GLORIA

GEOMAR Library Ocean Research Information Access

X

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Online Resource
    Online Resource
    Ice Columns and Frozen Rills in a Warm Snowpack, Green Lakes Valley, Colorado, U.S.A.
    IWA Publishing ; 2000
    In:  Hydrology Research Vol. 31, No. 3 ( 2000-06-01), p. 169-186
    Details
    In: Hydrology Research, IWA Publishing, Vol. 31, No. 3 ( 2000-06-01), p. 169-186
    Abstract: Here we provide information on ice columns and frozen rills found in late-season snowpacks in and near the Green Lakes Valley of the Colorado Front Range, USA. The presence of ice columns and frozen rills in late season snowpacks may provide insights with which to understand the spatial distribution of preferential flowpaths in melting snowpacks. In July and August of 1996 and 1997 we found ice columns in every one of the more than 50 snow fields we investigated. The ice columns showed a consistent morphology; each column was approximately 75 cm in vertical extent, with about 5 cm projecting above the snow surface and 70 cm extending into the snowpack. An analysis of variance test shows that the 81 ice columns on the south-facing slopes were significantly greater than the 57 ice columns on the north-facing slope (p = 0.01). There were about 3 ice columns per square metre on the southfacing slopes and 2 ice columns per square metre on the north-facing slopes. There was an interesting hysteresis in snow and ice temperatures that became stronger with increasing depth in adjacent thermocouple arrays. This hysteresis in the temperature profiles is consistent with the release of latent heat from the freezing of greater amounts of liquid water in and near the ice columns compared to the surrounding snowpack. At the Martinelli catchment, spacing between the frozen rills averaged 2.6 m (n = 73). We interpret these “ribs” of solid ice to be the remnants of surface rills. Vertical ice columns were connected to these frozen rills. The ice columns and frozen rills may provide a snapshot or “schematic” diagram of the major flowpaths in a ripe and draining snowpack.
    Type of Medium: Online Resource
    ISSN: 0029-1277 , 2224-7955
    URL: Article
    DOI: 10.2166/nh.2000.0011
    Language: English
    Publisher: IWA Publishing
    Publication Date: 2000
    detail.hit.zdb_id: 2411122-3
    detail.hit.zdb_id: 2142091-9
    SSG: 21,3
    SSG: 14
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 2
    Online Resource
    Online Resource
    Glacier volume estimation as an ill-posed inversion
    International Glaciological Society ; 2014
    In:  Journal of Glaciology Vol. 60, No. 223 ( 2014), p. 922-934
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 60, No. 223 ( 2014), p. 922-934
    Abstract: Estimating a glacier’s volume by inferring properties at depth (e.g. bed topography or basal slip) from properties observed at the surface (e.g. area and slope) creates a calculation instability that grows exponentially with the size of the glacier. Random errors from this inversion instability can overwhelm all other sources of error and can corrupt thickness and volume calculations, unless problematic short spatial wavelengths are specifically excluded. Volume/area scaling inherently filters these short wavelengths and automatically eliminates the instability, while numerical inversions can also give stable solutions by filtering the correct wavelengths explicitly, as is frequently done when ‘regularizing’ a model. Each of the scaling and numerical techniques has applications to which it is better suited, and there are trade-offs in resolution and accuracy; but when calculating volume, neither the modeling nor the scaling approach offers a fundamental advantage over the other. Both are significantly limited by the inherently ‘ill-posed’ inversion, and even though both provide stable volume solutions, neither can give unique solutions.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/2014JoG14J062
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2014
    detail.hit.zdb_id: 2140541-4
    SSG: 14
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 3
    Online Resource
    Online Resource
    Crossover scaling phenomena for glaciers and ice caps
    Cambridge University Press (CUP) ; 2016
    In:  Journal of Glaciology Vol. 62, No. 232 ( 2016-04), p. 299-309
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 62, No. 232 ( 2016-04), p. 299-309
    Abstract: While the terms ‘glacier’ and ‘ice cap’ have distinct morphological meanings, no easily defined boundary or transition distinguishes one from the other. Despite this, the exponent of the power law function relating volume to surface area differs sharply for glaciers and ice caps, suggesting a fundamental distinction beyond a smoothly transitioning morphology. A standard percolation technique from statistical physics is used to show that valley glaciers are in fact differentiated from ice caps by an abrupt geometric transition. The crossover is a function of increasing glacier thickness, but it owes its existence more to the nature of the underlying bedrock topography than to specifics of glacier mechanics: the crossover is caused by a switch from directed flow that is constrained by surrounding bedrock topography to unconstrained radial flow of thicker ice that has subsumed the topography. The crossover phenomenon is nonlinear and rapid so that few if any glaciers will have geometries or dynamics that blend the two extremes. The exponents of scaling relationships change abruptly at the crossover from one regime to another; in particular, the volume/area scaling exponent will switch from γ = 1.375 for glaciers to γ = 1.25 for ice caps, with few, if any, ice bodies having exponents that fall between these values.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/jog.2016.6
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2016
    detail.hit.zdb_id: 2140541-4
    SSG: 14
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 4
    Online Resource
    Online Resource
    Theoretical limitations to englacial velocity calculations
    Cambridge University Press (CUP) ; 1994
    In:  Journal of Glaciology Vol. 40, No. 136 ( 1994), p. 509-518
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 40, No. 136 ( 1994), p. 509-518
    Abstract: To study the dynamics of ice sheets and glaciers, velocities at the bed of a glacier must be measured directly or calculated using data gathered from boreholes and surface surveys. Boreholes to the bed are expensive and time-consuming to drill, so the determination of basal velocity is almost exclusively by numerical inversion of velocities observed at the surface. For non-linearly viscous glaciers, a perturbation analysis demonstrates that inversions for englacial velocities will magnify measurement errors at an exponential rate with depth. The rate at which calculation errors grow is proportional to a Lyapunov exponent, a measure of “information loss” which is shown to be a simple linear function of spatial frequency with a coefficient depending on Glen’s flow-law exponent, n . The coefficient decreases with increasing non-linearity, demonstrating that inversions with non-linearly viscous ice have smaller calculation errors than inversions with linearly viscous ice. In both the linear and nonlinear cases, the Lyapunov exponent (and rate of error growth) increases with decreasing wavelength, which limits velocity calculations at the bed to wavelengths on the order of one ice thickness or greater. This limitation is theoretical and cannot be countered by more accurate survey data or special numerical techniques.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/S0022143000012399
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 1994
    detail.hit.zdb_id: 2140541-4
    SSG: 14
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 5
    Online Resource
    Online Resource
    High-resolution study of layering within the percolation and soaked facies of the Greenland ice sheet
    International Glaciological Society ; 2011
    In:  Annals of Glaciology Vol. 52, No. 59 ( 2011), p. 35-42
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 52, No. 59 ( 2011), p. 35-42
    Abstract: Within the percolation and soaked facies of the Greenland ice sheet, the relationship between radar-derived internal reflection horizons and the layered structure of the firn column is unclear. We conducted two small-scale ground-penetrating radar (GPR) surveys in conjunction with 10 m firn cores that we collected within the percolation and soaked facies of the Greenland ice sheet. The two surveys were separated by a distance of ~50 km and ~340m of elevation leading to ~40 days of difference in the duration of average annual melt. At the higher site (~1997ma.s.l.), which receives less melt, we found that internal reflection horizons identified in GPR data were largely laterally continuous over the grid; however, stratigraphic layers identified in cores could not be traced between cores over any distance from 1.5 to 14.0 m. Thus, we found no correlation between firn core stratigraphy observed directly and radar-derived internal reflection horizons. At the lower site (~1660ma.s.l.), which receives more melt, we found massive ice layers 〉 0.5m thick and stratigraphic boundaries that span 〉 15m horizontally. Some ice layers and stratigraphic boundaries correlate well with internal reflection horizons that are laterally continuous over the area of the radar grid. Internal reflection horizons identified at ~1997ma.s.l. are likely annual isochrones, but the reflection horizons identified at ~1660ma.s.l. are likely multi-annual features. We find that mapping accumulation rates over long distances by tying core stratigraphy to radar horizons may lead to ambiguous results because: (1) there is no stratigraphic correlation between firn cores at the 1997 m location; and (2) the reflection horizons at the 1660m location are multi-annual features.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/172756411799096286
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2011
    detail.hit.zdb_id: 2122400-6
    SSG: 14
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 6
    Online Resource
    Online Resource
    Variations of near-surface firn density in the lower accumulation area of the Greenland ice sheet, Pâkitsoq, West Greenland
    Cambridge University Press (CUP) ; 1994
    In:  Journal of Glaciology Vol. 40, No. 136 ( 1994), p. 477-485
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 40, No. 136 ( 1994), p. 477-485
    Abstract: Firn-density variations have been studied in the lower accumulation area of the Greenland ice sheet (1440-1620 m a.s.l.) near Pâkitsoq, West Greenland. The main control on density in the near-surface firn layer (of 5-10 m thickness) is the formation of ice layers by the refreezing of meltwater that reaches depths of 2-4 m below the surface. The density variations are described by the ratio of annual surface melt M to the annual accumulation C . The ratio M/C is about 0.6 at the run-off limit (at about 1400 m a.s.l. in the study area) where refreezing of meltwater transforms snow into impermeable ice. The mean density of near-surface firn decreases with elevation, reflecting a decrease in melt with elevation. There is a surprising decrease in firn density at depths of more than about 4 m below the 1991 summer surface, which reflects lower melt rates and/or higher accumulation in the early 1980s and late 1970s when this firn was passing through the surface layer. The formation of such low-density firn may have partially contributed to the 1978-85 thickening of the ice sheet observed by satellite-radar altimetry. Near-surface firn density is therefore very sensitive to climate change and might be an attractive target for climate monitoring.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/S002214300001234X
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 1994
    detail.hit.zdb_id: 2140541-4
    SSG: 14
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 7
    Online Resource
    Online Resource
    Glaciers Dominate Eustatic Sea-Level Rise in the 21st Century
    American Association for the Advancement of Science (AAAS) ; 2007
    In:  Science Vol. 317, No. 5841 ( 2007-08-24), p. 1064-1067
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 317, No. 5841 ( 2007-08-24), p. 1064-1067
    Abstract: Ice loss to the sea currently accounts for virtually all of the sea-level rise that is not attributable to ocean warming, and about 60% of the ice loss is from glaciers and ice caps rather than from the two ice sheets. The contribution of these smaller glaciers has accelerated over the past decade, in part due to marked thinning and retreat of marine-terminating glaciers associated with a dynamic instability that is generally not considered in mass-balance and climate modeling. This acceleration of glacier melt may cause 0.1 to 0.25 meter of additional sea-level rise by 2100.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1143906
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2007
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 8
    Online Resource
    Online Resource
    Challenges to Understanding the Dynamic Response of Greenland's Marine Terminating Glaciers to Oceanic and Atmospheric Forcing
    American Meteorological Society ; 2013
    In:  Bulletin of the American Meteorological Society Vol. 94, No. 8 ( 2013-08-01), p. 1131-1144
    Details
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 94, No. 8 ( 2013-08-01), p. 1131-1144
    Abstract: The recent retreat and speedup of outlet glaciers, as well as enhanced surface melting around the ice sheet margin, have increased Greenland's contribution to sea level rise to 0.6 ± 0.1 mm yr−1 and its discharge of freshwater into the North Atlantic. The widespread, near-synchronous glacier retreat, and its coincidence with a period of oceanic and atmospheric warming, suggests a common climate driver. Evidence points to the marine margins of these glaciers as the region from which changes propagated inland. Yet, the forcings and mechanisms behind these dynamic responses are poorly understood and are either missing or crudely parameterized in climate and ice sheet models. Resulting projected sea level rise contributions from Greenland by 2100 remain highly uncertain. This paper summarizes the current state of knowledge and highlights key physical aspects of Greenland's coupled ice sheet–ocean–atmosphere system. Three research thrusts are identified to yield fundamental insights into ice sheet, ocean, sea ice, and atmosphere interactions, their role in Earth's climate system, and probable trajectories of future changes: 1) focused process studies addressing critical glacier, ocean, atmosphere, and coupled dynamics; 2) sustained observations at key sites; and 3) inclusion of relevant dynamics in Earth system models. Understanding the dynamic response of Greenland's glaciers to climate forcing constitutes both a scientific and technological frontier, given the challenges of obtaining the appropriate measurements from the glaciers' marine termini and the complexity of the dynamics involved, including the coupling of the ocean, atmosphere, glacier, and sea ice systems. Interdisciplinary and international cooperation are crucial to making progress on this novel and complex problem.
    Type of Medium: Online Resource
    ISSN: 1520-0477
    URL: Article
    DOI: 10.1175/BAMS-D-12-00100.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2013
    detail.hit.zdb_id: 2029396-3
    detail.hit.zdb_id: 419957-1
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 9
    Online Resource
    Online Resource
    Response time of glaciers as a function of size and mass balance: 1. Theory
    American Geophysical Union (AGU) ; 1998
    In:  Journal of Geophysical Research: Solid Earth Vol. 103, No. B5 ( 1998-05-10), p. 9777-9782
    Details
    In: Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), Vol. 103, No. B5 ( 1998-05-10), p. 9777-9782
    Abstract: A simple interpretation of the traditional definitions of glacier and ice sheet response time (e.g., thickness divided by mass balance rate, ) suggests that larger glaciers respond more slowly than small glaciers to a perturbation in climate. However, with reasonable choices for mass balance behavior, a scaling analysis shows that the response time of valley glaciers decreases as a function of increasing size when other variables are held constant. In essence, this is because larger valley glaciers push further into the ablation zone, and ablation increases more rapidly than the thickness (so that gets smaller). Ice sheets have different mass balance regimes than valley glaciers, and as they grow larger, the ablation does not increase faster than the thickness. Therefore, as ice sheets grow in surface area, the response time increases. For both ice sheets and valley glaciers, the response time also depends on a mass balance index, which is defined as the slope of the balance curve as a function of horizontal distance along the glacier surface (rather than elevation). The response time decreases as the balance index increases, so for valley glaciers, an increase in the balance index and an increase in glacier size have opposite effects on the response time. The balance index is typically larger for smaller valley glaciers. Therefore a small glacier will typically respond faster than a large glacier, but this quicker response is because of mass balance considerations and not because of the dynamic characteristics of the glacier arising from its small size, as often assumed.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/98JB00507
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1998
    detail.hit.zdb_id: 2033040-6
    detail.hit.zdb_id: 3094104-0
    detail.hit.zdb_id: 2130824-X
    detail.hit.zdb_id: 2016813-5
    detail.hit.zdb_id: 2016810-X
    detail.hit.zdb_id: 2403298-0
    detail.hit.zdb_id: 2016800-7
    detail.hit.zdb_id: 161666-3
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
    detail.hit.zdb_id: 161665-1
    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 3094181-7
    detail.hit.zdb_id: 3094219-6
    detail.hit.zdb_id: 3094167-2
    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 10
    Online Resource
    Online Resource
    Two modes of accelerated glacier sliding related to water
    American Geophysical Union (AGU) ; 2007
    In:  Geophysical Research Letters Vol. 34, No. 12 ( 2007-06-29)
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 34, No. 12 ( 2007-06-29)
    Type of Medium: Online Resource
    ISSN: 0094-8276
    URL: Article
    DOI: 10.1029/2007GL030233
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2007
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...