The concentration of dissolved oxygen in water tends to be lower at higher altitudes compared to lower altitudes. This is primarily due to the decrease in atmospheric pressure as you go higher in altitude. Lower atmospheric pressure means that there is less pressure forcing gases, including oxygen, to dissolve into water. However, the temperature and salinity of the water also play roles in determining the oxygen solubility.

Regarding the absorption of excess carbon dioxide (CO2) from the atmosphere by the oceans, this process occurs through a combination of physical and chemical mechanisms:

While the ocean's ability to absorb CO2 helps mitigate the impacts of excessive atmospheric CO2 on climate change, it also leads to ocean acidification. As CO2 is absorbed, it forms carbonic acid in seawater, reducing the pH and affecting marine ecosystems. Proper management of carbon emissions and sustainable environmental practices are essential to maintain the health and balance of ocean ecosystems.

Dr Gaurav H Tandon thank you for your contribution to the discussion

Water at lower altitudes can hold more dissolved oxygen than water at higher altitudes. A commonly recognized phenomenon is that as the altitude increases, the atmospheric pressure decreases. Decreased atmospheric pressure leads to a decrease in the oxygen saturation in water at higher altitudes. Therefore, the rivers and lakes at high elevations have a decreased capacity to carry dissolved oxygen (DO). Although the percentage of oxygen in inspired air is constant at different altitudes, the fall in atmospheric pressure at higher altitude decreases the partial pressure of inspired oxygen and hence the driving pressure for gas exchange in the lungs. As atmospheric pressure decreases, water boils at lower temperatures. At sea level, water boils at 212 °F. With each 500-feet increase in elevation, the boiling point of water is lowered by just less than 1 °F. At 7,500 feet, for, water boils at about 198 °F.This is due to the low air pressure. Air expands as it rises, and the fewer gas molecules—including nitrogen, oxygen, and carbon dioxide—have fewer chances to bump into each other. The human body struggles in high altitudes. Decreased air pressure means that less oxygen is available for breathing. At sea level, water boils at 100 °C (212 °F). For every 152.4-metre (500 ft) increase in elevation, water's boiling point is lowered by approximately 0.5 °C. At 2,438.4 metres (8,000 ft) in elevation, water boils at just 92 °C (198 °F).For eons, the world's oceans have been sucking carbon dioxide out of the atmosphere and releasing it again in a steady inhale and exhale. The ocean takes up carbon dioxide through photosynthesis by plant-like organisms (phytoplankton), as well as by simple chemistry: carbon dioxide dissolves in water. The ocean's average pH is now around 8.1, which is basic (or alkaline), but as the ocean continues to absorb more CO2, the pH decreases and the ocean becomes more acidic. Cold water is better at dissolving and absorbing gasses like CO2 compared to warmer water, which is why a large amount of it gets dissolved in the ocean's chilliest waters, according to the report. When that heavy water sinks to the deep sea, large portions of that CO2 can be stored for a long time. The ocean generates 50 percent of the oxygen we need, absorbs 25 percent of all carbon dioxide emissions and captures 90 percent of the excess heat generated by these emissions. It is not just 'the lungs of the planet' but also its largest 'carbon sink' – a vital buffer against the impacts of climate change. New observations from research aircraft indicate that the Southern Ocean absorbs more carbon from the atmosphere than it releases, confirming that it is a strong carbon sink and an important buffer for the effects of human-caused greenhouse gas emissions. Carbon dioxide also dissolves in seawater, where it is absorbed by seagrasses and algae. Seagrasses, which are plants adapted to live in the sea, are different from kelp and other algae in that they have roots, veins, leaves and even flowers and fruits.