Is the Arctic Going To Be Ice Free In An Decade?
Geoscience Weekly: Exploring Earth's Phenomena V
Monday 11th of March, recently there has been many studies conducted on the Arctic’s future and the impact of global sea level rise. In this newsletter, we will talk about how Antarctica’s coasts are becoming less icy, the effects of this on marine ecosystems and productivity, and how humans have driven the Earth’s freshwater cycle out of its stable state. Firstly, let’s look into the increase of polynyas in Antarctica which will help us explain the recent record low Antarctic sea ice coverage.
Polynyas
In summary, Scientists from the University of Otago in a recent study have shown that there has been an increase in polynyas in Antarctica. Polynyas are semi-permanent areas of open water in sea ice and there are two types of Polynyas. The two types are open-ocean and coastal. Coastal polynyas are located beyond landfast ice (sea ice which has formed from frozen seawater and does not move in response to the currents and winds unlike pack ice) caused by persistent local offshore winds and it tends to be smaller and shorter-lived than open-ocean polynyas. Open-ocean polynyas forms within the ice cover by the upwelling of deep warmer water. There is a large number of semi-permanent polynyas-the largest known as the North Water Polynya which can be up to 85,000 km². Why is this important? Well the study put forward that there is evidence that the area of polynyas around Antarctica is increasing dramatically following a cycle of growth and shrinking every 16 years driven by currents. This is interesting as an ice-free Arctic may be closer than we think as when these polynyas increase there will be an accompanying increase in the concentration of coastal plants and animals which may establish on the continent meaning we are slowly losing the Arctic. This will lead onto significant consequences for marine ecosystems.
The Complex Effects on Marine Ecosystems and Ocean Productivity
As we know, most of the sunlight which reaches the Arctic ocean is reflected back to space known as albedo. Albedo is the fraction of radiation reflected away by a surface and it lies on a scale from 0–1 with 1 being complete reflectance. Earth’s average albedo is 0.31 meaning the planet reflects around 31% of incoming solar radiation. Ice has an albedo of around 0.6–0.9 meaning some parts in Antarctica reflect 90% of incoming solar radiation. This means most of the light reaching the Arctic Ocean is reflected which shields ocean ecosystems from light but as the Arctic sea ice continues to melt which is occurring at an alarming rate this melting will affect marine ecosystems. Over the past 25 years, the amount of Arctic sea ice has decreased by an area of 1 million square kilometres. If there is less ice, the seafloor will experience more sunlight allowing for more photosynthesis to occur enhancing the ocean’s productivity. This may seem like a good thing but it’s very unclear about how ecosystems in the Arctic will evolve and adapt to this change. For example, the melting of Arctic sea ice will influence food web structures and energy flows. A decrease in sea ice will affect crabeater seal populations by increasing predation and decreasing breeding. This is all enhanced by human driven climate change; let’s see how climate change reduces the stability of the Earth’s freshwater cycle.
Earth’s Freshwater Cycle
Earth’s freshwater cycle is the constant exchange of water in its various forms of liquid, solid and gas between Earth’s surface, ocean and atmosphere. New analysis from Aalto University shows that human activity has pushed variation in Earth’s freshwater cycle outside of its pre-industrial range. In simple terms, effectively humans have been pushing the Earth’s freshwater system beyond the stable conditions before industrialisation. The scientists analysed streamflow and soil moisture at a spatial resolution of 50x50 km revealing that there has been an increase in frequency of exceptionally dry or wet conditions. This explains recent extremely dry streamflow in river basins such as the Nile. This is impacted by the melting of sea ice, another example of this is the dynamic region where freshwater meets seawater as if seawater rises this area will move upstream leading to saline intrusion which can damage many plants an animals while also directly affecting us humans as rivers, reservoirs and lakes are often important stores of freshwater drinking water. An increase in saline intrusion may be catastrophic as it continues to get worse.
An Ice-Free Arctic
So, will the Arctic become ice-free within a decade? The Arctic could see summer days with no sea ice as early as the next couple years according to the University of Colorado Boulder. By mid-century, the Arctic is also likely to see an entire month without sea ice during September. Ice-free Arctic means that the ocean has less than 1 million square kilometres of ice. Greenhouse gas emissions are the main contributor to sea ice loss as we get a dangerous positive feedback cycle. When ice melts, the albedo of the land surface decreases with more solar radiation being absorbed which exacerbates the warming of the atmosphere even further causing further melting continuing the positive feedback cycle. The melting of these ice sheets has an important impact on the oceans as the melting ice adds freshwater into the saline oceans which disrupts the thermohaline circulation. These are the deep-ocean currents which are driven by differences in the water’s density which is controlled by temperature and salinity. The melting ice makes the sea less saline which makes the oceans less dense meaning that water will not be able to sink and flow to the deep ocean disrupting the global pattern of ocean currents.
Conclusion
Is it possible that we will see an ice-free Arctic? Yes. Is this something to be worried about? Yes. Is this reversible? The answer is most certainly yes. If we can reduce carbon dioxide emissions and slow down climate change we can indefinitely reverse this process but currently is this likely? No. If the Earth is a system which always want’s be in a state of dynamic equilibrium by which the inputs and outputs are balanced then if human-induced global warming was to be reduced then the Earth would slowly return to its stable conditions. However, we need to see more change and and more events such as the upcoming Ocean Decade Conference on the 10–12th of April and COP29 for a miracle like this to happen.
Thank You
Thank you for reading, all information is taken from reputable sources and are linked below. All images are free to use under copyright laws.
EOS ‘ University of Colorado Boulder ‘ Aalto ‘ University of Southern Denmark ‘ University of Otago ‘ Britannica ‘ Exploratorium