Trends in Primary Production in the Canary Current Upwelling System—A Regional Perspective Comparing Remote Sensing Models

Abstract

After Bakun (1990) formulated his hypothesis of upwelling intensification caused by increasing global warming, contradictory results have been published on whether primary productivity is increasing or decreasing in Eastern Boundary Upwelling Ecosystems (EBUE). The present work is focused in comparing three net primary production (NPP) models-the VGPM (Vertically Generalized Production Model), the Eppley-VGPM and the CbPM (Carbon-based Production Model)-in the Canary Current (CanC) EBUE during the 1998-2015 period, making use of both SeaWiFS (Sea-viewing Wide Field-of-view Sensor) and MODIS (MODerate-resolution Imaging Spectroradiometer) derived data. We looked for the first time for seasonal to interannual trends of NPP under a regional perspective, with the aim of searching for temporal patterns that could support or reject the intensification hypothesis. According to previous studies based on the seasonality of the upwelling regime, the CanC EBUE was divided into three subregions: a seasonal upwelling zone (SUZ; 13-20 • N), a permanent upwelling zone (PUZ; 20-26 • N) and a weak permanent upwelling zone (WPUZ; 26-33 • N). Although differences in the output of the models are important, both at regional and subregional scales, our analyses do not show significant increasing trends in NPP with any of the productivity models used. Our results are in accordance with previous published studies that indicate, that unlike other EBUE, winds have weakened (or at least not intensified) in the CanC upwelling over time scales ranging up to 60 years. Nevertheless, the comparison made in this work shows disagreements between some of the best-known NPP models and calls for a validation effort in this region. Seasonal to decadal anomalies of NPP and sea-surface temperature (SST) are estimated and analyzed in relation to selected climate indices, yielding only significant correlations between SST and the North Atlantic Oscillation (NAO) indices.

Changes in the Dust‐Influenced Biological Carbon Pump in the Canary Current System: Implications From a Coastal and an Offshore Sediment Trap Record Off Cape Blanc, Mauritania

“…A progressive warming and decreasing productivity over the last two decades was suggested for the CC‐EBUEs as a whole (Arístegui et al, ), which would better match our flux records from the deep ocean sediment traps than the Bakun et al (, ) scenario of coastal upwelling intensification. Barton et al () and Gómez‐Letona et al () also found no evidence of increasing alongshore winds and productivity in the Canary Current System. However, one should keep in mind that the CC‐EBUEs is characterized by various subsystems which could react differently to global warming (e.g., Arístegui et al, ; Garcìa‐Reyes et al, ; Lathuilière et al, ; Sydeman et al, ).…”

Global Perspectives on Observing Ocean Boundary Current Systems

“…Products that combine SSH and drifter measurements have improved eddy kinetic energy and dynamic topography estimates (Maximenko et al, 2009;Lumpkin and Garzoli, 2011;Rio et al, 2014;Rio and Santoleri, 2018). Estimates of chlorophyll derived from satellite ocean color measurements provide information on biological productivity in boundary current systems worldwide (e.g., Messié and Chavez, 2015;Gómez-Letona et al, 2017). Because ocean color observations have higher resolution (O(1) km) than satellite altimetry measurements, they potentially provide insight into the rich fields of submesoscale instabilities that exist within boundary current systems (Figure 4; Everett et al, 2014;Lee and Kim, 2018).…”

Synergistic Use of Remote Sensing and Modeling for Estimating Net Primary Productivity in the Red Sea With VGPM, Eppley-VGPM, and CbPM Models Intercomparison

“…It has been noted that NPP can be influenced by varying climatic patterns [26], [82], [83] in different geographical areas other than the Red Sea. We analyzed different climate indices for their impact on the NPP products derived from the previously mentioned models.…”