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2.2 Climate change effects: Water – Flooding and Thawing

Author: Anneka Muther

ABSTRACT: Climate change and the Earth’s water cycle are closely connected to one another in different ways, both directly and indirectly. The primary impact of climate change on the water cycle is the influence over when, where, and how much precipitation falls. The influence of climate change on the nature of precipitation can lead to further impacts.

Water Cycle Map from NASA Science

MAIN:

Climate refers to the prevailing weather conditions such as temperature, air pressure, humidity, sunshine, clouds and winds. The Earth’s climate emerges from the interactions of the five major climate system components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (Earth’s crust and upper mantle) and the biosphere (living things).

The climate system is subject to changes because of external forcings, typically natural, as well as internal variability, which can be both natural and human induced. An example of a natural external forcing is what is commonly known as seasons, which is a result of the tilt in the Earth’s axis of rotation in relation to the Earth’s orbital plane of approximately 23.4 degrees. A natural internal variation refers to any changes of the climate system because of a natural external forcing (seasons), for example lower temperatures in the winter season or higher temperatures in the summer season.

Human induced internal variations are the multitude of ways humans create changes in the climate system both directly and indirectly. These factors that affect global climate change include atmospheric circulation, ocean currents, global climate, biogeography, distance between land and sea, shape of land and distance from the equator.

Water is an inorganic chemical substance that is the main constituent of earth’s hydrosphere (one of the five major climate system components), and the fluids of all living organisms. It is also vital for all known forms of life. Water on earth exists in four forms, making water a common aspect in each of the climate system components: atmospheric water as clouds and vapour, liquid water as oceans, lakes and rivers, frozen water as snow, ice and glaciers, and underground water as soil and rocks.

Water is always on the move, and it does this through the water cycle by changing through the different states and moving energy throughout the climate system. Water at the surface of the ocean, rivers and lakes can become water vapour and move into the atmosphere with little added energy from the sun, through a process called evaporation. Snow and ice can also become water vapour through a process called sublimation. Water vapour gets into the atmosphere from plants by a process called transpiration.

Because air is cooler at higher altitudes, water vapour cools as it rises higher in the atmosphere and transforms into water droplets by a process called condensation. The water droplets that form make up clouds. Water vapour can also condense into droplets near the ground, forming fog when the ground is cold. If the temperature is cold enough, ice crystals form instead of liquid water droplets. If the droplets or ice crystals with clouds grow in size, they eventually become too heavy to stay in the air, falling to the ground as rain, snow, or other types of precipitation.

The water cycle is associated with the exchange of energy which leads to temperature changes. As water evaporates, energy from the surroundings is taken in, creating a cooling effect on the environment. When water is condensed, energy is released, creating a warming effect on the environment.

Warming conditions have an impact on our planet. In general, it looks like more oceans, less ice, and changing weather. Because the water cycle is essential for the maintenance of most life and ecosystems on the planet, climate change effects on water are widespread.

Rising sea levels are a threat to coastal communities, wetlands, and coral reefs. This changes the biogeography as well as the shape of the land. The rising sea level is in part because of melting glaciers which runs down though streams and rivers into the ocean. This changes the shape of the land, the biogeography as well as the distance between the land and sea.

Though, each year sea ice forms and melts due to seasons, the amount of sea ice forming has decreased, while the amount of melting has increased. This affects ocean currents, atmospheric circulation as temperature and density of water changes.

Healthy soil is normally like a sponge that soaked up a lot of water. However, when we cut down the forests, plow the grasslands, expose the soil, and put concrete over top, heavy downpours compact the soil. The water cannot soak down into the compacted ground. Almost all of it stays above ground, and we have a flood. This can then lead to a flood-drought cycle.

The thawing permafrost and increased precipitation have made the land wetter. Snow and rain create a vicious cycle of thawing and flooding.

RESOURCES:

Fecht, Sarah. “How Climate Change Impacts Our Water.” State of the Planet, Columbia Climate School, 23 Sept. 2019, https://news.climate.columbia.edu/2019/09/23/climate-change-impacts-water/

Royal Meteorological Society. “In Depth – The Water Cycle .” MetLink, Royal Meteorological Society, 4 Jan. 2021, http://www.metlink.org/resource/in-depth-the-water-cycle-met-office/

ScienceBlog.com. “Arctic Permafrost Thaw Plays Greater Role in Climate Change than Previously Estimated.” ScienceBlog.com, 4 Feb. 2020, https://scienceblog.com/513915/arctic-permafrost-thaw-plays-greater-role-in-climate-change-than-previously-estimated/

NASA. “GPM water cycle map.” Global Precipitation Measurement: GPM Science Objectives. National Aeronautics and Space Administration. 9 Dec. 2021, https://www.nasa.gov/mission_pages/GPM/science/index.html   

NASA Science. (2007) “Water Cycle” Science Mission Directorate, NASA Science,https://science.nasa.gov/earth-science/oceanography/ocean-earth-system/ocean-water-cycle

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