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Stramma, Lothar; Fischer, Tim; Grundle, Damian; Krahmann, Gerd; Bange, Hermann Werner; Marandino, Christa A (2016): Observed El Niño conditions in the eastern tropical Pacific in October 2015. PANGAEA,, Supplement to: Stramma, L et al. (2016): Observed El Niño conditions in the eastern tropical Pacific in October 2015. Ocean Science, 12(4), 861-873,

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A strong El Niño developed in early 2015. Measurements from a research cruise on the RV Sonne in October 2015 near the equator east of the Galapagos Islands and off the shelf of Peru, are used to investigate changes related to El Niño in the upper ocean in comparison with earlier cruises in this region. At the equator at 85°30' W, a clear temperature increase leading to lower densities in the upper 350 m, despite a concurrent salinity increase from 40 to 350 m, developed in October 2015. Lower nutrient concentrations were also present in the upper 200 m, and higher oxygen concentrations were observed between 40 and 130 m. Except for the upper 60 m at 2°30' S, however, there was no obvious increase in oxygen concentrations at sampling stations just north (1° N) and south (2°30' S) of the equator at 85°30' W. In the equatorial current field, the Equatorial Undercurrent (EUC) east of the Galapagos Islands almost disappeared in October 2015, with a transport of only 0.02 Sv in the equatorial channel between 1° S and 1° N, and a weak current band of 0.78 Sv located between 1° S and 2°30' S. Such near-disappearances of the EUC in the eastern Pacific seem to occur only during strong El Niño events. Off the Peruvian shelf at ~9° S, where the sea surface temperature (SST) was elevated, upwelling was modified, and warm, saline and oxygen rich water was upwelled. Despite some weak El Niño related SST increase at ~12 to 16° S, the upwelling of cold, low salinity and oxygen-poor water was still active at the easternmost stations at three sections at ~12° S, ~14° S and ~16° S, while further west on these sections a transition to El Niño conditions appeared. Although in early 2015 the El Niño was strong and in October 2015 showed a clear El Niño influence on the EUC, in the eastern tropical Pacific the measurements only showed developing El Niño water mass distributions. In particular the oxygen distribution indicated the ongoing transition from 'typical' to El Niño conditions progressing southward along the Peruvian shelf.
Related to:
Bange, Hermann Werner (2013): Nutrients measured on water bottle samples during METEOR cruise M91. GEOMAR - Helmholtz Centre for Ocean Research Kiel, PANGAEA,
Funk, Andreas (2012): ADCP current measurements during METEOR cruise M77/4. IFM-GEOMAR Leibniz-Institute of Marine Sciences, Kiel University, PANGAEA,
Krahmann, Gerd (2014): Physical oceanography during METEOR cruise M90. GEOMAR - Helmholtz Centre for Ocean Research Kiel, PANGAEA,
Krahmann, Gerd; Czeschel, Rena; Fischer, Tim (2016): ADCP current measurements (38 and 75 kHz) during METEOR cruise M90. PANGAEA,
Krahmann, Gerd; Stramma, Lothar (2016): ADCP current measurements during SONNE cruise SO243: 75kHz part2. PANGAEA,
Stramma, Lothar; Lohmann, Martina (2016): Hydrochemistry of water samples during METEOR cruise M90. PANGAEA,
German Science Foundation (DFG), grant/award no. 27542298: Climate - Biogeochemistry Interactions in the Tropical Ocean
Median Latitude: -8.497790 * Median Longitude: -80.368587 * South-bound Latitude: -16.075100 * West-bound Longitude: -85.500320 * North-bound Latitude: 1.000070 * East-bound Longitude: -75.274450
Date/Time Start: 2015-10-07T00:00:00 * Date/Time End: 2015-10-20T00:40:00
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Datasets listed in this publication series

  1. Bange, HW (2016): Nutrients measured on water bottle samples during SONNE cruise SO243.
  2. Stramma, L; Krahmann, G (2016): Physical oceanography during SONNE cruise SO243.