Correction EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES Correction for “Global airborne sampling reveals a previously sphere over both seasons sampled, with MBL mixing ratios frequently unobserved dimethyl sulfide oxidation mechanism in the marine exceeding 10 ppt and periodically as large as 100 ppt (Fig. 2).” atmosphere,” by Patrick R. Veres, J. Andrew Neuman, Timothy Also on the same page, right column, second full paragraph, H. Bertram, Emmanuel Assaf, Glenn M. Wolfe, Christina line 6, “HPMTFwastypicallyobservedina1:1ratiowithDMSinthe J. Williamson, Bernadett Weinzierl, Simone Tilmes, Chelsea R. MBL; however, values in excess of 2:1 were frequently encountered. Thompson, Alexander B. Thames, Jason C. Schroder, Alfonso For example, the largest HPMTF mixing ratios of more than 300 ppt Saiz-Lopez, Andrew W. Rollins, James M. Roberts, Derek Price, were observed over the South Atlantic Ocean (46°S and 53°W) Jeff Peischl, Benjamin A. Nault, Kristian H. Møller, David O. during ATom-3” should instead appear as “HPMTF was typically Miller, Simone Meinardi, Qinyi Li, Jean-François Lamarque, observed in a 0.5:1 ratio with DMS in the MBL; however, values in Agnieszka Kupc, Henrik G. Kjaergaard, Douglas Kinnison, Jose excess of 1:1 were periodically encountered. For example, the largest L. Jimenez, Christopher M. Jernigan, Rebecca S. Hornbrook, Alan HPMTF mixing ratios of more than 150 ppt were observed over the Hills, Maximilian Dollner, Douglas A. Day, Carlos A. Cuevas, South Atlantic Ocean (46°S and 53°W) during ATom-3.” Pedro Campuzano-Jost, James Burkholder, T. Paul Bui, William In the SI Appendix, the authors note that “we originally stated H. Brune, Steven S. Brown, Charles A. Brock, Ilann Bourgeois, that ‘Cl2 quantification is possible using the iodide CIMS instru- Donald R. Blake, Eric C. Apel, and Thomas B. Ryerson, which was mentation (6) allowing for the determination of Cl• concentration first published February 18, 2020; 10.1073/pnas.1919344117 (Proc. following photolysis’ and later stated ‘Under these conditions we Natl. Acad. Sci. U.S.A. 117, 4505–4510). assume that the concentration of HPMTF produced is equivalent to The authors note that “hydroperoxymethyl thioformate (HPMTF) twice the measured concentration of Cl2 lost via photolysis.’ In the CORRECTION mixing ratios have been reduced, based upon recent experimental updated calibration procedure, the change in Cl2, from photolytic work that has identified a correction to the calibration method used loss and subsequent reaction with DMS, is below the detection limit to determine the instrument sensitivity for HPMTF measurements of the instrument. For quantification of Cl• concentration we utilize during ATom-3 and ATom-4. In the original calibration procedure, a more accurate actinometry of chlorine radicals.” described in SI Appendix, section 1, HPMTF was produced using Cl• Panel A of Fig. S8 has been removed. Therefore, the following radical reaction with dimethyl sulfide (DMS). The measured change statement is no longer applicable: “Fig. S8A shows an example of in Cl2 was used to determine HPMTF production; however, a con- a calibration experiment where loss of Cl2 is accompanied by an taminant yielded an overestimation in the measured Cl• radical increase in HPMTF during photolysis.” These sentences have concentration. More recent and more accurate actinometry of the been omitted in the updated SI Appendix. produced Cl radicals has shown that instrument sensitivity to On page 4, second full paragraph, line 1, “An absolute sensitivity HPMTF was underestimated in these initial experiments. of 2.4 ± 1.2 Hz ppt-1 was determined for the detection of HPMTF “HPMTF mixing ratios published in this manuscript are cor- using iodide-adduct TOF CIMS in ATom. This sensitivity is about 5x rected by applying a project average scaling factor of 0.62 ± 0.11 less than the most sensitive compounds (e.g. Cl2,ClNO2,N2O5)and (1 s) to the observations. The publicly available dataset has been similar to that for BrO” should instead appear as “The average updated through the Distributed Active Archive Center for normalized instrument sensitivity to the detection of HPMTF using Biogeochemical Dynamics (1). The HPMTF uncertainties have iodide-adduct TOF CIMS was 9.0 ± 3.2 (1σ)Hzppt-1, normalized to − also been updated and are now reported for 1-s data to be 17% + 1MHzIH2O averaged across ATom-3 and ATom-4. This sensitivity 0.3 ppt accuracy and 0.4 ppt precision for ATom-3 and 12% + is similar to the most sensitive compounds (e.g. Cl2,ClNO2,N2O5).” 0.4 ppt accuracy and 0.3 ppt precision for ATom-4.” In addition, the following changes have been made to the SI As a result of this change, Figs. 1–4 have been updated. The Appendix reference list: The authors note that ref. 6 “was used to corrected figures and their legends appear below. establish the mass spectrometer as a quantitative method for Cl2 Also as a result of this change, the authors note that some text measurement. The updated calibration procedure no longer utilizes in the main article and SI Appendix should be corrected. On page the observed change in Cl2 as a method for quantification of Cl 4506, right column, first paragraph, line 6, “Detection limits were radicals (Cl•) production; therefore, the reference is no longer rel- better than 1 parts per trillion as a mole fraction in dry air (ppt), evant to the manuscript.” Ref. 6 has been removed. Citations for refs. with an uncertainty of 55% + 0.06 ppt and a precision of 0.1 ppt for 57–59 were out of order and appeared earlier in the SI than indi- 1-s measurements (details in SI Appendix)” should instead appear as cated. The citations have been renumbered and refs. 57–59 now “Detection limits were better than 1 parts per trillion as a mole appear as references 19–21. Furthermore, refs. 50 and 61 were du- fraction in dry air (ppt), with an uncertainty of 17% + 0.4 ppt and a plicated and have now been combined into a single ref. 52. The SI precision of 0.4 ppt for 1-s measurements (details in SI Appendix).” Appendix reference list has been renumbered to reflect these changes. On the same page, right column, first full paragraph, line 8, Lastly, Figs. S1, S2, S5, and S8 are also affected by the correction to “HPMTF is globally ubiquitous in the lower atmosphere over both HPMTF data. The legend for Fig. S8 has been updated to reflect seasons sampled, with MBL mixing ratios frequently exceeding 50 ppt the changes. and periodically as large as several hundred ppt (Fig. 2)” should in- The online version has been updated to include the corrected text stead appear as “HPMTF is globally ubiquitous in the lower atmo- described above, the corrected Figs. 1–4, and the corrected SI Appendix. 1. S. C. Wofsy et al., ATom: Merged atmospheric chemistry, trace cases, and aerosols. Oak Ridge National Laboratory Distributed Active Archive Center. https://daac.ornl.gov/cgi- bin/dsviewer.pl?ds_id=1581. Deposited 28 March 2018. PNAS 2021 Vol. 118 No. 36 e2113268118 https://doi.org/10.1073/pnas.2113268118 | 1of3 Downloaded by guest on September 27, 2021 Fig. 1. Measurements of HPMTF during the ATom mission. NASA DC-8 flight tracks are colored and sized by atmospheric mixing ratios of HPMTF observed during ATom-3 and ATom-4, displayed as 5-min averages of observations above the 0.1-ppt detection limit. Climatological surface seawater DMS concen- trations are shown on a grayscale (20). A B Fig. 2. Global observations of HPMTF from ATom-3 and ATom-4. (A and B) Global observations of HPMTF made aboard the NASA DC-8 aircraft during the ATom-3 and ATom-4 circuits. The 1-Hz observations of HPMTF are colored according to the legend above. (C and D) Vertical distribution of all HPMTF 1-Hz observations. (E and F) HPMTF, DMS, and SO2 vertically binned (0.5 km resolution) mean observations. HPMTF, SO2, and DMS observations below the de- tection limit of the instrument were not included in the data presented. 2of3 | PNAS https://doi.org/10.1073/pnas.2113268118 Correction for Veres et al., Global airborne sampling reveals a previously unobserved dimethyl sulfide oxidation mechanism in the marine atmosphere Downloaded by guest on September 27, 2021 Fig. 3. Example time series of HPMTF removal by cloud uptake. In situ observations of HPMTF during ATom-3 and ATom-4 (black) are strongly anticorrelated with observed clouds (blue). Observations over the northern Atlantic Ocean (47°N and 135°W; Left) and the South Pacific Ocean (62°S and 150°W; Right) show a similar response to clouds suggesting that cloud removal of HPMTF is a dominant atmospheric loss process. CORRECTION Fig. 4. Evidence for DMS oxidation-driven particle formation and growth. In situ measurements made over the northern Atlantic Ocean (47°N and 135°W) of particle size and number concentration at altitudes of 1–3 km, above the MBL (Top), are strongly correlated with HPMTF mixing ratios (Bottom; black). A time series of total particle number for the size range below 10 nm is included in Bottom (green) to highlight the correlation between HPMTF and particles in the smallest size range observed. Cloud observations are indicated by the shaded regions (gray). Published under the PNAS license. Published August 27, 2021. www.pnas.org/cgi/doi/10.1073/pnas.2113268118 PNAS | 3of3 Correction for Veres et al., Global airborne sampling reveals a previously unobserved https://doi.org/10.1073/pnas.2113268118 dimethyl sulfide oxidation mechanism in the marine atmosphere Downloaded by guest on September 27, 2021 Global airborne sampling reveals a previously unobserved dimethyl sulfide oxidation mechanism in the marine atmosphere Patrick R. Veresa,1, J.