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Atmospheric N 2 O concentration was observed in the Pacific for the period 1991–2006, using commercial container ships sailing between Japan and North America and between Japan and Australia or New Zealand. The N 2 O concentration showed a secular increase and interannual variations at all sampling locations, but a seasonal cycle was detectable only at northern high latitudes. The annual mean N 2 O concentration showed little longitudinal variations (within ± 0.3 ppb) in the northern Pacific, but showed a clear north-south gradient of about 0.8 ppb, with higher values in the Northern Hemisphere. The annual mean N 2 O was also characterized by especially high values at 30°N due to strong local N 2 O emissions and by a steep latitudinal decrease from the equator to 20°S due to the suppression of interhemispheric exchange of air by the South Pacific Convergence Zone. The N 2 O growth rate showed an interannual variation with a period of about 3 yr (high-values in 1999 and 2000), with a delayed eastward and poleward phase propagation in the northern and western Pacific, respectively. The interannual variations of the N 2 O growth rate and soil water showed a good correlation, suggesting that the N 2 O emission from soils have an important causative role in the atmospheric N 2 O variation. DOI: 10.1111/j.1600-0889.2008.00406.x

A deep ice core drilled at Dome Fuji, East Antarctica was analyzed for the CO 2 concentration using a wet extraction method in order to reconstruct its atmospheric variations over the past 320 kyr, which includes three full glacial–interglacial climatic cycles, with a mean time resolution of about 1.1 kyr. The CO 2 concentration values derived for the past 65 kyr are very close to those obtained from other Antarctic ice cores using dry extraction methods, although the wet extraction method is generally thought to be inappropriate for the determination of the CO 2 concentration. The comparison between the CO 2 and Ca 2+ concentrations deduced from the Dome Fuji core suggests that calcium carbonate emitted from lands was mostly neutralized in the atmosphere before reaching the central part of Antarctica, or that only a small part of calcium carbonate was involved in CO 2 production during the wet extraction process. The CO 2 concentration for the past 320 kyr deduced from the Dome Fuji core varies between 190 and 300 ppmv, showing clear glacial–interglacial variations similar to the result of the Vostok ice core. However, for some periods, the concentration values of the Dome Fuji core are higher by up to 20 ppmv than those of the Vostok core. There is no clear indication that such differences are related to variations of chemical components of Ca 2+ , microparticle and acidity of the Dome Fuji core. DOI: 10.1034/j.1600-0889.2003.00050.x

In order to elucidate the seasonal and interannual variations of oceanic CO2 uptake in the Greenland Sea and the Barents Sea, the partial pressure of CO2 in the surface ocean (pCO2sea) was measured in all seasons between 1992 and 2001. We derived monthly varying relationships between pCO2sea and sea surface temperature (SST) and combined them with the SST data from the NCEP/NCAR reanalysis to determine pCO2sea and air–sea CO2 flux in these seas. The pCO2sea values were normalized to the year 1995 by assuming that pCO2sea increased at the same growth rate (1.5 μatm yr−1) of the pCO2 in the air (pCO2air) between 1992 and 2001. In 1995, the annual net air–sea CO2 fluxes were evaluated to be 52 ± 20 gC m−2 yr−1 in the Greenland Sea and 46 ± 18 gC m−2 yr−1 in the Barents Sea. The CO2 flux into the ocean reached its maximum in winter and minimum in summer. The wind speed and ΔpCO2 (=pCO2air–pCO2sea) exerted a greater influence on the seasonal variation than the sea ice coverage. The annual CO2uptake examined in this study (70°–80°N, 20°W–40°E) was estimated to be 0.050 ± 0.020 GtCyr−1 in 1995. The interannual variation in the annual CO2 uptake was found to be positively correlated with the North Atlantic Oscillation Index (NAOI) via wind strength but negatively correlated with ΔpCO2 and the sea ice coverage. The present results indicate that the variability in wind speed and sea ice coverage play a major role, while that in ΔpCO2 plays a minor role, in determining the interannual variation of CO2 uptake in this area.DOI: 10.1111/j.1600-0889.2006.00178.x

Using discrete air sampling, values of δ13C and δ18O in atmospheric CO2, as well as its concentration, were measured in a forest in the central part of the main island of Japan during the period from June 1994 to June 1996 to examine the biospheric contribution to their temporal variations. δ13C shows a prominent diurnal variation with high values in the daytime and low values in the nighttime, especially during the warm season. δ13C also vary seasonally, showing a maximum in summer and a minimum in spring. The diurnal and seasonal variations of δ13C are opposite in phase with those of the CO2 concentration. The rate of change in δ13C with respect to the CO2 concentration is found to be approximately -0.05‰/ppmv. This suggests that the diurnal and seasonal variations of the CO2concentration are produced primarily by diurnally- and seasonally-dependent photosynthetic-respiratory processes of the biosphere near the observation site, respectively. In the warm season, δ18O also increases in the daytime and decreased in the nighttime, which is similar to the diurnal variation of δ13C, but opposite to that of the CO2 concentration. The diurnal δ18O variation is thought to be caused by the release of isotopically heavy CO2during photosynthesis, and light CO2 during respiration. However, an interpretation of the seasonal δ18O variation is found to be much more difficult than those of δ13C and the CO2 concentration. This is likely due to complicated combinations of different seasonally varying fluxes of biospheric CO2 into the atmosphere, as well as to various weather-dependent factors governing the δ18O composition in CO2.DOI: 10.1034/j.1600-0889.49.issue4.3.x

Aircraft measurements of atmospheric CO2 concentration over Japan, initiated in January 1979, have been continued to the present. The average seasonal variation of atmospheric CO2 showed maximum concentration early in April and early in May, and minimum concentration in mid-August and mid-September for the lower-most and the upper-most layers of the troposphere, respectively. The peak-to-peak amplitudes of the seasonal variation were 14.5, 9.0 and 7.8 ppmv for the lower, middle and upper tropospheres, respectively. The average rate of annual increase of the C02 concentration over the last 6 years was about 1.3 ppmv yr-1 with considerable variation with time. The vertical profile of the annual mean value of the CO2 concentration was almost the same from year to year; the CO2 concentration decreased gradually with height and the concentration difference between the lowest and highest layers of the troposphere was about 2 ppmv.DOI: 10.1111/j.1600-0889.1987.tb00265.x

[1] To investigate spatial variations of CH4 concentration, δ13CH4, and δD-CH4 over Alaska, aircraft observations were conducted during the summer of 2006. CH4 concentrations elevated above the background level were observed over areas with wetlands and wildfires, important sources of CH4. Several flights showed elevated CH4 values, with corresponding δ13CH4 and δD-CH4 signatures of −63.4‰ ± 3.0‰ and −424‰ ± 79‰, respectively, which are based on the relationship between δ13CH4 (or δD-CH4) and CH4 concentration (single mixing relation), an indication of wetland source. It was also noted that both wetlands and wildfires influenced the CH4 concentrations observed over the wildfire area. Assuming certain emission ratios of CH4 to CO (ERCH4/CO) for the wildfire and certain values of δ13CH4 and δD-CH4 for wetland CH4, we derived δ13CH4 and δD-CH4 of CH4 emitted from the wildfire to be −27.5‰ ± 2.0‰ and −285‰ ± 111‰, respectively, which agreed relatively well with, but was slightly lower than, those obtained by previous studies at lower latitudes. To verify these estimates, bonfire experiments were conducted in the interior of Alaska using the same biomass material burned in the wildfire observed by the aircraft. The result showed that the previously reported ERCH4/CO value was plausible and that δ13CH4 and δD-CH4 obtained by the bonfire experiments agreed with the estimates by the aircraft observations. We also found that δ13CH4 and δD-CH4 values became enriched with increasing combustion efficiency. By using the relationship between δD-CH4 for biomass burning and δD of precipitation, global average of δD-CH4 emitted from biomass burning was estimated to be −204‰ ± 11‰.

第１回極域科学シンポジウム「極域大気圏を通して探る地球規模環境変動」12月1日（水） 国立極地研究所 ２階大会議室

第１回極域科学シンポジウム「極域大気圏を通して探る地球規模環境変動」12月1日（水） 国立極地研究所 ２階大会議室

第１回極域科学シンポジウム「極域大気圏を通して探る地球規模環境変動」ポスター発表

[1] The atmospheric N2O variations between the Earth's surface and the lower stratosphere, simulated by an atmospheric general circulation model–based chemistry transport model (ACTM), are compared with aircraft and satellite observations. We validate the newly developed ACTM simulations of N2O for loss rate and transport in the stratosphere using satellite observations from the Aura Microwave Limb Sounder (Aura-MLS), with optimized surface fluxes for reproducing N2O trends observed at the surface stations. Observations in the upper troposphere/lower stratosphere (UT/LS) obtained by the Japan AirLines commercial flights commuting between Narita (36°N), Japan, and Sydney (34°S), Australia, have been used to study the role of stratosphere-troposphere exchange (STE) on N2O variability near the tropopause. Low N2O concentration events in the UT region are shown to be captured statistically significantly by the ACTM simulation. This is attributed to successful reproduction of stratospheric air intrusion events and N2O vertical/horizontal gradients in the lower stratosphere. The meteorological fields and N2O concentrations reproduced in the ACTM are used to illustrate the mechanisms of STE and subsequent downward propagation of N2O-depleted stratospheric air in the troposphere. Aircraft observations of N2O vertical profile over Surgut (West Siberia, Russia; 61°N), Sendai-Fukuoka (Japan; 34°N–38°N), and Cape Grim (Tasmania, Australia; 41°S) have been used to estimate the relative contribution of surface fluxes, transport seasonality in the troposphere, and STE to N2O seasonal cycles at different altitude levels. Stratospheric N2O tracers are incorporated in the ACTM for quantitative estimation of the stratospheric influence on tropospheric N2O. The results suggest strong latitude dependency of the stratospheric contribution to the tropospheric N2O seasonal cycle. The periods of seasonal minimum in the upper troposphere, which are spring over Japan and summer over Surgut, are in good agreement between the ACTM and observation and indicate a different propagation path of the stratospheric signal between the two sites in the Northern Hemisphere. The stratospheric tracer simulations, when utilized with the observed seasonal cycle, also provide qualitative information on the seasonal variation in surface fluxes of N2O.

[1] Atmospheric CO2 concentration and its isotopes have been measured at the Takayama site in central Japan since 1994, together with δ18O in precipitation since 2002, to examine their temporal variations in a cool-temperate deciduous forest environment strongly influenced by the Asian monsoon. The CO2 concentration and δ13C at the observational site show prominent seasonal variations accompanied by a secular trend, suggesting that the average seasonal cycle is caused mainly by a seasonal-dependent CO2 exchange with C3 plants. However, the variation in summer is found to be related to CO2 exchange with a significantly heavier δ13C signal compared to the other seasons, indicating some influence at the Takayama site of atmospheric transport of CO2 impacted by exchange with C4 plants from upstream regions. Compared with CO2 and δ13C, δ18O measurements in atmospheric CO2 are scattered, showing no clear seasonal variation. From late spring to early fall, significant year-to-year differences in the variation of δ18O are observed, with low and high values associated with rainy and sunny summer conditions, respectively. Comparisons with data from other northern midlatitude sites suggest that the rapid decrease of δ18O seen at Takayama in the early summer of a rainy summer year is characteristic of the Asian monsoon region. On the other hand, the characteristic increase in δ18O observed from winter to spring is likely caused by long-range transport of air with enriched δ18O.

[1] We examined pCO2air and pCO2sea observed in the eastern Indian sector of the Southern Ocean (south of 50°S, 140°–150°E) during austral spring-summer from November 2001 to March 2002 using 4 research vessels. pCO2sea changed by as much as 200 μatm over the 5-month period in the Seasonal Sea Ice Zone (SSIZ), due mostly to very low values in January caused by stratification of water column and strong biological activity. In the SSIZ, the air-sea CO2 flux showed large temporal variations, from −2.9 g m−2 month−1 in January 2002 to −0.65 g m−2 month−1 in February 2002. The monthly oceanic CO2 uptake in the area covered by this study (1.5 × 1012 km2) was estimated to be in a range of 1.0 × 10−3 to 1.7 × 10−3 PgC month−1, with a mean value of 1.3 × 10−3 PgC month−1.

[1] Systematic observations of atmospheric carbon monoxide (CO) have been carried out in the western part of the Pacific Ocean since February 1990. The average CO concentration showed a latitudinal gradient, with higher values in the northern hemisphere than in the southern hemisphere. A clear seasonal CO cycle was found nearly at all sampling locations, showing maximum and minimum concentrations in spring and summer, respectively. In the 30°–35°N latitude zone, the average CO concentration was higher and the seasonal amplitude was larger compared with other latitudes. The CO concentration also showed a large interannual variability mainly in association with forest fires. In particular, the forest fires in Siberia in 1998 and Indonesia in 1997–1998 contributed to a remarkable increase in the regional CO concentration, followed by a recovery that took several months to a year. A three-dimensional atmospheric global chemical transport model (CHASER) was used to simulate the observed characteristics of the latitudinal distribution, seasonal cycle, and interannual variability relatively well. Tagged CO experiments with the model revealed that the contribution of CO emissions from various regions in the northern hemisphere to the CO concentrations at our sampling locations varied seasonally in association with Asian outflows and long-range transport from Europe and North America. In the southern hemisphere, biomass burnings significantly affected the regional seasonal CO cycle, in addition to the effect of CO oxidation with OH. It was also found that CHASER underestimates the average CO concentration in the northern hemisphere and its interannual variability.

[1] To investigate the gravitational separation of atmospheric components in the stratosphere, air samples collected over Japan, the Arctic and the Antarctic were analyzed for δ15N of N2 and δ18O of O2. The gravitational separation is a function of latitude, showing the largest effect inside the polar vortex over the Arctic. The relationship between the gravitational separation (calculated using a steady-state 1-dimensional eddy-diffusion/molecular-diffusion model) and the CO2 age (calculated using a 1-dimensional time dependent eddy-diffusion model) suggests that the observed gravitational separation is fundamentally a result of diffusive separation but modified by meridional circulation of air in the stratosphere. We also obtain a compact relationship between the gravitational separation and the N2O concentration. By comparing the gravitational separations at two height intervals with the N2O concentrations >125 ppb and

[1] Lower stratospheric O2/N2 ratios (δ(O2/N2)) at northern middle and high latitudes were measured by analyzing aircraft air samples collected between Nagoya, Japan and Svalbard Islands in the Arctic during the early spring of 2002. The measured values of δ(O2/N2) are relatively uniform horizontally in the lowermost part of the stratosphere but increase with height. Vertical distributions of δ(O2/N2) and the CO2 concentration observed over Svalbard Islands and Barrow, Alaska are negatively correlated. By examining the rates of change in δ(O2/N2) and δ13C of CO2 relative to the CO2 concentration, such a correlation observed is mainly attributable to upward propagation of their seasonal cycles produced on the ground surface for the troposphere and height-dependent air age for the stratosphere. However, from the vertical profiles of δ15N of N2, δ18O of O2 and δ(Ar/N2) measured in the lowermost part of the stratosphere over Svalbard Islands, it is suggested that the relationship between δ(O2/N2) and the CO2 concentration is affected by the gravitational separation. By correcting the measured δ(O2/N2) and δ13C values for this gravitational separation, the relationships of δ(O2/N2) and δ13C with the CO2 concentration are consistent with those expected from their secular trends in the troposphere.

Measurements of midday vertical atmospheric CO 2 distributions reveal annual-mean vertical CO 2 gradients that are inconsistent with atmospheric models that estimate a large transfer of terrestrial carbon from tropical to northern latitudes. The three models that most closely reproduce the observed annual-mean vertical CO 2 gradients estimate weaker northern uptake of –1.5 petagrams of carbon per year (Pg C year –1 ) and weaker tropical emission of +0.1 Pg C year –1 compared with previous consensus estimates of –2.4 and +1.8 Pg C year –1 , respectively. This suggests that northern terrestrial uptake of industrial CO 2 emissions plays a smaller role than previously thought and that, after subtracting land-use emissions, tropical ecosystems may currently be strong sinks for CO 2 .

[1] Histories of atmospheric N2O concentration and its δ15N and δ18O were reconstructed for the period 1952–2001 on the basis of the analyses of firn air collected at the North Greenland Ice Core Project (NGRIP), Greenland, and Dome Fuji and H72, Antarctica. The N2O concentration increased from 290 ppbv in 1952 to 316 ppbv in 2001, which agrees well with the results from atmospheric observations and polar ice core analyses. The δ15N and δ18O showed a secular decrease, the respective values being 8.9 and 21.5‰ in 1952 and 7.0 and 20.5‰ in 2001. Their rates of change also varied, from about −0.02‰ yr−1 in the 1950s to about −0.04‰ yr−1 in 1960–2001 for δ15N, and from about 0‰ yr−1 to −0.02‰ yr−1 for δ18O. The isotopic budgetary calculations using a two-box model indicated that anthropogenic N2O emission from soils played a main role in the atmospheric N2O increase after industrialization, as well as that the average isotopic ratio of anthropogenic N2O has potentially been changed temporally.

[1] Methyl chloride (CH3Cl) concentration was measured in air trapped in a deep ice core from Dome Fuji, Antarctica covering the last glacial–present interglacial (Holocene) change. The record shows that the CH3Cl concentration was relatively constant, being similar to the present levels, during the pre-industrial Holocene. In contrast, the CH3Cl concentration was significantly high and variable in the last glacial period, possibly due to impurity-related production of CH3Cl in ice sheet. Under the assumption that the production was the sole cause of the excess CH3Cl, the atmospheric CH3Cl concentration during the last glacial was estimated using simultaneously measured calcium data for the ice core to have been enhanced by 30% compared with the pre-industrial Holocene concentration. Because the major sink of CH3Cl was stronger during the last glacial than during the Holocene, the enhancement of CH3Cl during the last glacial was likely due to the glacial period source being enhanced.

The Milankovitch theory of climate change proposes that glacial interglacial cycles are driven by changes in summer insolation at high northern latitudes(1). The timing of climate change in the Southern Hemisphere at glacial-interglacial transitions (which are known as terminations) relative to variations in summer insolation in the Northern Hemisphere is an important test of this hypothesis. So far, it has only been possible to apply this test to the most recent termination(2,3), because the dating uncertainty associated with older terminations is too large to allow phase relationships to be determined. Here we present a new chronology of Antarctic climate change over the past 360,000 years that is based on the ratio of oxygen to nitrogen molecules in air trapped in the Dome Fuji and Vostok ice cores(4,5). This ratio is a proxy for local summer insolation(5), and thus allows the chronology to be constructed by orbital tuning without the need to assume a lag between a climate record and an orbital parameter. The accuracy of the chronology allows us to examine the phase relationships between climate records from the ice cores(6-9) and changes in insolation. Our results indicate that orbital-scale Antarctic climate change lags Northern Hemisphere insolation by a few millennia, and that the increases in Antarctic temperature and atmospheric carbon dioxide concentration during the last four terminations occurred within the rising phase of Northern Hemisphere summer insolation. These results support the Milankovitch theory that Northern Hemisphere summer insolation triggered the last four deglaciations(3,10,11).

This study assesses polar stratospheric nitrous oxide (N(2)O) and methane (CH(4)) data from the Improved Limb Atmospheric Spectrometer-II (ILAS-II) on board the Advanced Earth Observing Satellite-II (ADEOS-II) retrieved by the Version 1.4 retrieval algorithm. The data were measured between January and October 2003. Vertical profiles of ILAS-II volume mixing ratio (VMR) data are compared with data from two balloon-borne instruments, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B) and the MkIV instrument, as well as with two satellite sensors, the Odin Sub-Millimetre Radiometer (SMR) for N(2)O and the Halogen Occultation Experiment (HALOE) for CH(4). Relative percentage differences between the ILAS-II and balloon/satellite data and their median values are calculated in 10-ppbv-wide bins for N(2)O (from 0 to 400 ppbv) and in 0.05-ppmv-wide bins for CH(4) (from 0 to 2 ppmv) in order to assess systematic differences between the ILAS-II and balloon/satellite data. According to this study, the characteristics of the ILAS-II Version 1.4 N(2)O and CH(4) data differ between hemispheres. For ILAS-II N(2)O VMR larger than 250 ppbv, the ILAS-II N(2)O agrees with the balloon/SMR N(2)O within +/- 20% in both hemispheres. The ILAS-II N(2)O in the VMR range from 30-50 to 250 ppbv (corresponding to altitudes of similar to 17-30 km in the Northern Hemisphere (NH, mainly outside the polar vortex) and similar to 13-21 km in the Southern Hemisphere (SH, mainly inside the polar vortex) is smaller by similar to 10-30% than the balloon/SMR N(2)O. For ILAS-II N(2)O VMR smaller than 30 ppbv (>similar to 21 km) in the SH, the differences between the ILAS-II and SMR N(2)O are within +/- 10 ppbv. For ILAS-II CH(4) VMR larger than 1 ppmv ( similar to 30 km) and the ILAS-II CH(4) for its VMR smaller than 1 ppmv (>similar to 25 km) only in the NH, are abnormally small compared to the balloon/satellite data.

Systematic observations of the atmospheric CH4 mole fraction and its carbon isotope ratio δ 13 CH 4 have been carried out at Ny Alesund, Svalbard (78°55'N, 11°56'E) since 1991 and 1996, respectively. The CH4 and δ 13 CH 4 showed clear seasonal cycles with respective peak-to-peak amplitudes of 48 ppb and 0.42%o. By comparing the anomalies in the increase rate of the CH4 with those of δ 13 CH 4, it is suggested that the cause of the rapid increase in the CH4 mole fraction observed at Ny Alesund in 1998 could be attributable to an enhanced CH 4 release from wetland and biomass burning.

[1] To examine the spatial and temporal behavior of stratospheric O2, air samples were collected using a cryogenic sampler over Sanriku, Japan and Syowa, Antarctica and analyzed for δ(O2/N2), δ15N of N2 and δ18O of O2. The measured values of all these components decreased gradually with height. The differences in δ(O2/N2), δ15N and δ18O between the middle and lowermost levels of the stratosphere were about 250, 100, and 180 per meg, respectively. The observed stratospheric profiles of δ15N and δ18O were in agreement with those calculated using a steady-state 1-dimensional eddy-diffusion/molecular-diffusion model, which suggests that the upward decrease of stratospheric δ(O2/N2) is caused by a gravitational separation of O2 and N2 molecules. The averaged stratospheric δ(O2/N2) at heights above 20–25 km over Sanriku, corrected for the gravitational separation, was always higher than the upper tropospheric δ(O2/N2) value over Japan, and it decreased secularly. From the past temporal δ(O2/N2) variation deduced from the gravitational separation-corrected stratospheric δ(O2/N2) values and the mean ages of the respective air samples, which corresponds to its secular trend in the troposphere, average terrestrial biospheric and oceanic CO2 uptake for October 1993–September 2001 were estimated to be 1.1 ± 1.3 and 1.8 ± 1.3 GtC yr−1, respectively.

The long-term changes of the stratospheric mixing ratio of CH4 over the period of 1978-2003 are derived from balloon-borne data of H-2, CH4 and N2O. The data were obtained by collecting whole air samples and subsequent gas chromatographic analyses. To eliminate the short-term variability attributed to dynamical processes, the N2O mixing ratio is used as a proxy for altitude. A correlation analysis for the individual years is applied and the CH4 mixing ratios are interpolated to four different levels of N2O, corresponding to altitudes of approximately 17, 23, 26 and 30 km at midlatitudes. For the investigated period of 1978 to 2003 we find increases at the four levels of 207 +/- 32 ppb, 159 +/- 21 ppb, 140 +/- 34 ppb and 111 +/- 60 ppb, respectively. The CH4 trend has slowed down in recent years and is best fitted by a second-order polynomial. The increase of CH4 can account for only 25-34% of the increase in stratospheric H2O of 1%/yr over the last decades as derived from previous studies. The simultaneously measured time series of stratospheric H-2 mixing ratios shows that the contribution of stratospheric H-2 to the H2O trend in the period 1988-2003 is minor.

We developed a simple measurement system for delta17O in nanomole quantities of CO2 using continuous flow isotope ratio mass spectrometry (CF-IRMS). The analytical system consisted of a sample injection system, a helium-purged CO2 purification line, a capillary GC, a combustion unit, and CF-IRMS. A unique feature of the system is that we use molecular CO2 to determine the isotopic compositions including delta17O. The delta17O of CO2 in a sample is calculated from the mass ratios of both 45/44 and 46/44 of two different kinds of CO2, which have been purified quantitatively from different aliquots of a sample. While one aliquot (rCO2) flows into IRMS directly, the other (eCO2) flows through a CuO unit (900 degrees C) prior to injection into IRMS, to exchange oxygen atoms in the sample CO2 molecules with those in CuO for which we can assume Delta17O = 0. In our system, we introduce both rCO2 and eCO2 alternately to IRMS repeatedly by using an automatic multianalytical system to improve analytical precision statistically. The standard deviation of 0.35 per thousand for Delta17O can be realized using as little as 8.7 nmol CO2 in a approximately 3-h analysis. Based on this system, we have quantified delta17O in the stratospheric CO2 over Japan.

[1] In order to examine the role of terrestrial biospheric activity in the seasonal variation of δ18O of atmospheric CO2, we measured δ18O values of CO2 and H2O in the soil and the canopy air in a temperate forest in the northern part of the main island of Japan for the period August 2000–December 2001. It was found that the δ18O value of the soil water near the surface varied seasonally almost in phase with that of precipitation, except for spring. On the other hand, its seasonal variation at 70 cm depth showed a 3-month delay compared to those at 10 and 40 cm depths, owing to slow penetration of precipitation into the soil. The measured δ18O values of CO2 in the soil air at 10, 40, and 70 cm depths agreed well with the results calculated under the assumption that CO2 in the soil air was isotopically equilibrated with its surrounding soil water. On the basis of the measurement results, we derived the seasonally varying oxygen isotopic discrimination factors for respiration and photosynthesis processes. Using these discrimination factors as well as biospheric CO2 fluxes estimated by employing an ecosystem model, we calculated the seasonal variation of δ18O of atmospheric CO2 in the forest canopy. The result showed a good agreement with the observation, indicating that the isotopic contribution of photosynthesis to the atmospheric δ18O was strong in spring and fall, while that of respiration was dominant in summer and winter.

[1] Temporal and latitudinal variations of vertical profiles of N2O isotopomers were observed in the stratosphere over Japan (39°N, 142°E), Sweden (68°N, 20°E), and Antarctica (69°N, 40°E) during the period between 1990 and 2001. Samples were collected with a balloon-borne cryogenic sampler and analyzed by mass spectrometry in the laboratory. Observed enrichment factors for heavier isotopomers (15N14N16O, 14N15N16O, and 14N14N18O) relative to 14N14N16O were nearly constant in the lower stratosphere (less than ∼22 km) but increased at higher altitudes (∼22–35 km) while showing seasonal and latitudinal differences. Enrichment factors during the photolysis and photo-oxidation of N2O were also obtained in laboratory experiments and compared with those observed. We found that in the higher-altitude region (1) fractionation of the isotopomers is mainly determined by photolysis, but is also affected by physical processes, (2) subsidence of air masses in the winter polar vortex induces the intrusion of an upper stratospheric air mass depleted in N2O, and (3) decay of the vortex in the local spring leads to rapid horizontal advection of midlatitude air masses. At lower altitudes, isotopomer ratios are determined by photolysis, photo-oxidation, and the mixing of air masses within the stratosphere or between the stratosphere and the troposphere. Secular trend of isotopomer profiles was not detectable over Japan during 11 years. Assuming that the lower stratospheric air over midlatitudes is exchanged with the troposphere, isotopomer ratios of the N2O “back-flux” from the stratosphere were estimated. These values can be used in the isotopomeric mass balance model to constrain the global N2O budget.

[1] Vertical profiles of nitrous oxide and methane at high latitudes (57–72°N; 64–89°S) were observed by the Improved Limb Atmospheric Spectrometer (ILAS) solar occultation sensor aboard Advanced Earth Observing Satellite. These measurements were made continuously from November 1996 through June 1997 with some additional periods in September–October 1996. A validation study of the nitrous oxide and methane data processed with the Version 5.20 ILAS retrieval algorithm is presented in this paper. Comparisons are made with (1) nitrous oxide and methane obtained by the ILAS validation balloon campaigns at Kiruna, Sweden, and at Fairbanks, Alaska, in the Arctic; (2) nitrous oxide and methane by the Photochemistry of Ozone Loss in the Arctic Region in Summer aircraft campaign in the Arctic; (3) nitrous oxide by the ground-based spectroscopic measurements and by the aircraft-based remote sensing measurements in the Arctic; and (4) methane by satellite measurements of the Version 19 Halogen Occultation Experiment in the Arctic and Antarctic. Comparisons of ILAS nitrous oxide and methane with Upper Atmosphere Research Satellite Reference Atmosphere data are also made. The results of the comparisons and additional ILAS internal consistency analyses are as follows: (1) the uncertainty of ILAS nitrous oxide is better than 10% over 10–30 km in altitude, and is larger than 50% over 30–40 km, which is comparable to the expected total errors of the ILAS measurements; (2) the uncertainty of ILAS methane is better than 10% over 10–50 km, except for 15–30 km in winter with positive biases exceeding 20%, which is smaller than or comparable to the expected total errors of the ILAS measurements (the quality of ILAS methane in the polar lower stratosphere is better in summer than in winter). In summary, the characteristics of ILAS measurements, i.e., high sampling frequency in polar latitudes with high vertical resolution, along with the good quality of ILAS Version 5.20 nitrous oxide for 10–40 km and the good quality of ILAS Version 5.20 methane for 10–50 km except for 15–30 km in winter, make the ILAS nitrous oxide and methane data set valuable for scientific study of various polar stratospheric phenomena.

[1] Measurements of CFC-12 were made by the Improved Limb Atmospheric Spectrometer (ILAS) between 57°N and 72°N in the Northern Hemisphere and between 64°S and 89°S in the Southern Hemisphere. ILAS was launched on 17 August 1996 on board the Advanced Earth Observing Satellite (ADEOS). The ILAS validation balloon campaigns were carried out from Kiruna, Sweden (68°N, 21°E), in February and March 1997 and from Fairbanks, Alaska (65°N, 148°W), in April and May 1997. During these validation balloon campaigns, CFC-12 was measured with the in situ instruments ASTRID, BONBON, and SAKURA and the remote sensing spectrometers MIPAS-B, FIRS-2, and MkIV. ILAS version 6.0 CFC-12 profiles obtained at the nearest location to the validation balloon measurement are compared with these validation balloon measurements. The quality of ILAS CFC-12 data processed with the version 6.0 algorithm improved significantly compared to previous versions. Low relative differences between ILAS CFC-12 and the correlative measurements of about 10% were found between 13 and 20 km. The comparison of vertical profiles shows that ILAS CFC-12 data are useful below about 20–22 km inside the vortex and below about 25 km outside the vortex. However, at greater altitudes the relative percentage difference increases very strongly with increasing altitude. Further, correlations of CFC-12 with N2O show a good agreement with the correlative measurements for N2O values of N2O > 150 ppbv. In summary, ILAS CFC-12 data are now suitable for scientific studies in the lower stratosphere.

We present observations of CH 4 concentrations from the lower to upper troposphere (LT and UT) over Japan during 1988–2010 based on aircraft measurements from the Tohoku University (TU). The analysis is aided by simulation results using an atmospheric chemistry transport model (i.e. ACTM). Tropospheric CH 4 over Japan shows interannual and seasonal variations that are dependent on altitudes, primarily reflecting differences in air mass origins at different altitudes. The long-term trend and interannual variation of CH 4 in the LT are consistent with previous reports of measurements at surface baseline stations in the northern hemisphere. However, those in the UT show slightly different features from those in the LT. In the UT, CH 4 concentrations show a seasonal maximum in August due to efficient transport of air masses influenced by continental CH 4 sources, while LT CH 4 reaches its seasonal minimum during summer due to enhanced chemical loss. Vertical profiles of the CH 4 concentrations also vary with season, reflecting the seasonal cycles at the respective altitudes. In summer, transport of CH 4 -rich air from Asian regions elevates UT CH 4 levels, forming a uniform vertical profile above the mid-troposphere. On the other hand, CH 4 decreases nearly monotonically with altitude in winter–spring. The ACTM simulations with different emission scenarios reproduce general features of the tropospheric CH 4 variations over Japan. Tagged tracer simulations using the ACTM indicate substantial contributions of CH 4 sources in South Asia and East Asia to the summertime high CH 4 values observed in the UT. This suggests that our observations over Japan are highly sensitive to CH 4 emission signals particularly from Asia. Keywords: methane, aircraft observation, long-term variation, seasonality, vertical profile, Asian outflow, atmospheric chemistry transport model (Published: 22 May 2014) Citation: Tellus B 2014, 66 , 23837, http://dx.doi.org/10.3402/tellusb.v66.23837 To access the supplementary material to this article, please see Supplementary files under Article Tools online.

Detailed observations of O 2 :CO 2 exchange ratios were conducted in a cool temperate deciduous forest located in central Japan. The exchange ratios of soil respiration and net assimilation were found to be 1.11±0.01 and 1.02±0.03 from soil chamber and branch bag measurements, respectively. Continuous measurements of the atmospheric O 2 /N 2 ratio and the CO 2 concentration, made inside the canopy during a summer season, indicated that the average exchange ratio was lower in the daytime (0.87±0.02) than in the nighttime (1.03±0.02) with a daily mean value of 0.94±0.01. The observed average daytime and nighttime exchange ratios were nearly consistent with the corresponding values obtained from a one-box canopy O 2 /CO 2 budget model simulation of net turbulent O 2 and CO 2 fluxes between the atmosphere and the forest ecosystem. Our results suggest that the daily mean exchange ratios of the net turbulent O 2 and CO 2 fluxes depend sensitively on the forest ecosystem processes. Keywords: O 2 :CO 2 exchange ratio, forest ecosystem, atmospheric O 2 /N 2 ratio, continuous measurements (Published: 4 December 2013) Citation: Tellus B 2013, 65 , 21120, http://dx.doi.org/10.3402/tellusb.v65i0.21120

Simultaneous measurements of the atmospheric O 2 /N 2 ratio and CO 2 concentration were made at Ny-Alesund, Svalbard, and Syowa, Antarctica for the period 2001–2009. Based on these measurements, the observed atmospheric potential oxygen (APO) values were calculated. The APO variations produced by changes in the oceanic heat content were estimated using an atmospheric transport model and heat-driven air–sea O 2 (N 2 ) fluxes, and then subtracted from observed interannual variations of APO. The oceanic CO 2 uptake derived from the resulting ‘corrected’ secular trend of APO showed interannual variability of less than ±0.6 GtC yr −1 , significantly smaller than that derived from the ‘uncorrected’ trend of APO (±0.9 GtC yr −1 ). The average CO 2 uptake during the period 2001–2009 was estimated to be 2.9±0.7 and 0.8±0.9 GtC yr −1 for the ocean and terrestrial biosphere, respectively. By excluding the influence of El Nino around 2002–2003, the terrestrial biospheric CO 2 uptake for the period 2004–2009 increased to 1.5±0.9 GtC yr −1 , while the oceanic uptake decreased slightly to 2.8±0.8 GtC yr −1 . Keywords: atmospheric potential Oxygen (APO), air-sea O 2 (N 2 ) flux, Oceanic CO 2 uptake, terrestrial biospheric CO 2 uptake, oceanic heat content, atmospheric transport model (Published: 4 October 2012) Citation: Tellus B 2012, 64 , 18924, http://dx.doi.org/10.3402/tellusb.v64i0.18924

We present analysis of the temporal variation of atmospheric CO 2 in the subtropical region of East Asia, obtained aboard a ferry between Ishigaki Island and Hateruma Island, Japan for the period June 1993–April 2005. The annual mean CO 2 concentration increases from 360.1 ppmv in 1994 to 378.4 ppmv in 2004, showing an average growth rate of 1.8 ppmv yr -1 . The growth rate shows interannual variations with high values during ENSO events. The average seasonal CO 2 cycle reaches the maximum in early April and the minimum in mid-September, with a peak-to-peak amplitude of 8.5 ppmv. Numerical simulations using a three-dimensional atmospheric transport model show interannual variations of the CO 2 growth rate similar to the observation, but the amplitude of the seasonal cycle is larger, with maximum concentration appearing earlier than the observation by 1 month. Low CO 2 values observed during the spring of 1998 are likely associated with the 1997/1998 ENSO event. A backward trajectory analysis suggests that they were due to changes in atmospheric transport whereby maritime air masses from the Pacific Ocean dominated over polluted air masses from the Asian Continent. Extreme values (either high or low) of CO 2 are also occasionally observed. A comparison of backward trajectories of air parcels with CO 2 concentration fields calculated using the atmospheric transport model shows that these unusual CO 2 concentrations result from the transport of air affected not only by anthropogenic CO 2 emissions but also by terrestrial biospheric activities mainly in China. DOI: 10.1111/j.1600-0889.2007.00288.x

In order to elucidate the seasonal and interannual variations of oceanic CO 2 uptake in the Greenland Sea and the Barents Sea, the partial pressure of CO 2 in the surface ocean ( p CO 2 sea ) was measured in all seasons between 1992 and 2001. We derived monthly varying relationships between p CO 2 sea and sea surface temperature (SST) and combined them with the SST data from the NCEP/NCAR reanalysis to determine p CO 2 sea and air–sea CO 2 flux in these seas. The p CO 2 sea values were normalized to the year 1995 by assuming that p CO 2 sea increased at the same growth rate (1.5 μatm yr −1 ) of the p CO 2 in the air ( p CO 2 air ) between 1992 and 2001. In 1995, the annual net air–sea CO 2 fluxes were evaluated to be 52 ± 20 gC m −2 yr −1 in the Greenland Sea and 46 ± 18 gC m −2 yr −1 in the Barents Sea. The CO 2 flux into the ocean reached its maximum in winter and minimum in summer. The wind speed and Δ p CO 2 (= p CO 2 air – p CO 2 sea ) exerted a greater influence on the seasonal variation than the sea ice coverage. The annual CO 2 uptake examined in this study (70°–80°N, 20°W–40°E) was estimated to be 0.050 ± 0.020 GtCyr −1 in 1995. The interannual variation in the annual CO 2 uptake was found to be positively correlated with the North Atlantic Oscillation Index (NAOI) via wind strength but negatively correlated with Δ p CO 2 and the sea ice coverage. The present results indicate that the variability in wind speed and sea ice coverage play a major role, while that in Δ p CO 2 plays a minor role, in determining the interannual variation of CO 2 uptake in this area. DOI: 10.1111/j.1600-0889.2006.00178.x

Systematic and continuous measurements of the atmospheric CO 2 concentration have been carried out at Syowa Station, Antarctica since February 1984. The measurement system was renewed in 1995, but the continuity of the data from the two systems was confirmed by operating them simultaneously. The CO 2 data taken for 17 years from 1984 to 2000 showed clear evidence for a seasonal cycle, a secular trend and interannual variations. The seasonal cycle was variable from year to year, with especially larger amplitudes in 1992 and 1998 and a large phase delay in 1993. A rapid increase in the CO 2 concentration was observed in 1987, 1994 and 1998 in association with ENSO events. The average rate of the secular CO 2 increase for the last 17 years was calculated to be 1.49 ppmv yr −1 . Short-term CO 2 variations with amplitudes of around 1.0 ppmv were found in the austral summer season of several years after 1990, probably due to an intrusion of CO 2 -depleted air mass into the Antarctic region. DOI: 10.1034/j.1600-0889.2003.01471.x

Using discrete air sampling, values of δ 13 C and δ 18 O in atmospheric CO 2 , as well as its concentration, were measured in a forest in the central part of the main island of Japan during the period from June 1994 to June 1996 to examine the biospheric contribution to their temporal variations. δ 13 C shows a prominent diurnal variation with high values in the daytime and low values in the nighttime, especially during the warm season. δ 13 C also vary seasonally, showing a maximum in summer and a minimum in spring. The diurnal and seasonal variations of δ 13 C are opposite in phase with those of the CO 2 concentration. The rate of change in δ 13 C with respect to the CO 2 concentration is found to be approximately -0.05‰/ppmv. This suggests that the diurnal and seasonal variations of the CO 2 concentration are produced primarily by diurnally- and seasonally-dependent photosynthetic-respiratory processes of the biosphere near the observation site, respectively. In the warm season, δ 18 O also increases in the daytime and decreased in the nighttime, which is similar to the diurnal variation of δ 13 C, but opposite to that of the CO 2 concentration. The diurnal δ 18 O variation is thought to be caused by the release of isotopically heavy CO 2 during photosynthesis, and light CO 2 during respiration. However, an interpretation of the seasonal δ 18 O variation is found to be much more difficult than those of δ 13 C and the CO 2 concentration. This is likely due to complicated combinations of different seasonally varying fluxes of biospheric CO 2 into the atmosphere, as well as to various weather-dependent factors governing the δ 18 O composition in CO 2 . DOI: 10.1034/j.1600-0889.49.issue4.3.x

This article presents a basic framework for studying the following questions: (a) in what direction is the occupational environment for seamen likely to change; and (b) how should the occupation of seamen be reorganized in order to adjust itself to the new conditions? The article discusses the changes in the occupational environment of Japanese society in general and briefly examines the occupation of Japanese seamen; change of management environment for the shipping industry, change of seamen's consciousness and conduct, role and evaluation of seamen's position in the shipping industry, and review of seamen's working life, his tasks, organization and culture on board ship.

Stratospheric air samples were collected over Japan on August 31, 1994 using a balloon-borne cryogenic sampler and then analyzed for the CH4 concentration and δ13C in CH4. The δ13C value increased from about −47.5‰ at the tropopause to about −38.9‰ at 34.7 km, accompanied by a rapid decrease of the CH4 concentration with height. From the measured values of the CH4 concentration and δ13C, the apparent carbon isotopic fractionation factor was estimated to be 1.0131±0.0006. The contributions of the chemical CH4 reactions with OH, O(¹D) and Cl were also examined by using an one-dimensional photochemical-diffusion model. It is suggested from this examination that the reaction of CH4 with Cl is especially important for δ13C in the stratosphere.

Since 1984,continuous measurements of the atmospheric CO_2 concentration have been carried out at Syowa Station, Antarctica. Preliminary inspection of the data showed that; (1) a regular diurnal variation is not observable; (2) irregular variations are sometimes observed with an extremely small amplitude of 0.2ppmv at most; (3) a seasonal variation with the minimum concentration in mid-April and the maximum concentration in mid-October and peak-to-peak amplitude of about 1.2ppmv is detected; and (4) an annual mean value of CO_2 concentration is 342.6ppmv. The results obtained in 1985 are as follows : An annual mean value of CO_2 concentration is 343.8ppmv. The pattern of seasonal variation is almost the same as that of the previous year. But a secular increase trend of the CO_2 content is larger than 1984.