Complex networks of marine heatwaves reveal abrupt transitions in the global ocean

Abstract

Understanding how marine heatwaves (MHWs) unfold in space and time under anthropogenic climate change is key to anticipate future impacts on ecosystems and society. Yet, our knowledge of the spatiotemporal dynamics of MHWs is very limited. Here, I combine network theory with topological data analysis and event synchronization to high-resolution satellite data and to a set of Earth System Model simulations to reveal the dynamical organization of complex MHW networks. The analysis reveals that MHWs have already crossed a tipping point separating highly synchronized preindustrial MHWs from the more extreme, but less coherent warming events we experience today. This loose spatiotemporal organization persists under a reduced RCP 2.6 emission scenario, whereas a second abrupt transition towards a permanent state of highly synchronized MHWs is foreseen by 2075 under a business-as-usual RCP 8.5 scenario. These results highlight the risks of abrupt ocean transitions, which may dramatically affect marine life and humanity by eroding valuable time for adaptation to climate change.

Stabilizing effects of spatially heterogeneous disturbance via reduced spatial synchrony on a rocky shore community

“…In contrast, intense disturbances always reduced β diversity in our experiment, suggesting that strong perturbations can destabilize communities through biotic homogenization and increased spatial synchrony regardless of their spatial structure. This is consistent with the results of previous studies documenting biotic homogenization in response to pervasive environmental change (Dornelas et al, 2014;Magurran et al, 2015;Olden, 2006) and a positive relation between spatially correlated climate extremes (e.g., marine heatwaves [Benedetti-Cecchi, 2021]) and increasing trends of synchronization of many natural populations (Hansen et al, 2020). We note, however, that our system was dominated by sessile species, so the results may differ for systems with a prevalence of mobile organisms (Catal an et al, 2023).…”

Automated predictive analytics tool for rainfall forecasting

“…Just like any other region, variation in rainfall often influences water availability across Australia. The continent encounters varied rainfall patterns including dryness (absence of rainfall), floods (excessive rainfall) and droughts 5 . Some examples are the Millenium drought, which lasted over a decade from 1995 to 2009 6 , the 1970s dry shift in southwest Australia 7 , and the widespread flooding from 2009 to 2012 in the eastern Australian regions 8 .…”

Effects of Field Simulated Marine Heatwaves on Sedimentary Organic Matter Quantity, Biochemical Composition, and Degradation Rates

“…Our results indicate that benthic trophic status (in terms of organic matter quantity, composition, and nutritional quality) and ecosystem functioning (in terms of C degradation rates) of even very shallow nearshore marine sediments can be severely impaired by prolonged MHWs, with larger impacts associated with higher T anomalies. Based on these results, we can anticipate that the increase in frequency, intensity, and duration of MHWs, foreseen to cause abrupt ocean transitions in the coming decades [6,12] will cause not only direct effects on species and communities, hence overall threatening benthic biodiversity [18,21,80,82], but also provoke indirect effects by altering C biogeochemistry and the efficiency of energy transfer towards higher trophic levels.…”

“…Marine heatwaves (hereafter MHWs), as discrete but persistent (>5 days) positive (2-4 • C) anomalies in sea surface temperatures (SST) [3], are one of the most concerning and ubiquitous manifestations of global warming [4]. Marine warmth anomalies have become increasingly frequent in the last century [5], and episodes that have occurred across the last 20 years have caused severe biological, ecological, and economic consequences [6]. Recent projections indicate that such a surge in the frequency of MHWs could persevere for the whole current century [5] as the consequence of the persisting global ocean warming.…”