Yes, it's true that's the intensity of evaporatiion more water molecules heat up vaporized. While less or no evaporation in winter at polar regions. Sun declined because of seanal variations of equinoxes and solstices.

Dr Ibrahim Sufiyan thank you for your contribution to the discussion

Thank you Prof

The hot temperature near the equator reduces the dissolved oxygen from the ocean water and as we move at higher latitudes, the temperature decreases, and thus the dissolved oxygen increases in the ocean.In the Polar Regions sunlight hours are lesser in winter than summer​becauseof the earth's tilt and orbit around the sun, the poles receive less energy and heat from the sun. This results in only two polar seasons’ summer and winter. In summer at the poles, the sun does not set, and in winter the sun does not rise. If the Earth's axis were at right angles to its orbit there would be no seasons. Due to its inclination, however, the northern hemisphere faces toward the sun during the northern summer and receives more sunlight, but in the northern winter it is tilted away from the sun and thus receives less radiation. Earth receives different amounts of solar energy at different latitudes, with the most at the equator and the least at the poles. Both the Arctic (North Pole) and the Antarctic (South Pole) are very cold because they get very little direct sunlight. The Sun is always low on the horizon, even in the middle of summer. In winter, the Sun is so far below the horizon that it doesn't come up at all for months at a time. The Poles experience about six months of day and six months of night because of the tilt of the Earth on its axis. Because of this tilt each Pole is tilted towards and away from the Sun for about six months each. When the North Pole is tilted towards the Sun it experiences continuous daylight for six months. The oxygen minimum zone (OMZ), sometimes referred to as the shadow zone, is the zone in which oxygen saturation in seawater in the ocean is at its lowest. This zone occurs at depths of about 200 to 1,500 m (700–4,900 ft), depending on local circumstances. Extensive measurements have shown that the highest oxygen concentrations are found at high latitudes, where the ocean is cold, especially well-mixed and ventilated. The mid-latitudes, by contrast, especially on the western coasts of the continents, are characterized by marked oxygen-deficient zones.Excess nutrients delivered to a water body can lead to both overgrowth of algae and eutrophication. As dead algae decompose, oxygen is consumed in the process, resulting in low levels of oxygen in the water. In some cases, large areas of water may become hypoxic.

There are a few reasons why there is less oxygen in ocean water near the equator than in water at higher latitudes.

• Temperature: The solubility of oxygen in water decreases with increasing temperature. This means that warm water can hold less oxygen than cold water. The water near the equator is warmer than the water near the poles, so it has less oxygen.
• Upwelling: Upwelling is the process of deep, cold water rising to the surface. This brings oxygen-rich water to the surface, where it can be used by marine life. Upwelling is more common in the higher latitudes than in the equatorial regions.
• Circulation: The ocean currents help to mix the water and distribute oxygen throughout the ocean. The currents are stronger in the higher latitudes than in the equatorial regions, so they are better able to distribute oxygen.
• Respiration: Marine life respire, which means they take in oxygen and release carbon dioxide. The amount of respiration is higher in the equatorial regions than in the higher latitudes, because there is more life there.
• Climate change: Climate change is causing the oceans to warm, which is leading to a decrease in oxygen levels. This is especially true in the equatorial regions, where the water is already warm.

The sunlight hours are less in winter than in summer at the polar regions, but this does not have a significant impact on the oxygen levels in the ocean. The main reason for the low oxygen levels in the polar regions is the cold temperature.

The combination of these factors leads to lower oxygen levels in the ocean water near the equator than in water at higher latitudes. This can have a negative impact on marine life, as they need oxygen to survive.

Here are some additional things to note:

• The oxygen minimum zones (OMZs) are the places in the world ocean where oxygen saturation in the water column is at its lowest. These zones are typically found in the tropical and subtropical regions, where the water is warm and there is less upwelling.
• The OMZs are expanding and becoming more severe due to climate change. This is a major threat to marine life, as many species cannot survive in low-oxygen conditions.
• There are a number of things that can be done to help mitigate the problem of low oxygen levels in the ocean. These include reducing greenhouse gas emissions, improving water quality, and protecting marine ecosystems.

Dr Murtadha Shukur thank you for your contribution to the discussion

Yes, the Earth's axis were at right angles to its orbit there would be no seasons. Due to its inclination, however, the northern hemisphere faces toward the sun during the northern summer and receives more sunlight, but in the northern winter it is tilted away from the sun and thus receives less radiation. In the Polar Regions sunlight hours are lesser in winter than summer​Because of the earth's tilt and orbit around the sun, the poles receive less energy and heat from the sun. This results in only two polar seasons’ summer and winter. In summer at the poles, the sun does not set, and in winter the sun does not rise. In summer, the Northern hemisphere tilts towards the sun. This means regions around the North Pole receive many hours of sunlight every day. In winter, the Northern Hemisphere tilts away from the sun. This means the regions around the North Pole receive very little sunlight. Earth receives different amounts of solar energy at different latitudes, with the most at the equator and the least at the poles. Both the Arctic (North Pole) and the Antarctic (South Pole) are very cold because they get very little direct sunlight. The Sun is always low on the horizon, even in the middle of summer. In winter, the Sun is so far below the horizon that it doesn't come up at all for months at a time. Thus the tropics receive more intense sunlight and a greater amount of heating per unit of area than the Polar Regions. Because of the curvature of the Earth, the same amount of sunlight will be spread out over a larger area at the poles compared to the equator. Due to the spherical shape of the Earth, sunlight falls on different parts at different angles. Direct and focused sun rays falls on the equator and hence, the regions here are hotter and warmer. The Polar Regions receive diffused sun rays, which is why the areas there are colder. Oxygen gets into the sea in two ways: through photosynthesis, which takes place only near the top where light penetrates, or through the mixing of air and water at the surface by wind and waves. Deep ocean waters hold far less oxygen than surface waters because they haven't been in contact with air for centuries. The oxygen minimum zone (OMZ), sometimes referred to as the shadow zone, is the zone in which oxygen saturation in seawater in the ocean is at its lowest. This zone occurs at depths of about 200 to 1,500 m (700–4,900 ft), depending on local circumstances. Dissolved oxygen levels drop in a water body that contains a lot of dead, decomposing material. Elevation- the amount of oxygen in elevation increases. Since streams get much of their oxygen from the atmosphere, streams at higher elevations will generally have less oxygen.The amount of oxygen in the air goes down as you climb higher above sea level and becomes very low at altitudes above 8,000 feet. If you travel to a high altitude, you may feel ill because the air has less oxygen in it.

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