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Arctic Sea Ice Incredibly Thin Shocks Researchers

A winter expedition to the Arctic Ocean by a Norwegian research vessel, Lance, found that the winter sea ice near the North Pole was thinner and weaker than expected.

According to Mats Granskog a sea ice researcher from the Norwegian Polar Institute, Tromsø, the chief scientist of the expedition, The Norwegian Young Sea Ice (N-ICE2015) project, sea ice moves much faster, breaks up easier, and it is more vulnerable to storms and winds.

In January 2015 the research vessel was deliberately frozen into the ice pack to the north of the Svalbard Archipelago of Norway.  The research crew gathered data and camped on nearby ice flows as the ship drifted in the ice. The research project, which ended in June 2015, was the first major study to collect water data in that part of the Arctic. The surface heat budget of the Arctic (SHEBA) project between October 1997 and October 1998, which was the only previous large expedition to observe the Arctic’s winter sea ice, was funded by the US National Science Foundation that monitored the conditions to the north of Alaska.

As this research is considered to be quite dangerous measurements obtained in prior to the 2015 expedition is quite small.

It was necessary to move its operations several times because of the instability of the ice floes where it camped. As well as the darkness and cold, that were expected to have to work in, there were also violent storms and ice breaking up underfoot quite often, and they needed to escape from the ice and rescue their camps. They also had to keep a watch for polar bears.

Measurements obtained from expeditions in summer have shown that there was widespread thinning of the Arctic sea ice, though the conditions of sea ice in the winter were uncertain. The researchers described as a ‘New Arctic’ the condition of the Arctic sea ice that had greatly decreased in thickness, being only 3-4 ft thick, and the ice was functioning much differently from its behaviour 10 years earlier.

According to Amelie Meyer, an oceanographer, there were ripple effects below the sea ice; when storms passed through the ice was moved so rapidly that it stirred the water beneath the ice. As a result of this, it helped bring water from below much closer to the surface, actually inducing some ice melt from below.

In some areas the ice melted much faster than expected as spring returned to the Arctic. One morning, near the end of the expedition, they woke to find there was a crack in the ice that was growing rapidly where they had made their camp. They had to scramble to collect the gear and equipment before they sank into the sea, though they recovered everything in time.

A surprise was a phytoplankton bloom beneath the pack ice, which was snow-covered, in mid-May. This was the earliest and most northern bloom of phytoplankton that had been observed.

Regime change

30 years ago the majority of Arctic Ocean winter ice was thick multi-year ice that grew over multiple winters. Now more than ¾ of the Arctic Ocean is covered by first-year ice that is much younger and thinner in late winter.

Wintering in the High Arctic – Surprising Results²

The Norwegian research vessel Lance penetrated to the north of Svalbard to within 800 km of the North Pole with the assistance of Norwegian Coast Guard vessels, where it remained from January to June 2015. On this research expedition experiments were carried out that had never been done on site previously, especially during the northern winter.

Their findings of “drastic changes”, that what has been called the “new Arctic” surprised them, the results calling into question the state of scientific knowledge of the sea ice in the Arctic. An example is that even in winter the ice was much thinner that it was 20 years ago, being only about 1 m thick in places. And this ice has different behaviour from that of older, thicker ice. It moves more rapidly, cracks more easily, and is more susceptible to be damaged by storms and winds. In some places the ice was so thin it was flooded by seawater, because the weight of snow, which was much heavier than had been expected, pushed the ice below the surface of the ocean.

The waters of the Arctic Ocean were found by a 12 week study to be warmer than expected, and the warmest waters are far below the surface. Storms, that were more violent and more frequent than expected, stirred the waters of the ocean even beneath the ice. As a result warmer water, up to 4^oC, was brought closer to the surface, and helped to melt the ice from below.

The ice melted a few inches from below, which is significant as the ice is only a few feet thick. The amount of melt was described as huge, with as much as 25 cm of melting per day from below in summer. At that melt rate there aren’t many days to collect data.

Nutrients were also brought to the surface by the upwelling warm water leading to the first phytoplankton bloom ever recorded beneath ice that was snow covered in the Arctic Ocean. It was found that the blooms were aided by light transmission through the thin ice. Phytoplankton blooms typically absorb carbon dioxide and sink to the deep ocean where they sequester the carbon, though these algae didn’t sink very far in the water column, so did not contribute to the sequestration of carbon to the deep ocean.

The atmosphere above the Arctic ice was also studied on this expedition by Von Walden. The effects of winter storms on young, thin sea ice were studied for 1 month. It was found that there was either total cloud cover or no cloud cover, with no time when there was broken cloud cover. This was similar to findings on the SHEBA expedition 20 years earlier in the Pacific Arctic, the only previous observations during winter on the central ice pack.

Walden focused his research on storms and their effects, which differed from those that were experienced by the SHEBA expedition in the Pacific Arctic 20 years previously, which are the only previous observation of the ice pack in the central Arctic Ocean. In 2015 the storms were transported by a jet stream that was anomalous and powerful, which pushed them from the warmer North Atlantic into the high Arctic. These conditions had never before been observed, though they had been modelled. The thin ice is stressed by the winds that accompany the storms which help break up the ice. The winter Arctic sea ice maximum was the lowest extent that had ever been measured up to the point since the beginning of satellite observations. This record low was eclipsed in March 2916.

In the same month a storm was experienced that raised the air temperature from -40^oC to 0^oC in 48 hours. The wind, that had been calm, reached 80 km/hr and the humidity increased by a factor of 10, and the snowfall experienced for the entire 6 month expedition was recorded. It has not been well established, so the N-ICE measurements are important.

The feedback process, Arctic amplification, affects climate in the far north more rapidly than at lower latitudes, was observed directly. Heat is absorbed by the water and thin ice, so is not radiated back to space and would be by thick ice. Therefore it contributes to the greenhouse effect, and the cycle repeats.

There is still a lot to learn about the Arctic. The speed with which the Arctic sea ice will decrease as a result of climate change in this region has been consistently underestimated. In part this is because there are so few observations during critical times of year, including winter.

The scientists on the N-ICE expedition amassed and preserved unprecedented data on the new Arctic, in spite of the danger and curious polar bears. The change in the Arctic will affect the entire population of the Earth, so understanding how the Arctic functions and predicting its future is crucial.

Sources & Further reading

1. Monastersky, Richard, 14 December 2016, incredibly thin Arctic sea ice shocks researchers, Nature News, April 2017

2. Leifert, Harvey, 2017, “Wintering in the high Arctic reveals surprising results.”  Earth Magazine, April 2017: 12-13