Author: Dagmara Rusiecka

Cael, B. B., Begouen Demeaux, C., Henson, S., Stock, C. A., Taboada, F. G., John, J. G., & Barton, A. D. (2022). Marine Ecosystem Changepoints Spread Under Ocean Warming in an Earth System Model. Journal of Geophysical Research: Biogeosciences, 127(5), e2021JG006571. https://doi.org/10.1029/2021JG006571

 

Summary

Plankton are the backbone of pelagic ocean ecosystems and play important roles in regulating Earth’s climate. Plankton populations and community structures respond to climate change, but much remains unknown about how climate change will influence plankton in the future. In this study scientists looked for rapid changes, or changepoints, in the virtual plankton communities of a global model simulating Earth’s climate over the pre-industrial era, the 20th century, and a projection of 21^st-century climate change. The authors find, for all types of plankton in the model, that the ocean area where changepoints occur expands from the pre-industrial era into the 20th century and again from the 20th to the 21st century. At the same time, hotspot regions, where rapid changes occur at least a few times per century, tend to disappear for all plankton types, and for temperature. Large plankton are more susceptible to changepoints than small plankton, and zooplankton are more susceptible than phytoplankton. The model ecosystem response to climate change is complex and spatially variable but suggests that rapid shifts in plankton communities may become increasingly widespread but less frequent as the climate warms.

 

Policy relevant message

The model ecosystem response to climate change suggests that rapid shifts in plankton communities may become increasingly widespread but less frequent as the climate warms.

Vogt, L., Burger, F. A., Griffies, S. M., & Frölicher, T. L. (2022). Local Drivers of Marine Heatwaves: A Global Analysis With an Earth System Model. Frontiers in Climate, 4. https://doi.org/10.3389/fclim.2022.847995

 

Summary

Marine heatwaves (MHWs) are periods of extreme warm ocean temperatures that can have devastating impacts on marine organisms and socio-economic systems. Despite recent advances in understanding the underlying processes of individual events, a global view of the local oceanic and atmospheric drivers of MHWs is currently missing. In this study, the authors quantified the main local processes leading to the onset and decline of surface MHWs in different seasons. The onset of MHWs in the subtropics and mid-to-high latitudes is primarily driven by net ocean heat uptake associated with a reduction of latent heat loss in all seasons, increased shortwave heat absorption in summer and reduced sensible heat loss in winter, dampened by reduced vertical mixing, especially in summer. In the tropics, ocean heat uptake is reduced and lowered vertical local mixing and diffusion cause the warming. In the subsequent decline phase, increased ocean heat loss to the atmosphere due to enhanced latent heat loss in all seasons together with enhanced vertical local mixing and diffusion in the high latitudes during summer dominate the temperature decrease globally. The processes leading to the onset and decline of MHWs are similar for short and long MHWs, but there are differences in the drivers between summer and winter. Different types of MHWs with distinct driver combinations are identified within the large variability among events. This analysis contributes to a better understanding of MHW drivers and processes and may therefore help to improve the prediction of high-impact marine heatwaves.

Friedlingstein, P., Jones, M. W., O’Sullivan, M., Andrew, R. M., Bakker, D. C. E., Hauck, J., Le Quéré, C., Peters, G. P., Peters, W., Pongratz, J., Sitch, S., Canadell, J. G., Ciais, P., Jackson, R. B., Alin, S. R., Anthoni, P., Bates, N. R., Becker, M., Bellouin, N., … Zeng, J. (2022). Global Carbon Budget 2021. Earth System Science Data, 14(4), 1917–2005. https://doi.org/10.5194/essd-14-1917-2022

 

Summary

The Global Carbon Budget 2021 describes the data sets and methodology used to quantify the emissions of carbon dioxide and their partitioning among the atmosphere, land, and ocean. These living data are updated every year to provide the highest transparency and traceability in the reporting of CO₂, the key driver of climate change.

Mogen, S. C., Lovenduski, N. S., Dallmann, A. R., Gregor, L., Sutton, A. J., Bograd, S. J., Quiros, N. C., Di Lorenzo, E., Hazen, E. L., Jacox, M. G., Buil, M. P., & Yeager, S. (2022). Ocean Biogeochemical Signatures of the North Pacific Blob. Geophysical Research Letters, 49(9), e2021GL096938. https://doi.org/10.1029/2021GL096938

 

Summary

The global ocean is experiencing major changes due to human-made carbon emissions and climate change, leading to a warming ocean with increasing acidity and declining oxygen. On top of these long-term changes in the ocean are short-term extreme events, such as marine heatwaves. These extreme events quickly change the ocean state and can stress marine ecosystems in multiple ways. The Northeast Pacific marine heat wave (2013–2016) was one such marine heatwave. Here we focus on the early portion of this marine heatwave, called the “Blob”. While the ocean temperature changes during the event are well understood, the effects on ocean biogeochemistry have not been fully examined. In this study, a simulation of the Blob was performed to examine short-term changes in oxygen and acidity. The authors find that the warming signal leads to a decline in the effects of ocean acidification, mainly due to changes in the movement of carbon, and lowers the amount of oxygen, due primarily to temperature-driven effects. These results suggest that some effects of climate change may be exacerbated (warming) or mitigated (ocean acidification) by marine heatwaves.

Desmet, F., Gruber, N., Köhn, E. E., Münnich, M., & Vogt, M. (2022). Tracking the Space-Time Evolution of Ocean Acidification Extremes in the California Current System and Northeast Pacific. Journal of Geophysical Research: Oceans, 127(5), e2021JC018159. https://doi.org/10.1029/2021JC018159

 

Summary

The emission of carbon dioxide by human activities causes ocean acidification (OA), that is, the decrease of the pH and saturation level of seawater with respect to the carbonate mineral aragonite. Episodic events of unusually low pH and aragonite saturation levels punctuate these long-term declines, potentially intensifying stress on marine plankton. Particularly prone to extremes is the California current system off the U.S. West Coast due to its naturally low pH-aragonite waters and its strong variability. The authors identified and characterized extreme events associated with OA in this region, and their drivers. They find extremes to have a broad range of volumes, durations, and strengths, with a quarter of them carrying corrosive conditions for shelled organisms, that is, aragonite saturation levels below 1. The largest and longest-lived events are associated with cyclonic eddies (whirls of approximately 50–100 km in diameter) that trap upwelled low pH-aragonite waters near the coast. Although representing only 3% of the events, they cause most of the total excess of acidity induced by all identified extremes. The vertical extent and duration of extremes with corrosive mean conditions are expected to impact calcifying organisms, such as pteropods.

Frémont, P., Gehlen, M., Vrac, M., Leconte, J., Delmont, T. O., Wincker, P., Iudicone, D., & Jaillon, O. (2022). Restructuring of plankton genomic biogeography in the surface ocean under climate change. Nature Climate Change, 12(4), 393–401. https://doi.org/10.1038/s41558-022-01314-8

 

Summary

The impact of climate change on diversity, functioning and biogeography of marine plankton remains a major unresolved issue. In this study, environmental niches are evidenced for plankton communities at the genomic scale for six size fractions from viruses to meso-zooplankton. The spatial extrapolation of these niches portrays ocean partitionings south of 60° N into climato-genomic provinces characterized by signature genomes. By 2090, under the high emission scenario (RCP8.5), provinces are reorganized over half of the ocean area considered, and almost all provinces are displaced poleward. Particularly, tropical provinces expand at the expense of temperate ones. Sea surface temperature is identified as the main driver of changes (50%), followed by phosphate (11%) and salinity (10%). Compositional shifts among key planktonic groups suggest impacts on the nitrogen and carbon cycles. Provinces are linked to estimates of carbon export fluxes which are projected to decrease, on average, by 4% in response to biogeographical restructuring.

 

Policy relevant message

By 2090, under the high emission scenario (RCP8.5), provinces are reorganized over half of the ocean area considered, and almost all provinces are displaced poleward. Particularly, tropical provinces expand at the expense of temperate ones. Sea surface temperature is identified as the main driver of changes (50%), followed by phosphate (11%) and salinity (10%). Compositional shifts among key planktonic groups suggest impacts on the nitrogen and carbon cycles. Provinces are linked to estimates of carbon export fluxes which are projected to decrease, on average, by 4% in response to biogeographical restructuring.

Schwinger, J., Asaadi, A., Goris, N., & Lee, H. (2022). Possibility for strong northern hemisphere high-latitude cooling under negative emissions. Nature Communications, 13(1), 1095. https://doi.org/10.1038/s41467-022-28573-5

Summary

It is well established that a collapse or strong reduction of the Atlantic meridional overturning circulation (AMOC) would substantially cool the northern high latitudes. In this study the authors show that there is a possibility that such cooling could be amplified under deliberate CO₂ removal and result in a temporary undershoot of a targeted temperature level. This behaviour was found in Earth system models that show a strong AMOC decline in response to anthropogenic forcing. Idealised simulations of CO₂ removal with one of these models indicate that the timing of negative emissions relative to AMOC decline and recovery is key in setting the strength of the temporary cooling. This study shows that the pronounced temperature-fluctuations at high northern latitudes found in these simulations would entail considerable consequences for sea-ice and permafrost extent as well as for high latitude ecosystems.

Policy relevant message:

Cooling of the northern hemisphere as a result of a collapse or strong reduction of the Atlantic meridional overturning circulation (AMOC) can be amplified by Carbon dioxide removal (CDR) techniques. Therefore, not emitting CO₂ into the atmosphere is a preferable action over post emission CO₂ removal.