Km. Hinkel et al., Patterns of soil temperature and moisture in the active layer and upper permafrost at Barrow, Alaska: 1993-1999, GLOBAL PLAN, 29(3-4), 2001, pp. 293-309
Soil temperature has been monitored continuously at hourly intervals to a d
epth of 1 m since 1993 at a site near Barrow, AK. Time series of soil moist
ure from the active layer and upper permafrost have been collected since 19
96 at the same location. These records are supplemented by meteorological d
ata from NOAA's Barrow Climate Monitoring and Diagnostics Laboratory facili
ty and detailed description of depth-dependent soil properties at the site.
Soil sensors are situated within a low-centered ice-wedge polygon characte
rized by meadow tundra vegetation. A thin (7 cm) organic layer grades into
reworked marine silts at depth. The soil temperature and moisture are used
in a site-specific, multiyear thermal analysis of the atmosphere/snow/activ
e-layer/permafrost system. Fusion retards soil freezing during early winter
as soil water is converted to ice. Soil heat transfer is dominated by cond
uction in winter. Infiltration of snow meltwater in spring produces a serie
s of thermal pulses in the active layer, causing rapid warming of the upper
several decimeters by about 1 degreesC. The thermal impact is limited beca
use the soil tends to be nearly saturated at the time of freezeback. Volume
tric soil water content in summer is generally around 35-40% at a depth of
15 cm, while the base of the thawed zone remains saturated near 50%. The ne
ar-surface soil exhibits drying from evapotranspiration and rewetting from
precipitation events. During the period of thaw, the apparent thermal diffu
sivity is around 2-3 X 10(-7) m(2) s(-1) and increases with depth to reflec
t the greater soil water content. The maximum thaw depth at the site is typ
ically around 35 cm. However, end-of-season thaw depth has been monitored n
ear Barrow since 1994 and has increased between 1994 and 1998. This warming
trend is also reflected in the thawing degree days calculated for the thaw
ed soil volume. A strong correlation exists between maximum annual thaw dep
th and annual thawing degree days at this site over the period of record. (
C) 2001 Elsevier Science B.V. All rights reserved.