Antarctica is arguably the most inhospitable continent on planet Earth. Isolated from any other southern hemisphere continents, Antarctica is covered in 2 km deep ice and has a dangerously unstable environment. With strong winds, freezing temperatures (as low as -80°C!), and emphatic seasonality resulting in the continent being subjected to darkness for many of the winter months, organisms must be adapted to surviving in torrid environmental conditions. A rapid rate of climate change and exposure to harsh radiation means survival here is almost impossible. This is shown by how the continent has never been inhabited by humans and was only discovered in the last couple of centuries. Today we will be going over the Antarctic climate and some of the amazing species which inhabit this foreboding continent.
Antarctica Map
Fig. 1: Simplified map of Antarctica. Source: Wikimedia Commons
Above is a general map showing the different regions of Antarctica. Highlighted is Adare Basin which is an extensional rift basin that extends along the seafloor and joins the northern basin, forming Antarctica's western continental shelf. The northernmost extension of the Antarctic is the most studied area because of the contribution it makes to rising sea levels via retreating glaciers.
Antarctica Weather
Antarctica is subjected to some of the harshest conditions in the world. Here is an overview of those conditions.
Antarctica Temperature
The coastal areas of Antarctica are relatively temperate compared to the rest of the continent, boasting highs of around 10°C and lows of -40°C. These survivable temperatures have allowed scientists to build research laboratories closer to the coast. These buildings must be far enough into the continent to protect them from the annual melting of ice in the warmer regions.
Closer to the southern pole, temperatures are much less forgiving - ranging from -30°C in the summer all the way down to -80°C in the winter. Only the most specialised organisms will inhabit these regions and form ecosystems, including a plethora of extremophiles.
An extremophile is an organism which can withstand adverse conditions; for example:
- Freezing temperatures
- Low oxygen availability
- Extreme pressures.
In polar upwelling, the Coriolis effect coupled with the Antarctic Circumpolar Current creates the Antarctic Convergence, which is the point where the colder Antarctic water encounters the warmer sub-Antarctic water and forms the Antarctic intermediate current. This results in the upwelling of warmer, less salty water which warms the climate and increases glacial melting.
Precipitation and Blizzards
The air above regions nearer the southern pole is dry and clear, with minimal cloud formation. Extreme winds can make it challenging to measure precipitation levels (mainly in the form of snow or ice droplets). Harsh winds can result in drifting and snow blowing, reducing visibility. Blizzards may occur when gale force winds (strong and sustained surface winds) are present.
A blizzard is defined as a series of conditions, including freezing temperatures, gale force winds for over an hour, and visibility at 100m or less.
Wind Patterns
The environment of Antarctica is unique because it is made up of a low-pressure belt called the circumpolar trough. This surrounds the continent and regions of high pressure within it. These conditions result in consistent, continent-spanning katabatic winds. These katabatic winds are produced by the downwards movement of cold, dense air formed from the cooling of the air above regions surrounding the pole. The circumpolar trough often interacts with downwards travelling winds to augment these winds. Antarctic katabatic winds can flow at speeds above 150 km/h.
Katabatic winds, often called drainage winds, are winds carrying dense air down a slope while being pulled by the force of gravity. They are extremely strong and dangerous.
Antarctica Population
Compared to the abundance of wildlife inhabiting other continents, Antarctica's biomass is minimal. Considering the severe conditions organisms must face, many thriving terrestrial and marine ecosystems still call Antarctica home. Animals that live on the continent have thick layers of blubber to insulate their bodies. Antarctica is home to an abundance of lichens, bryophytes, algae, and fungi. These organisms don't have roots and consequently don't require the complex intake of nutrients like other plants to survive. More hospitable coastal areas contain most of the wildlife, with most Antarctic ecosystems depending on the productivity of the Southern Ocean.
This productivity is a result of the Antarctic Circumpolar Current (covered in the previous deep-dive) that upwells nutrient-rich waters which offer a substantial food source for producer populations.
Limitations of the Antarctic Environment
Plants are autotrophs, which synthesise valuable chemicals using energy harnessed from the sun. Availability of sunlight, water, nutrients, and carbon dioxide is scarce in the Antarctic. The rates at which producers can photosynthesise is limited by the temperature, the rate at which decomposers release recycled nutrients back into the soil, and the rate at which phosphate rocks are weathered. Animal consumers rely on producer populations for survival. So considering that the producer population of Antarctica is already small and the fact that biomass transfer between trophic levels is not very efficient, animal populations are minimal.
Autotrophs are photosynthesising organisms that harness energy from sunlight to produce their own food.
Decomposers are bacteria and fungi which act on dead organic matter and release stored up nutrients back into the ecosystem.
In the Southern Ocean, the food chain is phytoplankton, protozoa, krill, penguins, and killer whales. Some organisms feed at many trophic levels (penguins feed on protozoa and krill), and there may be other chains in the ecosystem (such as blue whales feeding on plankton), so a food web may be a more accurate description.
Fig. 3: Killer whale in the Ross Sea, Antarctica. Source: Wikimedia Commons
Terrestrial Ecosystems
Low temperatures and dry conditions allow only the most adaptable organisms to survive inland. Extremophilic producers such as fungi, lichen and mosses can survive in regions which are not covered by ice. These producers allow a limited ecosystem of small invertebrates and fungi.
Endolithic communities protect themselves from katabatic winds by growing in small gaps in rock formations to ensure protection from the winds but close enough to the surface to receive sunlight.
Frozen lakes are home to various species of cyanobacteria, which survive in shallow areas permeated by light.
Lakes which are not frozen over will be nutrient deficient, but certain algae and moss can survive here. Lakes with limited light penetration lack living organisms.
Lichens are prevalent in the Antarctic because of their symbiosis with cyanobacteria and fungi. Lichen requires minimal nutrients and sunlight to grow; they can grow directly on rocks and protect photosynthesising cyanobacteria and fungi.
Endolithic organisms are ones that live inside or on stone.
Research into lichen in the Antarctic desert could offer possibilities to use these organisms to colonise Mars! The success of cyanobacteria stems from their often extremophilic nature, meaning they can survive in the harshest environment. In the Antarctic desert, an extremophilic symbiosis between cyanobacteria and lichen has been discovered, in which the cyanobacteria provide the lichen with photosynthate and fixed nitrogen. These desserts are renowned for being the analogous terrestrial representation of the climate on Mars. Cyanobacteria in symbiosis with the cryptoendolithic lichen have the innate ability to produce exopolysaccharides, chemicals which offer cryoprotection at low temperatures and high salinity by inhibiting ice formation within cells.) Some examples of consumers who survive in the terrestrial regions of the Antarctic are nematodes (microscopic worms) and tardigrades (minuscule, segmented animals).
Marine Ecosystems
Despite being one of the scarcest continents for wildlife, the Southern Ocean is one of the most productive oceans in the world. This is because of the upwelling regions. Nutrient-rich, warm deep water replaces denser, colder water which has been made less salty by melting glaciers. Cold, sinking water will form deep, slow-moving currents and become part of the 'global conveyor belt'.
The global conveyor belt is a series of surface and deep-water currents that play a massive role in the worldwide nutrient distribution and climate.
High nutrient levels will promote phytoplankton growth. These autotrophic phytoplankton (e.g. dinoflagellates, cyanobacteria) are the foundations of all marine ecosystems.
During the winter months, algae become trapped beneath the ice.
In the summer months, nutrient-rich zones develop much closer to the southern pole with the melting ice.
Because of the harsh environment, food webs are not very diverse and contain only a few trophic levels.
The organisms in marine ecosystems have adapted to their environment. For example, the seasonal migration of fish and seabirds, huddling of penguins for warmth and developing a thick, insulating layer of blubber in some animals.
Examples of consumers in marine ecosystems are protozoans, krill, blue whales, penguins and killer whales.
Impacts of Climate Change in the Antarctic
Here are some of the impacts of climate change in the Antarctic:
Increased fossil fuel use and increased deforestation have led to massive amounts of carbon dioxide being released into the atmosphere. A substantial portion of this carbon dioxide will diffuse into the oceans, causing ocean acidification. The Southern Ocean is affected, too, with producers being unable to photosynthesise as efficiently in acidic conditions and calcareous shells and exoskeletons dissolving more easily.
Rising global temperatures have reduced sea ice, taking away the habitats of many creatures living in coastal areas.
This constantly changing coastal environment leads to variation in areas of productivity and therefore impacts the functioning of the ecosystem in the process.
Human research and exploitation also negatively impact the Antarctic, with human interference leading to habitat fragmentation, the introduction of foreign species, and pollution.
Antarctica - Key takeaways
The Antarctic continent is one of the harshest environments, with conditions such as gale force winds, freezing temperatures, complete lack of moisture, blizzards, and emphatic seasonality.
Low availability of sunlight, carbon dioxide and nutrients results in small producer populations.
Despite the adverse conditions, terrestrial lichen, fungi, cyanobacteria, and marine ecosystems continue to thrive.
The northernmost extension of the Antarctic is the most studied area because of the contribution it makes to rising sea levels via retreating glaciers.
The environment of Antarctica is unique because it is made up of a low-pressure belt called the circumpolar trough.
Ocean acidification, ice melting, and human interference negatively impact the Antarctic environment and ecosystems.
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