An exercise in glacier length modeling: Interannual climatic variability alone cannot explain Holocene glacier fluctuations in New Zealand

• Published in: Earth and planetary science letters 2017-07, Vol.470, p.48-53
• Main Authors: Doughty, Alice M., Mackintosh, Andrew N., Anderson, Brian M., Dadic, Ruzica, Putnam, Aaron E., Barrell, David J.A., Denton, George H., Chinn, Trevor J.H., Schaefer, Joerg M.
• Format: Article
• Language: English
• Subjects: glacier model; glacier sensitivity; interannual variability; mass balance variability; Moraine; paleoclimate
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2017.04.032

•New Zealand temperatures warmed by ∼1.4°C between Early and Late Holocene.•Terminus variability depends on slope, response time, and mass balance variability.•Moraines are valuable indicators of past climate. Recent model studies suggest that interannual climatic variability could be confounding the interpretation of glacier fluctuations as climate signals. Paleoclimate interpretations of moraine positions and associated cosmogenic exposure ages may have large uncertainties if the glacier in question was sensitive to interannual variability. Here we address the potential for interannual temperature and precipitation variability to cause large shifts in glacier length during the Holocene. Using a coupled ice-flow and mass-balance model, we simulate the response of Cameron Glacier, a small mountain glacier in New Zealand's Southern Alps, to two types of climate forcing: equilibrium climate and variable climate. Our equilibrium results suggest a net warming trend from the Early Holocene (10.69±0.41 ka; 2.7 °C cooler than present) to the Late Holocene (CE 1864; 1.3 °C cooler than present). Interannual climatic variability cannot account for the Holocene glacier fluctuations in this valley. Future studies should consider local environmental characteristics, such as a glacier's climatic setting and topography, to determine the magnitude of glacier length changes caused by interannual variability.