The Earth Story

A Lake of World Records

Lake Baikal is a sight to behold. Located in southern Siberia, the lake covers an area of almost 32,000 square kilometers (12,000 sq. mi). Often referred to as the pearl of Siberia, Lake Baikal boasts quite a few world records for lakes. It is the largest lake, by volume, in the world. (The largest lake by area award goes to the Caspian Sea.) Lake Baikal holds more water than all of the Great Lakes combined, an estimated 20% of the world’s unfrozen freshwater. It can hold so much water because it is extraordinarily deep. Lake Baikal’s maximum depth of 1,609 meters (5,387 feet) makes it the deepest lake in the world. It is the oldest lake in the world as well. Forming 25 million years ago, Lake Baikal, it is suspected, began as a river basin.

Lake Baikal is home to more than 2,000 species of plants and animals, two thirds of which can be found nowhere else in the world. This large number of unique, endemic species can be attributed to Lake Baikal’s isolation. Surrounded by mountains and forests, organisms here have had millions of years to meander evolutionarily from their closest relatives. One of these organisms is the Baikal seal, the only seal in the world that lives entirely in freshwater. Its closest relative, the Arctic Ringed Seal, is over 3,000 km of rugged terrain away. Baikal is a land of uniqueness, isolation, beauty and magnificent size.

KKS

Read about Baikal

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Photo courtesy of Russian Times

Original video caption:

How does meltwater from an ice shelf reach ocean depths?

The ice shelves of West Antarctica are losing mass at rapid rates over the recent past. This melting is primarily due to basal melting that is driven by the warm waters that originate from the mid-latitudes in the Southern Ocean. This melting also implies that these is an increase in the output of freshwater from the ice shelves which are substantial in understanding the fate of the sea ice cover, its effects on albedo (the amount of sunlight reflected back into space), the changes in the ecosystems of the Southern Ocean, and its ability to cycle carbon. However, our understanding of what happens to all this freshwater from the ice shelves and what happens to them when they interact with the surrounding ocean was limited until recently.

One of the key questions that remained unanswered till now was the vertical distribution of the freshwater. Climate models suggest that the meltwater remained on the surface although there were many observations of these freshwater masses along the Antarctic polar seas at depths of several hundred meters in the ‘thermocline’. To address this problem, researchers chose the gyre (large system of circulating ocean currents) at Pine Island Bay that brings warm circumpolar deep water to the base of the Pine Island glacier and moves fresh meltwater away from the base of the glacier’s cavity. The experiment was setup by taking vertical microstructure profiles (VMP) of the water along the calving front of the glacier to measure the turbulence of the meltwater as it flowed out of the cavity.

The results show that as the meltwater tries to rise-up to the surface (because freshwater is less dense than the surrounding saltwater). However, the Earth’s rotation causes it to spin on a vertical axis which ejects filaments of meltwater along the sides into the surrounding ocean – hence preventing the water from reaching the surface. This ‘centrifugal overturning instability’ helps turbulent mixing of the meltwater and finally they settle down at depths. Although oceanographers were aware of the role the Earth’s rotation plays in large-scale currents, this is the first evidence they have produce to show that the rotation of the Earth also affects small-scale mixing processes. This mechanism is also relevant to a broad range of ice shelves in Antarctica. Furthermore, these new findings should be incorporated in the climate and ocean circulation models

Image Credit: NASA Ice http://bit.ly/2lqfBvb

Sources: http://bit.ly/2ldAho3 http://go.nature.com/2kTEorg

The River Beneath the Amazon

The Amazon’s sheer size is enough to impress even the most stubborn “glass half empty” sort of person, not to mention the river’s incomprehensible power and force. The Amazon River extends from the peaks of the Andes Mountains all the way east and eventually spills into the Atlantic Ocean, some 6,400km away. The many wonders of the Amazon fascinate people from all regions of the world. Wonders that include the river’s infamous tidal bores, the diversity of wildlife, and now a newly discovered underground river which flows almost parallel to the Amazon. The river, named Rio Hamza, serves as a major drainage system for the surrounding Amazon Rainforest. This is quite convenient for the rainforest since nearly two-thirds of our planet’s freshwater is located in the Amazon Basin.

A team of researchers who examined 241 abandoned deep wells in the Amazon basin discovered the underground waterway. The team used a mathematical model that was based on change in well temperature in order to predict the underground water flow. The wells were originally dug in the 1970’s and 1980’s by a Petrochemical company called Petrobras. The researchers’ study says that water still flows almost entirely vertically through the rocks until a depth of around 2,000m and then it suddenly changes and flows horizontally.

Rio Hamza is thought to differ from the Amazon in both size and rate of drainage. As the Amazon’s width ranges from about 1km – 100km, Rio Hamza is believed to be as much as 200km – 400km wide. With that said, the Amazon stills flows much faster than its underground companion and therefore drains an estimated 129,100 metres3 more water per second than the more lethargic Rio Hamza. All of this freshwater in and around the Amazon basin feeds the Amazon Rainforest which is the largest rainforest in the world as well as one of the planet’s most dense concentrations of wildlife.

The discovery of Rio Hamza provides interesting insight into South America’s geology and underground irrigation systems that allow such extravagant plant life to flourish aboveground in the rainforests and mountains. Continued research in the greater Amazon basin will allow for more significant breakthroughs that will offer an even deeper look into one of our planet’s most impressive waterways. One can only imagine the new species that will be discovered kilometers underneath the Amazon in a river much darker and much more secluded from human beings.

--Pete D

Photo Credit: Pedro Martinelli/ISA

References: 1. http://www.guardian.co.uk/environment/2011/aug/26/underground-river-amazon 2. http://www.theaustralian.com.au/news/world/brazilian-scientisists-find-hidden-river-beneath-the-amazon/story-e6frg6so-1226122958496 3. http://www.wcupa.edu/aceer/amigos/cd/rainforest.htm 4. http://www.allvoices.com/contributed-news/10189365-huge-hidden-river-found-under-amazon 5. http://ga.water.usgs.gov/edu/riversofworld.html

Influence of the environment: The Marine, Freshwater and Terrestrial Environments.

The physical properties of salt water, freshwater and air have important implications for anatomy, physiology and behaviour of the animals inhabiting them. Let us take a look at the main features of marine, freshwater and terrestrial environments and their effects on animal life.

Post Two: The freshwater environment

Freshwater environments provide good buoyance for the animals that live in them, an excess of water so nitrogenous wastes can be excreted as ammonia and no danger of water loss by evaporation over respiratory surfaces. Apart from these points, however, they are much more variable than marine environments.

Freshwater bodies may vary greatly in turbidity, velocity and volume, and these factors may change rapidly in response to heavy rain. Drought may also be a factor, sometimes leading to the complete drying of a water body. Salt concentrations may also be variable in fresh water. In general, freshwater environments have lower salt concentrations than those found in animal tissues, so animals tend to gain weight by osmosis. The excess water must be removed while retaining important salts in the tissues, using a process called osmoregulation. However, in times of drought, evaporation may concentrate salt so that an inland water body may become saline, not fresh.

In such cases, freshwater animals must prevent excess water by osmosis into the surrounding saline water. In addition to this natural variability of the freshwater environment, freshwater animals may face other, externally imposed problems. Rivers and streams are often repositories for a range of human wastes and this pollution may have significant effects on freshwater life.

Freshwater animals are much less likely than marine animals to produce free-floating eggs, because they can be swept away by rapid currents. Instead, eggs are usually retained by the parent until they hatch, or attached firmly to the substrate. Larvae are rarer than in the marine environment and the eggs are often provided with a large yolk for nutrition.

So although freshwater animals benefit from buoyancy and the opportunity to excrete nitrogenous wastes as ammonia, they must cope with changes in the extent, turbidity and velocity of the water body that can impose problems.

Look out for Post Three: The terrestrial environment, coming next.

~ JM

Photo credit: Photograph by Michel Roggo, National Geographic. Sourced from http://on.natgeo.com/1J3c2AO on 21/04/2015

More Info: Gordon, M.S and Olsen, E.C. (1995). Invasions of the land: the transition of organisms from aquatic to terrestrial life. Columbia University Press, New York. Pechenik, J.A. (2005). Biology of the invertebrates. McGraw-Hill, Boston. 5th edn, Chapter 1. The Living Environment: http://bit.ly/1yK6pnv

Freshwater Environment:http://bit.ly/1IW4kqz