The Arctic sea ice minimum occurs in September when sea ice over the Northern Hemisphere ocean reaches its lowest extent of the year.
This is usually the greatest opportunity for ship captains seeking to sail across the Arctic, particularly in recent years. As a direct consequence of increasing carbon dioxide from human activity, sea ice cover there has shrunk by approximately half since the 1980s.
We study the causes and effects of sea ice change say NASA scientists. On September 16, 2021, the Arctic sea ice cover reached its lowest point. While it wasn’t a record low, a look back at the melt season reveals the Arctic sea ice’s steady decrease in the face of climate change.
According to the latest climate assessment from the United Nations’ Intergovernmental Panel on Climate Change, Arctic sea ice levels have been at their lowest for the annual mean since at least 1850 and for late summer for at least 1,000 years. According to the IPCC, “at least once before 2050, the Arctic will be virtually sea ice-free in September.” Less of the sun’s energy is reflected back to space when the Arctic’s brilliant ice is replaced by a darker open ocean surface, resulting in increased warmth and ice loss. This albedo feedback loop is one of many factors contributing to Arctic warming three times faster than the rest of the world.
Last winter set the tone for this year’s ice minimum. The Central Arctic’s thickest, oldest sea ice was driven into the Beaufort Sea, north of Alaska, by an unusually high-pressure system and strong clockwise winds. Scientists who study sea ice took notice.
Summer melt started in earnest in May, a month marked by numerous storms making landfall in the Arctic. This enhanced sea ice drifts while keeping temperatures low, reducing melt.
In June, which included a dominating low-pressure system and temperatures that were a few degrees warmer than normal, the amount and speed of melting rose considerably.
Conditions were approaching the record low established in 2012 at the beginning of July, but the pace of decrease slowed significantly in the second part of the month. Counterclockwise winds and ice drifts resulted from cyclones approaching the Arctic from Siberia. The quantity of ice flowing out of the Arctic via the Fram Strait, east of Greenland, is usually reduced by this counterclockwise ice circulation trend. This is most likely to blame for the Greenland Sea’s record-low summer sea ice.
This ice circulation pattern significantly boosted ice export from the Laptev Sea off the coast of Siberia, resulting in a new low for the early summer ice area in the region. Cloudiness rose across the Arctic due to the low-pressure system. Clouds block incoming solar radiation, decreasing sea ice melt, but they may also retain heat lost from the surface, thus their effect on sea ice melt is complicated.
Sea ice loss slowed significantly in August, with warm weather near the Siberian coast and colder weather north of Alaska. For the first time since 2008, the Northern Sea Route – which Russia has been pushing as a worldwide shipping route as the globe warms – was completely blocked by ice, but ice breaker-assisted transits were still feasible.
The sea ice pack is at its weakest at this point in the melt season, and it is very susceptible to the meteorological conditions of the day or week. Small changes may make a huge difference. The record low sea ice years of 2007 and 2012 were related to freak end-of-summer meteorological occurrences. An intriguing example is “The Great Arctic Cyclone of 2012.”
The impact they have is still a point of contention. However, experts believe that particular storms may not have had a significant role in causing that years’ record lows – weather and sea ice are seldom that simple.
The Arctic sea ice extent for 2021 was 4.72 million square kilometres on September 16, the 12th lowest on record.
So, despite all of the ups and downs, the 2021 melt season was rather typical of our new Arctic, with the September minimum ending up somewhat higher than the long-term decreasing trend would have predicted. In other months and Arctic areas, however, fresh record lows were established.
Arctic sea ice will begin to refreeze as the number of hours of sunshine diminishes and temperatures fall in the coming weeks. As the surrounding ocean surface temperatures fall below freezing, the ice pack will thicken and spread, releasing much of the heat that had been absorbed and stored during the summer.
In recent years, the refreeze has begun later, extending into October and even November. The more heat that is gained by the ocean throughout the summer, the more heat that must be released before ice may develop again. As a result, despite all the attention paid to summer ice losses, some of the most significant warming signals are seen in the autumn.
Understanding local ice conditions on a particular day or week is what matters most to those living and working in the high Arctic. It’s much more difficult to forecast Arctic sea ice at these smaller sizes.
Sea ice is extremely dynamic, as shown by the year 2021, moving and melting in response to daily weather patterns. Consider how difficult it is for forecasters to predict the weather where you live, when you have a solid knowledge of weather systems and a plethora of data, vs the Arctic, where there are few direct observations.
Local feedback loops may be set off by weather occurrences. For example, a freak heatwave may cause ice melt and additional warming. Winds and ocean currents also break up and disperse ice over the ocean, making it more susceptible to melting.
Scientists working on sea ice are working hard to better understand these processes and enhance our forecasting models. Ice thickness is a crucial piece of the jigsaw when it comes to understanding sea ice loss.
Volume is equal to thickness times area. Sea ice thickness has halved since the 1980s, implying that today’s Arctic ice pack is only roughly a quarter of what it was a few decades ago. Knowing the thickness of any ice they may encounter is essential for anybody trying to traverse the Arctic Ocean. It’s considerably more difficult to assess sea ice thickness from orbit in a regular manner. New technologies, such as ICESat-2, are, nevertheless, making significant advances.
Despite all of the uncertainties, summer ice-free Arctic conditions seem to be on the horizon. The good news is that the route ahead remains mainly reliant on future emissions, and there is currently no indication that the world has crossed a sea ice loss tipping point, indicating that humans remain firmly in control.
Source: Tribune India