Ice melt from Antarctica is increasing at an alarming rate, so much so that by 2100, Antarctic melting alone could lead to more than 40cm of sea level rise. However, sea levels are likely to rise more than this because as the ocean expands as it warms (thermal expansion), this could increase sea levels by a further 25cm. Sea level rise is the main effect we think of when we think of the melting of the Antarctic ice sheet. However, it is less known that there are minerals, like iron, that are trapped in the ice sheet which enter the oceans when ice melt occurs. If a lot of ice melts and enters the oceans with the trapped minerals, there will be an increase in the organisms in the ocean which require these minerals. This can be both a good and a bad thing. It can be positive if it leads to an increase in a species that doesn’t harm other organisms, however it can be negative when the organism in the ocean uses up too much oxygen for example.

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Recently, jarosite, which is a yellow-brown mineral, first discovered on Mars in 2004, was found inside an Antarctic ice sheet core. In order to form, jarosite requires water, iron, sulphate, potassium and acidic conditions. This is an important discovery as the science about iron within the Antarctic ice sheet is currently ongoing. As the water surrounding Antarctica has limited amounts of iron, this means that as the Antarctic ice sheet melts and releases more iron into the ocean, these waters will no longer be iron limited. This will likely lead to more primary production in the waters, causing more phytoplankton to grow, which could lead to oxygen deprivation for other organisms and species. 

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Fig 1 – Jarosite.

There are both positive and negative effects of increasing the amount of iron in the ocean (a process which is called iron fertilisation).

What does this increased iron in the ocean mean?

• More carbon could be stored in the deep ocean from the atmosphere. This is unlikely to make a large difference to the amount of carbon stored in the deep ocean because there is already enough iron for the microbes in the ocean to survive. Therefore, extra might not be used up.
  
• Changes in phytoplankton in the oceans and bacteria that feed on them. All phytoplankton need iron to photosynthesise however, some already have enough of it. Therefore, the phytoplankton which require and make use of the iron released from ice melt will grow, which will lead to more bacteria which feed on the type of phytoplankton which have just gained the iron they need to flourish. 
• Fish stocks could improve as there will be more phytoplankton for fish to feed on. However, there is an equal chance that fish stocks could decrease. This is because we don’t know which food chain pathways will be favoured in an increased iron scenario. If algal blooms occur from the increased iron, fish stocks would decrease because the algae would use up all the oxygen in the waters, leaving none for the fish.
  
• Iron fertilisation could impact other dissolved nutrients in the ocean. This would occur if more phytoplankton were to grow. The increased amount of phytoplankton would require more nutrients, which would remove those nutrients from the water, making it harder for fish and other organisms to survive.

These are just some of the impacts that could occur from the melting of the Antarctic ice sheet due to iron fertilisation. However, the extent to which each might occur is uncertain. The small amount of iron that has been added to the ocean by ice melt from Antarctica for thousands of years is a good thing as it provides the iron necessary for phytoplankton. However, large increases, such as what would happen in the medium/worst case melt scenarios would likely go well beyond this optimum, necessary amount of iron leading to the impacts mentioned above. Therefore, it is important for scientists to keep an eye on what is happening in terms of iron release into the oceans as we are unsure what scenario will occur.

Featured image by: Flickr 

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Warming ocean temperatures caused by the climate crisis have a profound effect on the ocean’s ability to function optimally. Besides sea level rise, other dangers facing the oceans include increased algal and seaweed growth in some areas, loss of coral reefs and impacts on fish location, abundance and migration patterns.

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Warming Ocean: Effects on Marine Life

Higher-than-normal temperatures are often the main trigger for the growth of harmful algal blooms which occur in lakes, rivers and oceans. Only a few of these blooms produce toxins, however, many more have a significant negative impact on the ecosystems around them as they act as canopies, reducing light reaching the species below and affecting their ability to grow. Algal blooms typically appear just off the continent in relatively warm water, near enough to the surface to receive sunlight. Although algae photosynthesise and produce oxygen, when they accumulate in large quantities, they begin to take in more oxygen through respiration than they emit. This has a knock-on effect for fish as they are consequently deprived of oxygen. Additionally, these blooms consume other minerals, such as nitrogen and phosphorus which other species require, therefore limiting the growth of these other species.

Harmful algal blooms often occur in coral reefs, as these waters often contain the ideal minerals for algae to grow. These blooms prevent sunlight from reaching the coral, a harmful impact as corals require sunlight for the different types of algae inside of them to photosynthesise in order to provide the reefs with oxygen.

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Further, anthropogenic climate change is causing bleaching of coral reefs. The Great Barrier Reef has been subject to bleaching over the recent years, with three intense coral bleaching events in five years. More than 50% of the reef has already been lost, with another 40% likely to disappear within 10 years.

Bleaching causes coral to turn white because its algae disappear or lose its ability to photosynthesise (as shown in the picture above). Further, as more greenhouse gases are emitted, sea temperatures rise, which put the coral under stress, causing them to expel the algae which live within them. As the algae provides energy for the coral, this causes the coral reefs to die. The Great Barrier Reef lost between 29% and 50% of its coral between 2014 and 2016 alone. To add to this, between 2016 and 2017, the number of new corals on the reef decreased by 89%.

Seaweeds, or macroalgae, are thriving in the environments that cause corals to become bleached. Corals grow in clear and low-nutrient waters. They survive through symbiosis with microalgae that live within the coral. The coral produces nutrients and carbon dioxide, which is used by the algae. Along with sunlight, the algae use these wastes to photosynthesise to produce oxygen and sugars that are used by the coral. However, as nutrient levels increase through pollution, ocean acidification and other factors, the environment becomes less suited for corals and more suited for seaweeds, a process that will exacerbate as warming intensifies.

Additionally, with rising temperatures comes the inability of fish to adapt to the changing conditions, which is causing the global distribution or migration of fish to change, as well as causing the extinction of some species altogether. With this warming, fish are migrating north to cooler waters; two areas where fish are migrating to are the North Atlantic and North Pacific. This migration has also caused cod populations in the North Sea to decline, affecting fisheries in the region.

As fish stocks are declining globally, two thirds of the fish stocks in the world are being overfished or fished to their limit. Overfishing has caused fish stocks to decline by 90% in recent years.

Ocean species are less capable of adapting to changing conditions than land species are, which is causing ocean species to be lost at a much faster rate. Many marine species are cold-blooded and rely on the surrounding temperature to adjust their body temperature, unlike land species; this, coupled with the lack of adequate shelter in the oceans from the dangers of these rising temperatures, is responsible for this difference in adaptability. 

Researchers have called for a reduction in greenhouse gas emissions, ceasing overfishing and limiting ocean habitat destruction. Because humans are better able to adapt to warming temperatures, we forget about the ocean dwellers, which are not so lucky, however we rely on the ocean for food, tourism and trade, so it is therefore in our best interest to protect the oceans and all that live in it from these dangers. 

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It has been established that those living in poverty will suffer disproportionately more from the adverse effects of the climate crisis than the rich, a phenomenon known as the ‘climate caste system’. How then, can poorer nations protect themselves from the damaging effects of the crisis? 

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Last year, Indonesia announced its plans to move its capital city from Jakarta to a province in Borneo because of the sea level rise that has left the city ravaged by a steady stream of floods and land subsidence, the latter caused by Jakarta’s excessive extraction of groundwater. The relocation aims to ease the pressure on Jakarta by moving its administrative functions about 1 000km to Kalimantan.

Construction on the new capital will begin next year and by around 2024, the government expects to start moving some of its 1.5 million civil servants to the new bureaucratic centre, but the majority of its nearly 10 million residents are likely to stay.

While Jakarta is one of the fastest sinking cities in the world, sinking up to 25cm a year, mainly due to thermal expansion of the oceans caused by the climate crisis, most of the more developed countries who have contributed to the exacerbation of the crisis- for example, the UK, who contributed significant emissions during the Industrial Revolution- are experiencing arguably less disastrous effects. Over the last decade, other less developed nations in the Pacific with lower GDPs have been lost to the sea, many being Small Island Developing States (SIDS). These include Nuatambu, an island in the Solomon Islands that has lost half of its inhabitable area since 2011. 

Meanwhile, massive swarms of locusts have swept across much of East Africa, including Uganda, Tanzania, Kenya, Ethiopia and Somalia, decimating food crops and threatening millions more people with hunger in an already fragile region. 

Like many states in the region, Kenya, Somalia and Ethiopia are positioned to be some of the countries most affected by climate change, despite their low carbon emissions. Kenya ranked in the top 50 most vulnerable countries by the Global Climate Risk Index in 2017, but contributes 0.13% of worldwide global emissions. 

Countries at higher latitudes are less affected by sea level rise and other impacts of climate change. This is the definition of climate injustice, also referred to as the ‘climate caste system’. 

Certain communities around the world that already experience multiple burdens, such as being unable to relocate or rebuild after a disaster or living in areas particularly vulnerable to the climate crisis (like along the coast), are also disproportionately affected by the climate crisis. Indonesia is again one example of this.

Many of the lower-income countries are located in tropical regions where the climate is similar year-round and crops have not adapted to a changing climate like they have in more temperate regions, thus causing crop failure (many crops in temperate regions become dormant during the winter, arguably preparing them more for changes in temperature). Therefore, the same amount of warming in temperate regions has less impact than it does in these tropical regions, many of which have agriculture-dependent economies. Current evidence suggests that poleward regions where agriculture is limited by short growing seasons are more likely to gain while subtropical and tropical regions may be more likely to suffer drought and losses in productivity.  

Rice is one major example of this. Many people in lower income countries, including Indonesia and Cambodia, rely on selling rice for their livelihood. However, because the crop is unable to adapt to changing climates, yields have been decreasing by 0.3% per year due to the climate crisis. In these countries, 16% and 6% respectively are surviving on $1.90 a day or less. These low-income workers suffer the most from the effects of climate change due to failing crops as a result of rising temperatures. Further, prices are increasing due to the scarcity of the grain, causing many to be unable to obtain it. As many people in lower income countries in tropical areas are more dependent on crops for their income, they are impacted by the climate caste system a lot more than people in higher income countries whose main source of employment is in high-paid tertiary sector jobs. 

Those governments of less developed countries (except India which is the 3rd largest emitter) often lack the ability to adequately address greenhouse gas emissions as their contributions to the problem are negligible. They are therefore forced to rely on those developed countries who emit these gases to make changes. However, these developed countries are not affected as much by the problem and in fact benefit from emissions, so they have less incentive to reduce their carbon footprint. This exacerbates climate inequality further as it gives vulnerable countries less power; the people in these countries have little to no opportunity to migrate to improve their quality of living. 

The climate caste system is not only happening between countries, but within countries as well. For example, the impacts of Hurricane Katrina in 2005 impacted poorer cities more than their wealthier counterparts, with the more deprived town of Biloxi in Mississippi suffering the most. The climate crisis increased the intensity of the hurricane and, as the sea level around Biloxi was already high and few defences were put in place due to a lack of funding for the area, the town was hit especially hard. The sea walls were between 6 inches and 4 feet high, however waves reached 20-30 feet high in this area. Even two years after the hurricane, houses in Biloxi were still deteriorating. Residents whose homes were destroyed in the hurricane were only re-homed by the government five years later and even then, casinos were the first to be rebuilt in an effort to bring money into the area (Climate Justice by Mary Robinson). 

It is often the poorest in society that are forced to live in areas that are at the greatest risk of being lost to the sea or last to be rebuilt after a severe climate crisis-induced disaster. It is imperative that governments of more developed nations work collaboratively with those of less developed countries to share technology, insights and funding to help buffer the poorer nations against the harmful effects of the climate crisis. 

Featured image by Abdul Majeed Goraya/IRIN

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