Gute Nachrichten: Der Klimawandel scheint Meerbrassen nichts anhaben zu können. Im Gegenteil: Ein wärmeres Meer lässt sie sogar besser wachsen. Sie sind echte Klimagewinner wie Coleman et al. im Fachblatt Global Change Biology im November 2018 feststellten:
Climate change does not affect the seafood quality of a commonly targeted fish
Climate change can affect marine and estuarine fish via alterations to their distributions, abundances, sizes, physiology and ecological interactions, threatening the provision of ecosystem goods and services. While we have an emerging understanding of such ecological impacts to fish, we know little about the potential influence of climate change on the provision of nutritional seafood to sustain human populations. In particular, the quantity, quality and/or taste of seafood may be altered by future environmental changes with implications for the economic viability of fisheries. In an orthogonal mesocosm experiment, we tested the influence of near‐future ocean warming and acidification on the growth, health and seafood quality of a recreationally and commercially important fish, yellowfin bream (Acanthopagrus australis). The growth of yellowfin bream significantly increased under near‐future temperature conditions (but not acidification), with little change in health (blood glucose and haematocrit) or tissue biochemistry and nutritional properties (fatty acids, lipids, macro‐ and micronutrients, moisture, ash and total N). Yellowfin bream appear to be highly resilient to predicted near‐future ocean climate change, which might be facilitated by their wide spatio‐temporal distribution across habitats and broad diet. Moreover, an increase in growth, but little change in tissue quality, suggests that near‐future ocean conditions will benefit fisheries and fishers that target yellowfin bream. The data reiterate the inherent resilience of yellowfin bream as an evolutionary consequence of their euryhaline status in often environmentally challenging habitats and imply their sustainable and viable fisheries into the future. We contend that widely distributed species that span large geographic areas and habitats can be “climate winners” by being resilient to the negative direct impacts of near‐future oceanic and estuarine climate change.
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Der Klimawandel wirkt an den Polen stärker als in den Tropen. Das wissen wir schon und macht auch Sinn. Störend waren bisher die Berichte aus der Antarktis. Im Maßstab der letzten 100 Jahre hat sich die Antarktis nicht erwärmt. Auch das ostantarktische Inlandeis ist ziemlich stabil, scheint in einigen Jahren eher zu wachsen als zu schmelzen. Im Jahr 2015 kam dann eine Überraschungsmeldung aus Bremen: In der Zentralantarktis besitzt der CO2-Treibhauseffekt offenbar keine erwärmende Wirkung.
Im November 2018 erschien nun in den Geophysical Research Letters eine neue Arbeit von Singh et al., die die unterschiedlichen Auswirkungen des Klimawandels auf Arktis und Antarktis untersuchte. Zunächst konzedierte die Arbeit die viel schwächeren Veränderungen in der Antarktis im Vergleich zur Arktis. Im weitere Verlauf erklären die Autoren, dass die CO2-Klimasensitivität in der Antarktis deutlich geringer als in der Arktis ist. Zudem wirken die ozeanischen Verstärkermechanismen am Südpol ganz anders als am Nordpol. Hier der Abstract:
How Asymmetries Between Arctic and Antarctic Climate Sensitivity Are Modified by the Ocean
Abstract: We investigate how the ocean response to CO2 forcing affects hemispheric asymmetries in polar climate sensitivity. Intermodel comparison of Phase 5 of the Coupled Model Intercomparison Project CO2 quadrupling experiments shows that even in models where hemispheric ocean heat uptake differences are small, Arctic warming still exceeds Antarctic warming. The polar climate impact of this evolving ocean response to CO2 forcing is then isolated using slab ocean experiments in a state‐of‐the‐art climate model. Overall, feedbacks over the Southern Hemisphere more effectively dissipate top‐of‐atmosphere anomalies than those over the Northern Hemisphere. Furthermore, a poleward shift in ocean heat convergence in both hemispheres amplifies destabilizing ice albedo and lapse rate feedbacks over the Arctic much more so than over the Antarctic. These results suggest that the Arctic is intrinsically more sensitive to both CO2 and oceanic forcings than the Antarctic and that ocean‐driven climate sensitivity asymmetry arises from feedback destabilization over the Arctic rather than feedback stabilization over the Antarctic.
Plain Language Summary: Anthropogenic greenhouse gas emissions impact climate globally, but nowhere more so than over the Arctic, a phenomenon known as polar amplification. Surprisingly, the climate response over the Antarctic is much more muted than the climate response over the Arctic, which has been attributed to the large uptake of heat over the Southern Ocean which cools the Southern Hemisphere. Here we show that a weaker climate response over the Antarctic is due, in part, to weaker intrinsic sensitivity to both greenhouse gas forcing and the state of the ocean. Even climate models with similar amounts of heat uptake into the deep ocean in both hemispheres warm more over the Arctic than the Antarctic. Furthermore, similar increases in winter season heat transport into the polar oceans in both hemispheres trigger more destabilizing climate feedbacks over the Arctic than the Antarctic. Therefore, greater climate change over the Arctic than the Antarctic can be expected even if ocean heat uptake or ocean heat transport changes are similar in both hemispheres.
