What do glaciers tell us about climate variability and climate change?

Roe, Gerard H.

doi:10.3189/002214311796905640

Cited by 77 publications

(89 citation statements)

References 42 publications

(96 reference statements)

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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: 63%

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: 63%

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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“…Vanmarcke, 1983), Roe (2011) derived the probability of a glacier exceeding a maximum total excursion, ΔL, in any given interval of time, T , assuming the extreme-excursion return times following a Poisson distribution:…”

Section: The Impact Of Persistence On Excursion Probabilitiesmentioning

confidence: 99%

“…In many places, reconstructions of glacier history provide the primary narrative of regional climate history, against which other proxy records are evaluated. In the past fifteen years, a series of studies has sought to characterize the response of glaciers to climate variability (Oerlemans, 2000(Oerlemans, , 2001Reichert and others, 2002;Huybers and Roe, 2009;Roe and O'Neal 2009;Roe, 2011;Roe and Baker, 2014;Anderson and others, 2014;Rowan and others, 2014). Here the relevant climate variable is mass balance.…”

Section: Introductionmentioning

confidence: 99%

The response of glaciers to climatic persistence

Roe

Baker

2016

J. Glaciol.

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ABSTRACT. The attribution of past glacier length fluctuations to changes in climate requires characterizing glacier mass-balance variability. Observational records, which are relatively short, are consistent with random fluctuations uncorrelated in time, plus an anthropogenic trend. However, longer records of other climate variables suggest that, in fact, there is a degree of temporal persistence associated with internal (i.e. unforced) climate variability, and that it varies with location and climate. Therefore, it is likely that persistence does exist for mass balance, but records are too short to confirm its presence, or establish its magnitude, with conventional statistical tests. Extending the previous work, we explore the impact of potential climatic persistence on glacier length fluctuations. We use a numerical model and a newly developed analytical model to establish that persistence, even of a degree so small as to be effectively undetectable in the longest mass-balance records, can significantly enhance the resulting glacier length fluctuations. This has a big impact on glacier-excursion probabilities: what was an extremely unlikely event (<1%) can become virtually certain (>99%), when persistence is incorporated. Since the actual degree of climatic persistence that applies to any given glacier is hard to establish, these results complicate the attribution of past glacier changes.

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“…Glaciers are complex recorders of past conditions. Their fluctuations depend on the surface mass balance, which is influenced by several factors, including temperature, precipitation and incoming radiation changes over the glacier, as well as by the glacier dynamics and thus local geometry (Oerlemans, 2001;Huss et al, 2008;Roe, 2011). Furthermore, because of their long response time, glaciers integrate forcing over periods ranging from a few years to several decades or even centuries (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Jòhannesson et al, 1989;Leysinger Vieli and Gudmundsson, 2004). Consequently, glacier length fluctuations cannot be directly compared to records with a much faster response or simply included in multi-proxy reconstructions of past climate changes (Oerlemans, 2005;Roe, 2011;Solomina et al, 2016;Roe et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Testing the consistency between changes in simulated climate and Alpine glacier length over the past millennium

et al. 2018

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Abstract.It is standard to compare climate model results covering the past millennium and reconstructions based on various archives in order to test the ability of models to reproduce the observed climate variability. Up to now, glacier length fluctuations have not been used systematically in this framework even though they offer information on multidecadal to centennial variations complementary to other records. One reason is that glacier length depends on several complex factors and so cannot be directly linked to the simulated climate. However, climate model skill can be measured by comparing the glacier length computed by a glacier model driven by simulated temperature and precipitation to observed glacier length variations. This is done here using the version 1.0 of the Open Global Glacier Model (OGGM) forced by fields derived from a range of simulations performed with global climate models over the past millennium. The glacier model is applied to a set of Alpine glaciers for which observations cover at least the 20th century. The observed glacier length fluctuations are generally well within the range of the simulations driven by the various climate model results, showing a general consistency with this ensemble of simulations. Sensitivity experiments indicate that the results are much more sensitive to the simulated climate than to OGGM parameters. This confirms that the simulations of glacier length can be used to evaluate the climate model performance, in particular the simulated summer temperatures that largely control the glacier changes in our region of interest. Simulated glacier length is strongly influenced by the internal variability in the system, putting limitations on the model-data comparison for some variables like the trends over the 20th century in the Alps. Nevertheless, comparison of glacier length fluctuations on longer timescales, for instance between the 18th century and the late 20th century, appear less influenced by the natural variability and indicate clear differences in the behaviour of the various climate models.

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What do glaciers tell us about climate variability and climate change?

Cited by 77 publications

References 42 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

The response of glaciers to climatic persistence

Testing the consistency between changes in simulated climate and Alpine glacier length over the past millennium

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