AUTHOR:
Katey Walter Anthony
Water and Environmental Research Center
525 Duckering Building
University of Alaska Fairbanks
Fairbanks, Alaska 99775
(907) 474-6095 voice
kmwalteranthony@alaska.edu

FUNDING SOURCE AND GRANT NUMBER:
NSF IPY AON, OPP #0632264
NSF IPY, OPP #0732735

DATA SET OVERVIEW:
Abstract: We collected ebullition data from thermokarst lakes in Siberia and Alaska during the years 2003-2010. Ebullition data were collected using submerged bubble traps placed over discrete ebullition seeps. Ebullition values are reported volumetrically (ml gas per seep per day) and on a methane mass basis (mg CH₄ per seep per day), the latter based on mean values of methane measured in ebullition seeps on the study lakes [A = 82�7 % CH₄; B = 83�12 % CH₄; C = 85�5 % CH₄; HS = 89�3 % CH₄]. Methods of ebullition flux measurements and seep classification (A, B, C or Hotspot (HS) type) are described in detail by Walter Anthony et al. 2010, Limnology and Oceanography Methods.
Note 1: The Alaska data shows lots of zeros on C type seeps because semi-automated flux traps allowed high temporal resolution data collection. In Siberia, volumetric flux measurements made with manual traps were sometimes interpolated over periods of multiple days.
Note 2: The non-interpolated columns show data resulting from tipping events on the wet-tip bubble traps. On days where there was only one tip event, the rate of gas accumulation in the tipping cup is unknown. The interpolated column averages the gas volume in the one-tip event over the number of days since the previous tipping event, which is the period over which gas in the one-tip event may have accumulated.

Time period: May 2003 - October 2010

INSTRUMENT DESCRIPTION:
Bubble traps are cone-shaped and submerged in the lake water so that bubbles rising out of the sediments enter in through the wide base of the cone, and get funneled into a bubble collection chamber. The volume of gas accumulated over a known period of time results in a volumetric flux in units of 'ml gas d-1' or ml hr-1'. To convert volumetric fluxes to mass-based fluxes it is necessary to determine the concentration of the bubble gas constituents, which are typically dominated by CH₄, but are balanced by N₂ with trace amounts of CO₂, O₂, Ar, etc . Since traps are placed over discreet ebullition seeps, fluxes in this data set are reported not as per meter squared (m-2), but as per seep (seep-1).

DATA FORMAT:
Microsoft Excel file
SiberianEbullitionData: columnA=Date of measurement, the rest of the columns have the methane ebullition (mg CH₄ spot-1 d-1) for each seep
AlaskaEbullitionData: columnA=Date of measurement, the rest of the columns have the methane ebullition data for each of the seeps (first measured as ml gas d-1, then converted to mg CH₄ d-1, some seeps have interpolated data (see Note2 in the above abstract))

DATA REMARKS:
This is not the final version of the data.

REFERENCES:
Walter Anthony, K.M., D.Vas, L. Brosius, F.S. Chapin III, S.A. Zimov, Q. Zhuang, 2010. Estimating methane emissions from northern lakes using ice bubble surveys. Limnology and Oceanography Methods 8, 592-609.