Arctic ice extent is turning – The Climate Clock

Icebergs in the North Atlantic [image credit:
maritime-executive.com]

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The ideas expressed here relate to effects of the well-known lunar nodal cycle of about 18.61 years. In 2021 researchers ‘confirmed that the ice edge position has a lunar-driven signature with periods of [1/2, 1, 4, 16] × 18.6 years. This means there is a ~297.76-year period (16 × 18.6 years) with maximum extent around 1867 and minimum extent around 2015.’ This marked the lowest extent of Arctic Ice East, so the prediction here is that ‘This means we can expect a gradual increase in Arctic Ice East extent, eventually reaching a maximum similar to that of the 1800s. Note that 4*18.61 = 74.44 years, and another research paper (Maroon et al, 2018) says: ‘The correlation between internal variability in 75-yr trends of global surface warming and AMOC* strength is statistically significant above the 95% confidence level during all ensemble periods shown, including for running trends computed from the long pre-industrial simulation (green markers, Fig. 4).’ [*Atlantic Meridional Overturning Circulation]. Of course 75-year cycles can’t be detected in satellite data starting in around 1980.
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The extent of Arctic ice in the Barents Sea has shown a declining trend since the 1860s, says Prof. Harald Yndestad @ The Climate Clock. A continuation of this trend would eventually result in an ice-free Arctic Ocean in summer.

An ice-free Arctic Ocean would, in effect, mean the opening of a new territory, a region allowing for shipping through the Northwest Passage and the exploitation of new seabed resources. At the same time, the Arctic has attracted increasing political interest.

Projecting past trends into the future yield’s uncertain forecasts. It is like driving a car while looking in the rear-view mirror.

The question is whether the extent of Arctic ice will continue its downward trend in the years ahead. The answer lies in understanding how Arctic ice is influenced by its surroundings.
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The signature of Arctic Ice East
Norwegian researcher Torgny Vinje conducted extensive work documenting Arctic ice extent. His studies were based on measurements, hunting logs, and observations from Arctic expeditions.

I recall that, while on a research mission in the Arctic, he sent me two time series of Arctic ice extent by a simple e-mail, the result of many years of work. The first series covered the extent of Arctic Ice East of Svalbard from 1864–1998, while the second covered Arctic Ice West over the same period.

My own study of Arctic Ice East showed that the ice extent had a lunar-driven signature with periods of [1/2, 1, 4] × 18.6 years. This matched the NAW (North Atlantic Water) signature for the inflow of warm Atlantic water into the Norwegian Sea, confirming that the extent of Arctic Ice East can be traced to changes in Earth’s rotation…
…Further analysis showed that the lunar-driven 4 × 18.6-year period reached an estimated maximum around 1955.
[Talkshop note: full science discussion in the linked article].
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Prevailing view
Arctic Ice East covers the area of sea ice in the Barents Sea, Norwegian Sea, and Kara Sea, bounded by 10°E, 80°N, and 70°E. Measurements of ice extent are based on April observations from 1864 to 1998 (Vinje, 2001).

The extent of Arctic ice has been in decline since the mid-1860s. The causes of Arctic ice reduction have been discussed for more than 100 years. Even in Nansen’s time, it was known that warm Atlantic water influences the extent of Arctic ice.

Another explanation involves changes in the salt balance. Melting ice and freshwater runoff alter salinity, affecting how cold surface water sinks to the deep ocean.

Some researchers suggest that pollution on the ice surface reduces sunlight reflection, leading to more melting. Over time, the prevailing view became that the reduction of Arctic ice is primarily due to human-induced global warming.

This led to the assumption that the downward trend would continue and that the Arctic would eventually become ice-free in summer.
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Scope of the study
This study was published in 2006 and has since been cited in about 100 scientific publications. It concluded that the extent of Arctic Ice East is driven by the inflow of warm Atlantic water, with a lunar-driven spectral signature.

The implication of the factual measurements is that the extent of Arctic Ice East is likely about to reverse its trend. This means we can expect a gradual increase in Arctic Ice East extent, eventually reaching a maximum similar to that of the 1800s.

Such a period of increased ice extent would have ripple effects on shipping, fisheries, the oil industry, and political assessments of Arctic regions.

Full article here.
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Image: Icebergs in the North Atlantic [credit:
maritime-executive.com]