recent wave of visual narrative forms have posed a particular challenge in terms of analysis: how might one read the sort of text that refuses to conform to visual genres as we have come to know them and yet draws upon a number of conventions from these genres and the media they typically appear in? As visual narrative forms like comics and their remediations become more ubiquitous, how do we read them and explicate what these forms have to offer in terms of meaning-making? One particularly compelling example can be found in The Photographer: Into War-Torn Afghanistan with Doctors Without Borders. This work incorporates a blend of media - such as prose, comics, and most especially photography - while eluding any easy designation into any one of those categories. Part travelogue and part photojournalism, The Photographer tells the story of Didier Lefevre's travels with Doctors Without Borders in Afghanistan during the war between the Soviet Union and the Afghan Mujahideen. Drawing upon scholars such as Barthes, Mitchell, Bolter and Grusin, as well as assorted comics scholars and commentators, I contend in this article that by positioning text against drawing and each against photography, The Photographer calls attention to the potential hegemonic function of any one of these discursive modes. Using close reading and rhetorical analysis, I explicate how the notion of hybridity informs the rhetorical work of the book in terms of its authorial voice(s), its form, and its content. By destabilizing fixed categories of medial and cultural identity, The Photographer enables its subjects to take on a sort of humanity than might otherwise be available to them in more traditional modes of representation and enables different forms of immediacy for its readers.

Recent observations of divergence between tree growth at high-latitude sites and temperature, as well as the decline of yellow cedar [Callitropsis nootkatensis (D. Don) Oerst. ex D.P. Little] in southeast Alaska due to warming, emphasize a need to investigate nonstationary climate response of Alaskan coastal forests to warming in other tree species. Comparison of annual tree growth in mountain hemlock [Tsuga mertensiana (Bong.) Carriere] to mean monthly temperature and precipitation data from Sitka, Alaska, from A.D. 1830s to 1990s along an elevational transect reveals nonstationarity in tree growth response to climate that suggests an ongoing biome shift. We observe a marked weakening in the positive relationship between annual growth and warmer growth season temperatures at low-elevation hemlock sites, and a concurrent increase in growth and sensitivity at higher elevations coupled with increased correlation between growth and April precipitation at all sites along our transects. As previously observed with yellow cedar, the mechanism of the hemlock biome shift may be due to an increased susceptibility of roots to damage from late frosts resulting from earlier seasonal loss of protective snowpack.

Yellow-cedar ( Callitropsis nootkatensis (D. Don) Örsted ex D.P. Little) is in a century-long decline coinciding with the end of the Little Ice Age (LIA). The leading hypothesis explaining this decline is a decrease in insulating snowpack due to warming and increased susceptibility to damaging frosts in the root zone. A ring-width series from yellow-cedar on Excursion Ridge (260 m a.s.l.) in Glacier Bay National Park and Preserve, Alaska, and another from trees on Pleasant Island (150 m a.s.l.) in the Tongass National Forest in Icy Strait were compared with regional monthly temperature and precipitation data from Sitka, Alaska, to investigate the changing growth response to temperature at these sites. Comparisons with monthly temperatures from 1832 to 1876 during the end of the Little Ice Age show that the high-elevation Excursion Ridge and the low-elevation Pleasant Island sites strongly favored warmer January through July temperatures. Both tree populations have markedly changed their response from a positive to a strong negative correlation with January through July temperatures since 1950. This strong negative response to warming by the yellow-cedar together with a positive relationship with total March and April precipitation suggests that these yellow-cedar sites may be susceptible to decline. Furthermore, these analyses are consistent with the hypothesis that the yellow-cedar decline is linked to decreased snowpack.

Establishing firm radiocarbon chronologies for Quaternary permafrost sequences remains a challenge because of the persistence of old carbon in younger deposits. To investigate carbon dynamics and establish ice wedge formation ages in Interior Alaska, we dated a late Pleistocene ice wedge, formerly assigned to Marine Isotope Stage (MIS) 3, and host sediments near Fairbanks, Alaska, with 24 radiocarbon analyses on wood, particulate organic carbon (POC), air-bubble CO2, and dissolved organic carbon (DOC). Our new CO2 and DOC ages are up to 11,170yr younger than ice wedge POC ages, indicating that POC is detrital in origin. We conclude an ice wedge formation age between 28 and 22calka BP during cold stadial conditions of MIS 2 and solar insolation minimum, possibly associated with Heinrich event 2 or the last glacial maximum. A DOC age for an ice lens in a thaw unconformity above the ice wedge returned a maximum age of 21,470±200calyr BP. Our variable 14C data indicate recycling of older carbon in ancient permafrost terrain, resulting in radiocarbon ages significantly older than the period of ice-wedge activity. Release of ancient carbon with climatic warming will therefore affect the global 14C budget.

Morainal banks are primary features at the margins of advancing and stable to quasi‐stable temperate tidewater glaciers, yet their roles in glacier dynamics and terminus stability are poorly defined by submarine observations. Analysis of new and archival multibeam data and Landsat images of the advancing Hubbard Glacier, southeast Alaska, reveal that between 1978 and 2010 the ice face and morainal bank advanced together at an average rate of ∼34 m/yr, varying spatially and temporally between 14 and 80 m/yr. Morphological features including gullies and a boulder lag suggest cyclical deposition and gravitational erosion on the proximal slope of the morainal bank (15–18°), and possible ice pushing in an area without recent sedimentation. In contrast, the morainal bank of the nearby, quasi‐stable (surging) Turner Glacier advanced steadily since 1978 by proximal sedimentation on the steep fjord wall below its hanging valley. Sedimentation in the deep (>220 m) basin of Disenchantment Bay increased from 0.88 m/yr spanning 1978 to 1999, to 1.22 m/yr thereafter. This change appears to be a combined response to glacier advance and sediment dispersal farther down‐fjord, and to an increase in sediment yield from other glacial and non‐glacial sources. Analysis of Hubbard Glacier illustrates the direct correlation between movement of the terminus and morainal bank in advancing the grounding line of a marine‐terminating glacier, and that morainal banks provide a fundamental stabilizing role for advance into a deep‐water fjord, compensating for changes in water depth at the grounding line.

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 (775yr) 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 545yr and is a floating ring-width series tied to radiocarbon ages of about 3000calyr 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 3000calyr 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.

Hubbard Glacier, near Yakutat, Alaska, is the largest non-polar tidewater glacier in the world. In contrast to most glaciers in southeast Alaska, Hubbard Glacier continues to advance and has thickened at an average rate of 35 m yr–1. Twice since 1986 Hubbard Glacier has advanced enough to cause a temporary closure of Russell Fiord. If Hubbard Glacier continues to advance, a permanent closure of Russell Fiord would ultimately cause significant damage to the town of Yakutat and the economic fisheries that sustain it. This report presents the results of a first-of-its-kind survey of the submarine and terrestrial environment of the Hubbard Glacier tidewater terminus and the area surrounding Gilbert Point. High-resolution, multibeam bathymetry and current velocity profiles, combined with simultaneously acquired high-resolution LiDAR topography, provide a detailed look at the section of the glacier where ice damming of Russell Fiord is likely to occur. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.