Oceans on high heat

Recent data shows that the oceans are warming at the fastest rate in history, creating harm to marine biodiversity, rising sea levels and increased risk of extreme weather events. What are we doing in Israel to prepare for this new reality?

Ran Ben Michael, Angle - Environmental Science News Agency

In an article published in February 2020 in the Journal of Atmospheric Sciences of the Chinese Academy of Sciences, a Chinese-American team that included 14 scientists from 11 research institutions surveyed the trend of ocean temperature changes in recent decades. Among the many numerical data in the report, the alarming picture of the situation is clearly depicted: in the 32 years from 1987 to 2019, the rate of warming of the upper 2000 meters of the oceans increased 4.5 times relative to the corresponding period until then (1986-1955) and the ongoing warming trend is even steadily accelerating In recent decades (1995-2019).

As the concentration of greenhouse gases increases in the atmosphere and more heat energy is trapped in the earth, the heat content stored in the oceans increases. It is estimated that the oceans absorb over 90 percent of the excess heat energy that is added due to the increased greenhouse effect by the increased emissions of greenhouse gases due to human activity.

According to these findings, the average temperature in the oceans in the water layer from the surface to a depth of 2,000 meters in 2019 was 0.075 degrees Celsius higher than the average temperature in 2010-1981. That doesn't sound like much, but it represents a huge amount of heat stored in the ocean water. how much 228 Zeta-Joule. Joule is a unit of energy and in terms of heat it is the energy required to raise one gram of water by 0.24 degrees Celsius. Zeta is 10 to the power of 21 (ie 21 zeros after the number 228) - in short, a tremendous amount of energy.

To describe it in other terms, the researchers compared the amount of heat accumulated by the oceans in the last 25 years to the amount that would be emitted from 3.6 billion atomic bombs like the one dropped on Hiroshima. Prof. Hezi Gildor, a physical oceanographer from the Institute of Earth Sciences at the Hebrew University believes that "such a figure could indicate a sea level rise of several centimeters".

Slow changes and extreme events

The accelerated warming of the oceans accelerates processes of sea level rise (both due to the thermal expansion of the ocean water and due to the acceleration of the melting of the glaciers), this alongside an increase in the acidity level of the sea water and increasing the potential for the formation of extreme weather events. Thus, for example, torrential rains are caused in part because of the rapid evaporation rate of the warming sea water. At the beginning of January 2020, such an event flooded Jakarta, the capital of Indonesia, during which at least 66 people were killed. The intensity of hurricanes Harvey and Florence (which occurred in 2017 and 2018, respectively) was also apparently higher due to the warming of the Atlantic Ocean.

Similar to the land, extreme heat waves occur in the ocean waters which cause the death of coral reefs ('bleaching events') and other damages to the biological diversity in the sea: in 2015-2013 such a heat wave, which was 2.5 degrees above average and spread over a huge area, wiped out 100 million cod fish in the vicinity to Alaska and caused 100 million dollars a year in damage to the fishing industry. The heat wave also caused the death of many other creatures, starting with tiny phytoplankton (microalgae and cyanobacteria), through about a million seabirds, and ending with whales that washed up dead on the beaches. A similar event occurred in 2013 off the coast of Australia, where the high temperatures led to a widespread bloom of toxic algae that caused the death of dozens of fish species and other marine creatures.

Less oxygen in the water

In 2019, some of the members of the Chinese-American team published an article in the journal Science in which they stated that the sea surface temperature is warming at a faster rate by 40 percent than previous estimates and linked this warming to a series of phenomena, one of which worries many experts - the depletion of oxygen in the water.

This happens because when the water warms, it is able to contain less dissolved oxygen, which may harm marine animals if the concentration of oxygen in the water drops below a critical threshold for their activity (as we suffer at low-oxygen altitudes). According to a report by the International Union for Conservation of Nature, there are currently 700 sites in the oceans that suffer from a lack of oxygen, this is mainly due to the discharge of fertilizers and sewage from land, which cause the marine environment to be enriched with nutrients (eutrophication), which causes increased activity of bacteria and increased oxygen consumption (in the 60s there was Only 45 such sites are known).

About three years ago, experts from the Ocean Research Institute estimated that since the middle of the 20th century, the amount of dissolved oxygen in the oceans has decreased by about 2 percent on average (a total decrease of 77 billion tons of oxygen), mainly in the upper water layers, which are rich in biological diversity, but in certain areas such as the coast of Southern California , it decreased by about 33 percent. In such areas, the abundance of species such as jellyfish increases and the presence of other species decreases - for example, of edible fish such as finfish or tuna fish - which causes economic and nutritional damage.

"In the eastern Mediterranean, the surface of the water heats up relatively quickly compared to other places. Warming is also evident in the middle water layer. The water column becomes more stable due to this and there are less natural mixing processes between the layers, so less nutrients come from the depth, and less oxygen comes from the surface. Beyond the effects on the weather, these changes have effects on the ecosystem," says Gildor

Various environmental organizations are pointing to a series of steps to prepare for the warming of the ocean waters, first of all the protection of 30 percent of the ocean surface by 2030, through international agreements and the establishment of national and multinational marine reserves, which are required to mitigate the climate crisis and save part of the biological diversity and benefits provided by nature the marine

Israel currently has only seven small marine reserves close to the coast, on the Mediterranean coast," says Dr. Nega Sokolover, the coordinator of the marine reserves program at the Israel Society for Ecology and Environmental Sciences. "The Nature Reserves and Gardens Authority is promoting a plan to announce a network of large reserves that will protect about 20 percent of Israel's economic water surface. The guiding principle in the planning of the reserves is to maintain a variety of habitats. Also a unique habitat like the Achziv Canyon, of which there is only one like it, and also sandy habitats that characterize most of the shallow area on our beaches."

"At the same time as the planning and bureaucratic operations until the declaration is completed, the Nature Reserves and Gardens Authority together with the Israel Association for Ecology and Environmental Sciences are promoting dedicated studies dealing with the functioning and management of these reserves. The studies discuss the spillover effect of fish outside the reserve, the effect of invasive oysters on the functioning of the ecosystem, mapping areas where there is high biological diversity or ecological importance for certain species, geological and biological mapping of areas where our knowledge is little, examining the connectivity between the proposed reserves, and examining monitoring plans are adapted to Shikomo reserves", Sokolover concludes.

More of the topic in Hayadan:

• Additional evidence of global warming is obtained from sea level measurements around Antarctica
• The corals reveal: the sea will rise, and quickly
• The coral reef in Eilat is still withstanding the rising sea water temperature, the question is until when