Increase in acidifying water in the western Arctic Ocean

Transcription

1 In the format provided by the authors and unedited. SUPPLEMENTARY INFORMATION DOI: 1.138/NCLIMATE3228 Increase in acidifying water in the western Arctic Ocean Di Qi 1,2, Liqi Chen 1 *, Baoshan Chen 3,4, Zhongyong Gao 1, Wenli Zhong 5, Richard A. Feely 6, Leif G. Anderson 7, Heng Sun 1, Jianfang Chen 8, Min Chen 2, Liyang Zhan 1, Yuanhui Zhang 1 change and Wei-Jun over the past Cai two 3,4 * decades. and sea-ice melt (I) are the two main processes for acidification The uptake of anthropogenic CO by the ocean decreases In this study we report the upper ocean (top 3 m) seawater 1 Key Laboratory of Global Change and Marine-Atmospheric Chemistry of State Oceanic Administration (SOA), Third Institute of Oceanography, SOA, Xiamen 3615, China. 2 College of Ocean and Earth Sciences, Xiamen University, Xiamen 3615, China. 3 School of Marine Science and Policy, University of Delaware, Newark, Delaware 19716, USA. 4 Department of Marine Sciences, University of Georgia, Athens, Georgia 362, USA. 5 Key Lab of Physical Oceanography, Ocean University of China, Qingdao 2661, China. 6 Pacific Marine Environmental Laboratory/NOAA Seattle, Washington 98115, USA. 7 Department of Marine Sciences, University of Gothenburg, Box 461, 453 Gothenburg, Sweden. 8 Second Institute of Oceanography, SOA, Hangzhou 3112, China. * chenliqi@tio.org.cn; wcai@udel.edu 1 NATURE CLIMATE CHANGE Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

2 1 2 3 Supplementary Figure 1 Southern Canada Basin Northern Canada Basin Markov Basin TA ( mol kg -1 ) TA ( mol kg -1 )-Corrected TA ( mol kg -1 ) TA ( mol kg -1 )-Corrected TA ( mol kg -1 ) TA ( mol kg -1 )-Corrected DIC ( mol kg -1 ) DIC ( mol kg -1 )-Corrected DIC ( mol kg -1 ) DIC ( mol kg -1 )-Corrected DIC ( mol kg -1 ) DIC ( mol kg -1 )-Corrected AOS1994 SHEBA ODEN25 CHINARE28 CHINARE21 Supplementary Figure 1. Comparison of TA, TA-Corrected, DIC, and DIC-Corrected between 1994, , 25, 28, and 21 at stations in the Canadian Basin.

3 7 8 9 Supplementary Figure 2 Potential Temperature (ºC) Salinity DIN (NO3+NO2+NH4) [μmol kg -1 ) Pure-Atlantic water (AW) line AW PSW PWW Pure-Pacific water (PW) line a DIN (NO3+NO2+NH4) [μmol kg -1 ) b Phosphate (μmol kg -1 ) TA/Sal Phosphate (μmol kg -1 ) Potential Temperature f PW (%) [ºC] DIN (NO3+NO2+NH4) [μmol kg -1 ) c DIN (NO3+NO2+NH4) [μmol kg -1 ) d Phosphate (μmol kg -1 ) Phosphate (μmol kg -1 ) Supplementary Figure 2. Nitrogen versus phosphorus, Potential temperature (PT), Salinity, TA/Sal and fpw(%) data for the 21 cruise. The data points are colored by, (a) Potential temperature, (b) Salinity, (c) TA/Sal and (d) f PW (%). The gray line and black dashed line indicate "pure-atlantic water line" and "pure-pacific water line", respectively, as reported by Refs 1, 2.

4 Supplementary Figure 3 a b c d e Supplementary Figure 3. Map of sampling stations (red dots) and annual mean sea ice motion (black arrows) in the Arctic Ocean. Here we use the sea ice motion vectors to roughly depict the surface circulation of the Arctic Ocean. Original monthly mean sea ice motion data was obtained from the Polar Pathfinder Daily 25 km EASE-Grid Sea Ice Motion Vectors data with a resolution of 25 km (Ref 3 ). Annual mean sea ice motion vectors were derived from the monthly mean data. The data are available at The yellow dot represents the center of the Beaufort Gyre, which was roughly determined by visually identifying the center of the anticyclonic sea ice motion.

5 Supplementary Figure 4 6 AOO index Abnormal Accumulation of PWW Year 1994 Divergence of PWW Supplementary Figure 4. Arctic Ocean Oscillation (AOO) index, a measure of circulation regime (clockwise/anticyclonic or counterclockwise/cyclonic) of the Arctic Ocean wind-driven circulation (refer to Positive (blue bars) AOO indices correspond to years with anticyclonic circulation regimes (ACCR) and negative (red) bars show cyclonic regimes (CCR). During an ACCR, PWW/freshwater is accumulated in the Beaufort Gyre of the Canada Basin due to Ekman Pumping convergence, which reduces PWW/freshwater transport toward the North Atlantic Subpolar Region 4-6. By contrast, during a CCR PWW/freshwater exports to the Northern Atlantic Ocean increases 7.

6 5 51 Supplementary Figure Supplementary Figure 5. Latitudinal distributions of salinity, potential temperature, TA/Sal ratio and fraction of Pacific water (f PW(%)) during the cruises from 1994 to 21, including the Arctic Ocean Section 1994 (AOS 1994), Surface Heat Budget of the Arctic Ocean 1998 (SHEBA 1998), Beringia 25 (ODEN 25), and Chinese National Arctic Research Expedition 28 and 21 (CHINARE 28 and CHINARE 21) cruises. As δ 18 O data are only available for 1994 and 21, f PW (%) are only calculated for 1994 and 21. Note that f PW (%) and TA/Sal are similar for 1994 and 21. Thus TA/Sal is used as a qualitative tracer for Pacific Winter Water (PWW) (see Methods).

7 Supplementary Figure 6 Ekman transport upwelling downwelling Slope SCB PSW PWW AW Supplementary Figure 6. Potential temperature (ºC) (color contour and solid contours) and potential density anomaly (kg m -3 ) (white dashed contours) along the eastern cruise track (~15-16ºW) of CHINARE 21. In the year of 21, two water masses are apparent, including Pacific Summer Water (PSW) characterized by a T maximum (~-.5ºC), and PWW mode at nearby freezing temperature (-1.5ºC), σθ= 26.5 ( ). The Ekman transport zone, the upwelling-affected zone and the downwelling zone are based on Refs 8 and 9, respectively.

8 8 81 Supplementary Table 1: The five zones of AOS 1994 and CHINARE 21. Region Station Date Longitude Latitude Depth Station Date Longitude Latitude Depth W N m E N m SR1 8/29/ /29/ SR11 8/29/ /29/ SR12 8/29/ Slope 7 7/29/ M6 8/28/ /3/ M7 8/28/ /31/ SR16 8/29/ Chukchi abyssal plain 1 7/31/ M1 8/26/ /1/ M2 8/26/ /2/ M3 8/26/ /3/ M4 8/28/ /3/ M5 8/28/ /4/ Southern Canada Basin S24 21/7/ S25 21/7/ S26 21/7/ S26 21/7/ MS1 21/7/ MS2 21/7/ MS3 21/7/ Northern Canada Basin 17 8/6/ BN5 8/1/ /6/ BN6 8/2/ /8/ BN7 8/3/ /8/ BN9 8/5/ /9/ SR17 8/25/ SR18 8/25/ SR2 8/24/ SR22 8/23/ Makarov Basin 23 8/1/ BN1 8/5/ /12/ BN11 8/6/ /13/ BN13 8/2/ /14/ /15/ /17/

9 Supplementary Table 2: Average concentrations and standard deviations (SD) of NDIC and NTA (μmol kg -1 ) in deep waters (>2 m) of the Canadian Basin (CB), including the southern Canada Basin (SCB), northern Canada Basin (), and Makarov Basin (), during the different cruises. Data were normalized to salinity 35. See cruise names and data sources in the footnotes. NDIC NTA Cruise a Year Mean b SD n Mean SD n ARKXII 1996 SCB SHEBA 1996 SCB JOIS 1997 SCB SHEBA SCB SBI spring 22 SCB SBI summer 22 SCB ODEN 25 SCB ARKXII 27 SCB CHINARE 28 SCB HLY 21 SCB HLY 211 SCB HLY 212 SCB

10 Supplementary Table 2: (continued) AOS 1994 SCB CHINARE 21 SCB mean SCB Total mean CB a Cruise names: ARKXII is the Polarstern Arctic 96 cruise. SHEBA is the Surface Heat Budget of the Arctic Ocean cruise in JOIS is the Joint Ocean Ice Study cruise in SBI indicates the Shelf-Basin Interactions Project in 22. ODEN is the Beringia 25 cruise. ARK-XXII/2 is the Polarstern 27 cruise to the Arctic. HLY is the R/V Healy cruises from 21 to 212. AOS is the Arctic Ocean Section cruise in CHINARE is the Chinese Arctic and Antarctic Research Expedition in 28 and 21. CHINARE data are available at The other cruises data are downloaded from CDIAC at b Values exceeding ± 2 standard deviations (SDs), approximately 5% of the total data size, could be outliers and were excluded for the calculation of average values.

11 Supplementary Table 3: End-member properties of Pacific winter water (PWW, σθ 26.5) at various locations and times. Cruise Year Salinity AOS 1994 SHEBA 1998 ODEN 25 CHINARE Potential Temperature [ C] Sigma-θ [kg m -3 ] DO AOU NO 3 - +NO 2- [µmol kg -1 ] PO 4 3- TAlk DIC Slope 33.3± ± ±.1 26±13 17± ± ± ± ±6 68.3±.1 99±3.75±.7 CPA 33.1± ± ± ±4 122± ± ± ± ±7 68.±.1 99±2.71±.3 SCB Mean Slope CPA 33.± ± ± ±14 75± ± ± ±13 22± ±.3 99±5.92±.8 SCB 32.96± ± ±.2 298±11 7± ± ± ±14 222±14 69.±.3 97±6.99± ± ± ±.14 29±14 79± ± ± ± ± ±.1 97±5.89±.7 Mean Slope CPA SCB 32.9± ± ± ±16 84± ± ± ±8 2214± ±.3 98±5.84± ± ± ±.1 251±6 115± ± ± ± ± ±.1 99±1.74±.3 Mean Slope 32.99± ± ± ± ±2 69.± ±.15 CPA 33.5± ± ± ±9 2213±7 68.6±.2.9±.8 SCB 32.97± ± ± ± ±2 68.6±.4.91± ± ± ± ±11 224± ±.3.86±.6 Mean Slope 32.97± ± ±.12 28±32 88± ± ± ±6 2237±3 68.8±.5 11±1.76±.16 CPA 32.91± ± ±.1 282±5 86±4 15.5± ± ±5 2211±7 68.7±.2 97±7.83±.5 SCB 32.93± ± ±.6 276±3 92±3 15.2± ± ±3 2218±5 68.8±.3 1±.83± ± ± ± ±16 112± ± ± ± ± ±.4 96±6.68±.1 Mean TA/Sal f (PW) (%) Ω arag

12 Supplementary Table 4: Endmember properties of AW (27.8 σθ 27.9) in the years between 1994 and 21 Cruise Year Salinity Potential Temperature [ C] Sigma-θ [kg m -3 ] DO AOU NO 3 - +NO 2 - PO 4 3- TAlk DIC [µmol kg 1 ] TAlk/Sal f (PW) (%) Ω arag AOS ±.6.58 ± ±.3 31 ±2 42 ± ± ± ± ± ±.1 ± ±.6 SHEBA ±.2.27± ±.1 295± 8 51± ±.26.86± ± ± ±.2 4 ± ±.9 ODEN ±.7.63± ± ± 5 52 ± ± ± ± ± ±.1 ± ±.6 CHINARE ±.4.63± ± ± ± ± ± ±.6.63 ± ± ± 9 52 ± ± ± ± ± ±.1-2± ±.7

13 Supplementary References 1 Jones, E. P., Anderson, L. G., Jutterström, S., Mintrop, L., & Swift, J. H. Pacific freshwater, river water and sea ice meltwater across Arctic Ocean basins: Results from the 25 Beringia Expedition. J. Geophys. Res. 113, (28). 2 Yamamoto Kawai, M, Mclaughlin, F. A., Carmack, E. C., Nishino, S., & Shimada, K. Freshwater budget of the Canada Basin, Arctic Ocean, from salinity, δ 18 O, and nutrients. J. Geophys. Res. 113, doi:1.129/26jc3858 (28). 3 Tschudi, M., Fowler, C., Maslanik, J., Stewart, J. S., & Meier,W. Polar Pathfinder Daily 25 km EASE-Grid Sea Ice Motion Vectors, Version 3. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: (216). 4 Giles, K. A., Laxon, S. W., Ridout, A. L., Wingham, D. J., & Bacon, S. Western Arctic Ocean freshwater storage increased by wind-driven spin-up of the Beaufort Gyre. Nat. Geosci. 5, (212). 5 Proshutinsky, A., Dukhovskoy, D., Timmermans, M. L., Krishfield, R., & Bamber, J. L. Arctic circulation regimes. Philos. Trans. A Math. Phys. Eng. Sci. 373, 1.198/rsta (215). 6 Rabe, B. et al. Arctic Ocean basin liquid freshwater storage trend Geophys. Res. Lett. 41, (214). 7 Stewart, K. D. & Haine, T. W. N. Wind-driven Arctic freshwater anomalies. Geophys. Res. Lett. 4, (213). 8 Mathis, J. T. et al. Storm-induced upwelling of high pco2 waters onto the continental shelf of the western Arctic Ocean and implications for carbonate mineral saturation states. Geophys. Res. Lett. 39, doi:1.129/212gl51574 (212). 9 McLaughlin, F. A. & Carmack, E. C. Deepening of the nutricline and chlorophyll maximum in the Canada Basin interior, Geophys. Res. Lett. 37, doi:1.129/21gl45459 (21).