2040 Ice-free Arctic? Wadhams says is bizarre
Dear Dr. Serreze: Is is true that 2017 had the lowest average ice volume in the Arctic? And is it true that the Arctic has lost over 75% of its ice volume? How do you think the Arctic won't be ice free until 2040? I live in Minnesota so I know a lake can have great "ice extent" as area whereas the volume gets very thin and then in a couple days the lake is ice free. Thanks, Drew Hempel
US Navy predicts summer ice free Arctic by 2016 | Nafeez Ahmed ...
https://www.theguardian.com › Environment › Climate change
http://www.telegraph.co.uk/
This “claim” was obviously nonsense and was
very irresponsible. Yes, the arctic sea ice is
losing volume (in all seasons) but I have
no idea where the cited number of 75% comes
from. When will the Arctic lose its summer
sea ice cover? Somewhere in the 2040s is a
Reasonable estimate, but natural climate
Variability is strong in the Arctic so it may
well be later or earlier. And of course there are unknowns
regarding future rates of carbon emissions.
It is also important to remember that there will
Be winter ice for centuries. It’s just that the
Winter ice will be thin and won’t survive the
Summer melt period. If you want to keep track of
What the sea ice is doing, google “arctic sea ice
news and analysis”; we have regularly updated
Maps and graphs regular discussion of what is
happening.
Mark C Serreze
Sent from my iPhone
Thank you Dr. Serreze!
Is this quote about 75% volume decline wrong? Thanks again! drew
“. . we can also say with great confidence that the decline in observed ice thickness is not just an effect of measurement sampling and that the total sea ice volume has been declining over the past 32 years at astonishing rates (for instance a 75% reduction in September volume from 1979 to 2011).”
From: 'Arctic Sea Ice Volume: PIOMAS, Prediction, and the Perils of Extrapolation', Guest Commentary by Axel Schweiger, Ron Lindsay, and Cecilia Bitzin in RealClimate.org, April 11, 2012.
“. . we can also say with great confidence that the decline in observed ice thickness is not just an effect of measurement sampling and that the total sea ice volume has been declining over the past 32 years at astonishing rates (for instance a 75% reduction in September volume from 1979 to 2011).”
From: 'Arctic Sea Ice Volume: PIOMAS, Prediction, and the Perils of Extrapolation', Guest Commentary by Axel Schweiger, Ron Lindsay, and Cecilia Bitzin in RealClimate.org, April 11, 2012.
OK,, good to see you are looking at
PIOMAS. I don't know what they said in 2012. However, September
of 2012 was a record low for extent and volume. From what I can
see in their latest discussion, the PIOMAS folk are saying that
October 2017 volume was 65% below the maximum October ice volume
in 1979, so we are certainly talking big numbers. Remember that
PIOMAS is a data assimilation model - it provides estimates, not
truth.
Serreze
Serreze
Thank you again Dr. Serreze!
I
appreciate your dialog Dr. Serreze because when I asked NASA Dr. Gavin
Schmidt why they used 1950 as their "pre-industrial" baseline for global
average temperature increase I got no response. Maybe you know the
answer? At any rate do you think http://arctic-news.blogspot.
Oct 25, 2017 - Recent news show the Arctic ice melting at a pace faster than scientists previously thought. An error in the satellite measurements showed they were wrong. ... The cause for this measurement error of the satellites is the salt found in the snow cover. This can speed up the melting process and we could end ...
http://nsidc.org/
Happy New Year,Vishnu Nandan, who is the lead author of the study we were mentioning in the beginning, declared for the University of Calgary
Sadly, Nandan thinks that the seasonal sea ice might disappear completely in the summer at some point between the years 2030 and 2040,
http://nsidc.org/
Drew
Sorry for the delay. I'm not all that familiar with the arctic-news site. I know a few of the names listed
as contributors but that is about it. It's probably OK overall, but I would treat it with the appropriate grain of salt.
That they highlight "abrupt methane eruptions" - a very low probability event as far as I am aware, is cause for pause.
Sensationalism is not helpful. If you want to know about what is going on about sea ice, our site
is very solid - a new post came out yesterday (https://nsidc.org/
As to why Schmidt uses 1950 as the pre-industrial baseline, are you sure about this? Looking the the GISS website (https://data.giss.nasa.gov/
Passive microwave retrievals retrievals have a number of sources of error, and salt in the snow is one of them. Ho important? I don't know so I am copying our pssive microwave expert, Walt Meier.
Cheers
Mark C. Serreze
Sorry for the delay. I'm not all that familiar with the arctic-news site. I know a few of the names listed
as contributors but that is about it. It's probably OK overall, but I would treat it with the appropriate grain of salt.
That they highlight "abrupt methane eruptions" - a very low probability event as far as I am aware, is cause for pause.
Sensationalism is not helpful. If you want to know about what is going on about sea ice, our site
is very solid - a new post came out yesterday (https://nsidc.org/
As to why Schmidt uses 1950 as the pre-industrial baseline, are you sure about this? Looking the the GISS website (https://data.giss.nasa.gov/
Passive microwave retrievals retrievals have a number of sources of error, and salt in the snow is one of them. Ho important? I don't know so I am copying our pssive microwave expert, Walt Meier.
Cheers
Mark C. Serreze
Hello Drew,
Mark
passed your email along to me because of your question about salt in
the snow on sea ice. You are referring to the recent Nandan et al.
(2017) paper that indicates that sea ice thickness estimates from the
ESA CryoSat-2 (CS2) sensor may have errors due to salinity in the
overlying snow cover. This is a nice paper that brings up an important
issue. CS2 is a radar altimeter that is measuring elevation by sending a
pulse of energy from the sensor and measuring the time it takes to
reflect off the surface back to the sensor. Since it is radar, the pulse
is assumed to generally penetrate through the snow to the sea ice
surface below. So it is assumed that is measuring the elevation of the
sea ice above the water (called freeboard). However, there is a lot of
uncertainty here. First, the snow weighs down the sea ice ice and needs
to be corrected for with the snow depth/density, but we don’t really
have good data for those values. There is also uncertainty in the ice
density depending on how much salt is trapped with in the ice. Nandan et
al. (2017) illuminate another source of uncertainty - the fact that
salt can get wicked up into the snow layer above the ice. Radar is quite
sensitive to salinity, so salt in the snow will affect where the radar
pulse reflects.
These errors will affect any
volume estimates that use CS2 data. However, the salinity does not
significantly affect the surface area/extent estimates from passive
microwave sensors that we at NSIDC primarily use. Salinity does affect
the microwave signal and first-year ice (ice formed since the previous
summer melt) is much more saline than multiyear ice (ice that has
survived at least one melt season) because melt water flushes out a lot
of the salt trapped in the ice. This allows us to distinguish first-year
ice from multi-year ice, but it doesn’t much affect the discrimination
of ice from water, so it doesn’t lead to greater uncertainty in area and
extent estimates.
Also, PIOMAS uses only the
passive microwave extent/area data in the model, not CS2 data, so the
Nandan et al. (2017) effect is not relevant for PIOMAS. In regards to
the PIOMAS thickness/volume estimates, yes, 2012 showed a volume
decrease of roughly 75%, but it has recovered a bit. There is a lot of
variability, so it’s important to look at the long-term trend to
understand the changes. It is still a significant decrease, but there is
still a lot of fairly thick ice remaining north of Greenland and the
Canadian Archipelago, partly because the winds blow toward that area and
pile up ice. The summers are very short in that region, so there isn’t
much time to melt ice, though some of that ice drifts out of the Arctic.
In reality, there is likely to be at least some ice in that region that
remains through the summer for the foreseeable future, but it will be a
small amount, which is why the general threshold for an “ice-free
Arctic Ocean” is 1 million sq km.
As Mark
notes, the general consensus among scientists is ~2040, but we see a lot
of variability in the data and models indicate that this results in at
least an uncertainty range of at least +/-10 years depending on the
natural variability in the system - i.e., the random chance of when
relatively warm and relatively cold years occur. A couple really warm
years in a row may put us at ice-free condition by 2030 or perhaps even
earlier, whereas if we get some cooler years, it could delay ice-free
conditions to 2050 or beyond. As Mark noted, predictions of ice-free by
2016 were preposterous and not seriously considered in the scientific
community - there was just to much ice to melt out by 2016.
Natural
variability is also an important factor in interpreting the Svalbard
sea surface temperature data (SST) on the Arctic News website. The
1981-2011 value is averaging out a lot of variability - that’s why it is
a nice smooth, slowly declining curve. That region is particularly
variable in October because the ice cover is so variable due to the
proximity of the location to the warm North Atlantic waters (essentially
remnants of the Gulf Stream) that flow into the region. If the currents
flow close to Svalbard it will keep the region ice-free longer; if the
currents turn away from Svalbard, ice will form sooner.
If
the ice is present, the SST is essentially 0 C, but without ice the SST
could be much warmer. As an example, say that location has ice two out
of three years on average, but in a warmer year when the ice hasn’t yet
formed, the SST is on average ~13 C. That gives you and average of about
4 C, which is what you see in the 1981-2011 average. But it means that
this year is something that may occur normally once out of every 3
years. So Oct 2017 was not necessarily an extreme year. No doubt there
is a generally warming trend, but I’d be very cautious about reading
much into the Svalbard SST Oct 2017 data. Again, the key thing is to
look at long-term trends (which is shown in the 0-100 m anomaly plot -
about a 0.3 C increase since 1980).
Hope this info helps. Let me know if you have further questions.
walt
------------------------------
Walt Meier, Senior Research Scientist
Walt Meier, Senior Research Scientist
DAAC Scientist
National Snow and Ice Data CenterCIRES/University of Colorado, UCB 449
Boulder, CO 80309
Tel: +1-303-735-6276
Email: walt@nsidc.org
"If we knew what we were doing, it would not be
called research, would it?" - Albert Einstein
------------------------------
National Snow and Ice Data CenterCIRES/University of Colorado, UCB 449
Boulder, CO 80309
Tel: +1-303-735-6276
Email: walt@nsidc.org
"If we knew what we were doing, it would not be
called research, would it?" - Albert Einstein
------------------------------
Thank
you Dr. Meier and Dr. Serreze: Regarding "abrupt methane eruptions" -
Dr. Natalia Shakhova, et. al., indicate this could happen within 5
years, as per her recent interview with Nick Breeze. http://envisionation.co.uk/
This is what we call the turning point. To me, I cannot take the responsibility in saying there is a right point between the linear and exponential yet, but following the logic of our investigation and all the evidence that we accumulated so far, it makes me think that we are very near this point. And in this particular point, each year matters.
As gas within the sedimentary basins of the ESAS have been accumulating for a million years with no way to be released earlier, the supply for currently occurring emissions is tremendous. Because the shelf area is very shallow (mean depth is less than 50 metres), a fraction of these emissions will reach the atmosphere. The problem is that this fraction would be enough to alter the climate on our planet drastically.
Do
you have any comments regarding Dr. Shakhova's concerns? Do you think
this is being "sensationalist" as her conclusions are based on empirical
data that she collected.
Thank you again for your very detailed response that was very informative.
Hello Drew,
I’m
not an expert in permafrost or subsea methane releases. I think it is a
concern and increases in methane emissions is not surprising. But I
think most experts in this area see a steady increase - not a sudden
release. So it would contribute to warming but not in a catastrophic
way. But I think as the article points out, there are still a lot of
uncertainties in this area, so it’s hard to give clear predictions at
this point.
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