To clarify the mechanisms of the Okhotsk Sea intermediate water formation, water samples collected in the Okhotsk Sea and neighboring western North Pacific were analyzed for δ 18 O as well as salinity and other routinely measured components. The δ 18 O‐salinity relation in the Okhotsk Sea was markedly different from that in the western subarctic Pacific feeding the Okhotsk Sea. The intermediate water of the Okhotsk Sea was less saline than that of the western subarctic water at the same density but was more saline at the same δ 18 O value, especially in the density range 26.5<σ θ <27.0. This could be due to mixing of dense shelf water formed during sea‐ice formation with neighboring water. The amount of fresh water removed by the sea‐ice formation was estimated from the salinity anomaly of the Okhotsk Sea intermediate water. The calculated amounts of fresh water removed from the Okhotsk Sea intermediate water corresponded to the amount of sea ice formed for 0.6–3.8 years in the Okhotsk Sea. This suggests that the residence time of the Okhotsk Sea intermediate water is a few years.
This research was carried out to estimate the winter fluxes of CO2 and CH4 using the concentration profile method and the chamber method in black spruce forest soils in central Alaska during the winter of 2004/5. The average winter fluxes of CO2 and CH4 by chamber and profile methods were 0.24 ± 0.06 (SE; standard error) and 0.21 ± 0.06 gCO2-C/m2/d, and 21.4 ± 5.6 and 21.4 ± 14 μgCH4-C/m2/hr. This suggests that the fluxes estimated by the two methods are not significantly different based on a one-way ANOVA with a 95% confidence level. The hypothesis on the processes of CH4 transport/production/emission in underlying snow-covered boreal forest soils is proven by the pressure differences between air and in soil at 30 cm depth. The winter CO2 emission corresponds to 23% of the annual CO2 emitted from Alaska black spruce forest soils, which resulted in the sum of mainly root respiration and microbial respiration during the winter based on the δ13CO2 of .22.5‰. The average wintertime emissions of CO2 and CH4 were 49 ± 13 gCO2-C/m2/season and 0.11 ± 0.07 gCH4-C/m2/season, respectively. This implies that winter emissions of CO2 and CH4 are an important part of the annual carbon budget in seasonally snow-covered terrain of typical boreal forest soils.
We explore the use of two cosmogenically produced nuclides in the atmosphere, 35 S (half‐life = 87 days) and 7 Be (half‐life = 53 days), as tracers of gaseous SO 2 and aerosol SO 4 and Be removal processes to the Earth's surface. Based on 35 S and 7 Be wet precipitation fluxes and 35 SO 2 , 35 SO 4 and 7 Be concentrations in air samples in the planetary boundary layer at New Haven, Connecticut (USA) we determine coefficients for incloud scavenging of 35 SO 2 , oxidation of 35 SO 2 to 35 SO 4 in both the planetary boundary layer and the free troposphere, and dry deposition. In addition, the distributions of 35 SO 2 , 35 SO 4 and 7 Be between the planetary boundary layer and the free troposphere are determined as well as the air exchange coefficient between the two reservoirs. Application to stable S yields a dry deposition flux to total flux ratio of about 0.20 for August, 1990.
Measurements of carbon-14 in small samples of methane from major biogenic sources, from biomass burning, and in "clean air" samples from both the Northern and Southern hemispheres reveal that methane from ruminants contains contemporary carbon, whereas that from wetlands, pat bogs, rice fields, and tundra is somewhat, depleted in carbon-14. Atmospheric (14)GH(4) seems to have increased from 1986 to 1987, and levels at the end of 1987 were 123.3 +/- 0.8 percent modern carbon (pMC) in the Northern Hemisphere and 120.0 +/- 0.7 pMC in the Southern Hemisphere. Model calculations of source partitioning based on the carbon-14 data, CH(4) concentrations, and delta(13)C in CH(4) indicate that 21 +/- 3% of atmospheric CH(4) was derived from fossil carbon at the end of 1987. The data also indicate that pressurized water reactors are an increasingly important source of (14)CH(4).
Spatial variations in the concentration and nature of colored dissolved organic matter (CDOM) in the western Arctic Ocean were examined by three‐dimensional excitation/emission matrix (3‐D EEM) spectroscopy. CDOM profiles showed distinctive features well correlated with hydrographic characteristics. CDOM fluorescence was particularly high at depths between 40 and 200 m (up to 3 fluorescence units (Fl.U.)) in both Chukchi Sea and Beaufort Sea transects. Penetration of the high CDOM signal, formed on the shelves, into the Canada Basin was confined to the upper halocline layer (salinity of ∼33.1). This layer had distinctive 3‐D EEM fingerprints in fluorescence spectra, showing a marked terrestrial humic signature. The presence of CDOM in the halocline layer likely resulted from two main processes: the brine rejection during sea ice formation and transport across the sediment‐water interface during early diagenesis. Despite the high primary productivity in the Chukchi shelf, CDOM contribution from in situ production seemed to have little influence on the overall CDOM distributions in the study area.
