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CARVE: L1 In-situ Carbon and CH4 Flux and Meteorology at EC Towers, Alaska, 2011-2015

Documentation Revision Date: 2016-12-09

Data Set Version: V1

Summary

This data set provides ground in situ flux and meteorological science data from fixed instruments at three eddy covariance tower sites located in the Alaskan Arctic tundra. Real and gap-filled observations of carbon dioxide, methane, water vapor, and latent energy flux in addition to standard meteorological and environmental variables are reported at half-hourly intervals between 2011 and 2015 for sites at Atqasuk, Barrow, and Ivotuk, Alaska. The three sites form a 300-km north-south transect on the North Slope of Alaska, each site representing distinct Arctic vegetation communities. These tower measurements create a long-term record of one of the largest, most volatile carbon stocks on the planet. Observations from these towers are being used to determine the seasonal and inter-annual patterns of CO2 and CH4 flux, and their relationship to changes in environmental factors.

There are 14 data files in comma-separated (*.csv) text format with this data set, one per year of data collected at each of the towers.

Micromols of methane per square meter per second observed at the Ivotuk site between Oct. 2-7, 2015.

Citation

Oechel, W., J. Verfaillie, G. Vourlitis, and R. Zulueta. 2016. CARVE: L1 In-situ Carbon and CH4 Flux and Meteorology at EC Towers, Alaska, 2011-2015. ORNL DAAC, Oak Ridge, Tennessee, USA. http://dx.doi.org/10.3334/ORNLDAAC/1424

Table of Contents

  1. Data Set Overview
  2. Data Characteristics
  3. Application and Derivation
  4. Quality Assessment
  5. Data Acquisition, Materials, and Methods
  6. Data Access
  7. References

Data Set Overview

Project: Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE)

The Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) is a NASA Earth Ventures (EV-1) investigation designed to quantify correlations between atmospheric and surface state variables for Alaskan terrestrial ecosystems through intensive seasonal aircraft campaigns, ground-based observations, and analysis sustained over a 5-year mission. CARVE collected detailed measurements of greenhouse gases on local to regional scales in the Alaskan Arctic and demonstrated new remote sensing and improved modeling capabilities to quantify Arctic carbon fluxes and carbon cycle-climate processes. CARVE science fills a critical gap in Earth science knowledge and satisfies high priority objectives across NASA’s Carbon Cycle and Ecosystems, Atmospheric Composition, and Climate Variability & Change focus areas as well as the Air Quality and Ecosystems elements of the Applied Sciences program. CARVE data also complements and enhances the science return from current NASA and non-NASA sensors.

Related Data:

A full list of CARVE data products is available at: https://carve.ornl.gov/dataproducts.html

Data Characteristics

Spatial Coverage: Atqasuk, Barrow, and Ivotuk eddy covariance towers, North Slope, Alaska

Spatial Resolution: Point resolution

Temporal Coverage: 20110530 - 20160107

Temporal Resolution: half-hourly

Study Area (coordinates in decimal degrees)

Site

Westernmost Longitude

Easternmost Longitude

Northernmost Latitude

Southernmost Latitude

Atqasuk (ATQ)

-157.409

-157.409

70.470

70.470

Barrow (BRW)

-156.597

-156.597

71.323

71.323

Ivotuk (IVO)

-155.748

-155.748

68.486

68.486

 

Data File Information

All data are stored in comma separated value (*.csv) text files. The value -9999 is used to denote missing values. Filenames contain the indicate the tower operator (San Diego State University), 3-letter tower code, and year of observations. Ex: SDSU_IVO_2012.csv

 

Table 1. Column headers, description, units, and instrument from Atqasuk (ATQ), Barrow (BRW), and Ivotuk (IVO) eddy covariance towers. 

Note: Quality flags are: 0 = observation value; 1 = interpolated value

Column Header Description Units Instrument
BP Barometric pressure mbar/10 CS106
CH4_Flux_7700 CH4 flux umol m-2 s-1 LI-7700
CH4_Flux_gf_7700 Gap-filled CH4 flux umol m-2 s-1 LI-7700
CH4_q_7700 Quality flag *  
CH4_Flux_LGR CH4 flux umol m-2 s-1 LGR FGGA
CH4_Flux_gf_LGR Gap-filled CH4 flux umol m-2 s-1 LGR FGGA
CH4_q_LGR Quality flag *  
CO2_Flux_7200 CO2 flux umol m-2 s-1 LI-7200
CO2_Flux_gf_7200 Gap-filled CO2 flux umol m-2 s-1 LI-7200
CO2_q_7200 Quality flag **  
CO2_Flux_LGR CO2 flux umol m-2 s-1 LGR FGGA
CO2_Flux_gf_LGR Gap-filled CO2 flux umol m-2 s-1 LGR FGGA
CO2_q_LGR Quality flag **  
Date Date yyyy-mm-dd HH:MM  
Day Day of year and decimal hour DOY.H  
Dsnow Snow depth m SR50a
ER_7200 Ecosystem respiration umol m-2 s-1 LI-7200
ER_LGR Ecosystem respiration umol m-2 s-1 LGR FGGA
G_1 Ground heat flux profile 1 Wm-2 HFT3
G_2 Ground heat flux profile 2 Wm-2 HFT3
G_3 Ground heat flux profile 3 Wm-2 HFT3
G_4 Ground heat flux profile 4 Wm-2 HFT3
Global_radiation Solar radiation Wm-2 Delta T v3
GPP_7200 Gross primary production umol m-2 s-1 LI-7200
GPP_LGR Gross primary production umol m-2 s-1 LGR FGGA
H_7200 Sensible heat flux Wm-2 CSAT-3
H_LGR Sensible heat flux Wm-2 CSAT-3
H2O_Flux_7200 H2O flux umol m-2 s-1 LI-7200
H2O_Flux_LGR H2O flux umol m-2 s-1 LGR FGGA
H2O_Flux_gf_LGR Gap-filled H2O flux umol m-2 s-1 LGR FGGA
H2O_q_LGR Quality flag **  
LE_Flux_7200 Latent energy flux Wm-2 LI-7200
LE_Flux_gf_7200 Gap-filled latent energy flux Wm-2 LI-7200
LE_Flux_q_7200 Quality flag **  
LE_LGR Latent energy flux Wm-2 LGR FGGA
LE_Flux_gf_LGR Gap-filled latent energy flux Wm-2 LGR FGGA
LE_q_LGR Quality flag **  
NEE_7200 Net ecosystem exchange g m-2 s-1 LI-7200
NEE_LGR Net ecosystem exchange g m-2 s-1 LGR FGGA
P1_SWC_5 Soil moisture at -5cm, profile 1 VWC CS616
P1_SWC_10 Soil moisture at -10cm, profile 1 VWC CS616
P1_SWC_15 Soil moisture at -15cm, profile 1 VWC CS616
P1_SWC_20 Soil moisture at -20cm, profile 1 VWC CS616
P1_SWC_30 Soil moisture at -30cm, profile 1 VWC CS616
P2_SWC_5 Soil moisture at -5cm, profile 2 VWC CS616
P2_SWC_10 Soil moisture at -10cm, profile 2 VWC CS616
P2_SWC_15 Soil moisture at -15cm, profile 2 VWC CS616
P2_SWC_20 Soil moisture at -20cm, profile 2 VWC CS616
P2_SWC_30 Soil moisture at -30cm, profile 2 VWC CS616
P3_SWC_5 Soil moisture at -5cm, profile 3 VWC CS616
P3_SWC_15 Soil moisture at -15cm, profile 3 VWC CS616
P3_SWC_30 Soil moisture at -30cm, profile 3 VWC CS616
PARdown Photosynthetically active radiation incoming µmols-1m-2 LI-190SB
PARup Photosynthetically active radiation outgoing µmols-1m-2 LI-190SB
PPT Precipitation mm TE525WS
RH Relative humidity % HMP-45c
Rnet Net radiation Wm-2 REBS Q7
Rsolar Solar radiation Wm-2 CMP3
SoilT1_Surf Soil temperature at surface, profile 1 C Type E thermocouple
SoilT1_5 Soil temperature at -5cm, profile 1 C Type E thermocouple
SoilT1_15 Soil temperature at -15cm, profile 1 C Type E thermocouple
SoilT1_30 Soil temperature at -30cm, profile 1 C Type E thermocouple
SoilT1_40 Soil temperature at -40cm, profile 1 C Type E thermocouple
SoilT2_Surf Soil temperature at surface, profile 2 C Type E thermocouple
SoilT2_5 Soil temperature at -5cm, profile 2 C Type E thermocouple
SoilT2_15 Soil temperature at -15cm, profile 2 C Type E thermocouple
SoilT2_30 Soil temperature at -30cm, profile 2 C Type E thermocouple
SoilT2_40 Soil temperature at -40cm, profile2 C Type E thermocouple
SoilT3_Surf Soil temperature at surface, profile 3 C Type E thermocouple
SoilT3_5 Soil temperature at -5cm, profile 3 C Type E thermocouple
SoilT3_15 Soil temperature at -15cm, profile 3 C Type E thermocouple
SoilT3_30 Soil temperature at -30cm, profile 3 C Type E thermocouple
SoilT3_40 Soil temperature at -40cm, profile 3 C Type E thermocouple
SoilT4_Surf Soil temperature at surface, profile 3 C Type E thermocouple
SoilT4_5 Soil temperature at -5cm, profile 4 C Type E thermocouple
SoilT4_15 Soil temperature at -15cm, profile 4 C Type E thermocouple
SoilT4_30 Soil temperature at -30cm, profile 4 C Type E thermocouple
SoilT4_40 Soil temperature at -40cm, profile 4 C Type E thermocouple
Tair Air temperature C HMP-155A
Tsurf Ground surface temperature C SI-111
u*_7200 Friction velocity ms-1 LI-7200
u*_LGR Friction velocity ms-1 LGR FGGA
WD Wind direction, degrees from north ° Young 05103
WS Wind speed ms-1 Young 05103

* Gap filling done using methods described in Watts et al, 2014

** Gap filling done with http://www.bgc-jena.mpg.de/~MDIwork/eddyproc/method.php

Application and Derivation

These data are used to monitor seasonal variation of CO2, H2O, and CH4 fluxes and the inter-annual differences in Arctic landscapes. The data may also be used to identify patterns in Arctic-boreal CO2 and CH4 fluxes to determine environmental drivers of GPP v. ecosystem respiration and changes in landscape carbon sink and source activity. Measurements from eddy covariance towers are also necessary to calibrate and validate ecosystem models.

 

Quality Assessment

Gap-filling of the observations from the three towers was performed using a satellite data driven modeling approach described in Watts et al. (2014). Gap-filled data are susceptible to model inaccuracies. CH4 gap-filling used a method devised by the Max Planck Institute for Biogeochemistry (http://www.bgc-jena.mpg.de/~MDIwork/eddyproc/method.php). Gap-filled data points are denoted by a value of in the quality flag columns of the data files.

Data Acquisition, Materials, and Methods

Flux data at each of the sites were calculated at half-hourly intervals following standard eddy covariance data processing procedures (Baldocchi et al., 1988). Carbon dioxide, methane, water vapor, sensible heat and latent energy fluxes were estimated using measurements from LI-7200 infrared open-path gas analyzers (LI-COR Biosciences) and Fast Greenhouse Gas Analyzers (Los Gatos Research) instruments. Environmental measurements include temperature and relative humidity (HMP45c; Vaisala), photosynthetically active radiation (LI-190SB; LI-COR Biosciences) soil temperature (Type-E thermocouples; Omega), net radiation (Q7; Radiation Energy Balance Systems), ground heat fluxes (HFT3; Radiation Energy Balance Systems), wind speed and direction (03001 Wind Sentry Set; R.M. Young), and precipitation (TE525WS; Texas Electronics).

Eddy covariance sites

Atqasuk

The Atqasuk tower site is located 100 km south of Barrow. Site elevation is 25 meters ASL and instrument heights are at 2 meters. Vegetation at the site is a variety of moist-wet coastal sedge tundra and moist-tussock tundra surfaces in the more well-drained upland. The International Geosphere-Biosphere Programme (IGBP) land cover is classified as permanent wetlands. 

Barrow

The Barrow tower site is located 10 km east of the town of Barrow, AK, adjacent to the NOAA CMDL Laboratory. Site elevation is 4 meters ASL and instrument heights are at 5 meters. The vegetation is mature in an unmanaged and undisturbed Arctic tundra environment and consist of wet sedges, grasses, moss, and assorted lichens. The IGBP land cover is classified as permanent wetlands. The local landscape surrounding the site has a history absent of any disturbances and the terrain was not heavily glaciated during the last period of glaciation. The Barrow tower is pictured in Figure 2 below.

 

Figure 2. The eddy covariance site at Barrow, Alaska

Ivotuk

The Ivotuk tower site is located 300 km south of Barrow, Alaska, in polar tundra at the foothills of the Brooks Range. Site elevation is 579 meters ASL and instrument height is at 4 meters. The IGBP land cover is classified as permanent wetlands and vegetation of the area is comprised of tussock sedge, dwarf-shrub, and moss tundra. 

Data Access

These data are available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

CARVE: L1 In-situ Carbon and CH4 Flux and Meteorology at EC Towers, Alaska, 2011-2015

Contact for Data Center Access Information:

References

Baldocchi, D.D., B. B. Hicks, and T. P. Meyers. 1988. Measuring biosphere-atmosphere exchanges of biologically related gases with micrometeorological methods. Ecology 69, 1331–1340.

Watts, J.D., J.S. Kimball, F.J.W. Parmentier, T. Sachs, J. Rinne, D. Zona, W. Oechel, T. Tagesson, M. Jackowicz-Korczynski, and M. Aurela. 2014. A satellite data driven biophysical modeling approach for estimating northern peatland and tundra CO2 and CH4 fluxes. Biogeosciences 11:1961-1980.