On the characterization of glacier response by a single time-scale

Harrison, W. D.; Elsberg, D. H.; Echelmeyer, Κ. A.; Krimmel, Robert M.

doi:10.3189/172756501781831837

Cited by 105 publications

(155 citation statements)

References 16 publications

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“…To extract a climate signal, linear assumptions between ice extent (area), ice volume (mass balance), climate and their geomorphological or proxy signal are commonly assumed in glacier reconstructions (e.g., Liestøl in Sissons, 1979;Bakke et al, 2005). Linearity is also commonly assumed in simplified models used to extract climate information from glacier variations (e.g., Harrison et al, 2001;Oerlemans, 2005;Lüthi, 2009;Roe, 2011). However, we find that these assumptions do not hold for Hardangerjøkulen and its outlet glaciers.…”

Section: Nonlinearity Asymmetry and Their Implicationsmentioning

confidence: 61%

Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change

et al. 2017

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Abstract. Understanding of long-term dynamics of glaciers and ice caps is vital to assess their recent and future changes, yet few long-term reconstructions using ice flow models exist. Here we present simulations of the maritime Hardangerjøkulen ice cap in Norway from the mid-Holocene through the Little Ice Age (LIA) to the present day, using a numerical ice flow model combined with glacier and climate reconstructions.In our simulation, under a linear climate forcing, we find that Hardangerjøkulen grows from ice-free conditions in the mid-Holocene to its maximum extent during the LIA in a nonlinear, spatially asynchronous fashion. During its fastest stage of growth (2300-1300 BP), the ice cap triples its volume in less than 1000 years. The modeled ice cap extent and outlet glacier length changes from the LIA until today agree well with available observations. Volume and area for Hardangerjøkulen and several of its outlet glaciers vary out-of-phase for several centuries during the Holocene. This volume-area disequilibrium varies in time and from one outlet glacier to the next, illustrating that linear relations between ice extent, volume and glacier proxy records, as generally used in paleoclimatic reconstructions, have only limited validity.We also show that the present-day ice cap is highly sensitive to surface mass balance changes and that the effect of the ice cap hypsometry on the mass balancealtitude feedback is essential to this sensitivity. A mass balance shift by +0.5 m w.e. relative to the mass balance from the last decades almost doubles ice volume, while a decrease of 0.2 m w.e. or more induces a strong mass balance-altitude feedback and makes Hardangerjøkulen disappear entirely. Furthermore, once disappeared, an additional +0.1 m w.e. relative to the present mass balance is needed to regrow the ice cap to its present-day extent. We expect that other ice caps with comparable geometry in, for example, Norway, Iceland, Patagonia and peripheral Greenland may behave similarly, making them particularly vulnerable to climate change.

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Section: Nonlinearity Asymmetry and Their Implicationsmentioning

confidence: 61%

Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change

et al. 2017

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“…Jóhannesson et al (1989a,b) do realise that their crucial assumption (see above) means that balance-elevation feedback is not accounted for and that their response time estimates may therefore be too short. Harrison et al (2001) attempt to correct this by including a term that explicitly addresses the balance-elevation feedback, but they still assume that all the area change is close to the terminus. Their treatment may not account for area-altitude changes remote from the region of the terminus, i.e.…”

Section: Discussionmentioning

confidence: 99%

“…One notable difference between their approach and ours is that they develop their argument in the coordinates of a map projection whereas our treatment looks at vertical profiles. The Harrison et al (2001) approach assumes that the change in glacier area is in the vicinity of the glacier terminus, whereas in our approach we consider changes in the area-altitude distribution.…”

Section: Introductionmentioning

confidence: 99%

“…For example, Jóhannesson et al (1989a) admit that their approach neglects the positive feedback that arises when an initial mass balance perturbation causes a change in glacier surface altitude such that the mass balance perturbation changes. Harrison et al (2001) address this problem by deriving a form of Eq. (1) that includes a term that explicitly accounts for changes in glacier surface altitude.…”

Section: Introductionmentioning

confidence: 99%

“…the response to a step change in mass balance (Nye, 1963). However, a number of authors have sought to express volume response time analytically as a relatively simple function of climate and glacier geometry (Jóhannesson et al, 1989a;Raper et al, 1996;Bahr et al, 1998;Pfeffer et al, 1998;Harrison et al, 2001;Oerlemans, 2001). Such functions should allow us to estimate characteristic response times for different glacier regions from their climatic and topographic settings.…”

Section: Introductionmentioning

confidence: 99%

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Glacier volume response time and its links to climate and topography based on a conceptual model of glacier hypsometry

2009

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Abstract.Glacier volume response time is a measure of the time taken for a glacier to adjust its geometry to a climate change. It has been previously proposed that the volume response time is given approximately by the ratio of glacier thickness to ablation at the glacier terminus. We propose a new conceptual model of glacier hypsometry (areaaltitude relation) and derive the volume response time where climatic and topographic parameters are separated. The former is expressed by mass balance gradients which we derive from glacier-climate modelling and the latter are quantified with data from the World Glacier Inventory. Aside from the well-known scaling relation between glacier volume and area, we establish a new scaling relation between glacier altitude range and area, and evaluate it for seven regions. The presence of this scaling parameter in our response time formula accounts for the mass balance elevation feedback and leads to longer response times than given by the simple ratio of glacier thickness to ablation at the terminus. Volume response times range from decades to thousands of years for glaciers in maritime (wet-warm) and continental (dry-cold) climates respectively. The combined effect of volume-area and altitude-area scaling relations is such that volume response time can increase with glacier area (Axel Heiberg Island and Svalbard), hardly change (Northern Scandinavia, Southern Norway and the Alps) or even get smaller (The Caucasus and New Zealand).

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A review of volume‐area scaling of glaciers

Bahr

Pfeffer

Kaser

2015

Reviews of Geophysics

176

191

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Volume‐area power law scaling, one of a set of analytical scaling techniques based on principals of dimensional analysis, has become an increasingly important and widely used method for estimating the future response of the world's glaciers and ice caps to environmental change. Over 60 papers since 1988 have been published in the glaciological and environmental change literature containing applications of volume‐area scaling, mostly for the purpose of estimating total global glacier and ice cap volume and modeling future contributions to sea level rise from glaciers and ice caps. The application of the theory is not entirely straightforward, however, and many of the recently published results contain analyses that are in conflict with the theory as originally described by Bahr et al. (1997). In this review we describe the general theory of scaling for glaciers in full three‐dimensional detail without simplifications, including an improved derivation of both the volume‐area scaling exponent γ and a new derivation of the multiplicative scaling parameter c. We discuss some common misconceptions of the theory, presenting examples of both appropriate and inappropriate applications. We also discuss potential future developments in power law scaling beyond its present uses, the relationship between power law scaling and other modeling approaches, and some of the advantages and limitations of scaling techniques.

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On the characterization of glacier response by a single time-scale

Cited by 105 publications

References 16 publications

Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change

Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change

Glacier volume response time and its links to climate and topography based on a conceptual model of glacier hypsometry

A review of volume‐area scaling of glaciers

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