EGU2020-12346
https://doi.org/10.5194/egusphere-egu2020-12346
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Potential state shifts in terrestrial ecosystems related to changes in El Niño-Southern Oscillation dynamics

Mateo Duque-Villegas1,2, Juan Fernando Salazar1, and Angela Maria Rendón1
Mateo Duque-Villegas et al.
  • 1Universidad de Antioquia, Facultad de Ingeniería, Escuela Ambiental, Medellin, Colombia
  • 2Now at: International Max Planck Research School on Earth System Modelling, Hamburg, Germany and Max Planck Institute for Meteorology, Hamburg, Germany

The El Niño-Southern Oscillation (ENSO) phenomenon is regarded as a policy-relevant tipping element of the Earth's climate system. It has a prominent planetary-scale influence on climatic variability and it is susceptible to anthropogenic forcing, which could alter irreversibly its dynamics. Changes in frequency and/or amplitude of ENSO would have major implications for terrestrial hydrology and ecosystems. The amount of extreme events such as droughts and floods could vary regionally, as well as their intensities. Here, we use an intermediate complexity climate model, namely the Planet Simulator (PlaSim), to study the potential impact on Earth's climate and its terrestrial ecosystems of changing ENSO dynamics in a couple of experiments. Initially we investigate the global effects of a permanent El Niño, and then we analyse changes in the amplitude of the fluctuation. We found that PlaSim model yields a sensible representation of current large-scale climatological patterns, including ENSO-related variability, as well as realistic estimates of global energy and water budgets. For the permanent El Niño state, there were significant differences in the global distribution of water and energy fluxes that led to asymmetrical effects on vegetation production, which increased in the tropics and decreased in temperate regions. In terrestrial ecosystems of regions such as western North America, the Amazon rainforest, south-eastern Africa and Australia, we found that these El Niño-induced changes could be associated with biome state transitions. Particularly for Australia, we found country-wide aridification as a result of sustained El Niño conditions, which is a potential state in which recent wildfires would be even more dramatic. When the amplitude of the ENSO fluctuation changes, we found that although mean climatological values do not change significantly, extreme values of variables such as temperature and precipitation become more extreme. Our approach aims at recognizing potential threats for terrestrial ecosystems in climate change scenarios in which there are more frequent El Niño phenomena or the intensities of the ENSO phases change. Although it is not enough to prove such effects will be observed, we show a consistent picture and it should raise awareness about conservation of global ecosystems.

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Presentation version 1 – uploaded on 29 Apr 2020
  • CC1: Comment on EGU2020-12346, John Bruun, 06 May 2020

    Dear Mateo this is really great work and I thought the ability to resove a change to the intensity and frequency of ENSO is important. 

    The ENSO process is a resonant wave phenomena of the earth system (see for example Bruun et al, 2017; Skakala and Bruun 2018) - so this means that the non-linear wave interactions and the forcing that are the ENSO mechanism are altering. 

    In your work it looks like the upper tail of the ENSO distribution is getting heavier.

    Using the Extreme value process approach (it is explained in Bruun, Evangelou, Sheen and Collins  EGU2020-11690) you can assess your system to see if the extreme ENSO changes the shape of the upper tail  (GEV process theory).

    We can for example apply this analysis to your data record. 

    Youe work could be an example of abrupt changes due to wave interaction effects. ENSO is so important - so this result impacts all earth system results. It would be good to work with you to see if the upper tail is actually altering. I'm at j.bruun@exeter.ac.uk.

    Best John

    • CC2: Reply to CC1, Paul Pukite, 06 May 2020

      "The ENSO process is a resonant wave phenomena of the earth system "

      The evidence doesn't support this. It appears to be more driven by tidal forces as can be seen by calibrating against the known angular momentum changes (from dLOD) and then applying a solution to Laplace's Tidal Equations along the equator

      • CC3: Reply to CC2, John Bruun, 06 May 2020

        This is a very topical conversation:

         

        For this it is useful to refer to the latest conversation on this by Timmerman:

        ENSO system: (Timmerman et al. , 2018) “warm pool heat advection processes have a key role in determining the long-term  memory..”. ENSO eigenmodes: ”operate not  far from criticality (zero growth rate) which implies that they can be easily excited by other processes.”

        How the two eigenmodes interact in the 2 - 8 year range (forcing includes tidal and seasonal processes) is key to understanding the forced ENSO resonance process.

        The changes Mateo is finding here could explain how these interactions are altering.   

        • CC4: Reply to CC3, Paul Pukite, 06 May 2020

          re ENSO on terrestrial ecosystems, this is an interesting paper

          Archibald, H. L. Relating the 4-year lemming ( Lemmus spp. and Dicrostonyx spp.) population cycle to a 3.8-year lunar cycle and ENSO. Can. J. Zool. 97, 1054–1063 (2019).

          And have many seen this paper ?

          Lin, J. & Qian, T. Switch Between El Nino and La Nina is Caused by Subsurface Ocean Waves Likely Driven by Lunar Tidal Forcing. Sci Rep 9, 1–10 (2019).
          • CC5: Reply to CC4, John Bruun, 08 May 2020

            Paul, I agree the types of forcing are important for how we assess and understand the ENSO response. Yes would expect high frequency, such as twice daily to play a role, as does seasonal though am not clear as to how daily forcing activates the specific wave modes that contribute to the ENSO oscillator. Do you know if their is a conceptual model that deals with this?  

            • CC6: Reply to CC5, Paul Pukite, 08 May 2020

              For processes that have a longer inertial response the diurnal or semidurnal tidal cycles are too rapid and get filtered. In that case the long-period tidal cycles take over. This is well-known for example in the Length-of-Day variations of the earth's and in suburface waves that are revealed in bottom pressure readings

              Woodworth, P.L. and Hibbert, A., 2018. "The nodal dependence of long-period ocean tides in the Drake Passage" Ocean Science14(4), pp.711-730.

              These are typical long-period tides that contribute to the forced solution of Laplace's Tidal Equations, which is the way that GCM's are constructed and solved (see also

    • AC1: Reply to CC1, Mateo Duque-Villegas, 08 May 2020

      Dear John and dear Paul, thank you so much for this discussion on the drivers of ENSO. I will take a look at the work you mention. I will be happy to share the data with you John. I will write you once we have finished our analysis and in the meantime I will get acquainted with the GEV process theory.