Mid-Piacenzian Arctic: Warm Climate & Seasonally Ice-Free Oceans

[Xnn]

For Wang and others to be correct we need an amplification. And an amplification does appear to be underway. I was impressed with this paper that I was a peer reviewer for.
http://www.the-cryosphere.net/3/11/2009/tc-3-11-2009.pdf. The emphasis is on observed temperature anomalies and increased heat flux from the open ocean from late summer-early winter.

mspelto;

Wow!
It is really great that we have a professional on board.
Most of us are just motivated amateurs with technical backgrounds.

From the paper:

To summarize: 1) Starting in the late 1990s and relative to
the 1979–2007 time period, Arctic Ocean SAT anomalies in
the NCEP reanalysis turned positive in autumn and have subsequently
grown; 2) Consistent with an anomalous surface
heating source, development of the autumn warming pattern
aligns with the observed reduction in September sea ice extent,
and temperature anomalies strengthen from the lower
troposphere to the surface; 3) Recent autumn warming is
stronger in the Arctic than in lower latitudes; 4) Recent low
level warming over the Arctic Ocean is less pronounced in
winter when most open water areas have refrozen; 5) There
is no enhanced surface warming in summer; 6) Conclusions
1–5 hold for both the NCEP and JRA-25 reanalyses, the major
difference being that temperature anomalies in JRA-25
are somewhat smaller.

One of the things that has been noted earlier in this forum is the
increasing seasonality of the Arctic sea ice. This seems especially pronounced over the last 3 seasons. The greatest deviation has been generally occurring in September. Sometimes, it occurs after sunset. Then there is a rapid rebound towards or sometimes just above the long term average.

 

[Xnn]

I believe the cryosphere today website defines "extent" as the area that has 50% cover or more of ice -- could be 30%, I am not sure. NSIDC uses "extent" as area with 15% cover or more. It may just be me, but I have found it hard to get the information from cryosphere today, by comparison with NSIDC.

Of course, if we are talking about ice free conditions then even 15% is too high.
However, I can imagine from a data analysis and processing perspective there are reasons to use other values.

 

[Xnn]

The main point is that, throughout the year, there is some variation in sea ice extents but there is a seasonal range that has not varied as much as the September minimum numbers make it look.

Of course, part of the reason for this is that sea ice is 3 dimensional and we are only looking at it in 2 dimensions. The winter ice thickness is thinner at maximum extent compared to the past than at the season minimum.

In addition, I suspect that seasonal albedo changes are beginning to become a factor.
However, albedo is relatively un-important between Sept 21 to March 21.

So, combine the dimensionality and the albedo factor and the most largest deviation will be occurring around Sept.

 

[mspelto]

The main source of the amplification seen is the heat released from the water. Think of a different but related amplification. The Great Lakes famous for their lake effect snows. The snow results from water evaporated and heat lost from the lakes. This snow amplification system shuts off when the lakes freeze. The lakes are still open at this point.
http://www.natice.noaa.gov/pub/ims_gif/DATA/cursnow_usa.gif

 

[Skyhunter]

I recall a report last October from the NSIDC that attributed the unusually warm Arctic temperatures to the release of latent heat from the phase change from liquid to solid.

[Edit]

On further review, it was the http://nsidc.org/arcticseaicenews/2008/111008.html"

Higher-than-average air temperatures

Over much of the Arctic, especially over the Arctic Ocean, air temperatures were unusually high. Near-surface air temperatures in the Beaufort Sea north of Alaska were more than 7 degrees Celsius (13 degrees Fahrenheit) above normal and the warming extended well into higher levels of the atmosphere. These warm conditions are consistent with rapid ice growth.

The freezing temperature of saline water is slightly lower than it is for fresh water, about –2 degrees Celsius (28 degrees Fahrenheit). While surface air temperatures in the Beaufort Sea region are well below freezing by late September, before sea ice can start to grow, the ocean must lose the heat it gained during the summer. One way the ocean does this is by transferring its heat to the atmosphere. This heat transfer is largely responsible for the anomalously high (but still below freezing) air temperatures over the Arctic Ocean seen in Figure 3. Only after the ocean loses its heat and cools to the freezing point, can ice begin to form. The process of ice formation also releases heat to the atmosphere. Part of the anomalous temperature pattern seen in Figure 3 is an expression of this process, which is generally called the latent heat of fusion.

In the past five years, the Arctic has shown a pattern of strong low-level atmospheric warming over the Arctic Ocean in autumn because of heat loss from the ocean back to the atmosphere. Climate models project that this atmospheric warming, known as Arctic amplification, will become more prominent in coming decades and extend into the winter season. As larger expanses of open water are left at the end of each melt season, the ocean will continue to hand off heat to the atmosphere.