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Title: Seasonal and Intra-annual Controls on CO 2 Flux in Arctic Alaska

Abstract

In order to advance the understanding of the patterns and controls on the carbon budget in the Arctic region, San Diego State University has maintained eddy covariance flux towers at three sites in Arctic Alaska, starting in 1997.

Authors:
 [1];  [1]
  1. San Diego State Univ., CA (United States)
Publication Date:
Research Org.:
San Diego State University Research Foundation, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1233182
Report Number(s):
DOE-SDSURF-05160
DOE Contract Number:
SC0005160
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES

Citation Formats

Oechel, Walter, and Kalhori, Aram. Seasonal and Intra-annual Controls on CO2 Flux in Arctic Alaska. United States: N. p., 2015. Web. doi:10.2172/1233182.
Oechel, Walter, & Kalhori, Aram. Seasonal and Intra-annual Controls on CO2 Flux in Arctic Alaska. United States. doi:10.2172/1233182.
Oechel, Walter, and Kalhori, Aram. Tue . "Seasonal and Intra-annual Controls on CO2 Flux in Arctic Alaska". United States. doi:10.2172/1233182. https://www.osti.gov/servlets/purl/1233182.
@article{osti_1233182,
title = {Seasonal and Intra-annual Controls on CO2 Flux in Arctic Alaska},
author = {Oechel, Walter and Kalhori, Aram},
abstractNote = {In order to advance the understanding of the patterns and controls on the carbon budget in the Arctic region, San Diego State University has maintained eddy covariance flux towers at three sites in Arctic Alaska, starting in 1997.},
doi = {10.2172/1233182},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Dec 01 00:00:00 EST 2015},
month = {Tue Dec 01 00:00:00 EST 2015}
}

Technical Report:

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  • Recent warming and drying in the arctic has resulted in a change from CO{sub 2} sink to CO{sub 2} source with respect to the atmosphere. The large stores of soil carbon of perhaps up to 177 PgC, and its sensitivity changes in soil temperature and soil moisture, mean that strong positive feedbacks on atmospheric CO{sub 2} and climate change are possible and make understanding the patterns of and controls on CO{sub 2} flux important. However, the large spatial variability in arctic tundra composition and trace gas fluxes make large-scale estimations challenging. We are using a combinations of rapid cuvette, tower-basedmore » eddy correlation, and aircraft-based eddy correlation measurements to estimate regional CO{sub 2} fluxes. Recent measurements indicate good agreement between chamber, tower-based measurements, and that most tundra sites are a source of CO{sub 2} to the atmosphere. Site specific changes in CO{sub 2} flux have been demonstrated. US IBP site 2, at Barrow, Alaska, was found to be a strong sink of CO{sub 2} of 25 g m{sup -2} y{sup -1} in the early 1970s, and is now seen to be a source of CO{sup 2} to the atmosphere of about 1.3 g C m{sup -2} y{sup -1}. A decrease in soil moisture content or water table has a greater effect on CO{sub 2} loss than does an increase in temperature. Methods of predicting fluxes from remotely sensed imagery and surface characteristics are being explored.« less
  • An ecophysiological model of carbon uptake and release was used to examine C02 fluxes in 17 mature forests near Fairbanks, Alaska. Under extant climatic conditions, ecosystem C02 flux ranged from a loss of 212 g C02 m-2 yr-1 in a black spruce stand to an uptake of 2882 g C02 m-2 yr-1 in a birch stand. Increased air temperature resulted in substantial soil warming. Without concomitant increases in nutrient availability, large climatic warming reduced ecosystem C02 uptake in all forests. Deciduous and white spruce stands were still a sink for C02, but black spruce stands became, on average, a netmore » source Of CO2- With increased nutrient availability that might accompany soil warming, enhanced tree growth increased C02 uptake in conifer stands.« less
  • A significant difference in net ecosystem carbon balance of wet sedge ecosystems in the Barrow, Alaska region was observed between CO{sub 2} flux measurements obtained during the International Biological Program in 1971 and measurements made during the 1991-1992 growing seasons. Currently, high-center polygons are net sources of CO{sub 2} to the atmosphere of {approx}14 gC{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1}, while low-center polygons are losing {approx}3.6 gC{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1}, and ice wedge habitats are accumulating 4.0 gC{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1}. On average, moist meadow habitats characteristic of the IBP-II site are currently sources of {approx}1.3 gC{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1} to the atmosphere compared to themore » reported accumulation of {approx}25 gC{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1} determined in 1971. This difference in ecosystem function over the last two decades may be due to the recently reported increase in surface temperatures resulting in decreases in the soil moisture status. These results point to the importance of long-term research sites and databases for determining the potential effects of climate change on ecosystem function. 44 refs., 10 figs., 1 tab.« less
  • Seasonal snow is present on the Arctic Slope of Alaska for nine months each year. Its presence or absence determines whether 80% of the solar radiation is reflected or absorbed, respectively. Although life on the Arctic Slope is adapted to, and in some cases dependent upon seasonal snow, little is known about it from a scientific point of view. Its quantity has been grossly underestimated, and knowledge of its distribution and the extent of wind transport and redistribution is very limited. This research project dealt with the amount, regional distribution and physical properties of wind blown snow and its biologicalmore » role in the R4D area of the Arctic Slope. Physical processes which operate within the snow that were studied included the flux of heat and vapor and the fractionation of stable isotopes through it during fall and winter, and the complex heat and mass transfer within the snow and between snow, its substrate and the overlying atmosphere during the melt period.« less