https://doi.org/10.5194/tc-2019-301 Preprint. Discussion started: 27 January 2020 c Author(s) 2020. CC BY 4.0 License. The contrasting response of outlet glaciers to interior and ocean forcing John Erich Christian1, Alexander Robel2, Cristian Proistosescu3,4,5, Gerard Roe1, Michelle Koutnik1, and Knut Christianson1 1Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA 2School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA 3Joint Institute for the Study of the Atmosphere and the Ocean, University of Washington, Seattle, Washington, USA 4Department of Atmospheric Sciences, University of Illinois, Urbana-Champaign, Illinois, USA 5Department of Geology, University of Illinois, Urbana-Champaign, Illinois, USA Correspondence: John Erich Christian (
[email protected]) Abstract. The dynamics of marine-terminating outlet glaciers are of fundamental interest in glaciology, and affect mass loss from ice sheets in a warming climate. In this study, we analyze the response of outlet glaciers to different sources of climate forcing. We find that outlet glaciers have a characteristically different transient response to surface-mass-balance forcing ap- plied over the interior than to oceanic forcing applied at the grounding line. A recently developed reduced model represents 5 outlet glacier dynamics via two widely-separated response timescales: a fast response associated with grounding-zone dynam- ics, and a slow response of interior ice. The reduced model is shown to emulate the behavior of a more complex numerical model of ice flow. Together, these models demonstrate that ocean forcing first engages the fast, local response, and then the slow adjustment of interior ice, whereas surface-mass-balance forcing is dominated by the slow interior adjustment.