Permafrost

are formed and where they are located. This paper investigates gas hydrate accumulation in a
permafrost area of the Prudhoe Bay-Kuparuk River oil field in Alaska, USA by approaching the
gas hydrate formation using a thermal analysis and the methane hydrate stability curves.
Ground thermal regime for the duration of the formation of permafrost in the area was
modeled using a finite element method, TEMP/W 2004. Ground thermal properties were
estimated using information from well bore data and logs including deposit characteristics such
as rock type and water content. Latent heat of fusion was considered using an unfrozen water
content function. Assumed values for the past average ground surface temperature was used for
several analysis runs. The value that yielded conditions reflecting current thermal gradient and
depth of permafrost was used in the final analysis.
The modeled thermal regime as a function of depth and time was then compared with the
appropriate methane hydrate phase boundary curve. As a result, depth zones for stable methane
hydrates were obtained with time. Further, the formed layer of methane hydrates, and the
penetration of the 0°C isotherm and their trapping effects on the free flow of water and gas to
the stable zone were considered to explain the logged layers of methane hydrates in the
Kuparuk Oil Field. The created model can be used as an example to create similar models in
other locations to be used in methane hydrate exploration and field evaluation.
Key words: Permafrost formation, Alaska-North Slope, paleoclimate, methane hydrates
100
The influence of frozen ground on dynamics in geomorphic processes
and sediment rates: case studies from N-Sweden and Svalbard
M. Gude
(Department of Geography, University of Jena, Löbdergraben 32, D-07743 Jena, Germany,
e-mail: martin.gude@uni-jena.de)
Abstract: Dynamics in geomorphic processes and sediment transfer rates are controlled by the
existence of frozen ground, among other factors. In this respect, not only permafrost, but also
seasonally frozen ground plays an important role.
The geomorphic dynamics in the investigated periglacial mountain landscapes in
N-Sweden (Abisko Mountains) and in NW-Svalbard (Liefdefjord) are characterized by a
variety of processes. In both areas, the major geomorphic processes and their sediment transfer
rates were measured and monitored in several field campaigns. Furthermore, an elaborate data
set from intensive field studies since the 1950 th is available for the catchment Kärkevagge in the
Abisko Mountains.
Based on these data sets a comparative study of sediment transfer rates in relation to the
processes is undertaken. The results demonstrate that (1) high magnitude and low frequency
processes like big rockfalls or slushflows significantly contribute to total sediment rates and (2)
the frozen ground is likely to influence especially the distribution and occurrence of these
extreme events.
Key words: geomorphic processes, dynamics, sediment rates, geomorphic events