Moisture Isotopes in the Biosphere and Atmosphere

Background and Justification

The International Atomic Energy Agency (IAEA), in cooperation with the WMO, has long been operating the Global Network of Isotopes in Precipitation (GNIP), which has provided global data to understand and simulate the water cycle under present and past climates. Recently, the IAEA initiated efforts to improve the availability of isotope data on other water cycle components in an effort to supplement GNIP data and integrate isotope applications in hydrological cycle, carbon cycle, and climate research. The group for Moisture Isotopes in the Biosphere and Atmosphere (IAEA-MIBA) was constituted and includes a group of scientists with diverse research interests ranging from local ecosystems to global scales. The motivation for this effort stems from the scarcity of experimental data on stable isotopes in biospheric and atmospheric moisture. Routine measurements of stable oxygen and hydrogen isotopes are crucial to the advancement of hydrological and climate research at the local, regional and global scales. The product of this effort will help in providing an alternative to our present dependency on model output for some key variables, and further advance our understanding of:

Regional scale hydrological budgets

Partitioning evapotranspiration fluxes into surface evaporation and vegetation transpiration; distinguishing evapotranspiration vs advection; quantifying local and regional water re-cycling; improving closure of continental, regional and watershed isotope mass balance.

The partitioning of annual carbon fluxes

The measured variables in the MIBA network drive the ¹⁸O composition of atmospheric CO₂. The measurement of ¹⁸O in CO₂ offers both an additional constraint and smaller uncertainties for CO₂ flux partitioning between the ocean and the terrestrial biosphere at the global scale; and between assimilation and respiration in land ecosystems.

The development of new global change indicators

¹⁸O and ²H in atmospheric vapour can be used as indicators for regional to global-scale reductions in evaporation perhaps in response to changes in global dimming and brightening.

Ecosystem functioning

Distinguishing productivity responses due to soil moisture stress vs. atmospheric humidity stress; ecosystem-specific effects on the ¹⁸O of atmospheric CO₂; ecosystem-specific patterns of water use (melt water, permafrost), and allowing the combined use of oxygen and carbon isotopes.

Interpretations of ¹³C and ¹⁸O analyses in organic matter

Improvement of tree-ring-based climate reconstructions; explaining the cause of genetic variation in C_i/C_a (net photosynthesis vs. stomatal conductance).

The validation of general circulation models

Particularly those weather prediction models that aim to couple carbon and water fluxes using stable isotopes to improve simulations of the water and carbon cycles.

Past global responses to climate change

Biospheric productivity forces a difference between the oxygen isotopes of ocean water and atmospheric O₂ (the Dole effect). The measurements from the MIBA network will allow further elucidation of the current Dole effect, and allow us to constrain estimates of past global productivity using H₂O and O₂ trapped in ice cores.

Initial Meetings and Protocol Development

The initial consultants´ meetings held in November 2003 and May 2004 resulted in the development of the basic network design and sampling concepts. It was decided that for this network that regular sampling of the isotopic composition of water in plant leaves, stems, soil and atmospheric vapour would help achieve the benefits to the research community outlined above. The plant and soil samples would be taken twice monthly during a given growing season and atmospheric water vapour would be sampled once a week where possible under a slightly different protocol as the current technological state of the art demands (see below for details). Sampling should, ideally, be coordinated with other climatic (e.g. ambient temperature and relative humidity) and flux measurements.

The general framework of the network is as follows: Regional representatives enroll field sites in broadly defined global regions to sample leaves, stems and soils. These sights will then send the samples to extraction and analysis labs. It was decided that the IAEA’s isotope hydrology laboratory and that of several group members will provide isotopic analyses for those participants who do not have the availability or capacity to perform the required analysis. The IAEA will provide the secretariat for the work of MIBA group and may provide modest financial support for facilitating sampling, particularly in the developing countries. Together, the group will also assist in providing training and logistics according to needs. Results of all analysis will be immediately made available on the web page to all participants who will be given priority in any public dissemination of data. Products of this network will lead to periodic meetings (organized by the IAEA) where participants will be invited to discuss results of their efforts.

Current State of the Network

On 1 June 2004, the enrollment of both regional representatives and sampling sites commenced with the goal for sampling programme commencement period of April/May 2005. The regional representatives and representatives from the central analysis laboratories met in Vienna during 2-4 May 2005 to discuss the results of the efforts made so far, analytical capacity and sampling protocols in an effort to assess the current state of the network and to decide on the future directions of the network.

Figure 1. Current site distribution of the IAEA-MIBA network. Pink dots are the sites that are currently online which means that participants have the capacity to collect, extract and analyze all samples. Yellow sites should be online within a year.

The meeting participants were:

All of these participants were instrumental in developing the MIBA network as it currently stands. Furthermore, we offer a warm welcome to this group two new members, Mr. Mubarik Ali from Pakistan and Mr. Tahir Diop from Senegal. Their input to the meeting was important and their future efforts for site recruitment and sample analysis will be an integral component to the success of the network.

Contacts by Region/Country.

MIBA Site Description

The data in this site are preliminary and unpublished, and are subject to revision. These data are provided to enable informal comparisons and analyses using the most up-to-date results. If using data from this site in a publication or presentation, the IAEA Isotope Hydrology Section and the primary site contacts MUST be notified to discuss how they should be acknowledged and if they should be offered participation as authors. It is assumed that an agreement on such matters will be reached before publishing and/or use of the data for publication. Feedback from users may also help us to improve the quality of the data and presentation and is highly encouraged.

Australia
China
Czech Republic
USA

Fair Use Policy

WARNING CONCERNING PUBLICATION AND DISTRIBUTION

The data in this site are preliminary and unpublished, and are subject to revision. These data are provided to enable informal comparisons and analyses using the most up-to-date results. If using data from this site in a publication or presentation, the IAEA Isotope Hydrology Section and the primary site contacts MUST be notified to discuss how they should be acknowledged and if they should be offered participation as authors. It is assumed that an agreement on such matters will be reached before publishing and/or use of the data for publication. Feedback from users may also help us to improve the quality of the data and presentation and is highly encouraged.

Citing the IAEA—MIBA Database

When using the data retrieved from the IAEA-MIBA database, please try to adhere to the following format if data from several stations (or laboratories) has been used: IAEA (2005). The IAEA Moisture Isotopes in the Biosphere and Atmosphere Group. The IAEA-MIBA Database. Accessible at: http://………..iaea.org When using data from one station or the stations operated by the regional representatives, please include the name of the laboratory and/or management institute in the acknowledgement.

Contact Information

MIBA Sampling Results

Country	Results
Australia	Sampling data / Isotope Plots
Brazil	Sampling data
Canada	Sampling data
China	Sampling data Isotope Plots
Czech Republic	Sampling data / Isotope Plots
Ecuador	Sampling data
Israel	Sampling data Isotope Plots
Pakistan	Sampling data Isotope Plots
Puerto Rico	Sampling data
United Kingdom of Great Britain	Sampling data Isotope Plots

Download

Vegetation Sampling Protocol
Vapour Sampling Protocol
Sample Spreadsheet
Calculate Water Vapour Volume
IAEA Country Code List