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• 31. [Article] Glacier Status and Contribution to Streamflow in the Olympic Mountains, USA

  The Olympic Peninsula, Washington, USA, currently holds 184 alpine glaciers larger than 0.01 km² and their combined area is 30.2 ± 0.95km². Only four glaciers are >1km² and 120 of the others are -¹ (1900–80) ...

  Citation × Citation Citation Abstract Copy Title: Glacier Status and Contribution to Streamflow in the Olympic Mountains, USA Author: Riedel, Jon L., Wilson, Steve, Baccus, William, Larrabee, Michael, Fudge, T.J., Fountain, Andrew G. Year: 2015 The Olympic Peninsula, Washington, USA, currently holds 184 alpine glaciers larger than 0.01 km² and their combined area is 30.2 ± 0.95km². Only four glaciers are >1km² and 120 of the others are -¹ (1900–80) to 0.54 km² a-¹ (1980–2009). Thinning rates on four of the largest glaciers averaged nearly 1ma-¹ from 1987 to 2010, resulting in estimated volume losses of 17–24%. Combined glacial snow, firn and ice melt in the Hoh watershed is in the range 63–79 ± 7 × 106m3, or 9–15% of total May–September streamflow. In the critical August–September period, the glacial fraction of total basin runoff increases to 18–30%, with one-third of the water directly from glacial ice (i.e. not snow and firn). Glaciers in the Elwha basin produce 12–15 ± 1.3 × 106m3 (2.5–4.0%), while those in the Dungeness basin contribute 2.5–3.1 ± 0.28 × 106m3 (3.0–3.8%). Title: Glacier Status and Contribution to Streamflow in the Olympic Mountains, USA Author: Riedel, Jon L., Wilson, Steve, Baccus, William, Larrabee, Michael, Fudge, T.J., Fountain, Andrew G. Year: 2015 The Olympic Peninsula, Washington, USA, currently holds 184 alpine glaciers larger than 0.01 km² and their combined area is 30.2 ± 0.95km². Only four glaciers are >1km² and 120 of the others are -¹ (1900–80) to 0.54 km² a-¹ (1980–2009). Thinning rates on four of the largest glaciers averaged nearly 1ma-¹ from 1987 to 2010, resulting in estimated volume losses of 17–24%. Combined glacial snow, firn and ice melt in the Hoh watershed is in the range 63–79 ± 7 × 106m3, or 9–15% of total May–September streamflow. In the critical August–September period, the glacial fraction of total basin runoff increases to 18–30%, with one-third of the water directly from glacial ice (i.e. not snow and firn). Glaciers in the Elwha basin produce 12–15 ± 1.3 × 106m3 (2.5–4.0%), while those in the Dungeness basin contribute 2.5–3.1 ± 0.28 × 106m3 (3.0–3.8%). Close

• 32. [Article] Geology, geomorphology, and dynamics of mass movement in parts of the Middle Santiam River drainage basin, western Cascades, Oregon

  Landforms sculpted by mass movements comprise much of the landscape in the Middle Santiam study area. Bedrock in the area is mostly basalt and andesite flows and varied volcaniclastic rocks of the Little ...

  Citation × Citation Citation Abstract Copy Title: Geology, geomorphology, and dynamics of mass movement in parts of the Middle Santiam River drainage basin, western Cascades, Oregon Author: Hicks, Bryan A. Landforms sculpted by mass movements comprise much of the landscape in the Middle Santiam study area. Bedrock in the area is mostly basalt and andesite flows and varied volcaniclastic rocks of the Little Butte Volcanic Series of Oligocene and early Miocene age, unconforniably overlain by andesite flows and tuffs of the Sardine Formation of middle and late Miocene age. Some mass movements in the study area may have originally occurred during glacial or interglacial periods of the late Pleistocene, although this is largely speculative. Active slump-earthflows, debris avalanches, and debris torrents impact streams, timber resources and man-made structures. Earthflows are associated with intercalated lava flows and volcaniclastics, especially stratified volcaniclastics which have low strength, high plasticity, and contain montmorillonite, an expandable clay mineral. Debris avalanches are associated with non-cohesive soils on steep slopes. Slump-earthflows show distinctive morphological and vegetative characteristics which reflect recency and rates of movement. Areas with different levels of activity can be mapped and the data used for certain land-planning applications. Surface movement rates can be measured on active earthflows by conventional surveying and the use of stake arrays. Results indicate that rapid surface movement exceeding 20 ft/yr is occurring on at least two earthflows, and that intraannual and annual periods of accelerated movement coincide with periods of greater water input from precipitation and snowmelt Movement of the Jude Creek earthflow also appears to be related to erosion of the toe by Jude Creek Movement on the Middle Santiam earthflow has greatly accelerated in the last three years (since 1978), compared with average rates for the previous 13 years Road construction in 1965 preceded the most recent pulse of movement at this site Inventory of debris avalanches in the study area indicate a link between road construction, storm history and debris avalanche occurrence Rates of soil transfer for road-related events is much greater than those for either forested or clearcut events. Title: Geology, geomorphology, and dynamics of mass movement in parts of the Middle Santiam River drainage basin, western Cascades, Oregon Author: Hicks, Bryan A. Landforms sculpted by mass movements comprise much of the landscape in the Middle Santiam study area. Bedrock in the area is mostly basalt and andesite flows and varied volcaniclastic rocks of the Little Butte Volcanic Series of Oligocene and early Miocene age, unconforniably overlain by andesite flows and tuffs of the Sardine Formation of middle and late Miocene age. Some mass movements in the study area may have originally occurred during glacial or interglacial periods of the late Pleistocene, although this is largely speculative. Active slump-earthflows, debris avalanches, and debris torrents impact streams, timber resources and man-made structures. Earthflows are associated with intercalated lava flows and volcaniclastics, especially stratified volcaniclastics which have low strength, high plasticity, and contain montmorillonite, an expandable clay mineral. Debris avalanches are associated with non-cohesive soils on steep slopes. Slump-earthflows show distinctive morphological and vegetative characteristics which reflect recency and rates of movement. Areas with different levels of activity can be mapped and the data used for certain land-planning applications. Surface movement rates can be measured on active earthflows by conventional surveying and the use of stake arrays. Results indicate that rapid surface movement exceeding 20 ft/yr is occurring on at least two earthflows, and that intraannual and annual periods of accelerated movement coincide with periods of greater water input from precipitation and snowmelt Movement of the Jude Creek earthflow also appears to be related to erosion of the toe by Jude Creek Movement on the Middle Santiam earthflow has greatly accelerated in the last three years (since 1978), compared with average rates for the previous 13 years Road construction in 1965 preceded the most recent pulse of movement at this site Inventory of debris avalanches in the study area indicate a link between road construction, storm history and debris avalanche occurrence Rates of soil transfer for road-related events is much greater than those for either forested or clearcut events. Close

• 33. [Article] Abrupt deglacial climate changes in the North Pacific and implications for climate tipping points

  Paleoclimate archives have revealed abrupt climate events that are superimposed on more gradual climate changes throughout the last glacial and deglacial periods. The underlying causes of such rapid climate ...

  Citation × Citation Citation Abstract Copy Title: Abrupt deglacial climate changes in the North Pacific and implications for climate tipping points Author: Praetorius, Summer Kate Paleoclimate archives have revealed abrupt climate events that are superimposed on more gradual climate changes throughout the last glacial and deglacial periods. The underlying causes of such rapid climate changes are still poorly understood, but the strong expression of these events in northern hemisphere records likely points to climatic mechanisms of a northern origin. A leading hypothesis for the trigger of these climate fluctuations has been changes in the strength of the Atlantic meridional overturning circulation (AMOC). However, the very rapid nature of some of the observed climate transitions (3-50 years) suggests a potential role for abrupt shifts in atmospheric circulation or nonlinear feedbacks within the climate system. Understanding the relative timing and magnitude of these events in different regions of the globe will help to identify the sources and possible amplifying mechanisms that have led to abrupt climate changes in the past, which will provide insight and constraints on the potential for abrupt climate changes in the future. This dissertation seeks to characterize climate changes occurring in the Northeast Pacific during the last deglaciation, a time period that encompasses the dynamic transition between the last ice age and the modern day interglacial period. So far, high-resolution records with precise chronologies from the North Pacific have been sparse, and paleoclimate models and proxy reconstructions disagree about the deglacial climate changes that are both predicted and observed to have occurred in this region. Marine sediment records from the Gulf of Alaska (GOA) have exceptionally high resolution (~1 cm/yr), making it possible to reconstruct climate changes in unprecedented detail for the North Pacific region. We establish new multi-decadal scale records of surface ocean variability using planktonic oxygen isotopes and sea-surface temperature (SST) estimates based on the alkenone U₃₇[superscript K'] unsaturation index, as well as regional records of ice-rafting and deglacial volcanic activity sourced from the Mt. Edgecumbe volcanic field (MEVF). The age models for these records are constrained by high-precision radiocarbon dating, tephra correlation, and "tuning" to the decadal-scale North Greenland Ice Core Project (NGRIP) oxygen isotope record. We combine new and previously published data from a depth transect of marine sites in the GOA and Northeast Pacific to place surface ocean changes in context of oceanic variability throughout the water column. These reconstructions are then used to evaluate three fundamental questions: 1) what are the timing and patterns of deglacial climate changes in the North Pacific relative to other regions, 2) what are the potential forcing mechanisms for deglacial climate variability in this region, and 3) how does the subsurface ocean respond to and influence abrupt climate change. In chapter two, we compare the timing and patterns of climate changes occurring between the North Pacific and North Atlantic regions. A major debate in the paleoclimate literature has been whether these regions operate in a synchronized or seesaw like mode. We compare the high resolution GOA and NGRIP oxygen isotope records as proxies for local temperature, and find that both synchronous and asynchronous climate patterns occur between regions throughout the past 18,000 years. The most abrupt climate transitions are preceded/accompanied by synchronous behavior, whereas times of relative climate stability exhibit asynchronous or anticorrelated (seesaw) patterns. This implies that coupling of North Pacific and North Atlantic heat transport could act as an amplifying mechanism in abrupt northern hemisphere climate change, whereas opposing oceanic regimes could act to balance northern hemisphere heat transport, and thus promote climate stability. In chapter three, we examine the timing between regional deglaciation and volcanism to evaluate potential feedbacks between climate and volcanic activity. Although volcanic eruptions have been observed to contribute to abrupt climate fluctuations with global effects in historical times, the role of volcanic forcing in climate variability of the more distant past (prior to the Holocene) has been neglected due to the very short-time scales in which volcanic events occur, and the difficulty of obtaining records with high enough resolution to capture these events and their associated climate effects. We evaluate the source and timing of a sequence of 23 tephra layers preserved in high-accumulation rate sediment cores proximal to the MEVF, and examine the regional climate response to this volcanic activity through comparison with reconstructions of sea surface temperatures, oxygen isotopes, and the δ¹⁸O of seawater. We find that the onset of enhanced volcanic activity coincides with abrupt warming at the onset of the Bølling Allerød, regional retreat of glaciers, and a period of rapid vertical land motion predicted from a model of regional isostatic rebound. These finding support the hypothesis that deglaciation may promote volcanism by removing crustal loading. The records of sea surface variability show large fluctuations during the episode of intense volcanic activity, suggesting that deglacial volcanic activity may not only respond to climate, but may also contribute to climate variance during the deglacial interval. In Chapter four, we examine the oceanographic changes that lead to two episodes of hypoxia in the GOA that lasted for millennia during the deglaciation. Similar hypoxic events have been documented across the North Pacific, indicating a widespread expansion of the oxygen minimum zone (OMZ) during the Bølling Allerød and early Holocene warm periods. These episodes have been linked to enhanced export productivity in many sites, however, the driving mechanisms for enhanced productivity and ocean deoxygenation remain elusive. Our alkenone temperature reconstructions reveal two abrupt warmings of 4-5°C that precisely coincide with the onset of increased export productivity and a sudden shift to hypoxic conditions, suggesting a strong link between ocean warming, marine productivity, and deoxygenation. Oxygen isotopes throughout the water column indicate that a transient subsurface warming of ~2°C might have accompanied the first hypoxic event during the BA. We propose that abrupt ocean warming lead to an expansion of the North Pacific OMZ through a reduction in oxygen solubility, enhanced thermal stratification, and a stimulation of marine productivity through the stabilization of the euphotic zone (related to stratification), combined with enhanced nutrient input from remobilization of iron in hypoxic shelf sediments. These studies indicate that large surface and subsurface ocean changes occurred in the North Pacific during the last deglaciation, with the potential for important feedbacks on global climate. Title: Abrupt deglacial climate changes in the North Pacific and implications for climate tipping points Author: Praetorius, Summer Kate Paleoclimate archives have revealed abrupt climate events that are superimposed on more gradual climate changes throughout the last glacial and deglacial periods. The underlying causes of such rapid climate changes are still poorly understood, but the strong expression of these events in northern hemisphere records likely points to climatic mechanisms of a northern origin. A leading hypothesis for the trigger of these climate fluctuations has been changes in the strength of the Atlantic meridional overturning circulation (AMOC). However, the very rapid nature of some of the observed climate transitions (3-50 years) suggests a potential role for abrupt shifts in atmospheric circulation or nonlinear feedbacks within the climate system. Understanding the relative timing and magnitude of these events in different regions of the globe will help to identify the sources and possible amplifying mechanisms that have led to abrupt climate changes in the past, which will provide insight and constraints on the potential for abrupt climate changes in the future. This dissertation seeks to characterize climate changes occurring in the Northeast Pacific during the last deglaciation, a time period that encompasses the dynamic transition between the last ice age and the modern day interglacial period. So far, high-resolution records with precise chronologies from the North Pacific have been sparse, and paleoclimate models and proxy reconstructions disagree about the deglacial climate changes that are both predicted and observed to have occurred in this region. Marine sediment records from the Gulf of Alaska (GOA) have exceptionally high resolution (~1 cm/yr), making it possible to reconstruct climate changes in unprecedented detail for the North Pacific region. We establish new multi-decadal scale records of surface ocean variability using planktonic oxygen isotopes and sea-surface temperature (SST) estimates based on the alkenone U₃₇[superscript K'] unsaturation index, as well as regional records of ice-rafting and deglacial volcanic activity sourced from the Mt. Edgecumbe volcanic field (MEVF). The age models for these records are constrained by high-precision radiocarbon dating, tephra correlation, and "tuning" to the decadal-scale North Greenland Ice Core Project (NGRIP) oxygen isotope record. We combine new and previously published data from a depth transect of marine sites in the GOA and Northeast Pacific to place surface ocean changes in context of oceanic variability throughout the water column. These reconstructions are then used to evaluate three fundamental questions: 1) what are the timing and patterns of deglacial climate changes in the North Pacific relative to other regions, 2) what are the potential forcing mechanisms for deglacial climate variability in this region, and 3) how does the subsurface ocean respond to and influence abrupt climate change. In chapter two, we compare the timing and patterns of climate changes occurring between the North Pacific and North Atlantic regions. A major debate in the paleoclimate literature has been whether these regions operate in a synchronized or seesaw like mode. We compare the high resolution GOA and NGRIP oxygen isotope records as proxies for local temperature, and find that both synchronous and asynchronous climate patterns occur between regions throughout the past 18,000 years. The most abrupt climate transitions are preceded/accompanied by synchronous behavior, whereas times of relative climate stability exhibit asynchronous or anticorrelated (seesaw) patterns. This implies that coupling of North Pacific and North Atlantic heat transport could act as an amplifying mechanism in abrupt northern hemisphere climate change, whereas opposing oceanic regimes could act to balance northern hemisphere heat transport, and thus promote climate stability. In chapter three, we examine the timing between regional deglaciation and volcanism to evaluate potential feedbacks between climate and volcanic activity. Although volcanic eruptions have been observed to contribute to abrupt climate fluctuations with global effects in historical times, the role of volcanic forcing in climate variability of the more distant past (prior to the Holocene) has been neglected due to the very short-time scales in which volcanic events occur, and the difficulty of obtaining records with high enough resolution to capture these events and their associated climate effects. We evaluate the source and timing of a sequence of 23 tephra layers preserved in high-accumulation rate sediment cores proximal to the MEVF, and examine the regional climate response to this volcanic activity through comparison with reconstructions of sea surface temperatures, oxygen isotopes, and the δ¹⁸O of seawater. We find that the onset of enhanced volcanic activity coincides with abrupt warming at the onset of the Bølling Allerød, regional retreat of glaciers, and a period of rapid vertical land motion predicted from a model of regional isostatic rebound. These finding support the hypothesis that deglaciation may promote volcanism by removing crustal loading. The records of sea surface variability show large fluctuations during the episode of intense volcanic activity, suggesting that deglacial volcanic activity may not only respond to climate, but may also contribute to climate variance during the deglacial interval. In Chapter four, we examine the oceanographic changes that lead to two episodes of hypoxia in the GOA that lasted for millennia during the deglaciation. Similar hypoxic events have been documented across the North Pacific, indicating a widespread expansion of the oxygen minimum zone (OMZ) during the Bølling Allerød and early Holocene warm periods. These episodes have been linked to enhanced export productivity in many sites, however, the driving mechanisms for enhanced productivity and ocean deoxygenation remain elusive. Our alkenone temperature reconstructions reveal two abrupt warmings of 4-5°C that precisely coincide with the onset of increased export productivity and a sudden shift to hypoxic conditions, suggesting a strong link between ocean warming, marine productivity, and deoxygenation. Oxygen isotopes throughout the water column indicate that a transient subsurface warming of ~2°C might have accompanied the first hypoxic event during the BA. We propose that abrupt ocean warming lead to an expansion of the North Pacific OMZ through a reduction in oxygen solubility, enhanced thermal stratification, and a stimulation of marine productivity through the stabilization of the euphotic zone (related to stratification), combined with enhanced nutrient input from remobilization of iron in hypoxic shelf sediments. These studies indicate that large surface and subsurface ocean changes occurred in the North Pacific during the last deglaciation, with the potential for important feedbacks on global climate. Close

• 34. [Article] Basal temperature evolution of North American ice sheets and implications for the 100-kyr cycle

  This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://www.agu.org/journals/gl/.

  Citation × Citation Citation Abstract Copy Title: Basal temperature evolution of North American ice sheets and implications for the 100-kyr cycle Author: Marshall, Shawn J., Clark, Peter U. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://www.agu.org/journals/gl/. Title: Basal temperature evolution of North American ice sheets and implications for the 100-kyr cycle Author: Marshall, Shawn J., Clark, Peter U. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://www.agu.org/journals/gl/. Close

• 35. [Article] Hydrologic Response to Extreme Warm and Cold Summers in the McMurdo Dry Valleys, East Antarctica

  The meteorological characteristics and hydrological response of an extreme warm, and cold summer in the McMurdo Dry Valleys are compared. The driver behind the warmer summer conditions was the occurrence ...

  Citation × Citation Citation Abstract Copy Title: Hydrologic Response to Extreme Warm and Cold Summers in the McMurdo Dry Valleys, East Antarctica Author: Doran, Peter T., McKay, Christopher P., Fountain, Andrew G., Nylen, Thomas H., McKnight, Diane M., Jaros, Chris, Barrett, John E. Year: 2008 The meteorological characteristics and hydrological response of an extreme warm, and cold summer in the McMurdo Dry Valleys are compared. The driver behind the warmer summer conditions was the occurrence of down-valley winds, which were not present during the colder summer. Occurrence of the summer down-valley winds coincided with lower than typical mean sea level pressure in the Ross Sea region. There was no significant difference in the amount of solar radiation received during the two summers. Compared to the cold summer, glaciological and hydrological response to the warm summer in Taylor Valley included significant glacier mass loss, and 3- to nearly 6000-fold increase in annual streamflow. Lake levels decreased slightly during the cold summer, and increased between 0.54 and 1.01 m during the warm summer, effectively erasing the prior 14 years of lake level lowering in a period of three months. Lake level rise during the warm summer was shown to be strongly associated with and increase in degree days above freezing at higher elevations. We suggest that strong summer down-valley winds may have been responsible for the generation of large glacial lakes during the Last Glacial Maximum when ice core records recorded annual temperatures significantly colder than present. Title: Hydrologic Response to Extreme Warm and Cold Summers in the McMurdo Dry Valleys, East Antarctica Author: Doran, Peter T., McKay, Christopher P., Fountain, Andrew G., Nylen, Thomas H., McKnight, Diane M., Jaros, Chris, Barrett, John E. Year: 2008 The meteorological characteristics and hydrological response of an extreme warm, and cold summer in the McMurdo Dry Valleys are compared. The driver behind the warmer summer conditions was the occurrence of down-valley winds, which were not present during the colder summer. Occurrence of the summer down-valley winds coincided with lower than typical mean sea level pressure in the Ross Sea region. There was no significant difference in the amount of solar radiation received during the two summers. Compared to the cold summer, glaciological and hydrological response to the warm summer in Taylor Valley included significant glacier mass loss, and 3- to nearly 6000-fold increase in annual streamflow. Lake levels decreased slightly during the cold summer, and increased between 0.54 and 1.01 m during the warm summer, effectively erasing the prior 14 years of lake level lowering in a period of three months. Lake level rise during the warm summer was shown to be strongly associated with and increase in degree days above freezing at higher elevations. We suggest that strong summer down-valley winds may have been responsible for the generation of large glacial lakes during the Last Glacial Maximum when ice core records recorded annual temperatures significantly colder than present. Close

• 36. [Article] Cenozoic biogenic silica sedimentation in the Antarctic Ocean, based on two deep sea drilling project sites

  The Antarctic Ocean during the Cenozoic experienced four periods of increased surface productivity: the Middle Eocene; the beginning of the Miocene; the Middle Miocene; and near the Miocene-Pliocene boundary. ...

  Citation × Citation Citation Abstract Copy Title: Cenozoic biogenic silica sedimentation in the Antarctic Ocean, based on two deep sea drilling project sites Author: Brewster, Nancy Ann The Antarctic Ocean during the Cenozoic experienced four periods of increased surface productivity: the Middle Eocene; the beginning of the Miocene; the Middle Miocene; and near the Miocene-Pliocene boundary. The fourth increase in productivity began five million years ago and has since progressively increased to the present level of intense surface productivity. The major control of Antarctic surface productivity is climate. Opal production in the Neogene increased during glacial times, due to the intensification of upwelling south of the Polar Front, caused from accelerated atmospheric circulation and an increased volume production of Antarctic Bottom Water. Cenozoic variations in surface productivity are also related to the tectonic changes in the Antarctic Ocean basin, which altered the patterns of surface and thermohaline circulation. Antarctic Surface Waters became more conducive to biological productivity with the progressive latitudinal and thermal isolation of Antarctica, The efficiency of surface productivity has progressed to such an extent that much of the global silica supply has been transferred to the Antarctic at the expense of other productive oceanic regions such as the Central Equatorial Pacific. In the Neogene, the preservation or dissolution of calcium carbonate is influenced by the rate of upwelling south of the Polar Front. During glacial times, the upwelling of COB_rich Circumpolar Deep Water accelerates and effectively raises the calcite compensation depth. Title: Cenozoic biogenic silica sedimentation in the Antarctic Ocean, based on two deep sea drilling project sites Author: Brewster, Nancy Ann The Antarctic Ocean during the Cenozoic experienced four periods of increased surface productivity: the Middle Eocene; the beginning of the Miocene; the Middle Miocene; and near the Miocene-Pliocene boundary. The fourth increase in productivity began five million years ago and has since progressively increased to the present level of intense surface productivity. The major control of Antarctic surface productivity is climate. Opal production in the Neogene increased during glacial times, due to the intensification of upwelling south of the Polar Front, caused from accelerated atmospheric circulation and an increased volume production of Antarctic Bottom Water. Cenozoic variations in surface productivity are also related to the tectonic changes in the Antarctic Ocean basin, which altered the patterns of surface and thermohaline circulation. Antarctic Surface Waters became more conducive to biological productivity with the progressive latitudinal and thermal isolation of Antarctica, The efficiency of surface productivity has progressed to such an extent that much of the global silica supply has been transferred to the Antarctic at the expense of other productive oceanic regions such as the Central Equatorial Pacific. In the Neogene, the preservation or dissolution of calcium carbonate is influenced by the rate of upwelling south of the Polar Front. During glacial times, the upwelling of COB_rich Circumpolar Deep Water accelerates and effectively raises the calcite compensation depth. Close

• 37. [Article] Origin of the Tucannon phase in Lower Snake River prehistory

  Approximately 5,500 years ago a discreet period of wetter and cooler environmental conditions prevailed across the southern Columbia Plateau. This period was marked by the first prominent episodes of erosion ...

  Citation × Citation Citation Abstract Copy Title: Origin of the Tucannon phase in Lower Snake River prehistory Author: Lucas, Steven W. Approximately 5,500 years ago a discreet period of wetter and cooler environmental conditions prevailed across the southern Columbia Plateau. This period was marked by the first prominent episodes of erosion to occur along the lower Snake River following the height of the Altithermal and eruption of Mt. Mazama during the mid post-glacial. In addition to the reactivation of small stream courses choked with debris and sediment, large stream channels began downcutting and scouring older terrace faces incorporated with large accumulations of Mazama ash. The resulting degradation of aquatic habitats forced concurrent changes within human economies adapted to the local riverine-environments. These adjustments reported for the Tucannon phase time period along the lower Snake River are notable and demonstrate the degree to which Cascade phase culture was unsuccessful in coping with environmental instability at the end of the Altithermal time period. This successionary event has demonstratively become the most significant post-glacial, qualitative change to occur in the lifeways of lower Snake River people prior to Euro-American influence. Title: Origin of the Tucannon phase in Lower Snake River prehistory Author: Lucas, Steven W. Approximately 5,500 years ago a discreet period of wetter and cooler environmental conditions prevailed across the southern Columbia Plateau. This period was marked by the first prominent episodes of erosion to occur along the lower Snake River following the height of the Altithermal and eruption of Mt. Mazama during the mid post-glacial. In addition to the reactivation of small stream courses choked with debris and sediment, large stream channels began downcutting and scouring older terrace faces incorporated with large accumulations of Mazama ash. The resulting degradation of aquatic habitats forced concurrent changes within human economies adapted to the local riverine-environments. These adjustments reported for the Tucannon phase time period along the lower Snake River are notable and demonstrate the degree to which Cascade phase culture was unsuccessful in coping with environmental instability at the end of the Altithermal time period. This successionary event has demonstratively become the most significant post-glacial, qualitative change to occur in the lifeways of lower Snake River people prior to Euro-American influence. Close

• 38. [Article] The changing glaciers of Mt. Hood, Oregon and Mt. Rainier, Washington : implications for periglacial debris flows

  Mountain glaciers are receding worldwide with numerous consequences including changing hydrology and geomorphology. This study focuses on changes in glacier area on Mt. Hood, Oregon and Mt. Rainier, Washington ...

  Citation × Citation Citation Abstract Copy Title: The changing glaciers of Mt. Hood, Oregon and Mt. Rainier, Washington : implications for periglacial debris flows Author: Ellinger, Jonathan R. Mountain glaciers are receding worldwide with numerous consequences including changing hydrology and geomorphology. This study focuses on changes in glacier area on Mt. Hood, Oregon and Mt. Rainier, Washington where damaging debris flows have occurred in glaciated basins. Landsat imagery is used to map debris-free ice on a decadal time scale from 1987 to 2005. Debris-free glacier ice is clearly delineated using a ratio of Landsat spectral bands in the near-infrared part of the spectrum (bands 4 & 5). Landsat scenes were chosen during the months of September and October to minimize snow cover left over from the accumulation season and maximize exposure of debris-free glacial ice. SNOTEL data were also used to find the lowest snow year for each decade to minimize the potential of misclassifying remnant snow as glacial ice. Changes in debris-free ice are mapped to produce the most up-to-date rates of glacier retreat. Average glacial slopes, derived from airborne LiDAR data are used to compute slope corrected debris-free ice areas for all glaciers. A threshold value for the Landsat NDGI scenes was selected based on threshold testing on the Eliot and Reid glaciers on Mt. Hood. Contradicting earlier studies that say the glaciers on Mt. Hood are receding faster than the glaciers on Mt. Rainier, results show that from 1987 to 2005 Mt. Rainier and Mt. Hood lost similar amounts of debris-free ice extent at 14.0% and 13.9%, respectively. For both Mt. Hood and Mt. Rainier the change in slope corrected debris-free ice area was greater than that of the projected area change due to the steep slopes of both mountains. For Mt. Rainier an increase in recession rate was shown from 1992-2005 compared to 1987-1992 while on Mt. Hood the opposite is seen. On Mt. Rainier it was found that highly fragmented glaciers at lower elevations such as the Inter, Pyramid, and the Van Trump Glaciers lost the highest percent of their original 1987 ice extent and were also shown to be associated with new debris flows in 2006. On Mt. Hood none of the 2006 debris flows initiated within zones of recent glacial recession, however, all debris flows from 2006 originated from streams with a direct connection to glaciers. The Newton Clark Glacier, having lost the most coverage of debris-free ice from 1987 to 2005, is also associated with the highest number of debris-flows in its drainage since 1980. Precipitation data for both mountains show no trend but there was a statistically significant increase in summer air temperature at Mt. Hood over the period 1984-2009. This study suggests that glaciers may play a role in the location of initiation sites, of debris flows, but there is not enough evidence to argue that glacier recession is responsible for producing debris flows. Title: The changing glaciers of Mt. Hood, Oregon and Mt. Rainier, Washington : implications for periglacial debris flows Author: Ellinger, Jonathan R. Mountain glaciers are receding worldwide with numerous consequences including changing hydrology and geomorphology. This study focuses on changes in glacier area on Mt. Hood, Oregon and Mt. Rainier, Washington where damaging debris flows have occurred in glaciated basins. Landsat imagery is used to map debris-free ice on a decadal time scale from 1987 to 2005. Debris-free glacier ice is clearly delineated using a ratio of Landsat spectral bands in the near-infrared part of the spectrum (bands 4 & 5). Landsat scenes were chosen during the months of September and October to minimize snow cover left over from the accumulation season and maximize exposure of debris-free glacial ice. SNOTEL data were also used to find the lowest snow year for each decade to minimize the potential of misclassifying remnant snow as glacial ice. Changes in debris-free ice are mapped to produce the most up-to-date rates of glacier retreat. Average glacial slopes, derived from airborne LiDAR data are used to compute slope corrected debris-free ice areas for all glaciers. A threshold value for the Landsat NDGI scenes was selected based on threshold testing on the Eliot and Reid glaciers on Mt. Hood. Contradicting earlier studies that say the glaciers on Mt. Hood are receding faster than the glaciers on Mt. Rainier, results show that from 1987 to 2005 Mt. Rainier and Mt. Hood lost similar amounts of debris-free ice extent at 14.0% and 13.9%, respectively. For both Mt. Hood and Mt. Rainier the change in slope corrected debris-free ice area was greater than that of the projected area change due to the steep slopes of both mountains. For Mt. Rainier an increase in recession rate was shown from 1992-2005 compared to 1987-1992 while on Mt. Hood the opposite is seen. On Mt. Rainier it was found that highly fragmented glaciers at lower elevations such as the Inter, Pyramid, and the Van Trump Glaciers lost the highest percent of their original 1987 ice extent and were also shown to be associated with new debris flows in 2006. On Mt. Hood none of the 2006 debris flows initiated within zones of recent glacial recession, however, all debris flows from 2006 originated from streams with a direct connection to glaciers. The Newton Clark Glacier, having lost the most coverage of debris-free ice from 1987 to 2005, is also associated with the highest number of debris-flows in its drainage since 1980. Precipitation data for both mountains show no trend but there was a statistically significant increase in summer air temperature at Mt. Hood over the period 1984-2009. This study suggests that glaciers may play a role in the location of initiation sites, of debris flows, but there is not enough evidence to argue that glacier recession is responsible for producing debris flows. Close

• 39. [Article] Late Quaternary paleoceanography in the Eastern Equatorial Pacific Ocean from Planktonic Foraminifiers : a high-resolution record from Site 846

  High-resolution records of δ¹⁸0 and relative abundances of planktonic foraminifers were generated for ODP Leg 138 Site 846 for the past 800 k.y., with an average sampling interval of 3.6 k.y. The time ...

  Citation × Citation Citation Abstract Copy Title: Late Quaternary paleoceanography in the Eastern Equatorial Pacific Ocean from Planktonic Foraminifiers : a high-resolution record from Site 846 Author: Shackleton, N.J., Le, J., Mix, Alan C. High-resolution records of δ¹⁸0 and relative abundances of planktonic foraminifers were generated for ODP Leg 138 Site 846 for the past 800 k.y., with an average sampling interval of 3.6 k.y. The time scale was constructed by correlating the benthic δ¹⁸0 record to the SPECMAP and ODP Site 677 δ¹⁸0 time scales using the mapping function technique of Martinson et al. (1981). Our observations show that variations in the foraminiferal assemblages, although influenced by dissolution, are interpretable in terms of changing characteristics of upper ocean waters. Carbonate dissolution as indicated by fragmentation of planktonic foraminifers shows concentrated variance that is coherent with δ¹⁸0 at the 100 and 41 k.y. orbital periods. At these periods, maximum dissolution occurs during interglacial extremes. This finding differs from previous studies that have indicated that in this region percent carbonate minimum lags global ice volume minimum. N. dutertrei and dextral N. pachyderma dominate the assemblages, but do not show consistent relationships relative to glacial-interglacial cycles. However, less abundant species G. ruber, G. menardii, G. glutinata and G. sacculifer show positive and G. bulloides negative correlation with the δ¹⁸0 record. Q-mode factor analysis of the Site 846 assemblages and comparison with modern assemblages suggest the following. Prior to and during interglacials, the area was considerably warmer and more subtropical than at present; during glacials, the area was colder than at present with greater upwelling and advection off the eastern boundary, and possibly a stronger Peru Current; the equatorial “cool tongue” was also possibly stronger. Title: Late Quaternary paleoceanography in the Eastern Equatorial Pacific Ocean from Planktonic Foraminifiers : a high-resolution record from Site 846 Author: Shackleton, N.J., Le, J., Mix, Alan C. High-resolution records of δ¹⁸0 and relative abundances of planktonic foraminifers were generated for ODP Leg 138 Site 846 for the past 800 k.y., with an average sampling interval of 3.6 k.y. The time scale was constructed by correlating the benthic δ¹⁸0 record to the SPECMAP and ODP Site 677 δ¹⁸0 time scales using the mapping function technique of Martinson et al. (1981). Our observations show that variations in the foraminiferal assemblages, although influenced by dissolution, are interpretable in terms of changing characteristics of upper ocean waters. Carbonate dissolution as indicated by fragmentation of planktonic foraminifers shows concentrated variance that is coherent with δ¹⁸0 at the 100 and 41 k.y. orbital periods. At these periods, maximum dissolution occurs during interglacial extremes. This finding differs from previous studies that have indicated that in this region percent carbonate minimum lags global ice volume minimum. N. dutertrei and dextral N. pachyderma dominate the assemblages, but do not show consistent relationships relative to glacial-interglacial cycles. However, less abundant species G. ruber, G. menardii, G. glutinata and G. sacculifer show positive and G. bulloides negative correlation with the δ¹⁸0 record. Q-mode factor analysis of the Site 846 assemblages and comparison with modern assemblages suggest the following. Prior to and during interglacials, the area was considerably warmer and more subtropical than at present; during glacials, the area was colder than at present with greater upwelling and advection off the eastern boundary, and possibly a stronger Peru Current; the equatorial “cool tongue” was also possibly stronger. Close

• 40. [Article] Increased dissolved terrestrial input to the coastal ocean during the last deglaciation

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: Increased dissolved terrestrial input to the coastal ocean during the last deglaciation Author: Haley, B. A., Klinkhammer, Gary P., Mix, Alan C. Copyrighted by American Geophysical Union. Title: Increased dissolved terrestrial input to the coastal ocean during the last deglaciation Author: Haley, B. A., Klinkhammer, Gary P., Mix, Alan C. Copyrighted by American Geophysical Union. Close