We present a decade and a half (1998?2013) of carbon dioxide fluxes from an old-growth stand in the American Pacific Northwest to identify ecosystem-level responses to Pacific teleconnection patterns, including the El Ni�o/Southern Oscillation (ENSO). This study provides the longest, continuous record of old-growth eddy flux data to date from one of the longest running Fluxnet stations in the world. From 1998 to 2013, average annual net ecosystem exchange (F<
sub>
NEE<
/sub>
) at Wind River AmeriFlux was ?32 � 84 g C m<
sup>
?2<
/sup>
yr<
sup>
?1<
/sup>
indicating that the late seral forest is on average a small net sink of atmospheric carbon. However, interannual variability is high (>
300 g C m<
sup>
?2<
/sup>
yr<
sup>
?1<
/sup>
) and shows that the stand switches from net carbon sink to source in response to climate drivers associated with ENSO. The old-growth forest is a much stronger sink during La Ni�a years (mean F<
sub>
NEE<
/sub>
= ?90 g C m<
sup>
?2<
/sup>
yr<
sup>
?1<
/sup>
) than during El Ni�o when the stand turns carbon neutral or into a small net carbon source (mean F<
sub>
NEE<
/sub>
= +17 g C m<
sup>
?2<
/sup>
yr<
sup>
?1<
/sup>
). Forest inventory data dating back to the 1930s show a similar correlation with the lower frequency Pacific North American (PNA) and Pacific Decadal Oscillation (PDO) whereby higher aboveground net primary productivity (F<
sub>
ANPP<
/sub>
) is associated with cool phases of both the PNA and PDO. Furthermore, these measurements add evidence that carbon exchange in old-growth stands may be more sensitive to climate variability across shorter time scales than once thought.