CARBON-14 MEASUREMENTS
Arctic Research Laboratory and
425
Project Husky. It is forecast that
Arlis II will enter the North Pacific sometime in the spring of 1965;
therefore a sampling site will then be established on floating ice island
T-3 to replace it,
The University of Washington oceanographic vessel, the Brown
Bear, collects samples at irregular intervals at locations roughly 100
miles west of the Washington coast.
In addition to collecting ground-level samples, we collect samples
in pod-mounted air samplers carried by jet trainers that operate out
of the Whidbey Island Naval Air Station. Flights are made at approximately weekly intervals. Except for the summer months, when the
tropopause is above the ceiling of this aircraft, samples are collected
in both the upper troposphere and the lower stratosphere.
Part of our studies include determinations of the role of storms in
effecting transfer of stratospheric air into the troposphere and in effecting exchange between CO, in the atmosphere and CO, dissolved in
the sea, During the passage of particular storm fronts over the Seattle
area in the spring of 1964, samples of CO, were takenat intervals of
3 to 4 hr at a locationnearthe summit of Hurricane Ridge on the Olympic Peninsula at an elevation of about 5000 ft.
The “C specific activity of the samples is determined in one of
two low-background radiocarbon counters, The normal, or pre-1945,
level of 4C in the atmosphere is taken to be 0.95 times the ‘*C specific
activity of the National Bureau of Standards oxalic acid standard used
in radiocarbon dating. The results of the measurements are then expressed in terms of percent above normal.
RESULTS
Figure 2 shows the ground-level 'C specific activities for samples
collected between August 1963 and July 1964, The specific activity
evidently decreased from a high of about 110% above normalin the
summer of 1963 to a low of about 88% above normal in the late winter
and early spring of 1964. Prior to the summerhigh in 1963, the Mc
specific activity of atmospheric CO, was less than 40% above normal.
A new summer rise during the summer of 1964 was also evident. It is
interesting to note that the values measuredat locations in the Arctic
basin do not differ significantly from those measured in the Puget
Sound area.
Since the total CO, in the atmosphere changes only very slightly
with the season of the year, a decrease in the specific activity must be
due to exchange with a reservoir of much lower specific activity. We
believe this reservoir to be the ocean. Falland early winter are stormy
periods in these latitudes, and high wind velocities favor exchange of
gas molecules between the atmosphere and the surface of the ocean.