Remotely-sensed L4 SST underestimates the thermal fingerprint of coastal upwelling

Claudia Meneghesso, Rui Seabra, Bernardo R. Broitman, David S. Wethey, Michael T. Burrows, Benny K.K. Chan, Tamar Guy-Haim, Pedro A. Ribeiro, Gil Rilov, António M. Santos, Lara L. Sousa, Fernando P. Lima

Research output: Contribution to journalArticlepeer-review

Abstract

Sea Surface Temperature (SST) is an essential variable for understanding key physical and biological processes. Blended and interpolated L4 SST products offer major advantages over alternative SST data sources due to their spatial and temporal completeness, yet their ability to discriminate upwelling-induced steep temperature transitions in coastal waters remains largely unassessed. Here we analysed the performance of eleven L4 GHRSST-compliant products in estimating in situ water temperatures recorded by a large network of shallow subtidal and intertidal temperature loggers deployed in shores covering regimes with a wide range of upwelling intensities. Results indicate that while most products perform satisfactorily for most of the year, performance is severely affected during the upwelling season in locations with strong upwelling. We show that upwelling negatively impacts all four metrics used to assess dataset performance (average bias, correlation, centred root-mean-square error and normalized standard deviation), leading to a considerable overestimation of coastal water temperatures (with average bias exceeding 2 °C in some cases). We also show that while the use of L3 data (i. e., prior to blending and interpolation) leads to an increase in performance compared to L4 GHRSST-compliant products, the gain is probably not substantial enough to offset issues related with their spatial and temporal inconsistency along coastlines. Our results suggest that the use of L4 GHRSST-compliant products can lead to a misrepresentation of the thermal fingerprint of upwelling, and thus should be limited (or even avoided) in locations dominated by its effects. Conversely, the use of L4 GHRSST-compliant products on locations with little to no upwelling appears to be warranted. The mismatch between in situ and remotely-sensed sea water temperatures here reported also highlights the need for implementation of long-term monitoring networks of in situ temperature loggers.

Original languageEnglish
Article number111588
JournalRemote Sensing of Environment
Volume237
DOIs
StatePublished - Feb 2020
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by ERDF funds through COMPETE [grant number POCI-01-0145-FEDER-031088], through PORTUGAL 2020 [PORBIOTA, grant number POCI-01-0145-FEDER-022127], and through POR Norte [grant numbers NORTE-01-0145-FEDER-031053], and by Portuguese national funds through FCT [grant numbers PTDC/BIA-BMA/31088/2017, PTDC/BIA-BMA/31053/2017, PTDC/MAR/121016/2010]. CM was supported by FCT [grant number PD/BD/114038/2015]. RS was supported by NORTE2020 through ERDF [MARINFO, grant number NORTE-01-0145-FEDER-000031]. BRB was funded by FONDECYT [grant number 1181300] and by the Millenium Center for the Study of Multiple-Drivers on Marine Socio-Ecological Systems. BKKC was supported by the Ministry of Science and Technology, Taiwan [grant number MOST-103-2621-B-001-005-MY3]. TGH and GR were funded by the Ministry of Environmental Protection as part of the Israel national monitoring program, Israel Science Foundation [grant number 117/10] and by the Ministry of Science and Technology, Israel, and by the Federal Ministry of Education and Research (BMBF), Germany. DSW was supported by NSF [grant number 1129401] and NASA [grant number NNX11AP77G]. PAR was supported by FCT through QREN and COMPETE [grant number SFRH/BPD/69232/2010]. FES2012 data were produced by Noveltis, Legos and CLS Space Oceanography Division and distributed by Aviso, with support from CNES (http://www.aviso.altimetry.fr/). We thank Nuno Queiroz, S?rgia Velho, Ana Gomes, Raquel Xavier, Ricardo Ara?jo, Signe Nielsen, Jo?o Gon?alves, Rita Carri?o, Ana Raposo and Gilberto Carreira for their help with field work.

Funding Information:
This work was supported by ERDF funds through COMPETE [grant number POCI-01-0145 - FEDER-031088 ], through PORTUGAL 2020 [ PORBIOTA , grant number POCI-01-0145-FEDER-022127 ], and through POR Norte [grant numbers NORTE-01-0145 - FEDER-031053 ], and by Portuguese national funds through FCT [grant numbers PTDC/BIA-BMA/31088/2017 , PTDC/BIA-BMA/31053/2017 , PTDC/MAR/121016/2010 ]. CM was supported by FCT [grant number PD/BD/114038/2015 ]. RS was supported by NORTE2020 through ERDF [MARINFO, grant number NORTE-01-0145-FEDER-000031 ]. BRB was funded by FONDECYT [grant number 1181300 ] and by the Millenium Center for the Study of Multiple-Drivers on Marine Socio-Ecological Systems . BKKC was supported by the Ministry of Science and Technology, Taiwan [grant number MOST-103-2621-B-001-005-MY3 ]. TGH and GR were funded by the Ministry of Environmental Protection as part of the Israel national monitoring program, Israel Science Foundation [grant number 117/10 ] and by the Ministry of Science and Technology, Israel , and by the Federal Ministry of Education and Research (BMBF), Germany. DSW was supported by NSF [grant number 1129401 ] and NASA [grant number NNX11AP77G ]. PAR was supported by FCT through QREN and COMPETE [grant number SFRH/BPD/69232/2010 ]. FES2012 data were produced by Noveltis, Legos and CLS Space Oceanography Division and distributed by Aviso, with support from CNES ( http://www.aviso.altimetry.fr/ ). We thank Nuno Queiroz, Sérgia Velho, Ana Gomes, Raquel Xavier, Ricardo Araújo, Signe Nielsen, João Gonçalves, Rita Carriço, Ana Raposo and Gilberto Carreira for their help with field work.

Publisher Copyright:
© 2019 Elsevier Inc.

Keywords

  • Coast
  • GHRSST
  • Sea surface temperature
  • Upwelling

ASJC Scopus subject areas

  • Soil Science
  • Geology
  • Computers in Earth Sciences

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