<p>The Alaskan region (comprising glaciers in Alaska, British Columbia and Yukon) contains ... more <p>The Alaskan region (comprising glaciers in Alaska, British Columbia and Yukon) contains the third largest ice volume outside of the Greenland and Antarctic ice sheets, and contributes more to global sea level rise than any other glacierised region defined by the Randolph Glacier Inventory. However, ice loss in this area is not linear, but in part controlled by glacier hypsometry as valley and outlet glaciers are at risk of becoming detached from their accumulation areas during thinning. Plateau icefields, such as Juneau Icefield in Alaska, are very sensitive to changes in Equilibrium Line Altitude (ELA) as this can result in rapidly shrinking accumulation areas. Here, we present detailed geomorphological mapping around Juneau Icefield and use this data to reconstruct the icefield during the &#8220;Little Ice Age&#8221;. We use topographic maps, archival aerial photographs, high-resolution satellite imagery and digital elevation models to map glacier lake and glacier area and volume change from the Little Ice Age to the present day (1770, 1948, 1979, 1990, 2005, 2015 and 2019 AD). Structural glaciological mapping (1979 and 2019) highlights structural and topographic controls on non-linear glacier recession.&#160; Our data shows pronounced glacier thinning and recession in response to widespread detachment of outlet glaciers from their plateau accumulation areas. Glacier detachments became common after 2005, and occurred with increasing frequency since then. Total summed rates of area change increased eightfold from 1770-1948 (-6.14 km<sup>2</sup> a<sup>-1</sup>) to 2015-2019 (-45.23 km<sup>2</sup> a<sup>-1</sup>). Total rates of recession were consistent from 1770 to 1990 AD, and grew increasingly rapid after 2005, in line with regional warming.</p>
Bulletin of the American Meteorological Society, 2019
Editor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-res... more Editor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
Observations show that glaciers around the world are in retreat and losing mass. Internationally ... more Observations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (∼42 000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations...
The thirty-eight-year record (1984–2021) of glacier mass balance measurement indicates a signific... more The thirty-eight-year record (1984–2021) of glacier mass balance measurement indicates a significant glacier response to climate change in the North Cascades, Washington that has led to declining glacier runoff in the Nooksack Basin. Glacier runoff in the Nooksack Basin is a major source of streamflow during the summer low-flow season and mitigates both low flow and warm water temperatures; this is particularly true during summer heat waves. Synchronous observations of glacier ablation and stream discharge immediately below Sholes Glacier from 2013–2017, independently identify daily discharge during the ablation season. The identified ablation rate is applied to glaciers across the North Fork Nooksack watershed, providing daily glacier runoff discharge to the North Fork Nooksack River. This is compared to observed daily discharge and temperature data of the North Fork Nooksack River and the unglaciated South Fork Nooksack River from the USGS. The ameliorating role of glacier runoff ...
Bulletin of the American Meteorological Society, 2019
Editor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-res... more Editor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
This study reports the changes in glacier extent and streamflow similar to many Himalayan studies... more This study reports the changes in glacier extent and streamflow similar to many Himalayan studies, but takes the unusual step of also linking these to downstream land use changes in Kashmir Valley. This study assessed changes in the area, snout, and equilibrium line altitude (ELA) of four parts of the Kolahoi Glacier using earth observation data from 1962 to 2018. Changes in the discharge of the two streams flowing out from Kolahoi Glacier into the Jhelum basin were also assessed between 1972 and 2018. Additionally, satellite data was used to track the downstream land system changes concerning agriculture, orchards, and built-up areas between 1980 and 2018. This analysis suggested a cumulative deglaciation of 23.6% at a rate of 0.42% per year from 1962 to 2018. The snout of two larger glaciers, G1 and G2, retreated at a rate of 18.3 m a−1 and 16.4 m a−1, respectively, from 1962 to 2018, although the rate of recession accelerated after 2000. Our analysis also suggested the upward shi...
Identification of present-day climate setting and alpine glacier-balance gradients indicates that... more Identification of present-day climate setting and alpine glacier-balance gradients indicates that the balance gradient of alpine glaciers is primarily determined by climatic conditions. Determination of balance gradients for specific climatic settings on present-day ice sheets provides an analog for determining the mass balance on paleo and future ice sheets.
The annual surface mass balance for 1983 and 1984 and the 10 year cumulative mass balances for 19... more The annual surface mass balance for 1983 and 1984 and the 10 year cumulative mass balances for 1975–85 were calculated for 60 south-east Alaskan and north-west British Columbia glaciers. At present, the mass balance is positive on nine, at equilibrium on nine, and negative on 42 glaciers. The ratio of glaciers with positive and equilibrium mass balance to glaciers with negative mass-balance has not changed significantly since 1946; however, the magnitude of negative balances has declined on 39 of the 42 glaciers. The annual mass balance of south-east Alaska and north-west British Columbia glaciers cannot be measured on more than a few glaciers. This paper presents the methods and results for a mass-balance model using as input local weather records, Juneau Icefield field studies, and satellite imagery. The primary variable in mass balance from one glacier to another is the budget gradient. The budget gradient varies predictably according to three parameters: ocean proximity, surface...
In 1983 the North Cascade Glacier Climate Project (NCGCP) began annual monitoring 10 glaciers thr... more In 1983 the North Cascade Glacier Climate Project (NCGCP) began annual monitoring 10 glaciers throughout the range, to identify their response to climate change. The annual observations include mass balance, terminus behaviour, and accumulation area ratio (AAR). Annual mass balance (Ba) measurements have been continued on 7 original glaciers that still exist. Two glaciers have disappeared: the Lewis Glacier and Spider Glacier. Foss Glacier was discontinued in 2014 as it has separated into several sections. In 1990, Easton Glacier and Sholes Glacier were added to the annual balance program. This comparatively long record from glaciers in one region conducted by the same research program using the same methods offers some useful comparative data to place the impact of regional climate warmth of 2015 in perspective. The mean annual balance of the North Cascade glaciers is reported in water equivalent thicknesses to the World Glacier Monitoring Service (WGMS). From 1984–2015 the mean Ba...
North Cascade glacier annual balance measured on 10 glaciers from 1984–2006 yielded mean an... more North Cascade glacier annual balance measured on 10 glaciers from 1984–2006 yielded mean annual balance (b<sub><i>a</i></sub>) of −0.54 m/a, and −12.38 m cumulatively. This is a significant loss for glaciers that average 30–60 m in thickness, 20–40% of their entire volume. Two observed glaciers, Lewis Glacier and Spider Glacier, no longer exist. <br></br> The b<sub><i>a</i></sub> of North Cascade glaciers is reliably calculated, correlation coefficient 0.91, using 1 April snowpack water equivalent and ablation season temperature. Utilizing b<sub><i>a</i></sub> from 10 glaciers 1984–2006 and net balance…
Identification of the transient snowline (TSL) from high spatial resolution Landsat imagery on Le... more Identification of the transient snowline (TSL) from high spatial resolution Landsat imagery on Lemon Creek Glacier (LCG), southeast Alaska, USA, and Mittivakkat Gletscher (MG), southeast Greenland, is used to determine snow ablation rates, the equilibrium-line altitude (ELA) and the accumulation-area ratio (AAR). The rate of rise of the TSL during the ablation season on a glacier where the balance gradient is known provides a measure of the snow ablation rate. On both LCG and MG, snow pits were completed in regions that the TSL subsequently transects. This further provides a direct measure of the snow ablation rates for a particular year. TSL observations from multiple dates during the ablation season from 1998 to 2011 at LCG and 1999 to 2012 at MG were used to explore the consistency of the TSL rise and snow ablation rate. On LCG and MG the satellite-derived mean TSL migration rates were 3.8 ± 0.6 and 9.4 ± 9.1 m d−1, respectively. The snow ablation rates were 0.028 ± 0.004 m w.e. ...
<p>The Alaskan region (comprising glaciers in Alaska, British Columbia and Yukon) contains ... more <p>The Alaskan region (comprising glaciers in Alaska, British Columbia and Yukon) contains the third largest ice volume outside of the Greenland and Antarctic ice sheets, and contributes more to global sea level rise than any other glacierised region defined by the Randolph Glacier Inventory. However, ice loss in this area is not linear, but in part controlled by glacier hypsometry as valley and outlet glaciers are at risk of becoming detached from their accumulation areas during thinning. Plateau icefields, such as Juneau Icefield in Alaska, are very sensitive to changes in Equilibrium Line Altitude (ELA) as this can result in rapidly shrinking accumulation areas. Here, we present detailed geomorphological mapping around Juneau Icefield and use this data to reconstruct the icefield during the &#8220;Little Ice Age&#8221;. We use topographic maps, archival aerial photographs, high-resolution satellite imagery and digital elevation models to map glacier lake and glacier area and volume change from the Little Ice Age to the present day (1770, 1948, 1979, 1990, 2005, 2015 and 2019 AD). Structural glaciological mapping (1979 and 2019) highlights structural and topographic controls on non-linear glacier recession.&#160; Our data shows pronounced glacier thinning and recession in response to widespread detachment of outlet glaciers from their plateau accumulation areas. Glacier detachments became common after 2005, and occurred with increasing frequency since then. Total summed rates of area change increased eightfold from 1770-1948 (-6.14 km<sup>2</sup> a<sup>-1</sup>) to 2015-2019 (-45.23 km<sup>2</sup> a<sup>-1</sup>). Total rates of recession were consistent from 1770 to 1990 AD, and grew increasingly rapid after 2005, in line with regional warming.</p>
Bulletin of the American Meteorological Society, 2019
Editor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-res... more Editor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
Observations show that glaciers around the world are in retreat and losing mass. Internationally ... more Observations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (∼42 000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations...
The thirty-eight-year record (1984–2021) of glacier mass balance measurement indicates a signific... more The thirty-eight-year record (1984–2021) of glacier mass balance measurement indicates a significant glacier response to climate change in the North Cascades, Washington that has led to declining glacier runoff in the Nooksack Basin. Glacier runoff in the Nooksack Basin is a major source of streamflow during the summer low-flow season and mitigates both low flow and warm water temperatures; this is particularly true during summer heat waves. Synchronous observations of glacier ablation and stream discharge immediately below Sholes Glacier from 2013–2017, independently identify daily discharge during the ablation season. The identified ablation rate is applied to glaciers across the North Fork Nooksack watershed, providing daily glacier runoff discharge to the North Fork Nooksack River. This is compared to observed daily discharge and temperature data of the North Fork Nooksack River and the unglaciated South Fork Nooksack River from the USGS. The ameliorating role of glacier runoff ...
Bulletin of the American Meteorological Society, 2019
Editor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-res... more Editor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
This study reports the changes in glacier extent and streamflow similar to many Himalayan studies... more This study reports the changes in glacier extent and streamflow similar to many Himalayan studies, but takes the unusual step of also linking these to downstream land use changes in Kashmir Valley. This study assessed changes in the area, snout, and equilibrium line altitude (ELA) of four parts of the Kolahoi Glacier using earth observation data from 1962 to 2018. Changes in the discharge of the two streams flowing out from Kolahoi Glacier into the Jhelum basin were also assessed between 1972 and 2018. Additionally, satellite data was used to track the downstream land system changes concerning agriculture, orchards, and built-up areas between 1980 and 2018. This analysis suggested a cumulative deglaciation of 23.6% at a rate of 0.42% per year from 1962 to 2018. The snout of two larger glaciers, G1 and G2, retreated at a rate of 18.3 m a−1 and 16.4 m a−1, respectively, from 1962 to 2018, although the rate of recession accelerated after 2000. Our analysis also suggested the upward shi...
Identification of present-day climate setting and alpine glacier-balance gradients indicates that... more Identification of present-day climate setting and alpine glacier-balance gradients indicates that the balance gradient of alpine glaciers is primarily determined by climatic conditions. Determination of balance gradients for specific climatic settings on present-day ice sheets provides an analog for determining the mass balance on paleo and future ice sheets.
The annual surface mass balance for 1983 and 1984 and the 10 year cumulative mass balances for 19... more The annual surface mass balance for 1983 and 1984 and the 10 year cumulative mass balances for 1975–85 were calculated for 60 south-east Alaskan and north-west British Columbia glaciers. At present, the mass balance is positive on nine, at equilibrium on nine, and negative on 42 glaciers. The ratio of glaciers with positive and equilibrium mass balance to glaciers with negative mass-balance has not changed significantly since 1946; however, the magnitude of negative balances has declined on 39 of the 42 glaciers. The annual mass balance of south-east Alaska and north-west British Columbia glaciers cannot be measured on more than a few glaciers. This paper presents the methods and results for a mass-balance model using as input local weather records, Juneau Icefield field studies, and satellite imagery. The primary variable in mass balance from one glacier to another is the budget gradient. The budget gradient varies predictably according to three parameters: ocean proximity, surface...
In 1983 the North Cascade Glacier Climate Project (NCGCP) began annual monitoring 10 glaciers thr... more In 1983 the North Cascade Glacier Climate Project (NCGCP) began annual monitoring 10 glaciers throughout the range, to identify their response to climate change. The annual observations include mass balance, terminus behaviour, and accumulation area ratio (AAR). Annual mass balance (Ba) measurements have been continued on 7 original glaciers that still exist. Two glaciers have disappeared: the Lewis Glacier and Spider Glacier. Foss Glacier was discontinued in 2014 as it has separated into several sections. In 1990, Easton Glacier and Sholes Glacier were added to the annual balance program. This comparatively long record from glaciers in one region conducted by the same research program using the same methods offers some useful comparative data to place the impact of regional climate warmth of 2015 in perspective. The mean annual balance of the North Cascade glaciers is reported in water equivalent thicknesses to the World Glacier Monitoring Service (WGMS). From 1984–2015 the mean Ba...
North Cascade glacier annual balance measured on 10 glaciers from 1984–2006 yielded mean an... more North Cascade glacier annual balance measured on 10 glaciers from 1984–2006 yielded mean annual balance (b<sub><i>a</i></sub>) of −0.54 m/a, and −12.38 m cumulatively. This is a significant loss for glaciers that average 30–60 m in thickness, 20–40% of their entire volume. Two observed glaciers, Lewis Glacier and Spider Glacier, no longer exist. <br></br> The b<sub><i>a</i></sub> of North Cascade glaciers is reliably calculated, correlation coefficient 0.91, using 1 April snowpack water equivalent and ablation season temperature. Utilizing b<sub><i>a</i></sub> from 10 glaciers 1984–2006 and net balance…
Identification of the transient snowline (TSL) from high spatial resolution Landsat imagery on Le... more Identification of the transient snowline (TSL) from high spatial resolution Landsat imagery on Lemon Creek Glacier (LCG), southeast Alaska, USA, and Mittivakkat Gletscher (MG), southeast Greenland, is used to determine snow ablation rates, the equilibrium-line altitude (ELA) and the accumulation-area ratio (AAR). The rate of rise of the TSL during the ablation season on a glacier where the balance gradient is known provides a measure of the snow ablation rate. On both LCG and MG, snow pits were completed in regions that the TSL subsequently transects. This further provides a direct measure of the snow ablation rates for a particular year. TSL observations from multiple dates during the ablation season from 1998 to 2011 at LCG and 1999 to 2012 at MG were used to explore the consistency of the TSL rise and snow ablation rate. On LCG and MG the satellite-derived mean TSL migration rates were 3.8 ± 0.6 and 9.4 ± 9.1 m d−1, respectively. The snow ablation rates were 0.028 ± 0.004 m w.e. ...
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