A tale of two seas review of RGS lecture

Journal Review: A tale of two seas

Ben and Ria

Oceanographer Professor Tom Rippeth has dedicated his academic life to the study and conservation of our oceans, and his excellent work has inspired this review. In his presentation, Professor Rippeth focuses on two recent environmental disasters involving our oceans – the Aral Sea (or rather lack of) and the retreating Arctic ice sheets. Both of these crises have certainly been exacerbated, if not caused, by human activity in recent years, and will continue to deteriorate in the future, if no significant actions are taken.

Located on the Border between Kazakhstan and Uzbekistan, the Aral Sea was once the fourth largest inland sea worldwide, spanning 68,000 km2, but since 1960, has seen a 60% reduction in surface area and an 80% reduction in volume. The Aral drainage basin encompasses nine countries, thus contains hundreds of significant tributaries, notably the Amu Darya and Syr Darya, which carry snow melt from mountainous areas. These tributaries previously balanced natural rates of evaporation and maintained a healthy water level but recently, unregulated and inefficient human interference has caused this fragile equilibrium to shift. In order to cope with an increasing population in the region, many of these tributaries have been diverted away from the Aral Sea and towards settlements where the water has agricultural,

industrial and personal uses, most notably as irrigation for cotton crops. Effectively, these canals act as distributaries and are outputs from the basin, yet there are no additional inputs to compensate. Inevitably, as more artificial diversions have been built alongside a constant evaporation rate, water levels have steadily fallen.

As the Basin dried up, the composition of its contents changed too – ionic salts dissolved in the water require high temperatures for evaporation compared to water, so the salts remain in solution whilst the water evaporates. This increases the salinity of the water, having severe impacts on the marine life/ local ecosystem. All signs of marine life had died out in the lake long before the water had dried up, resulting in severe consequences for local fisherman, who found themselves unable to make a living off the previously plentiful Orlova et al (1998). In: S. Bruk, D. Keyser, J. Kutscher and V. Moustafaev (Eds) Ecological Research and Monitoring of the Aral Sea Deltas: A Basis for Restoration, pp. 95-137. UNESCO, Aral Sea Project 1992-1996. Final Scientific Results. Paris.

supply of fish.

The basin’s size makes it hard to regulate – no one country can enforce change unless the eight others agree to it. This is unlikely because economically, the diverted water has sizeable monetary value compared to the Aral Sea, which can be hundreds of miles from the countries that drain its tributaries and therefore seem insignificant/ not their problem. There are strong links to the issues surrounding the construction of the Grand Renaissance Dam in Ethiopia, where less water would be allowed into downstream Sudan and Ethiopia, causing drought in the area and reduced crop yields.

Many people in the countries surrounding the Aral Sea were

heavily dependent on the natural environment, so the unexpected loss of this environment was devastating. In the 1960’s, 1/6 of all fish consumed by the Soviet Union population was from here, and many of the locals relied on artisanal fishing. Due to the increase in river salt levels, these fish populations died and people were unable to support their families. When cotton and rice farming became popular, the 1/3 of the river water feeding the basin was diverted in order to irrigate and flood fields. This meant the evaporation levels exceeded the water input and caused the surrounding deltas, the most fertile land, to dry out. As a result of the pesticides used in cotton farming, the water became polluted and many people lost access to clean drinking water. There was an increase in diseases and death, especially child mortality from respiratory diseases. However, the Aral sea is slowly beginning to recover, due to investments from the world bank and national governments towards a more stable dam. The climate crisis, doesn’t just affect physical environments, people around the world have been affected by the indirect impacts.

The second, arguably more pressing environmental disaster is that of retreating ice in the Arctic. Due to unusually high concentration of rivers in Northern Asia (mainly Russia) and Canada, including the Mackenzie river in the Northern Territory, the Arctic receives vast amounts of freshwater and is the freshest ocean worldwide. It is important to recognise natural seasonal variations in coverage and thickness of sea ice, but also to understand that long-term, there is a clear decline.

The Arctic and our weather are connected by the Jet Stream, a high altitude fast wind which ‘wanders’ latitudinally throughout the year, causing differences in pressure thus inducing weather across much of the Northern Hemisphere. This movement of the Jet stream has been shown to be linked to shrinking ice, epitomising the direct effect that shrinking ice has on us, despite the distance that separates us. Between 1980 and 2005, the average thickness of the sea ice in Autumn almost halved,

especially at the outermost extremities of the Arctic. This has changed the Albedo of the ice, resulting in much less reflection of incoming short-wave radiation and more absorption. These are re-emitted as infra-red radiation, warming the atmosphere via the enhanced greenhouse effect. However, for six months each year, the Arctic sees virtually no sun due to the tilt of the earth yet there is a near constant melting during this period which begs the question – where is the heat coming from? The answer lies deep below the ice, in vast networks of deep ocean currents which leaves some water as hot as 2 degrees celsius 500 meters down. However, until now, this warmer water was shielded from the surface ice by a layer of cold freshwater (<500m) thus had little/ no effect on the ice. This warm salty water is supplied by the deep Atlantic basin, which transports water from nearer to the equator. Also, the mid-Atlantic ridge is volcanically active so this deep water is unusually warm. The elevated salt content in the water is in part caused by the salt ions leaving the water upon freezing -salt water cannot freeze to form salty ice, only ice and salt in their separate states. This saltier water is more dense so sinks below the layer of fresher water, usually settling below 200 meters, below the Arctic Halocline and creating a salinity and temperature gradient between the ice and the deeper ocean, which is warmer and saltier.

Tom and his colleagues at the University of Bangor have conducted numerous expeditions to the Arctic, notably four between 2007 and 2013, to better understand this vast, interconnected system and its influence over us. Warming seas caused by the enhanced greenhouse effect has fuelled an unprecedented change across the Arctic which shows no signs of slowing down unless significant change is enforced by governments – sanctions on the perpetrators (whether they be corporations or countries) and investment into renewables, with an emphasis on sustainability, should be prioritised.

References https://www.rgs.org/geography/onlinelectures/a-tale-of-two-seas-professor-tomrippeth/ https://www.quora.com/What-are-thefactors-that-lead-to-the-shrinkage-of-thearal-sea https://slideplayer.com/slide/7090555/ https://www.climate.gov/news-features/ understanding-climate/climate-changeminimum-arctic-sea-ice-extent