Chemistry Unit

Properties of Water and their Relationship to Weather and Climate

The Three Phases of Water Solid: Ice Liquid: Water Gas: Water Vapor When water changes phases, a large amount of energy is absorbed or released.

Theoretically liquid water turns into… Ice at 0 o C – When water turns into ice it gives out a large amount of energy Vapor at 100 o C – When water turns into vapor it absorbs a very large amount of energy What causes water to change phase?

0n the Earth water can turn into the gas phase when the temperature is much lower than 100 o C. Evaporation can happen at any temperature, but as the temperature increases evaporation increases. Evaporation also relates to the humidity of the air and the availability of water on the ground. If it is over the ocean, then there is plenty of water to evaporate. Humidity: the amount of water vapor in the air. It indicates the likelihood of – Precipitation – Dew – Fog 100% humidity means that the air is fully saturated with water vapor. What causes water to change phase?

How are the different phases of water distributed on the Earth? Where are the liquid phases of water? – In the oceans (mostly) Where are the solid phases of water? – In ice Where are the gas phases of water? – In the air % of water is liquid, 1.7% solid, and only 0.001% as gas.

The distribution of the solid phase of water on the Earth. Icebergs and other sea ice floating on the ocean Ice sheets on land – Greenland – Antarctica – Alaska Mountain glaciers

The distribution of the solid phase of water on the Earth. Icebergs and other sea ice floating on the ocean Ice sheets on land – Greenland – Antarctica – Alaska Mountain glaciers

The distribution of the solid phase of water on the Earth. Icebergs and other sea ice floating on the ocean Ice sheets on land – Greenland – Antarctica – Alaska Mountain glaciers

By far most of the water is in the ocean – 96.5%! The distribution of the liquid phase of water on the Earth.

Ocean water contains dissolved minerals – “salt” – Salt water is denser than freshwater because of the dissolved salts -- the higher the salinity (more salt in the water) the greater the density. Salt water freezes at a lower temperature than fresh water. – The higher the salinity the lower the freezing/melting point. Salt water boils at a higher temperature than fresh water – The higher the salinity the higher the boiling/condensation point. The distribution of the liquid phase of water on the Earth – the oceans.

Density of seawater – Increases with increasing salinity and decreasing temperature. – Increases with increasing pressure – pressure increases with depth. Ocean layered according to density – Halocline: Salinity gradient – Thermocline: Temperature gradient – Pycnocline: Density gradient The distribution of the liquid phase of water on the Earth – the oceans.

Halocline: zone of rapid change of salinity with depth. Dense water is heavy and sinks below less dense layers. The distribution of the liquid phase of water on the Earth – the oceans

Thermocline: zone in which temperature decreases rapidly with depth. 3 zones in ocean based on temperature variation: – Surface zone – Thermocline – Deep zone Notice that temperature in the deep ocean is similar in low and high latitudes. Changes in the thermocline (e.g., the slope of it) can have a significant influence on global climate. The distribution of the liquid phase of water on the Earth – the oceans

Pycnocline: zone in which density increases rapidly with depth. – Thermocline & halocline together make the pycnocline. The distribution of the liquid phase of water on the Earth – the oceans

Water vapor in the air is called humidity. Humidity: the amount of water vapor in the air Water vapor content (humidity) decreases with increasing altitude. As the temperature of the air decreases the amount of water vapor (humidity) that can be held in the air decreases. The distribution of the gas phase of water on the Earth – the air.

How is water vapor distributed by latitude? These different “air masses” move around and cause weather phenomena, such as cold fronts and warm fronts. The distribution of the gas phase of water on the Earth – the air.

Temperature, density, and pressure differences in the atmosphere: Temperature varies as altitude increases. Density decreases as altitude increases. Pressure decreases as altitude increases. The distribution of the gas phase of water on the Earth – the air.

What happens to the gas phase when the vapor rises through the atmosphere and cools down? The water vapor will condense creating clouds When the clouds become supersaturated (have a humidity higher than 100%) they form rain (or snow depending on the air temperature). The distribution of the gas phase of water on the Earth – the air.

The distribution and movement of air with different temperature and water vapor content have significant control over weather conditions. For example: What makes a cold front? – Pressure differential – Temperature difference The distribution of the gas phase of water on the Earth – the air.

The distribution of solid, liquid, and gas phases of water affect weather and climate. The amount and distribution of different phases of water largely controls the earths weather and climate: – Short-term changes, e.g., in days to months, cause different weather conditions. – Long-term changes, e.g., in 10s to 100s of years, cause climate change.

Let’s look at the overall budget of water on earth. Percentage of the phases of water found on Earth – Solid: 1.7% – Liquid: % – Gas: 0.001% How does the distribution of solid, liquid, and gas phases of water affect weather and climate?

What if this particular balance changes?? Assume 1.7% in ice now. What if 2.7% of the water is in ice? Then there is 1% less water in the ocean. – That means sea level is much lower. So what if 0.7% of water is in ice? – That means sea level is much higher. How does the distribution of solid, liquid, and gas phases of water affect weather and climate?

Let’s think about what can change the water budget: – What would increase the amount of solid water on the earth? – What would increase the amount of liquid water on the earth? How does the distribution of solid, liquid, and gas phases of water affect weather and climate?