Norwegian researchers studied ancient ocean level fluctuations over a period of 320 million years and concluded that our planet underwent several periods of rapid true polar wandering in the past.
According to the results presented in the article published in the scientific journal Science, three such episodes were identified in the Mesozoic and one in the Cenozoic. The data obtained from the analysis of sea level changes partially align with previous conclusions based on paleomagnetic studies.
Researchers have discovered that planetary warming has the potential to modify the circulation of the Pacific Ocean, resulting in the 'aging' of its waters in certain areas, while other regions may become relatively 'younger'. This transformation can lead to negative consequences for marine life across multiple layers of the ocean.
The conclusion of this study was published in the journal AGU Advances. Using oceanic circulation models, the team investigated how rising temperatures modify the movement of water masses in the Pacific and identified the effects in different zones of the ocean.
It is important to note that, in this context, the 'age' of the water does not refer to the time existence of the molecules, but rather to the period during which that mass of water remained without interacting with the atmosphere. This atmospheric contact is crucial because it allows the water to absorb oxygen before being carried to greater depths.
'Young' water has had recent proximity to the surface and has been aerated by the atmosphere; subsequently, it can sink, carrying the absorbed oxygen. Conversely, 'old' water has spent a longer period isolated from the atmosphere while circulating in the depths, a time when marine organisms consume some of the dissolved oxygen, decreasing its concentration.
The scientists primarily focused on the Pacific thermocline, a layer located approximately between 200 and one thousand meters deep, where the contrast is pronounced. Subtropical regions that currently receive relatively new water may become older, while parts of the tropical Pacific, which already contain old and poorly ventilated waters, may become relatively younger.
A fundamental principle for understanding the findings is oceanic stratification. When the sea surface warms, it intensifies the disparity between surface water and deeper waters, hindering circulation between these levels.
In this area, the process leads to more superficial circulation. Water sinking in subtropical regions only ventilates a smaller layer of the ocean, which reduces the transport of young, oxygen-rich water to the deeper parts of the thermocline. Consequently, these waters tend to age and lose oxygen.
This phenomenon does not occur uniformly throughout the Pacific. In tropical zones, warming decreases the upward movement of deep waters, which normally bring old, low-oxygen water to the surface. With this reduction in flow, tropical waters may become relatively younger and suffer less oxygen loss compared to subtropical regions.
The information was obtained through models that simulated how global warming would modify the circulation of the Pacific Ocean. To validate the results, several scenarios were developed simulating temperature increases across the entire ocean and others where specific regions were warmed.
After simulating these scenarios, the authors compared the results with data from 14 climate models and oxygen measurements taken in the ocean, exposing possible changes.
Dissolved oxygen is vital for marine life established under such conditions. Therefore, any alteration in ocean circulation can profoundly impact various species residing in these areas.
In addition to the decrease in oxygen, the increase in water temperature itself can alter ecosystems. Species adapted to specific climatic and oxygen conditions may see their habitats reduced or be forced to migrate to other locations.
Given this, the researchers of the study advocate for deepening the analysis of this warming and the probable 'new circulation,' aiming for a better understanding of its impacts and the possibility of adaptation for affected marine life.
