Arctic decadal and interdecadal variability
Polyakov and Johnson
Abstract:
Atmospheric and oceanic variability in the Arctic shows the existence of several oscillatory modes. The decadal-scale mode associated with the Arctic Oscillation (AO) and a low-frequency oscillation (LFO) with an approximate time scale of 60–80 years, dominate.
Both modes were positive in the 1990s, signifying a prolonged phase of anomalously low atmospheric sea level pressure and above normal surface air temperature in the central Arctic. Consistent with an enhanced cyclonic component, the arctic anticyclone was weakened and vorticity of winds became positive.
The rapid reduction of arctic ice thickness in the 1990s may be one manifestation of the intense atmosphere and ice cyclonic circulation regime due to the synchronous actions of the AO and LFO. Our results suggest that the decadal AO and multidecadal LFO drive large amplitude natural variability in the Arctic making detection of possible long-term trends induced by greenhouse gas warming most difficult.
In my view, you are reaching. I don’t see any data that specifically supports
but your links are quite technical (e.g., sea ice extent is not the same as ice mass).
I will note that your first reference starts the Introduction with
“Since the late 1970s, the Arctic sea-ice extent has exhibited a significant decline in all seasons, which is due to human influence (IPCC, 2021) and is expected to continue.”
I think that sea ice extent is actually more important than mass/volume. The sea ice extent (SIE) obviously affects albedo. It increases or decreases the ocean-heat flux to the atmosphere, changing temperature gradients and thus influencing large-scale wind flows. The halocline (the top 100+ meters of the ocean where the salinity varies rapidly) is also changed.
It’s not clear that there are any mulitidecadal oscillations. Michael Mann of hockey stick fame was a strong proponent of the existence of multidecadal oscillations. He published several papers doing statistical analysis of various climate datasets demonstrating their properties.
Then, in 2020 he published an article that contradicts his, and many others, previous work, claiming that multidecadal oscillations are a statistical artifact:
"Here we use a combination of observational data and state-of-the-art forced and control climate model simulations to demonstrate the absence of consistent evidence for decadal or longer-term internal oscillatory signals that are distinguishable from climatic noise. "
Lot’s of papers are still being published about the PDO and NAO, so I don’t know how much consensus there is around Mann’s conclusion that it’s all just noise.
Since there is no well-defined, agreed-upon preinstrumental AMO time series that could be. Model failure to find oscillations may be just that, model failures.
Stroeve et al. found a 60/40 split between external forcing and internal variability through 2011. Since then Arctic sea ice extent has continued to go sideways, so the unforced portion may be higher than 40%.
“Kay et al. concluded that approximately half (56%) of the observed rate of decline from 1979 to 2005 was externally forced…Based on the CMIP5 multi-model ensemble mean, approximately 60% of the observed rate of decline from 1979-2011 is externally forced…”
Well, you can switch to sea ice extent as a metric, but you asserted multi-decadal oscillatons for ice mass and I’m not seeing much data upthread to support that assertion.
Instead, from the NSIDC upthread, they say:
Glaciologists have found, in study after study, that both of the planet’s remaining ice sheets are losing overall mass at an accelerating rate.
I’m inclined to go with their view, at least right now.
The mass of the ice sheets (which would be Greenland and Antarctica) is not the same as Arctic sea ice extent.
Both ice sheets are losing mass, although I’m not sure the loss rate is accelerating. Look at these two graphs from JPL; the decline looks pretty linear.
At the same time, Arctic SIE has not been decreasing over the last 17 years according to the National Snow & Ice Data Center. Do you have any thoughts on why?
The National Snow & Ice Data Center (NSIDC) follows conditions in the polar regions, including the Arctic minimum sea ice extent each September. This year’s number is 4.28 million sq km.
For the last 18 years (2007-2024) the trend is -0.011 per year, not significantly different from zero (p=0.60).
Arctic sea ice minimum has large natural variability within the long term decline. Swart and co-authors looked at large numbers of climate model simulations to estimate the variability.
Internal climate variability can mask or enhance human-induced sea-ice loss on timescales ranging from years to decades. It must be properly accounted for when considering observations, understanding projections and evaluating models.
Probability of a pause as a function of pause length in the Historical-RCP4.5 experiment over 1979–2013 (black), and in the future over 2066–2100 under the RCP2.6 (blue), RCP4.5 (cyan) and RCP8.5 (red) experiments.
Assuming the planet is close to RCP4.5, the models estimate the probability of an 18 year pause before 2013 to be about 10%, growing to about 30% after 2066.
The article is from January 2015 – climate models predicted the possibility of the current pause nearly 10 years ago. Yet another example of climate model success.
As noted upthread, for the 18 years there has been no significant trend in minimum Arctic sea ice. In other good news, Antarctic ice sheet mass has shown no loss over the last five years.
The melting of sea ice in the Arctic has slowed dramatically in the past 20 years, scientists have reported, with no statistically significant decline in its extent since 2005.
Recent slowing of Arctic sea ice melt tied to multidecadal NAO variability https://www.nature.com/articles/s41467-025-63520-0 Here, we demonstrate that the recent slowdown in September sea ice melt is closely coupled with the multi-decadal variability of the preceding summer North Atlantic Oscillation (NAO), which has transitioned from the lowest point of its negative phase in the early 2010s to a positive phase.
That’s an incomplete picture. (no surprise to folks here)
Greenland and Antarctica ice sheets account for 2/3 of the planet’s freshwater.
They are losing mass in a clear downward trend.
Ice sheets, which store large amounts of fresh water on land, are melting as Earth’s air and ocean temperatures warm. Antarctica is losing ice mass at an average rate of about 135 billion tons per year, and Greenland is losing about 266 billion tons per year. As ice melts, the resulting water drains into the ocean and contributes to sea level rise.
