Global warming is causing global mean sea level to rise in two ways. First, glaciers and ice sheets worldwide are melting and adding water to the ocean. Second, the volume of the ocean is expanding as the water warms.

Melting ice causes more warming. As global warming causes more snow and ice to melt each summer, the ocean and land that were underneath the ice are exposed at the Earth’s surface. Because they are darker in color, the ocean and land absorb more incoming solar radiation, and then release the heat to the atmosphere.

If all the ice covering Antarctica , Greenland, and in mountain glaciers around the world were to melt, sea level would rise about 70 meters (230 feet). The ocean would cover all the coastal cities. And land area would shrink significantly. That’s because the ice doesn’t just melt.

When glaciers melt, because that water is stored on land, the runoff significantly increases the amount of water in the ocean, contributing to global sea level rise.

The primary reason is the salinity. The salt lowers the freezing point and increases the density. So saltier water freezes at a lower temperature and sinks to the bottom. So any cold water near the ocean bottom that is nearing the freezing point will generally rise, lower its salinity, and then not freeze.

We know that fresh water freezes at 32 degrees Fahrenheit. However, the mixture of water and salt needs much colder temperatures to freeze. This is why the ocean only freezes in very cold places, near land closer to the north and south poles.

When sunlight hits the ocean, water absorbs the red, orange, yellow, and green wavelengths of light so that we see just the remaining wavelengths of blue and violet. If you’ve ever been out to sea, you know that the further out you go, the darker blue the water gets as it gets deeper.

The ideal temperature for swimming at sea is 84 degrees 66°F to 70°F (19°C to 22°C): You swim on the west coast. 78°F to 84°F (27°C to 29°C): That is the ideal bathing temperature for long bathing. Entry into the water is not aggressive and relatively bearable. This is a standard lagoon temperature.

77-82F(25-28C) Swimming pool temperature range for Olympic competition. 70F(21C) Water feels quite cold to most people. Treat any water temperature below 70F (21C) with caution. 40F(4.4C) or lower Water is painfully cold.

According to the World Health Organization, water temperatures ranging from 78 to 86 degrees Fahrenheit are generally comfortable and safe for those engaging in moderate physical activity in a pool. Conversely, swimming in temperatures below 70 degrees Fahrenheit can lead to increased heart rate and blood pressure.

Hypothermia can occur when you are exposed to cold air, water, wind, or rain. Your body temperature can drop to a low level at temperatures of 50°F (10°C) or higher in wet and windy weather, or if you are in 60°F (16°C) to 70°F (21°C) water.