Arctic Sea Ice Gone By September 2019?
Arctic sea ice minimum extent typically occurs about half September. In 2012, minimum extent was reached on September 17, 2012, when extent was 3.387 million km².
On July 28, 2019, Arctic sea ice extent was 6.576 million km². How much extent do you think will be by September 17, 2019? From July 28, 2019, to September 17, 2019, that’s a period of 52 days during which a lot of melting can occur. Could there be a Blue Ocean Event in 2019, with virtually all sea ice disappearing in the Arctic?
Consider this. Extent was 6.926 million km² on September 17, 1989. Extent was 3.387 million km² on September 17, 2012, so 3.539 million km² had disappeared in 23 years. Over those years, more ice extent disappeared than what was left on September 17, 1989.
The question is how much sea ice extent will be left when it will reach its minimum this year, i.e. in September 2019. The red dashed line continues the path of the recent fall in sea ice extent, pointing at zero sea ice in September 2019.
Very high temperatures are forecast for the Arctic over the next few days. Above map shows temperature forecast for Greenland for July 31, 2019, with temperatures at one location as high as 22.9°C or 73.1°F and at another location – in the north – as high as 14.1°C or 57.3°F.
The map on the right shows sea surface temperature anomalies compared to 1961-1990 as on July 29, 2019. Note the high anomalies in the areas where the sea ice did disappear during the past few months. The reason for these high anomalies is that the buffer has disappeared that kept consuming heat in the process of melting.
Where that buffer is gone, the heat has to go somewhere else, so it will be absorbed by the water and it will also speed up heating of the atmosphere over the Arctic.
Sea ice melting is accelerating for a number of reasons:
- Much of the melting of the sea ice occurs from below and is caused by heat arriving in the Arctic Ocean from the Atlantic Ocean and the Pacific Ocean. The inflow of heat can increase strongly as winds increase in intensity. Storms can push huge amounts of hot, salty water into the Arctic Ocean.
- Hot air will melt the ice from above and this kind of melting can increase strongly due to changing wind patterns.
- Heatwaves over land can extend over the Arctic Ocean and they also heat up river water flowing into the Arctic Ocean. Changing wind patterns can also increase the intensity and duration of such heatwaves that can also come with fires resulting in huge amounts of greenhouse gas emissions, thus further speeding up the temperature rise, and also cause huge emissions of soot that, when settling on sea ice, speeds up melting, as also discussed in a recent post.
In conclusion, as the Arctic is heating up faster than the rest of the world, it is also more strongly affected by the resulting extreme weather events, such as heatwaves, fires, strong winds, rain and hail storms, and such events can strongly speed up the melting of the sea ice.
All around Greenland, sea ice has now virtually disappeared. This is the more alarming considering that the thickest sea ice was once located north of Greenland. This indicates that the buffer is almost gone.
Why is disappearance of Arctic sea ice so important? As long as there is sea ice in the water, this sea ice will keep absorbing heat, so the temperature doesn’t rise at the sea surface.
The amount of energy absorbed by melting ice is as much as it takes to heat an equivalent mass of water from zero to 80°C. Once the sea ice is gone, further heat must go elsewhere, i.e. it will typically raise the temperature of the water. The atmosphere will also warm up faster. More evaporation will also occur once the sea ice is gone, further warming up the atmosphere (technically know as latent heat of vaporization). As temperatures in the Arctic are rising faster than at the Equator, the Jet Stream will change, making it easier for warm air to enter the Arctic. More clouds will form over the Arctic, which will reflect more sunlight into space, but which will also make that less outward IR radiation can escape into space over the Arctic, with a net warming effect.
One huge danger is that, as the buffer disappears that until now has consumed huge amounts of heat, further heat will reach methane hydrates at the seafloor of the Arctic Ocean, causing them to get destabilized and release methane.