Air samples collected at Pt. Barrow, USA.(71N,156W) SIL ID # Identification Number used at the Stable Isotope Lab, University of Washington. Date Date that this sample was collected. CH4-SIL Methane concentration (ppm) determined manometrically at SIL with precision of ± 2%, see Quay et al. (1). CH4-CMDL Methane concentration (ppm) determined by gas chromatography by NOAA/CMDL laboratory with precsion of ±0.2%, see Dlugokencky et al. (2). Del 13C Measured 13C/12C in per mil (0/00) units, where del 13C(0/00) ={[(13C/12C)sample/(13C/12C)standard - 1]*1000} and the standard is VPDB, see Quay et al. (1). Del 13C (0/00) corrected for standard drift, see Quay et al. (1). SIL ID # Date CH4-SIL CH4-CMDL Del 13C TTBM0043 8-FEB-88 1.95 1.806 -47.80 TTBM0044 21-MAR-88 1.80 1.782 -47.69 TTBM0045 16-APR-88 1.82 1.781 -47.75 TTBM0046 11-JUN-88 1.77 1.741 -47.47 TTBM0047 26-JUN-88 1.77 -47.62 TTBM0048 2-JUL-88 1.73 -47.58 TTBM0050 13-JUL-88 1.78 1.766 -47.85 TTBM0049 17-JUL-88 1.79 1.734 -47.55 TTBM0051 8-AUG-88 1.80 1.778 -48.11 TTBM0052 21-AUG-88 1.79 1.734 -47.75 TTBM0053 27-AUG-88 1.95 1.744 -47.56 TTBM0054 6-SEP-88 1.89 1.769 -47.93 TTBM0056 6-OCT-88 1.76 1.764 -48.01 TTBM0057 17-OCT-88 1.82 1.778 -48.01 TTBM0058 7-NOV-88 1.79 1.778 -47.93 TTBM0060 20-NOV-88 1.82 -47.92 TTBM0059 28-NOV-88 1.81 -47.88 TTBM0061 3-DEC-88 1.80 1.792 -47.87 TTBM0062 29-DEC-88 1.84 -47.92 TTBM0063 8-JAN-89 1.81 1.785 -47.76 TTBM0064 14-JAN-89 1.95 1.852 -47.85 TTBM0065 21-JAN-89 1.86 1.823 -47.61 TTBM0065A 11-FEB-89 1.82 1.796 -47.74 TTBM0067 19-FEB-89 1.71 1.750 -47.58 TTBM0066 4-MAR-89 1.84 1.804 -47.73 TTBM0068 23-MAR-89 1.76 1.797 -47.77 TTBM0069 6-APR-89 1.81 1.795 -47.61 TTBM0071 6-MAY-89 1.77 1.763 -47.47 TTBM0072 19-MAY-89 1.87 1.771 -47.28 TTBM0073 8-JUN-89 1.77 -47.65 TTBM0074 6-JUL-89 1.78 -47.83 TTBM0075 16-JUL-89 1.78 1.745 -47.39 TTBM0076 25-JUL-89 1.86 1.793 -48.00 TTBM0077 30-JUL-89 1.81 1.783 -48.00 TTBM0079 1-SEP-89 1.80 1.775 -47.93 TTBM0080 11-SEP-89 1.82 1.795 -47.93 TTBM0082 23-SEP-89 1.79 -47.87 TTBM0081 5-OCT-89 1.82 1.776 -48.21 TTBM0083 13-OCT-89 1.81 -48.17 TTBM0084 31-OCT-89 1.83 1.794 -48.07 TTBM0085 4-NOV-89 1.80 1.783 -47.86 TTBM0086 13-NOV-89 1.81 1.790 -47.94 TTBM0086A 2-DEC-89 1.85 -47.96 TTBM0088 9-DEC-89 1.83 1.812 -47.86 TTBM0091 22-JAN-90 1.70 1.814 -47.82 TTBM0092 29-JAN-90 1.82 1.799 -47.66 TTBM0093 5-FEB-90 1.92 1.832 -47.30 TTBM0094 10-FEB-90 1.83 -47.57 TTBM0095 24-FEB-90 1.87 1.921 -47.80 TTBM0099 9-MAR-90 1.84 -47.83 TTBM0098 6-APR-90 1.83 1.792 -47.65 TTBM0100 20-APR-90 1.80 1.779 -47.28 TTBM0101 27-APR-90 1.81 1.807 -47.67 TTBM0102 4-MAY-90 1.87 1.793 -47.51 TTBM0103 25-MAY-90 1.81 1.803 -47.67 TTBM0104 8-JUN-90 1.82 1.769 -47.53 TTBM0106 22-JUN-90 1.82 1.788 -47.86 TTBM0105 27-JUN-90 1.79 1.756 -47.64 TTBM0107 13-JUL-90 1.81 1.782 -47.93 TTBM0109 27-JUL-90 1.75 1.756 -47.53 TTBM0108 3-AUG-90 1.76 1.752 -47.72 TTBM0110 15-AUG-90 1.77 1.675 -47.61 TTBM0111 8-SEP-90 1.78 1.769 -47.68 TTBM0112 14-SEP-90 1.81 1.805 -48.30 TTBM0113 21-SEP-90 1.77 1.762 -47.89 TTBM0114 5-OCT-90 1.80 1.800 -47.89 TTBM0115 19-OCT-90 1.82 1.791 -48.23 TTBM0116 2-NOV-90 1.82 1.814 -48.25 TTBM0117 9-NOV-90 1.83 1.830 -48.11 TTBM0119 7-DEC-90 1.84 1.817 -48.04 TTBM0118 10-DEC-90 1.88 1.789 -48.55 TTBM0120 22-DEC-90 1.85 1.854 -47.94 TTBM0121 12-JAN-91 1.85 1.844 -47.74 TTBM0122 19-JAN-91 1.85 1.831 -47.73 TTBM0124 15-FEB-91 1.78 1.806 -47.58 TTBM0125 8-MAR-91 1.85 1.837 -47.87 TTBM0127 23-MAR-91 1.83 -47.59 TTBM0129 29-MAR-91 1.82 1.843 -47.40 TTBM0130 6-APR-91 1.82 1.838 -47.68 TTBM0128 26-APR-91 1.80 1.790 -47.67 TTBM0131 11-MAY-91 1.78 1.780 -47.55 TTBM0132 17-MAY-91 1.79 1.775 -47.70 TTBM0133 24-MAY-91 1.79 1.772 -47.54 TTBM0134 13-JUN-91 1.77 1.771 -47.65 TTBM0135 21-JUN-91 1.76 1.781 -47.44 TTBM0138 19-JUL-91 1.84 1.806 -47.96 TTBM0137 9-AUG-91 1.76 -47.84 TTBM0140 20-SEP-91 1.82 1.796 -47.86 TTBM0141 12-OCT-91 1.80 1.808 -47.97 TTBM0144 8-NOV-91 1.82 1.818 -47.81 TTBM0145 22-NOV-91 1.87 1.850 -48.14 TTBM0146 24-JAN-92 1.85 1.808 -47.78 TTBM0147 20-FEB-92 1.90 1.860 -47.54 TTBM0148 27-MAY-92 1.91 1.802 -47.64 TTBM0149 27-MAY-92 1.82 1.802 -47.53 TTBM0150 13-JUN-92 1.81 1.791 -47.79 TTBM0149A 25-JUN-92 1.84 1.788 -47.63 TTBM0151 31-JUL-92 1.83 1.777 -47.77 TTBM0153 22-AUG-92 1.85 1.803 -47.97 TTBM0154 3-SEP-92 1.84 1.783 -47.67 TTBM0155 18-SEP-92 1.83 1.777 -47.56 TTBM0156 18-SEP-92 1.80 1.777 -47.67 TTBM0157 2-OCT-92 1.86 1.845 -47.65 TTBM0158 2-OCT-92 1.83 1.845 -47.28 TTBM0160 23-OCT-92 1.82 1.804 -47.73 TTBM0159 23-OCT-92 1.81 1.804 -47.86 TTBMO161 21-NOV-92 1.85 1.813 -47.87 TTBM0162 21-NOV-92 1.83 1.813 -47.83 TTBM0163 10-DEC-92 1.87 1.811 -47.64 TTBM0164 10-DEC-92 1.94 1.811 -47.63 TTBM0165 24-DEC-92 1.91 1.843 -47.80 TTBM0166 24-DEC-92 1.89 1.843 -47.74 TTBMO168 25-JAN-93 1.81 1.825 -47.76 TTBM0167 25-JAN-93 1.85 1.825 -47.51 TTBM0169 19-FEB-93 1.86 1.818 -47.44 TTBM0170 19-FEB-93 1.86 1.818 -47.43 TTBM0171 10-MAR-93 1.84 1.819 -47.66 TTBM0172 20-MAR-93 1.89 1.860 -47.56 TTBM0173 7-APR-93 1.84 1.797 -47.55 TTBM0174 21-APR-93 1.85 1.802 -47.44 TTBM0176 6-MAY-93 1.81 1.819 -47.55 TTBM0176 25-JUN-93 1.81 1.779 -47.53 TTBM0177 25-JUN-93 1.81 1.779 -47.50 TTBM0178 9-JUL-93 1.82 1.785 -47.66 TTBM0179 23-JUL-93 1.82 1.804 -47.83 TTBM0181 13-AUG-93 1.82 1.781 -47.66 TTBM0180 3-SEP-93 1.88 1.840 -48.32 TTBM0182 8-OCT-93 1.86 1.818 -47.98 TTBM0183 22-OCT-93 1.82 1.804 -47.38 TTBM0185 11-DEC-93 1.85 1.803 -47.63 TTBM0188 31-DEC-93 1.89 1.848 -47.59 TTBM0187 4-FEB-94 1.85 1.819 -47.36 TTBM0189 12-FEB-94 1.89 1.868 -47.45 TTBM0190 2-MAR-94 1.87 1.853 -47.69 TTBM0192 21-MAR-94 1.82 1.837 -47.77 TTBM0191 21-MAR-94 1.82 1.837 -47.72 TTBM0194 1-APR-94 1.87 1.832 -47.64 TTBM0195 19-APR-94 1.86 1.805 -47.53 TTBM0193 22-APR-94 1.81 1.810 -47.51 TTBM0198 26-MAY-94 1.80 1.791 -47.34 TTBM0200 10-JUN-94 1.83 1.802 -47.31 TTBM0196 1-JUL-94 1.81 1.788 -47.76 TTBM0197 4-AUG-94 1.87 1.826 -48.30 TTBM0199 15-SEP-94 1.82 1.796 -47.72 TTBM0202 8-OCT-94 1.91 1.878 -48.45 TTBM0203 25-NOV-94 1.91 1.853 -47.74 TTBM0204 17-DEC-94 1.99 1.831 -47.70 TTBM0209 10-JAN-95 1.86 1.815 -47.51 TTBM0206 17-FEB-95 1.86 1.848 -47.72 TTBM0207 28-FEB-95 1.89 1.852 -47.56 TTBM0208 17-MAR-95 1.89 1.833 -47.41 TTBM0210 29-MAR-95 1.84 1.822 -47.59 TTBM0211 20-APR-95 1.86 1.828 -47.63 TTBM0214 3-MAY-95 1.84 1.805 -47.43 TTBM0215 28-JUN-95 1.83 1.792 -47.36 TTBM0217 15-JUL-95 1.79 1.788 -47.46 TTBM0218 28-JUL-95 1.83 1.792 -47.44 TTBM0222 28-JUL-95 1.81 -47.50 TTBM0220 26-AUG-95 1.80 1.804 -47.39 TTBM0219 31-AUG-95 1.83 1.809 -47.56 TTBM0226 7-SEP-95 1.82 1.808 -47.76 TTBM0221 20-SEP-95 1.84 1.827 -48.11 TTBM0225 8-OCT-95 1.79 1.802 -47.88 TTBM0226 7-SEP-95 1.82 1.808 -47.76 TTBM0227 1-NOV-95 1.81 1.823 -47.82 TTBM0229 5-DEC-95 1.88 1.840 -47.52 TTBM0230 7-JAN-96 1.91 1.871 -47.77 TTBM0231 7-JAN-96 1.89 1.871 -47.87 TTBM0233A 20-JAN-96 1.82 1.836 -47.66 TTBM0233 2-FEB-96 1.88 -47.60 TTBM0235 1-MAR-96 1.86 1.847 -47.62 TTBM0236 23-MAR-96 1.85 1.833 -47.80 TTBM0237 6-APR-96 1.86 1.829 -47.70 TTBM0238 17-APR-96 1.99 1.820 -47.44 TTBMO239 4-MAY-96 1.96 1.823 -47.57 TTBM0240 4-MAY-96 1.87 1.823 -47.55 (1) Quay, P.D., J. Stutsman, D. Wilbur, A. Snover, E. Dlugokenky and T. Brown, (submitted), Isotopic Composition of Atmospheric Methane, Global Biogeochemical Cycles. (2) DLUGOKENCKY, E.J., K.A. MASARIE, P.M. LANG, P.P. TANS, L.P. Steele, and E.G. Nisbet. A dramatic decrease in the growth rate of atmospheric methane in the northern hemisphere during 1992. Geophysical Research Letters 20(1):45-48 (1994).