| 1. |
- Andin, Caroline, et al.
(författare)
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Synoptic variability of extreme snowfall in the St. Elias Mountains,Yukon, Canada
- 2015
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Konferensbidrag (refereegranskat)abstract
- Glaciers in the Wrangell and St. Elias Mountains (Alaska and Yukon) are presently experiencing some of thehighest regional wastage rates worldwide. While the effect of regional temperatures on glacier melt rates in thisregion has been investigated, comparatively little is known about how synoptic climate variations, for example inthe position and strength of the Aleutian Low, modulate snow accumulation on these glaciers. Such informationis needed to accurately forecast future wastage rates, glacier-water resource availability, and contributions tosea-level rise. Starting in 2000, automated weather stations (AWS) were established in the central St-EliasMountains (Yukon) at altitudes ranging from 1190 to 5400 m asl, to collect climatological data in support ofglaciological research. These data are the longest continuous year-round observations of surface climate everobtained from this vast glaciated region. Here we present an analysis of snowfall events in the icefields of theSt-Elias Mountains based on a decade-long series of AWS observations of snow accumulation. Specifically,we investigated the synoptic patterns and air mass trajectories associated with the largest snowfall events (> 25cm/12 hours) that occurred between 2002 and 2012. Nearly 80% of these events occurred during the cold season(October-March), and in 74 % of cases the precipitating air masses originated from the North Pacific south of50N. Zonal air mass advection over Alaska, or from the Bering Sea or the Arctic Ocean, was comparativelyrare (20%). Somewhat counter-intuitively, dominant surface winds in the St. Elias Mountains during highsnowfall events were predominantly easterly, probably due to boundary-layer frictional drag and topographicfunneling effects. Composite maps of sea-level pressure and 700 mb winds reveal that intense snowfall eventsbetween 2002 and 2012 were associated with synoptic situations characterized by a split, eastwardly-shifted orlongitudinally-stretched Aleutian Low (AL) having an easternmost node near the Kenai Peninsula, conditionsthat drove a strong southwesterly upper airstream across the Gulf of Alaska towards the coast. Situations with asingle-node, westerly-shifted AL were comparatively rare. The spatial configuration of the synoptic AL pressurepattern appears to play a greater role in determining snowfall amount in the central St. Elias Mountains than dopressure anomalies within the AL. The estimated snowfall gradient from coastal Alaska to the central St. EliasMountains during intense snowfall events averaged +2.0 0.7 mm/km (SWE), while the continental-side gradientfrom the mountains towards the Yukon plateau averaged -3.3 0.9 mm/km (SWE). The findings presented herecan better constrain the climatic interpretation of long proxy records of snow accumulation variations developedfrom glacier cores drilled in the St. Elias Mountains or nearby regions.
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| 2. |
- Copland, Luke, et al.
(författare)
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Surface Elevation Changes Over the Past Decade Across Penny Ice Cap, Baffin Island, Canada
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Geodetic methods have been relied on heavily to quantify the response of glaciers and ice caps to warmingover the past few decades (e.g. Abdalati et al., 2004; Gardner et al., 2011; Gardner et al., 2012). Typicallyin such studies, the observed surface elevation change of a glacier or ice cap over a given time interval is used to directly calculate its mass loss. However, there can be a change elevation due to a change in firndensification rate or ice dynamics without actual mass loss. For example, at the summit of Penny Ice Cap,Baffin Island, the firn density increased due to the formation of infiltration ice layers, resulting in a 6%increase in cumulative ice‐equivalent thickness between 1995 and 2010 (Zdanowicz et al., 2012).To our knowledge no studies have previously measured the vertical component of ice motion (firncompaction and/or ice dynamics) or adjusted geodetic data over an entire ice cap in the Canadian Arctic. Inthis study we use NASA Airborne Topographic Mapper (ATM) laser altimetry data, ICESat data, as well as insitu geodetic and surface mass balance measurements, to determine surface elevation changes over Penny Ice Cap from 2005‐2013, and correct these data to account for the effects of vertical motion due to ice dynamics and firn densification. Our results show that failure to account for vertical ice motion and firn densification would result in an~19% overestimation of mass loss for this ice cap.
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| 3. |
- Schaffer, Nicole, et al.
(författare)
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Ice velocity changes on Penny Ice Cap, Baffin Island, since the 1950s
- 2017
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Ingår i: Journal of Glaciology. - : Cambridge University Press (CUP). - 0022-1430 .- 1727-5652. ; 63:240, s. 716-730
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Tidskriftsartikel (refereegranskat)abstract
- Predicting the velocity response of glaciers to increased surface melt is a major topic of ongoing research with significant implications for accurate sea level rise forecasting. In this study we use optical and radar satellite imagery as well as comparisons with historical ground measurements to produce a multi-decadal record of ice velocity variations on Penny Ice Cap, Baffin Island. Over the period 1985 to 2011, the six largest outlet glaciers on the ice cap decelerated at an average rate of 21 m a-1 , or 12% per decade. The change was not monotonous, however, as most glaciers accelerated until the 1990s, then decelerated. A comparison of recent imagery with historical velocity measurements on Highway Glacier, on the southern part of Penny Ice Cap,shows that this glacier decelerated by 71% between 1953 and 2009/11, from 57 to 17 m a-1 . The recent slowdown of outlet glaciers has coincided with increases in mass loss, terminus retreat and an inferred reduction in basal sliding. Measured decelerations are greater than the total short term variability measured from both seasonal and interannual fluctuations, and supports the hypothesis that glacier thinning and/or increased meltwater production promotes a long-term reduction in ice motion.
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| 4. |
- Schaffer, Nicole, et al.
(författare)
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Modeling the surface mass balance of Penny Ice Cap, Baffin Island, 1959–2099
- 2023
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Ingår i: Annals of Glaciology. - : Cambridge University Press. - 0260-3055 .- 1727-5644.
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Tidskriftsartikel (refereegranskat)abstract
- Glaciers of Baffin Island and nearby islands of Arctic Canada have experienced rapid mass losses over recent decades. However, projections of loss rates into the 21st century have so far been limited by the availability of model calibration and validation data. In this study, we model the surface mass balance of the largest ice cap on Baffin Island, Penny Ice Cap, since 1959, using an enhanced temperature index model calibrated with in situ data from 2006–2014. Subsequently, we project changes to 2099 based on the RCP4.5 climate scenario. Since the mid-1990s, the surface mass balance over Penny Ice Cap has become increasingly negative, particularly after 2005. Using volume–area scaling to account for glacier retreat, peak net mass loss is projected to occur between ~2040 and 2080, and the ice cap is expected to lose 22% (377.4 Gt or 60 m w.e.) of its 2014 ice mass by 2099, contributing 1.0 mm to sea level rise. Our 2015–2099 projections are approximately nine times more sensitive to changes in temperature than precipitation, with an absolute cumulative difference of 566 Gt a–1 (90 m w.e.) between +2 and −2°C scenarios, and 63 Gt a–1 (10 m w.e.) between +20% and −20% precipitation scenarios.
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| 5. |
- Schaffer, Nicole, et al.
(författare)
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Revised estimates of recent mass loss rates for Penny Ice Cap, Baffin Island, based on 2005-2014 elevation changes modified for firn densification
- 2020
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Ingår i: Journal of Geophysical Research - Earth Surface. - : American Geophysical Union (AGU). - 2169-9003 .- 2169-9011. ; 125:8
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Tidskriftsartikel (refereegranskat)abstract
- Repeat airborne or satellite measurements of surface elevation over ice caps are often used tocalculate glacier‐wide surface mass changes over time. However, these measurements typically do notaccount for vertical ice motion caused by firn densification and/or ice flow, so the effect of these factors formass change measurements over an entire ice cap are currently poorly constrained. In this study, we updateNASA Airborne Topographic Mapper (ATM) altimetry elevation changes across Penny Ice Cap (BaffinIsland, Canada) to assess total changes in ice mass from 2005–2014, relative to 1995–2000. Dual‐frequencyGPS measurements and temporal changes in ice core density profiles are used to calculate firn densificationand ice flow to isolate the component of elevation change due to surface mass change. Envisat satelliteimagery is used to delineate the areas impacted by firn densification. These calculations, the first for aCanadian Arctic ice cap, indicate that accounting for firn densification may reduce the inferred surface massloss by ~13–15%. Overall, there has been a fourfold increase in mass loss from Penny Ice Cap between1995–2000 (−1.3 ± 0.7 Gt a−1) and 2005–2013 (−5.4 ± 1.9 Gt a−1). The rapid upglacier migration of theequilibrium line has left large areas of subsurface firn in the current ablation area and has far outpaced theice flow response, illustrating that the ice cap is not in equilibrium and out of balance with the currentclimate.
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| 6. |
- Schaffer, Nicole, et al.
(författare)
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Volume and mass changes over Penny Ice Cap, Baf-fin Island, from 2005-2013 determined from repeat air-borne laser altimetry.
- 2014
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Ingår i: Proceedings of the 2014 IASC Workshop on the dynamics and mass budget of Arctic glaciers.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Recent observations of accelerated glacier wastage in Greenland and Alaska haveprompted reassessments of mass balance trends and volume changes on Cana-dian Arctic glaciers and ice caps. While long surface mass balance measurementsare available from glaciers and ice caps in the Queen Elizabeth Islands (e.g., WhiteGlacier, Devon Ice Cap, Meighen Ice Cap), no such records exist for Baffin Islandglaciers. In the absence of such data, air- and space-borne measurements canbe used in combination with in situ data to evaluate historical and recent trendsin ice cover changes. Here, we use repeat laser airborne altimetry surveys con-ducted in 2005 and 2013 by NASA to estimate recent volume and mass changesof Penny Ice Cap, the southernmost large ice cap on Baffin Island ( 66N). Thesedata are validated against in-situ surface mass balance measurements from 2013and IceSat derived elevation change from 2003-2009. Once validated, surface el-evation changes along altimetry lines are extrapolated to the entire ice cap usinga digital elevation model (DEM). Changes in areal extent of the ice cap are con-strained using satellite imagery (e.g. Landsat). From these data we estimate thetotal mass wastage of the ice cap and its recent contribution to sea level rise. Thiswork builds on previous surveys for the period 1995-2005 (Abdalati et al.,2004;Gardneret al.,2012).
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