Ecosystem impacts of marine heat waves in the Northeast Pacific

Wyatt, Abigale M.; Resplandy, Laure; Marchetti, Adrian

doi:10.5194/egusphere-2022-17

Cited by 2 publications

(5 citation statements)

References 18 publications

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“…In general, the shift towards larger phytoplankton occurs over regions where small phytoplankton are dominant and vice versa. Other studies have previously documented phytoplankton shifts during MHWs (Yang et al, 2018;Wyatt et al, 2022). Wyatt et al (2022), for example, described a relative shift towards small phytoplankton in the northeast Pacific during the 2014-2015 Blob due to a stronger response of large phytoplankton to reduced nutrient levels and a stronger response of small phytoplankton to increased light availability driven by shallower mixed layers.…”

Section: Discussionmentioning

confidence: 92%

“…Wyatt et al (2022), for example, described a relative shift towards small phytoplankton in the northeast Pacific during the 2014-2015 Blob due to a stronger response of large phytoplankton to reduced nutrient levels and a stronger response of small phytoplankton to increased light availability driven by shallower mixed layers. Small phytoplankton even increased during the Blob over the Gulf of Alaska (Wyatt et al, 2022), in agreement with CESM2-LE, which simulates increased small-phytoplankton NPP during MHW-NPPX events in the northern high latitudes (Fig. 3c).…”

Section: Discussionmentioning

confidence: 99%

“…For example, Whitney (2015) shows that in winter 2013/14 during the Blob, anomalous winds weakened nutrient transport to the northeastern Pacific transition zone and decreased phytoplankton NPP, resulting in the lowest chlorophyll concentrations ever measured using satellite observations. Wyatt et al (2022) suggest that nutrient limitation during MHWs generally reduces the biomass of small and large phytoplankton in the northeast Pacific transition zone. However, not all warming events are accompanied by NPPX events.…”

Section: Introductionmentioning

confidence: 96%

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Hotspots and drivers of compound marine heatwaves and low net primary production extremes

et al. 2022

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Abstract. Extreme events can severely impact marine organisms and ecosystems. Of particular concern are multivariate compound events, namely when conditions are simultaneously extreme for multiple ocean ecosystem stressors. In 2013–2015 for example, an extensive marine heatwave (MHW), known as the Blob, co-occurred locally with extremely low net primary productivity (NPPX) and negatively impacted marine life in the northeast Pacific. Yet, little is known about the characteristics and drivers of such multivariate compound MHW–NPPX events. Using five different satellite-derived net primary productivity (NPP) estimates and large-ensemble-simulation output of two widely used and comprehensive Earth system models, the Geophysical Fluid Dynamics Laboratory (GFDL) ESM2M-LE and Community Earth System Model version 2 (CESM2-LE), we assess the present-day distribution of compound MHW–NPPX events and investigate their potential drivers on the global scale. The satellite-based estimates and both models reveal hotspots of frequent compound events in the center of the equatorial Pacific and in the subtropical Indian Ocean, where their occurrence is at least 3 times higher (more than 10 d yr−1) than if MHWs (temperature above the seasonally varying 90th-percentile threshold) and NPPX events (NPP below the seasonally varying 10th-percentile threshold) were to occur independently. However, the models show disparities in the northern high latitudes, where compound events are rare in the satellite-based estimates and GFDL ESM2M-LE (less than 3 d yr−1) but relatively frequent in CESM2-LE. In the Southern Ocean south of 60∘ S, low agreement between the observation-based estimates makes it difficult to determine which of the two models better simulates MHW–NPPX events. The frequency patterns can be explained by the drivers of compound events, which vary among the two models and phytoplankton types. In the low latitudes, MHWs are associated with enhanced nutrient limitation on phytoplankton growth, which results in frequent compound MHW–NPPX events in both models. In the high latitudes, NPPX events in GFDL ESM2M-LE are driven by enhanced light limitation, which rarely co-occurs with MHWs, resulting in rare compound events. In contrast, in CESM2-LE, NPPX events in the high latitudes are driven by reduced nutrient supply that often co-occurs with MHWs, moderates phytoplankton growth, and causes biomass to decrease. Compound MHW–NPPX events are associated with a relative shift towards larger phytoplankton in most regions, except in the eastern equatorial Pacific in both models, as well as in the northern high latitudes and between 35 and 50∘ S in CESM2-LE, where the models suggest a shift towards smaller phytoplankton, with potential repercussions on marine ecosystems. Overall, our analysis reveals that the likelihood of compound MHW–NPPX events is contingent on model representation of the factors limiting phytoplankton production. This identifies an important need for improved process understanding in Earth system models used for predicting and projecting compound MHW–NPPX events and their impacts.

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Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

See 1 more Smart Citation

Hotspots and drivers of compound marine heatwaves and low net primary production extremes

et al. 2022

View full text Add to dashboard Cite

show abstract

“…In general, the shift towards larger phytoplankton occurs over regions where small phytoplankton are dominant and vice-versa. Other studies have previously documented phytoplankton shifts during MHWs (Yang et al, 2018;Wyatt et al, 2022). Wyatt et al (2022), for example, described a relative shift towards small phytoplankton in the northeast Pacific during the 2014-2015 Blob due to a stronger response of large phytoplankton to reduced nutrient levels and a stronger response of small phytoplankton to increased light availability driven by shallower mixed layers.…”

Section: Summary Of Driving Processesmentioning

confidence: 92%

“…For example, Whitney (2015) show that in winter 2013/2014 during the 'The Blob' anomalous winds weakened nutrient transport to the northeastern Pacific transition zone and decreased phytoplankton NPP, resulting in the lowest chlorophyll concentrations ever measured. Wyatt et al (2022) suggest that nutrient limitation during MHWs generally reduces the biomass of small and large phytoplankton in the northeast Pacific transition zone. However, not all warming events are accompanied by NPPX events.…”

Section: Introductionmentioning

confidence: 96%

Hotspots and drivers of compound marine heatwave and low net primary production extremes

Grix

Zscheischler²,

Rodgers³

et al. 2022

Preprint

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Abstract. Extreme events can severely impact marine organisms and ecosystems. Of particular concern are multivariate compound events, namely when conditions are simultaneously extreme for multiple ocean ecosystem stressors. In 2013–2015 for example, an extensive marine heatwave (MHW), known as the Blob, co-occurred locally with extremely low net primary productivity (NPPX) and negatively impacted marine life in the northeast Pacific. Yet, little is known about the characteristics and drivers of such multivariate compound MHW-NPPX events. Using five different satellite-derived NPP estimates and large ensemble simulation output of two widely-used and comprehensive Earth system models, GFDL-ESM2M-LE and CESM2-LE, we assess the present-day distribution of compound MHW-NPPX events and investigate their potential drivers on the global scale. The satellite-based estimates and both models reveal hotspots of frequent compound events in the center of the equatorial Pacific and in the subtropical Indian Ocean, where their occurrence is at least three times higher (more than 10 days per year) than if MHWs (temperature above the 90th percentile threshold) and NPPX events (NPP below the 10th percentile threshold) were to occur independently. However, the models show disparities in the northern high latitudes, where compound events are rare in the satellite-based estimates and GFDL-ESM2M-LE (less than 3 days per year), but relatively frequent in CESM2-LE. In the Southern Ocean south of 60° S, low agreement between the observation-based estimates makes it difficult to determine which of the two models better simulates MHW-NPPX events. The frequency patterns can be explained by the drivers of compound events, which vary among the two models and phytoplankton types. In the low latitudes, MHWs are associated with enhanced nutrient limitation on phytoplankton growth, which results in frequent compound MHW-NPPX events in both models. In the high latitudes, NPPX events in GFDL-ESM2M-LE are driven by enhanced light limitation, which rarely co-occurs with MHWs, resulting in rare compound events. In contrast, in CESM2-LE, NPPX events in the high latitudes are driven by reduced nutrient supply that often co-occurs with MHWs, moderates phytoplankton growth and causes biomass to decrease. Compound MHW-NPPX events are associated with a relative shift towards larger phytoplankton in most regions, except in the eastern equatorial Pacific in both models, as well as in the northern high latitudes and between 35° S and 50° S in CESM2-LE, where the models suggest a shift towards smaller phytoplankton, with potential repercussions on marine ecosystems. Overall, our analysis reveals that the likelihood of compound MHW-NPPX events is contingent on model representation of the factors limiting phytoplankton production. This identifies an important need for improved process understanding in Earth system models used for predicting and projecting compound MHW-NPPX events and their impacts.

show abstract

Ecosystem impacts of marine heat waves in the Northeast Pacific

Cited by 2 publications

References 18 publications

Hotspots and drivers of compound marine heatwaves and low net primary production extremes

Hotspots and drivers of compound marine heatwaves and low net primary production extremes

Hotspots and drivers of compound marine heatwave and low net primary production extremes

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