Phytoplankton decline in the eastern North Pacific transition zone associated with atmospheric blocking

Abstract

Global climate change can significantly influence oceanic phytoplankton dynamics, and thus biogeochemical cycles and marine food webs. However, associative explanations based on the correlation between chlorophyll-a concentration (Chl-a) and climatic indices is inadequate to describe the mechanism of the connection between climate change, large-scale atmospheric dynamics, and phytoplankton variability. Here, by analyzing multiple satellite observations of Chl-a and atmospheric conditions from National Center for Environmental Prediction/National Center for Atmospheric Research reanalysis datasets, we show that high-latitude atmospheric blocking events over Alaska are the primary drivers of the recent decline of Chl-a in the eastern North Pacific transition zone. These blocking events were associated with the persistence of large-scale atmosphere pressure fields that decreased westerly winds and southward Ekman transport over the subarctic ocean gyre. Reduced southward Ekman transport leads to reductions in nutrient availability to phytoplankton in the transition zone. The findings describe a previously unidentified climatic factor that contributed to the recent decline of phytoplankton in this region and propose a mechanism of the top-down teleconnection between the high-latitude atmospheric circulation anomalies and the subtropical oceanic primary productivity.The results also highlight the importance of understanding teleconnection among atmosphere-ocean interactions as a means to anticipate future climate change impacts on oceanic primary production.

Ecosystem impacts of marine heat waves in the Northeast Pacific

“…To understand the biological impacts of marine heat waves, we examine the composite of the nine simulated warm events. As expected from observations (Whitney 2015;Le et al 2019), the model simulates the greatest biological anomalies in the NPTZ, including a negative Chl anomaly (-0.03 mg m -3 , Fig. 6a) comparable with satellite 235 observations (Fig.…”

“…9b Previous studies have demonstrated there is a decrease in primary production in the NPTZ caused by reduced nitrate concentrations during MHWs. This decrease in nitrate concentrations was attributed to warmer upper ocean conditions, which drive a reduction in winter mixing (Amaya et al 2021), and atmospheric blocking by an atmospheric ridge (Le et al 2019), which decreases the wind-driven Ekman transport that carries nitrate from the northern Alaskan 335 gyre southward, and otherwise supports up to 40 % of the new production (Ayers and Lozier 2010). Our results agree with this literature, with both observations (Line P, Argo floats) and the MOM6-COBALT model indicating lower nitrate concentrations during MHW across the Alaskan gyre (which also has lower iron) and the NPTZ (Fig.…”

Relationships Between Northern Hemisphere Teleconnection Patterns and Phytoplankton Productivity in the Neva Estuary (Northeastern Baltic Sea)

“…The problem of the mass development of phytoplankton in recent decades has become especially acute due to climate change, which can aggravate the negative consequences for the water ecosystems from human activities (e.g., Behrenfeld et al, 2006;Doney et al, 2012;Golubkov and Golubkov, 2020;Golubkov, 2021). However, the mechanisms of the eutrophication process as a result of climate change are not well understood (Le et al, 2019). The impact of climate variability on marine and estuarine ecosystem has been extensively discussed in recent decades (e.g., Stenseth et al, 2002;Doney, 2006;Doney et al, 2012;Bogatov and Fedorovskiy, 2016;Le et al, 2019;Golubkov and Golubkov, 2020).…”

“…However, the mechanisms of the eutrophication process as a result of climate change are not well understood (Le et al, 2019). The impact of climate variability on marine and estuarine ecosystem has been extensively discussed in recent decades (e.g., Stenseth et al, 2002;Doney, 2006;Doney et al, 2012;Bogatov and Fedorovskiy, 2016;Le et al, 2019;Golubkov and Golubkov, 2020). Climate fluctuations are exogenous and hidden driving forces that are causing profound large-scale changes in marine ecosystems, affecting the state of their environment and biotic interactions on interannual and longer time scales (Andersen et al, 2011;Doney et al, 2012;Kashkooli et al, 2017;Golubkov, 2021).…”

“…Due to this, a relationship between various biological processes and climatic indices has been found in many aquatic ecosystems (Straile and Adrian, 2000;Blenckner and Hillerbrand, 2002;Weyhenmeyer, 2008;Sharov et al, 2014;Gubelit, 2015;Kashkooli et al, 2017;Greaves et al, 2020;Maximov et al, 2021). Climatic indices are used to predict the productivity of open ocean waters (Le et al, 2019;Greaves et al, 2020) and inland seas (Kashkooli et al, 2017). Teleconnection patterns can also be used for paleoreconstructions (Diz et al, 2018), since there are examples of reconstructing data of their values back to 1675 (Luterbacher et al, 1999) or even to 1500 (Luterbacher et al, 2004).…”