School of Earth Sciences - Research Publications

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Type: Journal Article × Author: Karoly, David × Start date: 2002 × End date: 2009 × Subject: glacier length variations ×

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    Comparison of glacier-inferred temperatures with observations and climate model simulations
    Ren, Diandong ; KAROLY, DAVID (American Geophysical Union, 2006)
    A reconstructed temperature history for different regions of the globe was prepared by Oerlemans (2005) from length changes of 169 glaciers. In this study, we compare the glacier-inferred temperature variations over 1900–1990 with observed and climate model simulated temperatures for the global average and for five regions: Southern Hemisphere, northwest America, Atlantic, Asia, and the Alps. There is reasonable agreement between the glacier-inferred temperature trends and the observed temperature trends for the globe and in four of the five regions (except northwest America, NWAme). The trends for the globe and in these regions are significantly different from zero, cannot be explained by natural variability (again except for NWAme), and are consistent with the model-simulated response to anthropogenic forcing in all regions. Hence, it is likely that the glacier length reductions are outside the range of natural variations and due in part to regional warming associated with increasing concentrations of greenhouse gases in the atmosphere.
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    Predicting the response of seven Asian glaciers to future climate scenarios using a simple linear glacier model
    Ren, D ; Karoly, DJ (AMER GEOPHYSICAL UNION, 2008-03-11)
    Observations from seven Central Asian glaciers (35–55°N; 70–95°E) are used, together with regional temperature data, to infer uncertain parameters for a simple linear model of the glacier length variations. The glacier model is based on first order glacier dynamics and requires the knowledge of reference states of forcing and glacier perturbation magnitude. An adjoint‐based variational method is used to optimally determine the glacier reference states in 1900 and the uncertain glacier model parameters. The simple glacier model is then used to estimate the glacier length variations until 2060 using regional temperature projections from an ensemble of climate model simulations for a future climate change scenario (SRES A2). For the period 2000–2060, all glaciers are projected to experience substantial further shrinkage, especially those with gentle slopes (e.g., Glacier Chogo Lungma retreats ∼4 km). Although nearly one‐third of the year 2000 length will be reduced for some small glaciers, the existence of the glaciers studied here is not threatened by year 2060. The differences between the individual glacier responses are large. No straightforward relationship is found between glacier size and the projected fractional change of its length.