There are two main reasons why there is more oxygen at sea level than at higher altitudes.

• The amount of air molecules decreases as altitude increases. This is because the atmosphere is held to the Earth by gravity, and the higher up you go, the less gravity there is to hold the air molecules in place. As a result, the air molecules spread out more and there are fewer of them per unit volume.
• The atmospheric pressure decreases as altitude increases. Atmospheric pressure is the force exerted by the weight of the air above us. As altitude increases, the air column above us gets shorter, so the pressure exerted by the air decreases. This means that there is less pressure pushing the oxygen molecules into our lungs when we breathe.

The ocean holds more carbon than the atmosphere because of the following reasons:

• The ocean is much larger than the atmosphere. The ocean covers about 71% of the Earth's surface, while the atmosphere only covers about 0.001% of the Earth's surface. This means that there is much more water in the ocean than there is air in the atmosphere.
• Carbon is more soluble in water than in air. This means that carbon molecules can more easily dissolve in water than they can in air. This is why we find carbon dioxide dissolved in the ocean, but not in the atmosphere.
• The ocean is a major sink for carbon dioxide. The ocean absorbs carbon dioxide from the atmosphere through a process called photosynthesis. Photosynthesis is the process by which plants use sunlight to convert carbon dioxide and water into oxygen and sugar. The ocean is home to a vast amount of plant life, so it absorbs a lot of carbon dioxide from the atmosphere.

In addition to these reasons, the ocean also holds more carbon than the atmosphere because of the following factors:

• The ocean is constantly circulating. This mixing helps to distribute carbon throughout the ocean, making it more difficult for it to escape into the atmosphere.
• The ocean is deep. The ocean is very deep, and carbon can be stored in the deep ocean for thousands of years.
• The ocean is cold. Carbon dioxide is more soluble in cold water than in warm water. This means that the ocean can store more carbon when it is cold.

As a result of these factors, the ocean holds about 50 times more carbon than the atmosphere.

The concentration of oxygen in the atmosphere is fairly consistent up to an altitude of about 10,000 meters (32,800 feet), which is roughly the cruising altitude of commercial airplanes. Above this altitude, oxygen concentrations start to decrease due to the lower atmospheric pressure at higher altitudes. At sea level, the atmospheric pressure is greater, which means that a larger number of oxygen molecules are present in a given volume of air compared to higher altitudes where the pressure is lower.

The relationship between altitude and oxygen concentration is described by the barometric formula, which states that the partial pressure of a gas in a mixture (like the atmosphere) decreases exponentially with increasing altitude. As you go higher in altitude, the air pressure decreases, and so does the partial pressure of oxygen. This is why people can experience altitude sickness or reduced oxygen levels at high altitudes.

As for the ocean holding more carbon than the atmosphere, this is primarily due to the ocean's larger capacity to dissolve gases like carbon dioxide (CO2) and its various mechanisms for carbon storage:

Overall, the ocean's immense size, its solubility properties, and its dynamic processes make it a crucial component of the Earth's carbon cycle and a major sink for carbon dioxide. However, excessive carbon emissions can lead to ocean acidification and other environmental impacts, highlighting the importance of responsible carbon management and climate mitigation efforts.

Dr Srinivasa Rao Neerukattu and Dr Gaurav H Tandon thank you for your contribution to the discussion

The air at higher altitudes is colder, less dense, and contains fewer oxygen molecules. This means that you need to take more breaths in order to get the same amount of oxygen as you would at lower altitudes. The higher the elevation, the more difficult breathing becomes. The lower the altitude, the richer the mix of oxygen in the air. A move from a high altitude to a significantly lower altitude will very likely lessen your need for an oxygen tank to deal with COPD. 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. Sea air, which contains iodine, salt, and magnesium, encourages respiratory health and can reduce the symptoms of asthma, promote respiratory health, improve allergies and skin problems, and stimulate the immune system. At rest, ventilation increases by firstly increasing the tidal volume, at least up to 3500 m above this altitude, also the breathing rate significantly increases. Atmospheric pressure decreases with increase in altitude. Therefore, as we go higher the pressure within the blood vessels exceeds the outside pressure. This causes the blood vessels to rupture. As a result, a mountaineer suffer nose bleeding, ear bleeding etc. Carbonic acid releases hydrogen ions, which combine with carbonate in seawater to form bicarbonate, a form of carbon that doesn't escape the ocean easily. As we burn fossil fuels and atmospheric carbon dioxide levels go up, the ocean absorbs more carbon dioxide to stay in balance. The total amount of carbon in the ocean is about 50 times greater than the amount in the atmosphere, and is exchanged with the atmosphere on a time-scale of several hundred years. At least 1/2 of the oxygen we breathe comes from the photosynthesis of marine plants. he ocean absorbs carbon dioxide from the atmosphere wherever air meets water. Wind causes waves and turbulence, giving more opportunity for the water to absorb the carbon dioxide. Fish and other animals in the ocean breathe oxygen and give off carbon dioxide (CO2), just like land animals. The ocean plays a critical role in carbon storage, as it holds about 50 times more carbon than the atmosphere. Two-way carbon exchange can occur quickly between the ocean's surface waters and the atmosphere, but carbon may be stored for centuries at the deepest ocean depths.