A million seabirds (common murres) died in a 12-month period as the result of hot ocean waters. This mass die-off occurred between the summer of 2015 and the spring of 2016. The fate of these birds was sealed by a large patch of warm ocean water nicknamed “the Blob.”
The formation of “the Blob” in 2015-16 was not a singular event. This particular series of events occurred in the Pacific Ocean, with three major areas of elevated temperature. Two of these areas were off the coast of Alaska, and one was off the coast of Southern California.
Under the right conditions, these vast areas of overly warm seawater also form in other places around the globe. One formed at the end of 2019 just to the east of New Zealand.
These patches of superheated water are enormous. The “Blob” off New Zealand covered a million square kilometers (the size of Texas), and water temperatures were up to 5 degrees Celsius higher than normal.
How to form a “Blob”
Oceans cover 71% of the earth’s surface, and they absorb tremendous amounts of heat from solar radiation. Typically the oceans seek to dissipate this heat by circulating the water from warmer latitudes to colder latitudes. A second way to transfer heat is by releasing it into the atmosphere. This method requires that winds are stirring up the shallower waters and continually moving cooler air over the ocean surface.
When these two heat dispersal mechanisms break down, then the ocean loses its ability to transfer heat. Sunlight relentlessly beats down on the ocean day after day, warming the water. If the heat can’t escape, then the surface of the ocean has no alternative but absorb even more solar radiation. Temperatures rise, and there is no relief from the heat.
As time passes, vast areas of water at the ocean’s surface become hyper-warm. Large stretches of water develop temperatures that are 3 to 6 degrees Celsius higher than usual.
Effects on marine life
The heat from these events kills in both direct and indirect ways. A million birds did not die because of overheating; they died from starvation. Marine food chains are driven from the bottom up, and the base trophic level (bottom of the food chain) consists of phytoplankton and algae. The unfortunate fate of the murres started with a heat-induced decline of the phytoplankton/algae populations.
This population decline set off intense competition farther up the chain. So, with less food available at the base, species farther up the chain struggled to get their share of the goods. Murres compete with fish like salmon, cod, and halibut for small or medium-small sized fish. The decline in small fish
Ocean ecosystems depend on high productivity at the base of the food chain. Factors like heat and ocean acidification can effectively reduce the phytoplankton population, and thus indirectly cause the collapse of species higher up the chain.
ArcheanWeb:
Acid and phytoplankton in the ocean’s food chain (Source: ArcheanWeb) – https://archeanweb.com/2020/01/28/acid-and-phytoplankton-the-oceans-food-chain/ Also:
Changing currents cause North Atlantic ecosystem drift (Source: ArcheanWeb) – https://archeanweb.com/2020/05/07/changing-currents-cause-north-atlantic-ecosystem-drift/ Also:
Species adaptation to climate change (Source: ArcheanWeb) – https://archeanweb.com/2020/03/31/species-adaptation-to-climate-change/ Also:
Sources:
A blob of hot water in the Pacific Ocean killed a million seabirds, scientists say (By Jessie Yeung, CNN) – https://www.cnn.com/2020/01/16/world/blob-seabird-study-intl-hnk-scli-scn/index.html Also:
Feature Image: Thick-billed murres (by Greg Thomson) (Modified) – This work is in the public domain in the United States because it is a work prepared by an officer or employee of the United States Government as part of that person’s official duties
