FluxLetter The Newsletter of FLUXNET Vol. 2 No. 2, June, 2009 Highlighting Sites in Northern Alaska & North East Highlight FLUXNET sites Russia The Arctic Observatory Network by Eugénie S. Euskirchen and M. Syndonia Bret-Harte Flux stations were recently Arctic Observatory Network models. In This Issue: established in two locations in (AON) program. The other flux In northern Alaska during the the Arctic during the Interna- stations that participate in this summer of 2007, we established tional Polar Year (2007 -2009). network are located near two flux stations on either side These flux stations are located in Abisko, Sweden and Zackenberg, of a flux station that had been FLUXNET site: Greenland, as well as a series of previously established in 2005. northern Alaska, near the Toolik “The Arctic Observatory Field Station, which is owned sites across Arctic Canada. The This forms a transect of three Network” and operated by the Institute of goal of making flux measure- stations in three representative Eugénie S. Euskirchen and M. Syndo- ments made at these sites is to: undisturbed ecosystem types of Arctic Biology, University of nia Bret-Harte …….. .….Pages 1-3 Alaska, Fairbanks, and which is 1) quantify and understand the the arctic foothills of the Brooks the site of the Arctic Long-Term controls of carbon, water, and Range: heath tundra, tussock Editorial: Ecological Research (LTER) pro- energy exchange at each site, 2) tundra, and wet sedge tundra Conservation of Surface Fluxes in a gram, and at the North East permit cross-site synthesis of the (fen). Furthermore, the largest- Numerical Model Science Station near Cherskii, carbon, water, and energy fluxes ever tundra fire in northern Jinkyu Hong……….…......Pages 4-5 Russia. These two observatories across the representative terres- Alaska occurred ~39 km north- help to establish a network of trial ecosystems in the Arctic, west of our sites in the summer observatories across the Arctic, and 3) parameterize and validate of 2007, burning ~90,000 ha. which is funded through the NSF ecosystem and land-surface This provided the opportunity to FLUXNET graduate student : establish three more flux sta- Donatella Zona ...................Pages 6-7 tions during the summer of 2008 in tussock tundra ecosystems of varying burn severity: severely FLUXNET young scientist: burned, moderately burned, and Adrian V. Rocha…….... ...........Page 8 an unburned control site. The objective of establishing sites in these disturbed ecosystems is to Research: obtain information about the Measuring air-ice CO2 fluxes in integrated impacts of tundra fires the Arctic on terrestrial ecosystems in the Heinesch B, Yernaux M, Aubinet M, tundra foothills, and to begin Geilfus N-X, Papakyriakou T, Carnat documenting the recovery proc- G, Eicken H, Tison J-L, B.Delille ..................................Pages 9-10 ess. In addition to measuring the carbon, water, and energy fluxes at these sites, a full suite of me- Presence and absence of permafrost teorological data is also col- Torben R. Christensen, Mikhail lected. We also use chambers Mastepanov and Margareta Johans- to measure NEE during summer son…………………….Pages 11-13 field campaigns. Figure 1: Map of sites in the Arctic Observatory Network FLUXNET SITE cont. on page 2 Page 2 Sites in Northern Alaska & North East Russia FLUXNET SITE cont. from page 1 At the end of August, 2008, a A micrometeorological station was installed on a tall tower (40 m) near the North East Science Station. The greater height of this tower is necessary to ac- count for the heterogeneity of the landscape and vegetation. The ecosystems of the North East Science Station are repre- sentative of the coastal plain of Northeast Siberia, a one million km2 area of carbon-rich loess soils that accumulated carbon during the Pleistocene and have been gradually been releasing this carbon to the atmosphere and ocean through thawing of previously frozen soils during the Holocene. The carbon content of these soils is much greater than that of the perma- frost soils in North America. This system at the North East B Science Station includes: 1) an eddy covariance system to measure the fluxes of water, carbon, and energy, 2) A meth- ane analyzer to measure the concentration of methane at a height of 30m which will subse- quently be used by NOAA in Figure 2: Coarse root CO2 efflux measurement at the Kissoko site the development of a regional methane flux model, 3) a closed -path eddy-covariance system to be used in conjunction with the methane analyzer to meas- ure a local methane flux, and 4) a full suite of meteorological data. Three existing 10 m tall eddy covariance towers are also located near this tower, and have been collecting data for 8 years. Maintaining flux stations over a full annual cycle in the Arctic is Figure 2: In (a), maintaining the eddy covariance equipment in northern Alaska is a challenge in winter. In (b), the tundra fire in northern Alaska burned for approximately 3 months, and was the largest tundra fire ever recorded in Alaska. Three flux towers have subsequently a challenge due to the long, been located within the burned area. Photo Credits: Roy Stehle (a); Bureau of Land Management Fire Service (b); FLUXNET SITE cont. on page 3 Page 3 Sites in Northern Alaska & North East Russia FLUXNET SITE cont. from page 2 cold, dark winters that make the sites less accessible and cause ice to form on the sensitive equip- A ment. Snow is on the ground for most of the year, with the snow season starting at the be- ginning of September and ending by the first week of June. Fur- thermore, line power is not available, and power outages are a problem. Routine site visits are essential during the snow season, and are often extended in order to diagnose and fix any problems. We have held two workshops in 2008 for the AON participants in which we identified topics of synthesis based on data collected at the sites across network. We will hold another workshop in 2010. We have also estab- lished an AON website: http:// aon.iab.uaf.edu/index.html where more information about the project and data are available. B Research team: University of Alaska Fairbanks: Brian M. Barnes, M. Syndonia Bret-Harte, Eugénie S. Euskirchen, Anja N. Kade, Glenn J. Scott, Katey M. Walter Ecosystems Center, Marine Biological Laboratory: John E. Hobbie, Bonnie L. Kwiatkowski, Edward B. Rastetter, Adrian V. Rocha, Gaius Shaver, Gabrielle Tomalsky-Holmes, North East Science Station: Sergei Zimov, Nikita Zimov Contact information: Eugénie Euskirchen [email protected] Figure 3: In (a), the tall (40 m) tower in Northeast Russia, and in (b) a smaller tower located within the footprint of the tall tower. Photo Credit: Sergei Zimov Page 4 Opinion Contribution: Conservation of Surface Fluxes in a Numerical Model by Jinkyu Hong The Atmospheric numerical increasing grid resolution in a However, due to nonlinear re- are fed into a fine grid simulation models solve the differential biosphere model due to nonlin- sponses of surface fluxes to for initial and boundary condi- equations of conservation of ear responses of surface fluxes environmental conditions, sur- tions. Accordingly, it is inevitable momentum, mass and thermody- to spatial variations in surface face fluxes are not conserved in to have some bias in surface namic energy. As a result, the properties, and a concept of different grid resolutions (i.e., fluxes simulated from a coarse conservation of momentum, scale-invariance of surface fluxes F ≠ F grid size due to Jensen’s inequal- M mass and thermodynamic energy was proposed so that a bio- ity. is a strong constraint and thus sphere model made consistent Numerical models from LES It was concluded that the nonlin- has been carefully checked in estimates of surface fluxes as (Large-eddy simulation) to ear effects were negligible and modeling atmospheric flows. grid resolution changed (Fig. 1). mesoscale, regional climate and thus the scale-invariance of sur- However, the concept of surface Ideally, the scale-invariance of earth system models apply nest- face fluxes was satisfied (Sellers flux conservation with different surface fluxes produces similar ing procedure to examine the et al., 1992, 1995, 1997). How- grid sizes had not been clearly surface fluxes in spite of different detail structures of small domain. ever, we should note that there addressed before Sellers et al. grid sizes following Jensen’s ine- In this nesting procedure, atmos- was no interaction between (1992, 1995, 1997). These pio- quality (e.g., pheric and surface conditions surface fluxes and atmospheric neering studies focused on artifi- FF= conditions due to an off-line M from a mother domain (i.e. a cial loss/gain of surface fluxes as domain having coarse grid size) simulation in their studies. That is, it was assumed that atmos- pheric conditions such as down- ward radiation, wind, tempera- ture and humidity were homoge- neous in a whole domain. In- deed, the test of this scaling issue in fully coupled models (e.g., LES, mesoscale model or earth system model) has re- mained unresolved so far. We recently checked the conserva- tion of surface fluxes in an at- mospheric mesoscale model and found that surface fluxes were not conserved as grid size in the model increased (Hong and Kim, 2008) (Fig. 2). In the early stage of numerical integration, radia- tive forcing and surface condi- tions are considerably homoge- neous because relatively homo- geneous fields were fed from a Figure 1. The concept of (dis)aggregation and scale-invariance of surface fluxes in the model adapted from Sellers et al. (1992). F is surface mother domain to a domain of Ffxxx= (123 , , ,...) flux as a function of xi (e.g.