Auxiliary material for manuscript:
Natural variability and anthropogenic change in equatorial Pacific surface ocean p CO
2
and pH
Authors: Adrienne J. Sutton*
1,2
, Richard A. Feely
2
, Christopher L. Sabine
2
, Michael J.
McPhaden
2
, Taro Takahashi
3
, Francisco P. Chavez
4
, Gernot E. Friederich
4
, and Jeremy T.
Mathis
2
*Corresponding author, adrienne.sutton@noaa.gov
1 Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle,
WA, USA, 98105
2 Pacific Marine Environmental Laboratory, NOAA, Seattle, WA, USA, 98115
3 Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA, 10964
4 Monterey Bay Aquarium Research Institute, Monterey Bay, CA, USA, 95039
1 Introduction:
2 This auxiliary material includes two examples illustrating the method of deseasonalization of
3 seawater p CO
2
and pH described in section 2.2 of the manuscript. Deseasonalization corrections
4 are based on the methods of Takahashi et al. [2009]. Figure S1 shows calculated monthly means
5
6 of seawater p CO
2
over the entire time series (i.e., the overall monthly means) for El Niño, neutral, and La Niña periods at 0°, 155°W. Figure S2 illustrates the deseasonalized monthly
7 p CO
2
observations that result from applying the seasonal corrections derived from Figure S1 to
8
9
10 the monthly means. Deseasonalized monthly p CO
2
observations are regressed linearly against time to determine the mean rate of change, or growth rate, for El Niño periods, neutral periods,
La Niña periods, and the full time series (Figure S2).

11
12
13
Figure S1. Seawater p CO
2
mooring observations (circles) and means (squares) by month during
El Niño, neutral, and La Niña periods at 0°, 155°W. The difference between monthly means and
14 the time series mean (solid line) are the seasonal corrections applied to deseasonalize each
15 monthly mean throughout the record.
16
17 Figure S2. Deseasonalized monthly means (squares) of p CO
2
calculated using seasonal
18
19 corrections from Figure S1 during a) El Niño events, b) neutral periods, c) La Niña events, and d) the full time series at 0°, 155°W. The line is the linear regression of the monthly means.
20 Original observations are also shown (gray points).