Phone: (406) 243-5867
Office: CHCB 317
My research is focused on the interactions and feedbacks between the cryosphere and the climate system. This work is motivated by societal need to understand climate dynamics, project sea level rise, and manage snow water resources in the face of changing climate. I employ methods of computer modeling, data analysis, and field instrumentation. My field research is conducted on the Greenland Ice Sheet, small glaciers in Alaska and Montana, and seasonal snow in Montana. My research is funded by the U.S. National Science Foundation, NASA, and the Swedish Nuclear Waste Management Company.
GEOS 108: Climate Change, Past and Future
GEOS 488: Snow Ice and Climate
GEOS 595: Fundamentals of Academic Research
GEOS 548: Topics in the Cryosphere
Field of Study
Harper, J., N. Humphrey, W. Pfeffer, J. Brown, and X. Fettweis, Greenland contribution to sea level rise buffered by meltwater storage in firn. Nature, 2012. 491, 240-243, 10.1038/nature11566.
Mikesell, T.D., K. van Wijk, M.M. Haney, J.H. Bradford, H.P. Marshall, and J.T. Harper, Monitoring glacier surface seismicity in time and space using Rayleigh waves. Journal of Geophysical Research, 2012. 117(F2): p. F02020.10.1029/2011JF002259
Humphrey, N.F., J.T. Harper, and W.T. Pfeffer, Thermal tracking of meltwater retention in Greenland's accumulation area. Journal of Geophysical Research, 2012. 117(F1): p. F01010.10.1029/2011JF002083.
Brown, J., J. Bradford, J. Harper, W.T. Pfeffer, N. Humphrey, and E. Mosley-Thompson, Georadar-derived estimates of firn density in the percolation zone, western Greenland ice sheet. Journal of Geophysical Research, 2012. 117(F1): p. F01011.10.1029/2011JF002089
Harper, J., N. Humphrey, W.T. Pfeffer, and J. Brown, Firn Stratigraphy and Temperature to 10 m Depth in the Percolation Zone of Western Greenland, 2007–2009. INSTAAR, Occasional Paper, 2011. ISSN 0069-6145(60).
Brown, J., J. Harper, W.T. Pfeffer, N. Humphrey, and J. Bradford, High-resolution study of layering within the percolation and soaked facies of the Greenland ice sheet. Annals of Glaciology, 2011. 52(59): p. 35-42.
Brinkerhoff, D.J., T.W. Meierbachtol, J.V. Johnson, and J.T. Harper, Sensitivity of the frozen/melted basal boundary to perturbations of basal traction and geothermal heat flux: Isunnguata Sermia, western Greenland. Annals of Glaciology, 2011. 52(59): p. 43-50.
Harper, J.T., J.H. Bradford, N.F. Humphrey, and T.W. Meierbachtol, Vertical Extension of the Subglacial Drainage System Into Basal Crevasses. Nature, 2010. 467: p. 579-582.10.1038/nature09398.
Gillan, B.J., J.T. Harper, and J.N. Moore, Timing of present and future snowmelt from high elevations in northwest Montana. Water Resources Research, 2010. 46: p. W01507.doi:10.1029/2009WR007861.
Brown, J., J. Harper, and N. Humphrey, Cirque Glacier Sensitivity to 21st Century Climate Change: Sperry Glacier, Montana. Global and Planetary Change, 2010. 74(2): p. 91-98.10.1016/j.gloplacha.2010.09.001
Fudge, T.J., J.T. Harper, N.F. Humphrey, and W.T. Pfeffer, Rapid Glacier Sliding, Reverse Ice Motion, and Subglacial Water Pressure During an Autumn Rainstorm. Annals of Glaciology, 2009. 50(51): p. 1-9.
Brown, J., J. Harper, and J. Bradford, A radar transparent layer in a temperate valley glacier: Bench Glacier, Alaska. Earth Surface Processes and Landforms, 2009. 34: p. 1497-1506.doi: 10.1002/esp.1835.
Bradford, J.H., J. Nichols, M.T. D., and J.T. Harper, Continuous Profiles Of Electromagnetic Wave Velocity and Water Content in Glaciers. Annals of Glaciology, 2009. 50(51): p. 1-9.
Bradford, J.H., J.T. Harper, and J. Brown, Complex dielectric permittivity measurements from ground-penetrating radar data to estimate snow liquid water content in the pendular regime. Water Resources Research, 2009. 45: p. 1-12.doi: 10.1029/2008WR007341.
Pfeffer, W.T., J.T. Harper, and S. O'Neel, Kinematic constraints on glacier contributions to 21st-century sea-level rise. Science, 2008. 321 (5894): p. 1340-1343.doi: 0.1126/science.1159099.
Meierbachtol, T., J.T. Harper, N.F. Humphrey, J. Shaha, and J. Bradford, Air compression as a mechanism for the underdamped slug test response in fractured glacier ice. Journal of Geophysical Research Earth Surface, 2008. 113(F04009): p. 1-14.doi: 10.1029/2007JF000908.
Fudge, T.J., N.F. Humphrey, J.T. Harper, and W.T. Pfeffer, Diurnal Fluctuations in Borehole Water Levels: Configuration of the Drainage System Beneath Bench Glacier, Alaska. Journal of Glaciology, 2008. 54(185): p. 297-306, doi 10.3189/002214308784886072.
Moore, J.N., J.T. Harper, and M.C. Greenwood, Significance of trends toward earlier snowmelt runoff, Columbia and Missouri Basin headwaters, western United States. Journal of Geophysical Research, 2007. 34: p. L16402, doi:10.1029/2007GL031022.doi:10.1029/2007GL031022.
Harper, J.T., N.F. Humphrey, W.T. Pfeffer, and B. Lazar, Two modes of Accelerated Glacier Sliding Related to Water. Geophysical Research Letters, 2007. 34(12): p. L12503.doi: 10.1029/2007GL030233.
Bleha, J.A. and J.T. Harper. Snowmelt Water Generation in a Large Mountain Basin of Northwest Montana from a MODIS Driven Model. in Symposium on Environmental Sensing. 2007. Boise, ID: Inland Northwest Research Alliance.
Bradford, J.H. and J.T. Harper, Measuring complex dielectric permittivity from GPR to estimate liquid water content in snow. Society of Exploration Geophysicists Technical Program, 2006. 25: p. 1352-1356, doi:10.1190/1.2369770.doi:10.1190/1.2369770.
Harper, J.T., N.F. Humphrey, W.T. Pfeffer, T. Fudge, and S. O'Neel, Evolution of subglacial water pressure along a glacier's length. Annals of Glaciology, 2005. 40: p. 31-36.
Fudge, T.J., J.T. Harper, N.F. Humphrey, and W.T. Pfeffer, Timing and pattern of termination of diurnal water pressure fluctuations: Bench Glacier, Alaska. Annals of Glaciology, 2005. 40: p. 102-106.
Bradford, J.H. and J.T. Harper, Wavefield Migration as a Tool for Estimating Spatially Continuous Radar Velocity and Water Content in Glaciers. Geophysical Research Letters, 2005. 32: p. L08502, doi:10.1029/2004GL021770.doi:10.1029/2004GL021770.
Harper, J.T. and N.F. Humphrey, High altitude Himalayan climate inferred from glacial ice flux. Geophysical Research Letters, 2003. 30(14): p. 1764-1769, doi:10.1029/2003GL017329.10.1029/2003GL017329.
Harper, J.T. and J.H. Bradford, Snow stratigraphy over a uniform depositional surface: spatial variability and measurement tools. Cold Regions Science and Technology, 2003. 37(3): p. 289-298.
Marshall, H.P., J.T. Harper, W.T. Pfeffer, and N.F. Humphrey, Depth-varying constitutive properties observed in an isothermal glacier. Geophysical Research Letters, 2002. 29(61): p. 1-4.
Harper, J.T., N.F. Humphrey, and M.C. Greenwood, Basal conditions and glacier motion during the winter/spring transition, Worthington Glacier, Alaska, U.S.A. Journal of Glaciology, 2002. 48(160): p. 42-50.doi: 10.3189/172756502781831629.
Harper, J.T. and J.H. Bradford. Spatial variability of snow stratification in the absence of terrain factors. in International Snow Science Workshop. 2002. Penticton, B.C. Canada: International Snow Science Workshop Canada Inc.
Harper, J.T., N.F. Humphrey, W.T. Pfeffer, S.V. Huzurbazar, D.B. Bahr, and B.C. Welch, Spatial variability in the flow of a valley glacier: Deformation of a large array of boreholes. Journal of Geophysical Research, 2001. 106(B5): p. 8547-8562.doi: 10.1029/2000JB900440.
Pfeffer, W.T., N.F. Humphrey, B. Amadei, J.T. Harper, and W. J., In-situ stress tensor measured in an Alaskan glacier. Annals of Glaciology, 2000. 31: p. 229-235.
Welch, B.C., W.T. Pfeffer, J.T. Harper, and N.F. Humphrey, Mapping subglacial surfaces below temperate valley glaciers using 3-dimensional radio-echo sounding techniques. Journal of Glaciology, 1998. 44(146): p. 164-170.
Jones, L.S. and J.T. Harper, Channel avulsions and related processes, and large-scale sedimentation patterns since 1875, Rio Grande, San Luis Valley, Colorado. Geological Society of America Bulletin, 1998. 110(3): p. 411-421.
Harper, J.T., N.F. Humphrey, and W.T. Pfeffer, Crevasse patterns and the strain rate tensor: a high resolution comparison. Journal of Glaciology, 1998. 44(146): p. 68-76.
Harper, J.T., N.F. Humphrey, and W.T. Pfeffer, Three-dimensional deformation measured in an Alaskan Glacier. Science, 1998. 281(5381): p. 1340-1342.
Welch, B.C., W.T. Pfeffer, J.T. Harper, and N.F. Humphrey, A maximum glacier-bed surface obtained by radio-echo sounding, in Glaciers, Ice Sheets and Volcanoes, S.C. Colbeck, Editor. 1996, U.S. Army Cold Regions Research and Engineering Laboratory: Hanover, N.H. p. 105-110.
Harper, J.T., N.F. Humphrey, W.T. Pfeffer, and B.C. Welch, Short wavelength variations in the horizontal velocity field of a valley glacier, in Glaciers, Ice Sheets and Volcanoes, S.C. Colbeck, Editor. 1996, U.S. Army Cold Regions Research and Engineering Laboratory: Hanover, N.H. p. 41-48.
Harper, J.T. and N.F. Humphrey, Borehole video analysis of a temperate glacier's englacial and subglacial structure; implications for glacier flow models. Geology, 1995. 23(10): p. 901-904.
Harper, J.T., Glacier terminus fluctuations on Mount Baker, Washington, U.S.A., 1940-1990, and climatic variations. Arctic and Alpine Research, 1993. 25(4): p. 332-340.