[Image: M.H. in snow pit]

Dr. Maria Hörhold


E-Mail: m_hoerhold (at) iup.physik.uni-bremen.de
Phone: +49 (0)421 218 62184

Mailing Address:

Institute of Environmental Physics
University of Bremen, FB1
P.O.Box 330440
28334 Bremen
[SPP logo]

The DFG-funded project SAFIR - SAtellite Remote Sensing for polar FIRn properties

The project SAFIR is funded within the DFG "Schwerpunktprogramm 1158 - Antarktisforschung mit vergleichenden Untersuchungen in arktischen Eisgebieten". The layering of polar snow and firn is studied. Main interest is the influence of the layering on microwave emission. The impact of accumulation rate on the creation and structure of the layering is investigated. Main goal of the project is to test the hypothesis, that the accumulation rate at the Antarctic and Greenland Ice sheet can be detected with passive microwave emission via the layering properties of the firn.

Motivation for SAFIR

For future sea level projections the contribution of the polar ice sheets of Greenland and Antarctica to sea level rise due to climate change remain unknown. Huge efforts are undertaken to estimate the ice sheets' mass-balance - i.e., the amount of snow and ice gained and lost every year. Local measurements and observations through ice core studies or stake field measurements are not only constrictive in their spatial meaning. Due to the remoteness of the place the acquisition of these data is also very expensive and time consuming. Therefore the observation of the mass balance via satellite remote sensing offers a valuable alternative. However, in order to interpret satellite images we need to understand the interaction of the remote sensing techniques and the snow, firn and ice of the ice sheets.The project SAFIR studies the influence of the firn structure on the microwave emission of the firn observed by passive microwave sensors.

Structure of SAFIR

Structure of SAFIR

Within the project first available high-resolution density data depicting the layered structure of the firn are analysed in order to understand the impact of local accumulation rate and thus the amount of mass added every year on the genesis and structure of the layering. Secondly the influence of the layering on microwave emission is investigated. Therefore microwave emission models of layered media are used in order to test different layering set-ups for their impact on emissivity. Additionally measured brightness temperatures of different sites in Greenland and Antarctica with different accumulation rates are collected and compared. Finally the results will be merged in order to set up a way of determining the accumulation rate with satellite remote sensing via the layering of the firn.

What is firn?

The term firn is used for snow which does not melt over the summer, as it happens at the top of the polar ice sheets in Greenland and Antarctica. Each snow deposition event is preserved as a single layer with its very specific physical properties such as density and microstructure. These layers accumulate on top of each other, change their density and microstructure with time and slowly get suppressed downwards within the firn column. After reaching the density of 917 kg/m³ the firn is then called ice. The preservation of these layers leads to a very unique climate archive from which information of past climate conditions can be deduced. Ice cores drilled in Greenland and Antarctica tell us the story of climate history because single layers are formed at the surface of the ice sheet and keep their information of local climate conditions such as surface temperature or chemical composition of the atmosphere.

[Layering of firn]
Snow pit (3m deep) at Summit Station, Greenland. The layers of single snow deposition events can be easily distinguished with the eye.

Scientist of SAFIR

The principal investigator of the project SAFIR is Dr. Maria Hörhold. She has obtained her PhD at the Alfred-Wegener-Institute for polar and marine research studying firn microstructure and physical properties. She has visited the Greenland ice sheet twice.

Research Interests

Curriculum Vitae


2000-2003studied Geosciences/ Geophysics at the University of Potsdam, Germany
2003-2004studied Arctic Geophysics at the University Centre at Svalbard (UNIS), Spitzbergen, Norway
2004-2006 studied Geosciences at the University of Bremen, Germany
Diploma thesis at the Alfred-Wegener-Institute for polar and marine Research (AWI) and at the Cold Region Engineering Laboratory (CRREL) Hanover, New Hampshire, USA
2007-2010 PhD at the AWI, expeditions to Greenland 2007 and 2008
Doctoral degree summa cum laude

Working Experience

2010-2012Head of school lab deltax at Helmholtz Zentrum Dresden-Rossendorf, Germany
since 2012PostDoc at the Institute of Environmental Physics, University of Bremen, Germany

Funding and awards

2006 Deutscher Akademischer Austauschdienst (DAAD) funding for three-months stay at CRREL (USA)
2007 Posterpreis, AWI-PhD-days
2012 DFG funded project SAFIR, Antrag auf eigene Stelle

Publications (peer reviewed)