Ice melting at Arctic Sea 4: effects, bad or good?

Continuing the previous series, this will be the last post about sea ice melting. From the early posts, both observations and simulations show that sea ice at Arctic sea has declined significantly with melting rate accelerated. Sea ice would be likely to decrease continuously within this century, and might reach nearly ice-free status. So, what are the effects?

 Climate 

Arctic sea ice affects global climate change through complex processes. Firstly, there is positive feedback between warming and ice melting (as showed in Figure 1, Dessler, 2011). Current global warming has caused and will cause more sea ice melting at Arctic sea. Decreasing ice cover while increasing sea surface leads to the decrease in albedo, as sea surface reflects less and absorbs more solar radiations than ice surface. More absorbed energy leads to extra warming, thus, melting more ice. Therefore, ice melting at Arctic sea will amplify the global warming in this century. 

Meanwhile, sea ice also insulates the below sea water from the atmosphere, preventing thermal exchange and gas exchange between the ocean and the atmosphere. Sea ice loss at Arctic sea changes the interaction between the ocean and the atmosphere. Melting water decreases the salinity of sea water as well, which changes the density of sea water affecting ocean circulation. This will affects the climate at global scale.

Figure 1. Ice-albedo feedback

 Ecosystem

Sea ice is the habitat to many species, from fungus to large mammals like polar bears. However, sea ice loss has threatened their survival, affecting the population of the species. The US Geological Survey studied how the Pacific walrus and polar bears response to the rapid decrease of sea ice at Arctic sea. They found that stampeding events (Oakley et al., 2012) could be to blame for the high mortality in young walruses, as walruses had to crowd living on the shores of Alaska and Russia with less sea ice available. They also found that longer swimming distance could be blame for the decrease in the survival of polar bears (Oakley et al., 2012), with less sea ice available as well. Loss of hunting habitats could also cause the decline in polar bear's population (IPCC WG2, 2014). An earlier study (Stirling and Parkinson, 2006) found that the decline could be substantially. 

Source: USGS

Sea ice loss has also challenged the local biodiversity. One problem is hybrid. A hybrid of a grizzly and a polar bear was hunted in the Arctic in 2006 (Kelly et al., 2010). The explanation could be that polar bears live in the same area as grizzlies because of the loss in their habitats, sea ice.


 Human activities

Though ice melting leads to many bad impacts, there is a good news for human. Nearly ice-free status can provide open Arctic ocean. Ships may be able to navigate through Arctic ocean within this century, saving lots of time. Melia et al. (2016) simulated routes through Arctic, and concluded that shipping from Europe to Asia through the Arctic could become more than 10 days faster, and could save 4 days from N. America to Asia.