How does global warming affect the azorean marine life?

What’s happening?

The planet is warming. Since 1880 the average temperature of the Earth’s surface has risen by about 1 degree Celsius, a trend that is driven largely by the increase in carbon dioxide and other emissions produced by the hand of men in the planet’s atmosphere. It should be noted that much of global warming has occurred in the last three decades (Vose et al., 2012).

Yearly global surface temperature from 1900–2017 compared to the 1981-2010 average (dashed line). The different colors represent different research groups’ analysis of the historical temperature record. NOAA Climate.gov graph adapted from State of the Climate in 2017

The consequences of the increase in temperatures are not hypothetical future situations to wait, the reality is that the effects are already visible today. The heat is melting glaciers and sea ice, modifying precipitation patterns and causing animals to leave their natural habitat.

One of the most worrying events that we should not forget is the increase in the temperature of the oceans. Oceans and seas absorb enormous amounts of carbon dioxide. In turn, phytoplankton absorb carbon dioxide and release oxygen, which makes them indispensable for the creation of life and essential for the survival of human beings. In addition, they regulate the climate and define to a large extent the distribution of fauna and flora. They are an immeasurable source of resources among other important functions. A small increase in its temperature could have catastrophic consequences. 

Atlantic Ocean specific case: Atlantic Meridional Overturning Circulation 

The Atlantic Meridional Overturning Circulation (AMOC) is a net of oceanic currents all around the Atlantic Ocean. Its two main components, both involved in the global termohaline circulation, are a superficial northward flow of warm salty water and a deep southward flow of colder water. These different flows converge in regions of the Nordic and Labrador seas, where the cold dense flow sinks deep into the ocean, and in the Southern Ocean, where it gets pulled back to the surface in a process called “upwelling”.

The AMOC (and the termohaline circulation) is directly involved on Earth’s climate, redistributing heat and influencing the carbon cycle in great measure, its correct functioning and stability are essential for life on Earth.

Although the evolution of the AMOC during the industrial era is poorly known, a weakening has been observed in recent years. There’s evidence that Labrador Sea deep convection and the AMOC have been anomalously weak over the past 150 years or so compared with the preceding 1,500 years (Thornalley et al., 2018). 

How is Azores archipelago affected? 

The Azores archipelago is directly affected by these oceanic currents, located on one of the south branches of the Gulf Stream that then continues its way towards the Canary Islands. Any disturbance on the AMOC could affect greatly to marine life on these islands and the whole culture around it. For example, some recently published studies, have reported the increase of sightings of tropical fishes in the archipelago in the last few years (Afonso, 2013). 

What about the fauna?

There is a growing concern suggesting that many marine ecosystems in European seas are affected by rising sea temperature and the warming of the air. Some organisms, like long-finned pilot whales (Globicephala melas), are now appearing earlier in their seasonal cycles than in the past as they track changing surface temperatures that define their thermal niche (Gibson et al. 2007).  Others are changing their distribution or adapting it to the distribution of its prey. The ranges of 88% of cetaceans may be affected by changes in water temperature resulting from global climate change (MacLeod et al., 2009). Marine species are able to adapt genetically to changing conditions. However, with the current pace of climate warming this may not happen fast enough because genetic changes require several reproductive cycles to occur. We may have arrived to an irreversible point, but we have to stay hopeful and act immediately towards a more sustainable future. From a wider perspective, governments need to adapt their policies to prioritise natural conservation and fossil-free energy among many other initiatives. From a closer perspective each one of us can contribute to a cleaner world: reducing, reusing and recycling, using public transport, saving energy, educating ourselves and sharing our knowledge. Many drops make an ocean.

Article by marine biologist, Iñaki Ibarzabal 

References

Vose, R. S. et al. (2012) NOAA’s Merged Land–Ocean Surface Temperature Analysis. Bulletin of the American Meteorological Society

Thornalley, D. et al. (2018) Anomalously weak Labrador Sea convection and Atlantic overturning during the past 150 years. Nature 556(7700)

Afonso, P. et al. (2013) New and rare coastal fishes in the Azores islands: occasional events or tropicalization process?. DOI: 10.1111/jfb.12162.

Gibson, N. et al. (2007) Potential Effects Of Climate Change On Marine Mammals. DOI: 10.1201/9781420006391.ch8.

MacLeod, C. et al. (2009) Global climate change, range changes and potential implications for the conservation of marine cetaceans: a review and synthesis. Endang Species Res 7: 125–136