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Graduate Students

Benjamin Hmiel headshot

Benjamin Hmiel

Postdoctoral Associate

B13  Hutchison Hall
(585) 276-4947
bhmiel@ur.rochester.edu


Education

  • PhD, Geosciences, 2020, University of Rochester
  • MS, Geology, 2015, University of Rochester
  • MS, Chemistry, 2012, University of Rochester
  • BS, Chemistry, 2010, University of Delaware

Research Overview

In cold regions of the planet such as Greenland and Antarctica, snow that falls during the year never melts and accumulates into large continental ice sheets.  Compressed snow (firn) becomes more compacted with each subsequent year’s accumulation and eventually transitions into ice below a certain depth (50-120m depending on temperature and accumulation rate).  Firn is a porous medium and as a result of the compression of overlying layers, the pores in the snow transform into bubbles within the ice at depth.  These bubbles trap a portion of the atmosphere within the pores as the firn transitions into ice at the close-off depth.  As a result of this natural process, the ancient atmosphere can be directly sampled by drilling for ice cores in such cold regions. 

My PhD research focused on a complete characterization of 14C through all zones of accumulating ice. Two separate mechanisms are responsible for the entrapment of 14C-contatining gases in ice cores: (1) trapping of atmospheric air that diffuses through the porous firn column at the top of an ice sheet, and (2) direct in situ production by cosmic rays within the ice lattice. This study utilized measurements of 14CH4, 14CO2 and 14CO in the firn air, firn matrix and ice below close off at summit Greenland.  Combined with a firn air diffusion model that incorporated the production of in situ cosmogenic 14C from first principles, I characterized the magnitude and speciation of 14C in situ cosmogenic between the three major phases.   Understanding the relative abundance and distribution of 14C as it transitions into ice will unlock ice core 14C measurements as a new paleoclimate proxy, allowing us to answer more questions about how climate has changed in the past relative to today.  

For my short postdoc, I’m continuing with my expertise in modeling the behavior of gases in the firn column to (1) invert measurements of the stable isotopes of CO into an atmospheric history and (2) characterize the magnitude of in situ cosmogenic 14CO production at Law Dome, Antarctica for assistance in in our group’s project of reconstructing the past oxidative capacity of the atmosphere through measurements of ice core 14CO.

Outreach and Science Communication

Selected Publications

  • B. Hmiel, V.V Petrenko, M.N. Dyonisius, C. Buizert, A.M. Smith, P.F. Place, C. Harth, R. Beaudette, Q. Hua, B. Yang, I. Vimont, S.E. Michel, J.P. Severinghaus, D. Etheridge, T. Bromley, J. Schmitt, X. Faïn, R.F. Weiss, E.J. Dlugokencky, Preindustrial 14CH4 indicates greater anthropogenic fossil CH4 emissions, Nature. 2020 doi.org/10.1038/s41586-020-1991-8
  • M.N. Dyonisius, V.V. Petrenko, A.M. Smith, Q. Hua, B. Yang, J. Schmitt, J. Beck, B. Seth, M.Bock, B. Hmiel, I. Vimont, J.A. Menking, S.A. Shackleton, D. Baggenstos, T.K. Bauska, R.H. Rhodes, P. Sperlich, R. Beaudette, C. Harth, M. Kalk, E.J. Brook, H. Fischer, J.P. Severinghaus, R.F. Weiss, Old carbon reservoirs were not important in the deglacial methane budget, Science, 2019 doi.org/10.1126/science.aax0504
  • Mühle, C.M Trudinger, L.M Western, M. Rigby, M.K. Vollmer, S. Park, A.J. Manning, D. Say,Ganesan, L.P Steele, D.J. Ivy, T. Arnold, S. Li, A. Stohl, C.M. Harth, P.K. Salameh, A. McCulloch, S. O'Doherty, M.K. Park, C.O. Jo, D. Young, K.M. Stanley, P.B. Krummel, B. Mitrevski, O. Hermansen, C. Lunder, N. Evangeliou, B. Yao, J. Kim, B. Hmiel, C. Buizert, V.V. Petrenko, J. Arduini, M. Maione, D.M. Etheridge, E. Michalopoulou, M. Czerniak, J.P. Severinghaus, S. Reimann, P.G. Simmonds, P.J. Fraser, R.G. Prinn, R.F. Weiss. Perfluorocyclobutane (PFC-318, c-C4F8) in the global atmosphere. Atmospheric Chemistry and Physics, 2019, doi.org/10.5194/acp-19-10335-2019
  • B. Hmiel, V.V. Petrenko, A.M. Smith, C. Buizert, C. Harth, R. Beaudette, P.F. Place, Q. Hua, B Yang, I. Vimont, R.F. Weiss, J.P. Severinghaus, E.J. Brook, J.W. White (2016). "Understanding the production and retention of in situ cosmogenic 14C in polar firn", IPICS 2nd Open Science Conference, Hobart, Tasmania (Poster)

Teaching

  • 2016-2018 Introduction to Climate Change Lab & Lecture TA (2 classes)
  • 2014, Atmospheric Geochemistry Lecture TA (1 class)
  • 2012, Advanced Nuclear Science and Technology Laboratory Lab TA (1 class)
  • 2010-2012 General Chemistry I & II Lab & Lecture TA (6 classes)
  • 2010-2012 General Chemistry I & II Lab & Lecture TA
  • 2014, Atmospheric Geochemistry Lecture TA

Field Experience

  • 2013, May, Summit Station, Greenland
  • 2013, Nov-Dec, Taylor Glacier, Antarctica
  • 2014, May-June, Summit Station, Greenland (Field Leader)
  • 2015, May-June, Summit Station, Greenland (Field Leader)