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Last update: 7 Dec. 2005

ECRP-seminar titles and abstracts 2004

December 9 (Thu), 2004

Hisashi SATO

Development of a dynamic global vegetation model for global change prediction

While climate condition can strongly influence terrestrial ecosystem, it can also affect the climate, particularly through changes in evapotranspiration, carbon cycle, and albedo. Thus, for providing reliable predictions for the change of global climate, integrated terrestrial ecosystem models that include biogeochemical processes and vegetation dynamics would be required.

To fulfill this need, I, A. Ito, and T. Kohyama are developing a Dynamic Global Vegetation Model (DGVM) that can simulate changes in ecosystem functions (ex: carbon and water flux) as well as ecosystem structures (ex:distribution and composition). This model links several modules, which have different computation time steps. Some of the modules are functions of environmental factors, letting the model simulate ecosystem responses to climate changes.

By now, model design and program coding have been completed. Currently, we are estimating parameter sets by repeating preliminary simulations. After veryfying the model performance, we will combine our model with the integrated-earth-system-model of the kyousei2 project.


Preliminary results of global warming experiments using KISSME (Kyousei Integrated Synergetic System Model of the Earth)

Global warming experiments using an integrated earth system model are planned in the Kyousei 2 group. We have conducted global warming preliminary experiments with an A&OGCM which includes marine and terrestrial carbon cycle models. The model is forced with about 1 %/year increase of CO2 emission. We have conducted experiments with and without interactions between climate and carbon cycle. The global mean CO2 concentration is 290 ppm at 1850 and rises to 390 ppm at 2040. According as the CO2 increase, the global mean temperature increases about 1.5 oC in the case of with-interactions. The land-ocean uptake of CO2 is near 0 at 1850 and rises to about 6 PgC/year at 2040. The change in the uptake caused by the warming is only a few, as suggested by previous studies. For the actual run of C4MIP Phase 2 experiment, we are now carrying out tuning of this model.

November 18 (Thu), 2004

Kazuaki Tadokoro

Interannual variations in biomass and developmental timing of Neocalanus copepod populations in the Oyashio waters of western subarctic North Pacific

In order to clarify the interannual variations in biomass and production of Neocalanus copepod in the Oyashio waters, we analyzed mesozooplankton samples "the Odate Collection" collected offshore waters of northeast Japan from 1970 to 2000. The interannual variation in the developmental timing was determined by the date when copepodite stage 5 made up 50% of the copepodite abundance (Mackas et al. 1998). The developmental timing of N. flemingeri and N. cristatus populations did not showed decadal scale oscillation. On the other hand, the developmental timing in N. plumchrus populations showed decadal scale oscillations. Differences in the patterns suggested that mechanisms of the interannual variations in N. flemingeri populations developmental timing are different from that of N. plumchrus and N. cristatus. I will discuss the possible causes of the interannual variations in biomass and developmental timing of Neocalanus copepod populations in the Oyashio waters including physical environmental variations and abundance of mesozooplankton predator as Japanese sardine.

Rikie Suzuki

Intercomparison of interannual changes in NDVI from PAL and GIMMS in relation to evapotranspiration over northern Asia

The authors' previous study found an interannual covariability between actual evapotranspiration (ET) and the Normalized Difference Vegetation Index (NDVI: a satellite sensed value) over northern Asia. This result suggested that vegetation con-trols interannual variation in ET. In this prior study, NDVI data from the Pathfinder AVHRR Land (PAL) dataset were analyzed. However, studies of NDVI interannual change are subject to uncertainty, because NDVI data often contain errors associated with sensor- and atmosphere-related effects. This study is aimed toward reducing this uncertainty by employing NDVI dataset, from the Global Inventory Moni-toring and Modeling Studies (GIMMS) group, in addition to PAL. The analysis was carried out for the northern Asia region from 1982 to 2000. 19-year interannual change in PAL-NDVI and GIMMS-NDVI were both compared with interannual change in model-assimilated ET. Although the correlation coefficient between GIMMS-NDVI and ET is slightly less than for PAL-NDVI and ET, for both NDVI datasets the annual maximum correlation with ET occurs in June, which is near the central period of the growing season. A significant positive correlation between GIMMS-NDVI and ET was observed over most of the vegetated land area in June as well as PAL-NDVI and ET. These results reinforce the authors' prior research that indicates the control of interannual change in ET is dominated by interannual change in vegetation activity.

October 14 (Thu), 2004

Akihiko Ito

Regional variability in the terrestrial carbon-cycle feedback to global warming during the 21st century: simulation analysis with AOGCM-based climate projections

Regional variability in the carbon-cycle feedback of terrestrial ecosystems to global warming was simulated with a spatially explicit, process-based model (Sim-CYCLE) and analyzed for 22 regions worldwide. The net budget of carbon dioxide (CO2) during the period 2001-2099 was globally simulated on the basis of greenhouse gas emission scenarios (IPCC-SRES) and climate projections by coupled atmosphere-ocean general circulation models (AOGCMs). Most terrestrial ecosystems acted as net carbon sinks (negative feedback) but with different magnitudes among the experiments (globally, 24 to 286 Pg C). Substantial inter-regional variability was found in terrestrial carbon-cycle feedback, because of differences in biome distributions and climate-change regimes. Moreover, among the experiments using the same CO2 scenario but different AOGCM climate projections, inconsistent results were obtained in the Amazon basin, Africa, Australia, and northern Asia, indicating the need for further research.

Yoshikazu Sasai

Ocean circulation in the Japan Sea from the CFC-11 distribution - Results of CFC-11 simulation in an eddy-resolving OGCM -

We have investigated ocean circulation in the Japan Sea using the simulated CFC-11 distribution. Estimated CFC-11 inventory in the Japan Sea is as much as that in the northern North Atlantic and the Southern Ocean, which are important regions to form the deep waters. Along the Primorye coast of Russia, much CFC-11 is absorbed at the sea surface because of the deep mixed layer development in the winter season. Absorbed CFC-11 spreads on the isopycnal surface into the interior ocean. On the isopycnal surface (27.0Ѓ), the CFC-11 spreads eastward along the 42N and southward along the 131E. The CFC-11 may spread by the isopycnal surface circulation, which is implied by the observed salinity.

September 16 (Thu), 2004


Effects of transient motions on meridional volume and Chlorofluorocarbon flux in eddy-permitting and eddy-resolving ocean general circulation models

To improve our understanding of the processes determining the oceanic uptake and distribution of transient tracers, the results of Chlorofluorocarbon (CFC) simulations using two models with different spatial resolutions have been analyzed. One is the OFES (OGCM for the Earth Simulator) which can resolve explicitly mesoscale eddies with 1/10 degree horizontal grid spacing. Another is the model with 1/4 degree which is called eddy-permitting or marginally eddy-resolving model. The comparison of CFC distribution between the models and observation shows that there are some improvements OFES such as high CFC concentrations similar to the observation in the lower thermocline in the Pacific Ocean. The isopycnal distribution indicates that more CFC spreads equatorward from the Subarctic and Subantarctic regions.

The meridional overturning cells and CFC flux are estimated by zonally integrating the meridional velocity and CFC flux in density layers. The contributions of mean eddy, and seasonal variation are discussed. The mean contribution is dominant in both surface and thermocline layer, however, there is a significant contribution by eddies which compensate the mean CFC flux in the equatorial regions. In contrast to the equatorial regions, more contribution by seasonal variation of ocean circulation in subtropical region is identified in eddy-resolving model. This suggests that not only high-frequency but also low-frequency motions may have an impact on the tracer distribution.


Net primary production in Southeast Asia following a large reduction in photosynthetically active radiation due to smoke

July 15 (Thu), 2004

Tomomichi KATO

CO2 Exchanges between the Atmosphere and an Alpine Meadow Ecosystem on the Qinghai-Tibetan Plateau

I examined the CO2 exchange between the atmosphere and an alpine Kobresia meadow (lat 37.29-45 N, long 101.12-23 E, 3250 m a.s.l.) on the northeastern Qinghai-Tibetan Plateau. The ecosystem CO2 flux was measured continuously using the eddy-covariance method from August 2001 to December 2002. The major findings from the CO2 flux measurements were as follows: (1) The maximum daily CO2 uptake (3.9 g C m-2 day-1) in this site was smaller than that in other grassland ecosystems at almost the same latitude, although the maximum LAI was larger. The 78.5 g C m-2 yr-1 annual NEP in 2002 was lower than those of warmer ecosystems, e.g. temperate and tropical grassland ecosystems, and as much as those of other cool ecosystems, e.g. alpine and boreal ecosystems. (2) The CO2 efflux in the nighttime was suppressed by soil moisture increase.

I further explored the long-term pattern of carbon dynamics in the alpine ecosystem using meteorological and biomass data available for the period from 1981 to 2000 with a simulation model of the carbon cycle in terrestrial ecosystems (Sim-CYCLE). The model simulation showed the following major findings. (3) The transition experiment for 1981-2000 showed that the annual NEP ranged from -70 to +70 g C m-2 yr-1 over the 20 years. (4) Increases in temperature decreased the NEP on all temporal scales, through enhancement of the heterotrophic respiration in the interannual changes. (5) The model sensitivity analysis showed that GPP, autotrophic respiration, NPP and plant biomass responded quickly and the heterotrophic respiration, litter and soil biomass responded very slowly to the climate change. The GPP was increased by temperature increases of 5C and decreased by those over 7.5C


Are there global synchronies in lower trophic level marine ecosystem? - review and introduction of the retrospective approach in the western subarctic North Pacific, the "Odate project"

June 17 (Thu), 2004

S. Lan Smith, Beatriz E. Casareto, Mohan P. Niraula, Yoshimi Suzuki, Julia C. Hargreaves, and James D. Annan

Simulating the Ecosystem and Nitrogen Cycle in Incubation Experiments using Data Assimilation CO2 Exchanges between the Atmosphere and an Alpine Meadow Ecosystem on the Qinghai-Tibetan Plateau

We have developed a new, multi-element ecosystem model to simulate a set of batch incubation experiments of natural phytoplankton assemblages. The model divides organisms into classes based on differences in size and function and simulates the flexible-composition of phytoplankton. Nutrient concentrations and plankton community differed among the incubations, allowing us to examine the functioning of the ecosystem by comparison. Data included concentrations of nutrients, organic matter (particulate and dissolved) and plankton (biomass by species). We used a Monte Carlo Markov Chain method to assimilate these data into our model and examined the distributions of simulated values from the ensemble of simulations. The model simulated well the changes in C:N ratio of bulk particulate organic matter (POM), and its difference between experiments. We examined the simulated gross flows of carbon and nitrogen (which cannot be directly measured), dividing the ecosystem between the Microbial Food Web (MFW) and Grazing Food Web (GFW) based on the size of organisms. The MFW dominated the flow of nitrogen in all incubations. The bulk POC:PON ratio varied inversely with the gross amount of nitrogen remineralized in a given incubation. The flexible composition of phytoplankton is a key link between remineralization and the dynamic stoichiometry of POM.

Dennis Dye

Current Challenges and Recent Achievements in Modeling and Monitoring of the Role of Photosynthetically Active Radiation in the Terrestrial Carbon Cycle

Apr. 23 (Fri), 2004


Effects of fine-scale resource availability on regeneration of tree species in lowland rainforests

While we have some mechanistic understanding of tree regeneration in forests based on large-scale and long-term monitoring, we know little of the processes controlling tree responses to changes in fine-scale resource availability such as light, nutrient, water, etc. In a freshwater peat-swamp forest of Central Kalimantan, Indonesian Borneo, undulating micro-topography influenced tree survival in contrasting way during the drought (1997-98) and the post-drought (1998-2000) periods. In hummocks, decomposition and mineralization of the large mass of litter provided high nitrogen concentration. In the waterlogged bottom of hollows, acidic peat reflected components toxic to microorganisms decomposing plant debris.

Both area and height of inhabited hummocks were positively related to the survival of peat-swamp trees during the post-drought period, while hummock height was negatively related during the drought period. The availability of nitrogen and water was clearly demonstrated to be an important determinant of tree dynamics in peat-swamp forests. Habitat-induced changes in tree performance were conspicuous during the drought period. In Borneo, 14 severe droughts were recorded between 1917 and 1998. Frequency of drought events will ultimately influence the spatial and temporal patterns of regeneration of Bornean lowland forests.


Interannual variation in Neocalanus biomass in the Oyashio waters of the western North Pacific

We examined the interannual variation in Neocalanus copepod biomass in the Oyashio waters in spring and summer from 1972-1999. In the mid 1970s, mesozooplankton biomass in spring was high; however, it decreased significantly in the late 1970s. The timing of the decrease in mesozooplankton biomass corresponded to the 1976/77 climatic regime shift. The biomass of N. flemingeri, which dominated the Neocalanus community, was roughly constant from 1980 to 1999. Although species-level estimates of Neocalanus biomass were not available for the 1970s, a previous study reported that Neocalanus copepods were the predominant mesozooplankton in the Oyashio waters in spring during the 1970s. Neocalanus copepods dominated the mesozooplankton community throughout the 1970s, and their biomass decreased in the late 1970s. Springtime net community production (NCP), an index of new production, also decreased in the late 1970s. We suggest that the reduction in new production negatively affected Neocalanus food availability and resulted in a decrease in copepod biomass. New production may have been limited by a combination of subsurface iron supply, increased vertical density gradient, and reduced vertical water mixing in winter, which resulted in diminished iron entrainment in winter. In summer, mesozooplankton biomass significantly decreased and increased synchronously with the 1976/77 and 1988/89 climatic regime shifts. The biomass of N. plumchrus, which dominated the Neocalanus community, was low in the 1980s and increased in the early 1990s. Neocalanus copepods were reported to be a dominant component of the mesozooplankton community in the 1970s. The biomass of Neocalanus was high in the mid 1970s and decreased in the late 1970s. Japanese sardine (Sardinops melanostictus) is an important predator of Neocalanus copepods, and interannual variation in the standing stock of this species was inversely related to mesozooplankton biomass. At their peak in 1984, sardines consumed 32-136% of the daily Neocalanus production during summer. Therefore, predation pressure by Japanese sardine on Neocalanus is likely to affect interannual variation in mesozooplankton biomass during the summer.

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