Antarctica – officially desert, technically the largest freshwater reservoir

Antarctic H2O

About 98% of Antarctica is covered by ice that averages 1.9 km in thickness, which extends to all but the northernmost reaches of the Antarctic Peninsula. Because of its massive glacier layer, the continent is the largest reservoir of fresh water in the world. Antarctica is a desert, with annual precipitation of only 50-200 mm along the coast and far less inland.

Quick facts

The lowest measured temperature was recorded in 1983 by Russian explorers near Russian research station called Vostok. The temperature then dropped to –89, 2 °C (which is also the lowest temperature ever recorded on Earth). The climate is so harsh in Antarctica that no people have ever settled here. All commodities (including fuel, food and fresh water) are imported by aircrafts or by icebreakers (and then tracked via the South Pole Traverse to the inland areas). The only inhabitants of this continent are scientists who are working on research projects in scientific facilities or research stations. Organisms native to Antarctica include many types of bacteria, plants and certain animals, such as mites, penguins, seals, and tardigrades. Vegetation, where it occurs, is tundra.

Antarctic bottom water

The Antarctic bottom water is a type of water mass in the Southern Ocean surrounding Antarctica with temperatures ranging from −0.8 to 2 °C. Antarctic bottom water is the densest and one of the saltiest water mass of all ocean. Its high level of salinity its density causes that the water does not freeze when its temperature drops below 0 ° C. Antarctic Bottom Water is formed in a few distinct locations around Antarctica, where seawater is cooled by the overlying air and made saltier by ice formation. The dense water then sinks to the sea floor and spreads northward, filling most of the deep ocean around the world as it slowly mixes with warmer waters above it.

A layer of Antarctic Bottom Water colder than 0ºC (colors, with darkest blue areas having the thickest layer, and white none) covers the ocean floor around Antarctica (center, shaded grey). Rates at which this layer is thinning during the study period (red numbers in meters per decade) are shown for for each deep basin (outlined by thin grey lines). These rates are estimated using data from repeated oceanographic expeditions (ship tracks shown by thick black lines). Note that seawater at the ocean surface stays liquid even at temperatures approaching -2ºC because of its high salt content.
Credit: NOAA

Because of this phenomenal, Antarctic bottom water is flowing from the South Pole towards the North as a massive stream carrying icy water across Indian and Atlantic Ocean.

Precise location of Antarctic bottom water

Antarctic bottom water is spreading across the oceans in depth of 4 000 meters and during this journey is water slowly mixing with the surrounding warmer water. According to Science Daily and Journal of Climate, the average temperature of the Antarctic bottom water is rapidly increasing.

“Because of its high density, Antarctic Bottom Water fills most of the deep ocean basins around the world, but we found that the amount of this water has been decreasing at a surprisingly fast rate over the last few decades,” said lead author Sarah Purkey, graduate student at the School of Oceanography at the University of Washington in Seattle, Wash. “In every oceanographic survey repeated around the Southern Ocean since about the 1980s, Antarctic Bottom Water has been shrinking at a similar mean rate, giving us confidence that this surprisingly large contraction is robust.”

AABW is formed in the Southern Ocean from surface water cooling in polynyas
Credit: Wikipedia

Antarctic Bottom Water is formed in a few distinct locations around Antarctica, where seawater is cooled by the overlying air and made saltier by ice formation. The dense water then sinks to the sea floor and spreads northward, filling most of the deep ocean around the world as it slowly mixes with warmer waters above it.

The world’s deep ocean currents play a critical role in transporting heat and carbon around the planet, thus regulating our climate.

Antarctica – a source of fresh water?

The Antarctic ice cap contains about 91% of all the ice in the world and about 86% of all freshwater that occurs in the form of ice (look at the first graph on the previous page). But despite all this freshwater, Antarctica is considered one of the aridest places on Earth.

Melt bell at Mawson
Credit: Ewan Curtis

Extraction of freshwater

It is extremely hard to obtain fresh drinkable water in Antarctica. Method of getting water differs between the stations across Antarctica. For example, Australian scientists working in Casey and Mawson camp managed to build a melt bell. In earlier days, snow and ice were shoveled into large tanks and heated to form water. Today is water pumped from a melt lake behind the station and stored in a heated tank house.

The melt bell is the centerpiece of a warm water circuit that is continuously running so that the melt bell stays at about 65-70 degrees. Then it is lowered into an ice crack and slowly melts the surrounding ice until a water pool is created; it is from this water pool that the station draws its water on a daily basis.