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AbruptSLR

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Antarctic Weather and Meteorology
« on: May 14, 2013, 05:05:21 PM »
I am opening this new thread, not because I know a lot about Antarctic Weather and Meteorology, but because this is a critical topic and needs to be covered, particularly with regard to: ice surface melting temperatures, precipitation, wind patterns, storm action and regional oscillation weather patterns .  I can recommend the two following websites for monitoring Antarctic weather forecasts:
http://www.weather-forecast.com/maps/Antarctica
http://www.weather-forecast.com/maps/Antarctica

As an example of the importance of weather related ice surface melting temperatures, I provide the attached image of Antarctic areas subjected to surface ice melting in January 2005, and the following summary (from June 2012) is from the Norwegian Polar Institute website, which emphasizes the important role that such surface melt water has on ice mass loss from both ice shelves and grounded ice:

Sun-heated surface water contributes towards melting under ice shelves in Dronning Maud Land.

"About half of the melting of the Antarctic ice cap occurs on the underside of ice shelves – floating glaciers several hundred metres thick. Research recently published in Geophysical Research Letters shows that surface water heated by the sun is a crucial source of heat, and contributes to melting in the sea under the Fimbul Ice Shelf in Dronning Maud Land. It was previously known that hot water from the depths also causes the bottom of the ice shelf to melt.
– “It came as a surprise to us that warm water from the surface plays such an important role for ice melting in Dronning Maud Land,” says the article’s first author, researcher Tore Hattermann from the Norwegian Polar Institute.
 
Tore Hattermann has been participating in field work at Fimbulisen for three years in a row; he and his colleagues have analysed two years’ worth of data collected from three rigs that were deployed in 2010. When glaciers in Antarctica melt, the sea level rises all around the globe, including the Arctic. Hattermann emphasises that knowledge about the melting of the ice cap is crucial for understanding and predicting changes in sea level.

– “If we wish to understand what will happen to the ice in Antarctica and the future climate, we must understand the interactions between the ongoing changes in the atmosphere and the melting that occurs hundreds of metres below the sea surface,” says Hattermann.

To date, very few measurements of sea temperature have been done under the Antarctic ice shelves. In some places in West Antarctica, there is extremely rapid melting owing to direct contact between the ice and warm water from the ocean depths. In East Antarctica, where the Fimbul Ice Shelf is located, the new measurements show that melting is limited because warm water is in contact with the ice only for part of the year.

The researchers surmise that the amount of warm water that comes in contact with the ice varies depending on the extent of sea ice and wind conditions along the coast of Dronning Maud Land. These new results provide important clues about the processes that control melting along the coast of Dronning Maud Land.

The study is part of the ICE-Fimbul Ice Shelf project and is being carried out by researchers from the Norwegian Polar Institute in collaboration with other research institutes from Norway and abroad."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #1 on: May 14, 2013, 06:30:46 PM »
The Antarctic oscillation (AAO, to distinguish it from the Arctic oscillation or AO) is a low-frequency mode of atmospheric variability of the southern hemisphere. It is also known as the Southern Annular Mode (SAM) or Southern Hemisphere Annular Mode (SHAM).  As the SAM is an important factor in Antarctic weather, I attach the accompanying image illustrating it.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #2 on: May 14, 2013, 06:32:00 PM »
The following website can be visited to get daily satellite generated infrared images of the Antarctic (such as the attached image).

http://ossfoundation.us/projects/environment/global-warming/projects/environment/global-warming/current-climate-conditions/storm-trends#section-2

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #3 on: May 14, 2013, 07:40:00 PM »
I recommend visiting the following website for the Antarctic Meteorological Research Center (AMRC) and the Automatic Weather Station (AWS) program of the US Antarctic Program (USAP), for research, analysis and real-time and archived meteorological data.  The attached image is an example of a product from satellite data showing typical geopotential heights and wind speed contours around the Antarctic showing how the circumpolar pattern distinguishes the Antarctic from other areas of the world. 

https://amrc.ssec.wisc.edu/


The website also links to related Antarctic related news such as the following (from redorbit March 12, 2013):

"One would not assume that cloud cover over Antactica’s Southern Ocean could cause rainfall in Zambia or the tropical island of Java. New research from the University of Washington, however, finds that a phantom band of rainfall just south of the equator that does not occur in reality is caused by poor simulation of the cloud cover thousands of miles farther to the south. This illusionary band of rainfall is one of the most persistent biases in global climate models.
Atmospheric scientists at Washington hope that their results will help explain why global climate models duplicate the inter-tropical convergence zone, a band of heavy rainfall in the northern tropics, on the other side of the equator by mistake.
The results of the study appear in a recent issue of Proceedings of the National Academy of Sciences (PNAS).
“There have been tons of efforts to get the tropical precipitation right, but they have looked in the tropics only,” said Yen-Ting Hwang, a UW doctoral student in atmospheric sciences who found the culprit in one of the most remote areas of the planet.
“What we found, and that was surprising to us, is the models tend to be not cloudy enough in the Southern Ocean so too much sunlight reaches the ocean surface and it gets too hot there,” Hwang said. “People think of clouds locally, but we found that these changes spread into the lower latitudes.”
Prior studies examined tropical sea-surface temperatures, or better ways to represent tropical winds and clouds. None managed to correctly stimulate rainfall in the tropics, however, which is an important region for global climate models since small shifts in rainfall patterns can have huge effects on climate and agriculture.
“The rain bands are very sharp in this area,” commented Dargan Frierson, a UW associate professor of atmospheric sciences. “You go from some of the rainiest places on Earth to some of the driest in [less than a few hundred miles].”
Recent theories have suggested that tropical rainfall might be linked to global processes. The new research looked for possible connections to ocean temperatures, air temperatures, winds and cloud cover.
“For the longest time we were expecting that it would be a combination of different factors,” Frierson said, “but this one just stood out.”
Cloud biases over the Southern Ocean are the primary contributor to the phantom double rain band problem existing in most modern climate models, the research showed.
“It almost correlates perfectly,” Hwang said in a statement. “The models that are doing better in tropical rainfall are the ones that have more cloud cover in the Southern Ocean.”


And the following website announce of new Antarctic meteorological records for the month of March 2013:
New Records for South Pole for March 2013!

Day 9: The peak wind speed of 27 knots/31 mph broke the previous record of 26 knots/30 mph set in 2010.
Day 10: The temperature of -35.8°C/-32.4°F tied the previous maximum temperature record set in 2010.
Day 15: The peak wind speed of 27 knots/31 mph broke the previous record of 25 knots/29 mph set in 2004.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Apocalypse4Real

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Re: Antarctic Weather and Meteorology
« Reply #4 on: May 14, 2013, 08:18:19 PM »
Hi Abrupt SLR,

This may not exactly match the categroy, but the video illustrates the interplay of ice conditions, weather and season and the rich biodviersity of the Antarctic seas.



A4R

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #5 on: May 14, 2013, 08:44:07 PM »
The attached selected images regarding Antarctic Meteorology are from:
Fifty-year Amundsen–Scott South Pole station surface climatologyBy Lazzara et al; Atmospheric Research 118 (2012) 240–259.

As this article has many other relevant figures, I recommend downloading the article from the journal homepage: www.elsevier.com/locate/atmos

This figures show that normally the Antarctic surface temps are too cold for ice surface melting, but that the atmospheric pressures are slowly dropping with time.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #6 on: May 14, 2013, 10:35:07 PM »
The two attached figures from  Fogt et al 2011, so first a SAM and sea ice extent patterns for 2010 (showing high postive SAM values for that year); and second an illustration of the how both SAM and ENSO events can lead to the formation of atmospheric Rossby wavetrains that can serve to transfer atmospheric energy primarily from the Pacific Ocean to the Western Antarctic (resulting in warming).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #7 on: May 15, 2013, 02:17:33 AM »
The two accompanying images are from Bertler et al 2006, note: LAS = Amundsen Sea Low, show the interaction of La Nina and El Nino events with first the warm cyclonic wind blowing onshore and second with the ocean SST in both the Amundsen and Ross Seas.  Also, see the Feb 23rd post in the "Collapse" thread for an indication of the increate in local cyclonic action.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #8 on: May 15, 2013, 03:34:46 PM »
The first image shows the seasonal Cyclone System Density from 1979 to 2001 for the Amundsen, and Ross, Seas, 1979-2001; while the second images the cyclone system density Standard Deviation, 1979-2001 for the same area, both images are from Fogt et al. 2011.  I believe that this type of cyclone pattern in the Amundsen and Ross Seas will re-accrue when the current El Nino hiatus period comes to and end (possibly at the end of 2013 or in 2014).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Apocalypse4Real

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Re: Antarctic Weather and Meteorology
« Reply #9 on: May 15, 2013, 11:46:29 PM »
For those interested in ongoing research into the interaction of Antarctic weather, climate and sea ice decline, for this last season 2012-2013, here is a blog of interest.

See: http://iceshelf.wordpress.com/

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #10 on: May 20, 2013, 01:07:16 AM »
For those who have not already noticed, the Antarctic is consistantly warming these days during the austral-winter as indicated by the attached image of the average temperature anomoly for the past 7-days, from the following website:

http://www.esrl.noaa.gov/psd/map/images/fnl/sfctmpmer_07b.fnl.html

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #11 on: June 23, 2013, 03:57:20 AM »
For serious non-professional readers interested in Antarctic meterology, I highly recommend going to the following website and looking at all of the excellent presentations from the 10-12 June 2013 AMMOMF Workshop:

http://amrc.ssec.wisc.edu/meetings/meeting2013/program.shtml

The first attached image from this program comes from:

What can AMPS (& ERA‐Interim) tell us about the warming in West Antarctica?
By: Julien Nicolas & David Bromwich

This first attached figure shows the very strong surface temperature tend line for increasing temperatures measured at the Byrd station in West Antarctica from 1957 to 2010; which almost indicates a trend of about 0.5 C temperature increase per decade at Byrd.  The presenters recommend that these readings be verified by taking an ice borehole at Byrd.  I note that if the indicated linear trend line becomes non-linear with increasing global warming that surface ice melting could/should become a serious driver of ice mass loss (VAF) this century, from West Antarctica.

The second attached image from this program comes from:

Investigating and Predicting West Antarctic Surface Melting with Reanalysis and GCM-driven Polar WRF
By: David B. Reusch, Derrick Lampkin, Chris Karmosky and David Schneider

The second attached images shows the largest area and longest duration surface melting event in West Antarctica from 12-25-91 to 1-14-92.  As I am not sure of the analysis performed for future projections, all that I will say is that with global warming we can expect more/large/longer surface melting events in West Antarctica.

The third and fourth attached images taken from this program are from:

May 2009 Atmospheric River Event in the Dronning Maud Land
By: Maria Tsukernik, Amanda Lynch, Maya Wei and Irina Gorodetskaya

The third attached shows the accumulative and per day precipitation in Dronning Maud Land from 1979 to the end of 2011; which indicates exceptional (unusually high) snowfall/accumulation in this area particularly in May of 2009.  The fourth figure indicates that this (and possibly other subsequent) high precipitation event was due to an Atmospheric River event coming from the Indian Ocean tropical region.  While many scientists who have projected low ice mass loss from AIS have grabbed rather desperately on to this (and possible subsequent) high precipitation event to say that the future accumulation of large amounts of snow in East Antarctica will largely offset the projected future dynamic ice mass loss in West Antarctica, I do not fell good about any such use of this precipitation data as: (a) The atmospheric rivers are not captured in the GCM models used by these reticent researchers; yet they are happy to grab desperately to field data without a long trend line and which could be a natural fluctuation; and (b) with increasing global warming future atmospheric river events may bring sufficient warm water from the tropics to Antarctica so that the precipitation falls as rain and not snow; which contribute to episodic rapid ice mass loss from any such impacted area.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #12 on: July 04, 2013, 04:49:04 PM »
I have copied the following overview of Antarctic wind types from the following website:

http://www.antarcticconnection.com/shopcontent.asp?type=weather-wind



Types of Winds

The Wild Westerlies
A broad band of strong westerly winds occurs between 30°S and 65°S. The latitudes in this region have been referred to as the Roaring Forties, Furious Fifties, and Screaming Sixties!

Antarctic Circumpolar Trough Winds
Between 60°S and 65°S latitudes lies the Antarctic Circumpolar Trough, a zone of low pressure that contains variable winds flowing from west to east. In this region, fierce storms sweep warm moist air from the middle latitudes toward the pole, causing clouds and precipitation. Storms usually last for a few days, before a brief clearing, then another storm system.

The Coastal (Polar) Easterlies
Between the Antarctic Circumpolar Trough and the continent, a narrow ring of easterly winds exists. Cold winds flowing off the continent are diverted to the west as a result of the Coriolis effect. Conditions here are often calmer and clearer than in the Antarctic Circumpolar Trough.

On the Polar Plateau
The center of the East Antarctic Ice Sheet is called the Polar Plateau because its average height is almost a mile above sea level. Its surface is relatively smooth with a slight slope. On average, a zone of high pressure exists here throughout the year resulting in lighter winds and clearer days, although oceanic storms do occasionally penetrate inland to create hazardous conditions.

Inversion Winds
Some of the fiercest and most deadly Antarctic winds are created by temperature inversions on the high interior ice plateau. The Polar Plateau offers a constant source of extremely cold air which settles close to the ground due to the force of gravity. This pool of dense air flows from the high continental interior down toward the coast, just like a river. The Coriolis effect deflects these inversion winds toward the west, creating the coastal easterlies.

Katabatic Winds
Most of the interior surface winds move over a gentle slope. However, indentations and channels in the landscape can force the airflow to converge, like placing a finger partway over a flowing water hose. This strengthening and intensifying effect on air flow creates what are called katabatic winds (katabasis is Greek for descent). Katabatic winds begin as inversion winds. Like inversion winds, they are gravity-driven but they flow down the much steeper slopes of the coastal regions. The winds are surface winds, only reaching heights of about 1500 feet, although this height varies. Wind speeds can accelerate suddenly from quiet conditions to 60 feet per second (40 mph).

The most famous site for Katabatic Winds, and the windiest spot on Earth, is Cape Dennison at Commonwealth Bay. Convergent katabatic flow from the East Antarctic Ice Sheet results in a mean annual wind speed of 50 miles per hour (80 kilometers per hour)!

The first attached image comes from the Antarctic Connection's discussion of wind types.

The second attached image (from the website give below) of the pattern of High & Low pressure systems and the associated wind patterns around Antarctica on July 4th 2013, make it clear that the circumpolar wind patterns in Antarctica are much more dominant than in the Arctic.

http://www.weather-forecast.com/maps/Antarctica
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #13 on: July 15, 2013, 03:12:08 AM »
For those who have not yet got the message that Central West Antarctica is one of the most rapidly warming places on Earth, please read the following:

D.H. Bromwich et al. Central West Antarctica among the most rapidly warming regions on Earth. Nature Geoscience. Vol. 6, February 2013, p. 139. doi:10.1038/ngeo1671.

Abstract: "There is clear evidence that the West Antarctic Ice Sheet is contributing to sea-level rise. In contrast, West Antarctic temperature changes in recent decades remain uncertain. West Antarctica has probably warmed since the 1950s, but there is disagreement regarding the magnitude, seasonality and spatial extent of this warming. This is primarily because long-term near-surface temperature observations are restricted to Byrd Station in central West Antarctica, a data set with substantial gaps. Here, we present a complete temperature record for Byrd Station, in which observations have been corrected, and gaps have been filled using global reanalysis data and spatial interpolation. The record reveals a linear increase in annual temperature between 1958 and 2010 by 2.4±1.2 °C, establishing central West Antarctica as one of the fastest-warming regions globally. We confirm previous reports of West Antarctic warming, in annual average and in austral spring and winter, but find substantially larger temperature increases. In contrast to previous studies, we report statistically significant warming during austral summer, particularly in December–January, the peak of the melting season. A continued rise in summer temperatures could lead to more frequent and extensive episodes of surface melting of the West Antarctic Ice Sheet. These results argue for a robust long-term meteorological observation network in the region."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #14 on: July 15, 2013, 03:21:48 AM »
For those who do not realize that the East Antarctic has also been warming in recent years, please read the following:

G.J. Marshall, A. Orr and J. Turner. A predominant reversal in the relationship between the SAM and East Antarctic temperatures during the 21st century. Journal of Climate. Published online February 4, 2013. doi:10.1175/JCLI-D-12-00671.1.

Abstract:
"The scientific literature portrays a temporally invariant spatial relationship between the phase of the southern annular mode (SAM) and the sign of surface air temperature (SAT) anomalies across Antarctica. However, here the authors describe a predominant switch from a negative to positive SAM–temperature relationship (STR) across East Antarctica in austral summer/autumn during the first decade of the twenty-first century, when the SAM was generally weakly positive. Of the nine years that had a positive regional STR from 1957 to 2010, seven occurred during the last decade. This reversal appears to be a response to anomalous high pressure over East Antarctica, resulting from variability in the phase and amplitude of the local component of the zonal wavenumber 3 pressure pattern. In years when a reversed (positive) regional STR exists the anomalous circulation is such that there is greater energy flux into the region, while enhanced katabatic drainage across the continental interior disrupts the surface temperature inversion leading to warmer SATs inland, too. The average summer/autumn SAT increase across East Antarctica for years with reversed versus standard STR is ~1°C. Anthropogenically forced models fail to reproduce the trend toward the anomalous high pressure pattern so it is likely that the STR switch is due to natural internal climate variability. That such broadscale STR reversals can take place on decadal time scales needs to be considered when detecting and attributing recent Antarctic climate change and when utilizing isotope data from the East Antarctic ice core record to provide a proxy SAM index prior to the instrumental record."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #15 on: July 15, 2013, 05:13:08 PM »
Regarding the topic of my last post (about the SAM temperature relationship, STR, causing the East Antarctic to warm since the turn of the century); at the risk of questioning something that I am not an expert on; nevertheless I will make the following observations:

- Regarding Marshall et al 2013's statement that: "Anthropogenically forced models fail to reproduce the trend toward the anomalous high pressure pattern so it is likely that the STR switch is due to natural internal climate variability."; this should not give people too much comfort because the "anthropogenically forced models" may be biased and there may well be a long-term trend developing together with "natural internal climate variability".

- Marshal et al 2013 also note that a portion of this increase in surface air temperature (SAT) is due to an increase in "katabatic drainage"; and I note here that this affect was a significant factor contributing to the early collapse of Larsen Ice Shelf B; and that if this pattern continues in East Antarctica, then this katabatic air heating effect may in the future contribute to the early collapse of various East Antarctic ice shelves; which could in turn accelerate ice mass loss from the glaciers that such ice shelves are buttressing.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #16 on: July 20, 2013, 04:12:56 PM »
In broad terms polar amplification is driven by both an increase in local atmospheric specific humidity, and a decrease in regional albedo (together with telecommunication of subtropical atmospheric and oceanic energy) ; and as these two factors have been changing faster in the Arctic than in the Antarctic, polar amplification has currently proceeded faster in the Arctic than in the Antarctic [partly due to the early melting of snow in Alaska, Canada and Siberia (as well as loss of summer Arctic Sea Ice) reducing regional albedo].  While albedo is slower to change in Antarctica, the change in atmospheric specific humidity is also slower to change as indicated in the following reference & abstract, which discuss some of the differences between Antarctic and Arctic specific humidity.  Such excellent work established a clear baseline for the expected changes to come in Antarctic atmospheric specific humidity:
 
Antarctic Low-Tropospheric Humidity Inversions: 10-Yr Climatology
by: Nygård, Tiina, Teresa Valkonen, Timo Vihma, 2013: J. Climate, 26, 5205–5219.  doi: http://dx.doi.org/10.1175/JCLI-D-12-00446.1

Abstract: "Humidity inversions are nearly permanently present in the coastal Antarctic atmosphere. This is shown based on an investigation of statistical characteristics of humidity inversions at 11 Antarctic coastal stations using radiosonde data from the Integrated Global Radiosonde Archive (IGRA) from 2000 to 2009. The humidity inversion occurrence was highest in winter and spring, and high atmospheric pressure and cloud-free conditions generally increased the occurrence. A typical humidity inversion was less than 200 m deep and 0.2 g kg−1 strong, and a typical humidity profile contained several separate inversion layers. The inversion base height had notable seasonal variations, but generally the humidity inversions were located at higher altitudes than temperature inversions. Roughly half of the humidity inversions were associated with temperature inversions, especially near the surface, and humidity and temperature inversion strengths as well as depths correlated at several stations. On the other hand, approximately 60% of the humidity inversions were accompanied by horizontal advection of water vapor increasing with height, which is also a probable factor supporting humidity inversions. The spatial variability of humidity inversions was linked to the topography and the water vapor content of the air. Compared to previous results for the Arctic, the most striking differences in humidity inversions in the Antarctic were a much higher frequency of occurrence in summer, at least under clear skies, and a reverse seasonal cycle of the inversion height. The results can be used as a baseline for validation of weather prediction and climate models and for studies addressing changes in atmospheric moisture budget in the Antarctic."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #17 on: July 20, 2013, 05:27:08 PM »
The following reference and abstract provides valuable analysis of weather data from a relatively recently installed station in Dronning Maud Land; which of importance in the continuing discussion of the very high snow fall events in this area after 2009; which I have over simplified as Atmospheric River events.  Gaining a better understanding of the factors involved in such events is critical to developing better ice mass loss projections for the East Antarctic.  While accurately projecting the such events is beyond the state of the art for regional circulation models, RCMS, and global circulation models, GCMs; nevertheless, I will make the following comments: (a) the frequency of such events may increase with climate change due to increased blocking events associated with a meandering  jet stream; but also by atmospheric oscillations such as SAM, PDO, ENSO etc and in the past such events have been infrequent;  (b) any accumulation of snow associated with such events will accelerate the gravitational driving force on the associated glaciers resulting in more glacial ice mass loss; and (c) at some point in the future, the precipitation from such events may fall in the form of rain instead of snow.

Meteorological regimes and accumulation patterns at Utsteinen, Dronning Maud Land, East Antarctica: Analysis of two contrasting years
by: I. V. Gorodetskaya, N. P. M. Van Lipzig, M. R. Van den Broeke, A. Mangold,W. Boot, and C. H. Reijmer; JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES, VOL. 118, 1–16, doi:10.1002/jgrd.50177, 2013

Abstract: "Since February 2009, an automatic weather station (AWS) has been operating near Utsteinen Nunatak, north of the Sør Rondane Mountains, in Dronning Maud Land at the ascent to the East Antarctic Plateau. This paper gives an assessment of the meteorological conditions, radiative fluxes, and snow accumulation for the first 2 years of operation, 2009 to 2010, analyzed in terms of meteorological regimes. Three major meteorological regimes— cold katabatic, warm synoptic, and transitional synoptic—are identified using cluster analysis based on five parameters derived from the AWS measurements (wind speed, specific humidity, near-surface temperature inversion, surface pressure, and incoming longwave flux indicative of cloud forcing). For its location, the relatively mild climate at Utsteinen can be explained by the high frequency of synoptic events (observed 41%–48% of the time), and a lack of drainage of cold air from the plateau due to mountain sheltering. During the cold katabatic regime, a strong surface cooling leads to a strong near-surface temperature inversion buildup. A large difference in accumulation is recorded by the AWS for the first 2 years: 235mm water equivalent in 2009 and 27mm water equivalent in 2010. Several large accumulation events during the warm synoptic regime occurring mainly in winter were responsible for the majority of the accumulation in 2009. Mostly, small accumulation events occurred during 2010, frequently followed by snow removal. This interannual variability in snow accumulation at the site is related to the intensity of the local synoptic events as recorded by meteorological regime characteristics."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #18 on: July 24, 2013, 02:36:27 PM »
The accompanying figure regarding surface melt rates in the Antarctic in the 2010 to 2011 melt season, indicates that some of the areas with high snowfall also have relatively high surface melt rates (which can be expected to increase in the future); requiring the appropriate adjustments in order to determine SMB.  This figure comes from:

State of the Climate in 2011: Special Supplement to the Bulletin of the American Meteorological Society, Vol. 93, No. 7, July 2012
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #19 on: July 24, 2013, 02:51:02 PM »
To get more Antarctic medium-range weather forecasts go to:

www.ecmwf.int

(see "free access" under the forecast item on the home page, then go to Southern Hemisphere), or go to (and change the date in the e-address line):

http://www.ecmwf.int/products/forecasts/d/charts/medium/deterministic/msl_uv850_z500!Wind%20850%20and%20mslp!0!South%20hemisphere!pop!od!oper!public_plots!2013072400!!/
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Re: Antarctic Weather and Meteorology
« Reply #20 on: July 25, 2013, 02:50:15 AM »
This following reference indicates just how unique the Amundsen Sea sector is to the Southern Ocean - Antarctic interaction (and from there to the world):


Atmospheric Meridional Moisture Flux over the Southern Ocean: A Story of the Amundsen Sea
by: Maria Tsukernik and Amanda H. Lynch, Journal of Climate 2013;  doi: http://dx.doi.org/10.1175/JCLI-D-12-00381.1

Abstract:
"The Antarctic ice sheet constitutes the largest reservoir of freshwater on earth, representing tens of meters of sea level rise if it was to melt completely. However, due to the remote location of the continent and the concomitant sparse data coverage, much remains unknown regarding the climate variability in Antarctica and the surrounding Southern Ocean. This study uses the high resolution ERA-Interim data 1979-2010 to calculate the meridional moisture transport associated with the mean circulation, planetary waves and synoptic scale systems. The resulting moisture flux, which is dominated by the synoptic scales, is largely consistent with results from theoretical assumptions and previous studies. Here we find high interannual and regional variability in the total meridional moisture flux, with no significant trend over the last 30 years. Further, the variability of the meridional moisture flux cannot by explained by the Southern Annular Mode or El Niño-Southern Oscillation, even in the Pacific sector. In addition, the Amundsen Sea sector, where the total meridional moisture transport is the highest, reveals a statistically significant decrease in the moisture flux at synoptic scales along the coastal zone. We suggest that the Amundsen Sea provides a window on the complex nature of atmospheric moisture transport in the high Southern latitudes."
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Re: Antarctic Weather and Meteorology
« Reply #21 on: July 25, 2013, 02:55:35 AM »
The following reference not only indicates how important/unique the Bellingshausen - Amundsen Seas Sector is but also just how poorly the current GCMs, and RCMs, model this critical area (note my previous posts about how the ABSL together with El Nino events can accelerate ice mass loss from the Amundsen-Bellingshausen Seas Sector Ice Sheets):

The influence of the Amundsen-Bellingshausen Seas Low on the climate of West Antarctica and its representation in coupled climate model simulations.
J. Scott Hosking, Andrew Orr, Gareth J. Marshall, John Turner, and Tony Phillips, Journal of Climate 2013; doi: http://dx.doi.org/10.1175/JCLI-D-12-00813.1
Abstract:
"In contrast to earlier studies, we describe the climatological deep low-pressure system that exists over the South Pacific sector of the Southern Ocean, referred to as the Amundsen-Bellingshausen Seas Low (ABSL), in terms of its relative (rather than actual) central pressure by removing the background area-averaged mean sea level pressure (MSLP). In doing so, we remove much of the influence of large-scale variability across the ABSL sector region (e.g., due to the Southern Annular Mode), allowing a clearer understanding of ABSL variability and its effect on the regional climate of West Antarctica. Using ERA-Interim reanalysis fields the annual cycle of the relative central pressure of the ABSL for the period 1979 to 2011 shows a minimum (maximum) during winter (summer), differing considerably from the earlier studies based on actual central pressure which suggests a semi-annual oscillation. The annual cycle of the longitudinal position of the ABSL is insensitive to the background pressure, and shows it shifting westwards from ~250° E to ~220° E between summer and winter, in agreement with earlier studies. We demonstrate that ABSL variability, and in particular its longitudinal position, plays an important role in controlling the surface climate of West Antarctica and the surrounding ocean by quantifying its influence on key meteorological parameters. Examination of the ABSL annual cycle in seventeen CMIP5 climate models run with historical forcing showed that the majority of them have definite biases, especially in terms of longitudinal position, and a correspondingly poor representation of West Antarctic climate."
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Re: Antarctic Weather and Meteorology
« Reply #22 on: July 25, 2013, 06:31:53 PM »
Levy et al DOI: 10.1038/srep02269

The Dry Valleys in Antarctica , thought to be stable permafrost, are melting, Driven by isolation and albedo change.
Shades of Greenland, indeed.

Journal is open access.

sidd

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Re: Antarctic Weather and Meteorology
« Reply #23 on: July 25, 2013, 11:43:49 PM »
For those who are interested, I provide the following reference on an Antarctic Atmospheric Energy Budget framework:

The Antarctic Atmospheric Energy Budget. Part I: Climatology and Intraseasonal-to-Interannual Variability
by: Michael Previdi, Karen L. Smith, and Lorenzo M. Polvani; Journal of Climate 2013; doi: http://dx.doi.org/10.1175/JCLI-D-12-00640.1

Abstract
"We present a new, observationally based estimate of the atmospheric energy budget for the Antarctic polar cap (the region poleward of 70°S). This energy budget is constructed using state-of-the-art reanalysis products from ECMWF (the ERA-Interim reanalysis), and CERES top-of-atmosphere (TOA) radiative fluxes, for the period 2001-2010. The climatological mean Antarctic energy budget is characterized by an approximate balance between the TOA net outgoing radiation and the horizontal convergence of atmospheric energy transport, with the net surface energy flux and atmospheric energy storage generally being small in comparison. Variability in the energy budget on intraseasonal-to-interannual timescales bears a strong signature of the Southern Annular Mode (SAM), with the El Niño-Southern Oscillation (ENSO) having a smaller impact. The energy budget framework is shown to be a useful alternative to the SAM for interpreting surface climate variability in the Antarctic region."
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Re: Antarctic Weather and Meteorology
« Reply #24 on: August 04, 2013, 01:35:37 AM »
I thought that I would post the attached image from the linked website (note that you may need to click on the Southern Hemisphere button at the website) to let people know how very high the austral winter wind speeds (in meters per second) are around the Southern Ocean:

http://www.ecmwf.int/products/forecasts/d/charts/medium/deterministic/msl_uv850_z500!Wind%20850%20and%20mslp!0!South%20hemisphere!pop!od!oper!public_plots!2013080312!!/
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Re: Antarctic Weather and Meteorology
« Reply #25 on: August 04, 2013, 01:54:17 AM »

The article at the following website discuss how the austral winter of 2013 has set multiple high temperature records over the Antarctic:

http://antarcticsun.usap.gov/science/contenthandler.cfm?id=2875
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Re: Antarctic Weather and Meteorology
« Reply #26 on: August 04, 2013, 02:01:37 AM »
The attached image gives a sample of the type of Antarctic jetstream wind speed data that can be obtained at the following website:

http://squall.sfsu.edu/gif/jetstream_sohem_00.gif
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Re: Antarctic Weather and Meteorology
« Reply #27 on: August 06, 2013, 05:19:44 PM »
The attached image and the article at the link below describes the tug-a-war between the "recovery" of the Antarctic ozone hole and the increase in GHG on maintaining the strong low-pressure vortex over Antarctica:

http://www.nature.com/nclimate/journal/v1/n1/full/nclimate1065.html

Based on the continuing high circumpolar wind speeds, the geopotential heights over Antarctica, the relatively high temperatures over Antarctica, and the high measured methane concentrations over Antarctica; it appears that the GHG is winning the current tug-a-war.
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Re: Antarctic Weather and Meteorology
« Reply #28 on: August 06, 2013, 06:15:56 PM »
I am posting this image because I like the way that it illustrates: (a) the relative geopotential heights of the Hadley, Ferrel and Polar cells; (b) the predominant directions of the warm (red arrows) and cold (blue arrows) winds; and (c) the location of the vortex over Antarctica:
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Re: Antarctic Weather and Meteorology
« Reply #29 on: August 07, 2013, 10:09:42 PM »
You can download a free pdf of this paper from the following weblink.  This paper finds that prior GCM projections using RCM 8.5 scenarios under estimate radiative forcing from methane due to the influence of interactive ozone and methane chemistry.  The paper also provides specific discussion about the Antarctic case (but does not consider concentrated local methane emissions for the Antarctic case as is being observed now):

http://www.atmos-chem-phys.net/13/2653/2013/acp-13-2653-2013.html

Shindell, D.T., O. Pechony, A. Voulgarakis, G. Faluvegi, L. Nazarenko, J.-F. Lamarque, K. Bowman, G. Milly, B. Kovari, R. Ruedy, and G. Schmidt, 2013: Interactive ozone and methane chemistry in GISS-E2 historical and future climate simulations. Atmos. Chem. Phys., 13, 2653-2689, doi:10.5194/acp-13-2653-2013.
"The new generation GISS climate model includes fully interactive chemistry related to ozone in historical and future simulations, and interactive methane in future simulations. Evaluation of ozone, its tropospheric precursors, and methane shows that the model captures much of the large-scale spatial structure seen in recent observations. While the model is much improved compared with the previous chemistry-climate model, especially for ozone seasonality in the stratosphere, there is still slightly too rapid stratospheric circulation, too little stratosphere-to-troposphere ozone flux in the Southern Hemisphere and an Antarctic ozone hole that is too large and persists too long. Quantitative metrics of spatial and temporal correlations with satellite datasets as well as spatial autocorrelation to examine transport and mixing are presented to document improvements in model skill and provide a benchmark for future evaluations. The difference in radiative forcing (RF) calculated using modeled tropospheric ozone versus tropospheric ozone observed by TES is only 0.016 W/m2. Historical 20th Century simulations show a steady increase in whole atmosphere ozone RF through 1970 after which there is a decrease through 2000 due to stratospheric ozone depletion. Ozone forcing increases throughout the 21st century under RCP8.5 owing to a projected recovery of stratospheric ozone depletion and increases in methane, but decreases under RCP4.5 and 2.6 due to reductions in emissions of other ozone precursors. RF from methane is 0.05 to 0.18 W/m2 higher in our model calculations than in the RCP RF estimates. The surface temperature response to ozone through 1970 follows the increase in forcing due to tropospheric ozone. After that time, surface temperatures decrease as ozone RF declines due to stratospheric depletion. The stratospheric ozone depletion also induces substantial changes in surface winds and the Southern Ocean circulation, which may play a role in a slightly stronger response per unit forcing during later decades. Tropical precipitation shifts south during boreal summer from 1850 to 1970, but then shifts northward from 1970 to 2000, following upper tropospheric temperature gradients more strongly than those at the surface."
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Re: Antarctic Weather and Meteorology
« Reply #30 on: August 07, 2013, 10:20:06 PM »
The following reference examines/compares black carbon deposition in Antarctica, the Arctic and the Himalayas:

Bauer, S.E., A. Bausch, L. Nazarenko, K. Tsigaridis, B. Xu, R. Edwards, M. Bisiaux, and J. McConnell, 2013: Historical and future black carbon deposition on the three ice caps: Ice-core measurements and model simulations from 1850 to 2100.
J. Geophys. Res., doi:10.1002/jgrd.50612.

"Ice core measurements in conjunction with climate model simulations are of tremendous value when examining anthropogenic and natural aerosol loads and their role in past and future climates. Refractory black carbon (BC) records from the Arctic, the Antarctic, and the Himalayas are analyzed using three transient climate simulations performed with the Goddard Institute for Space Studies ModelE. Simulations differ in aerosol schemes (bulk aerosols vs. aerosol microphysics) and ocean couplings (fully coupled vs. prescribed ocean). Regional analyses for past (1850-2005) and future (2005-2100) carbonaceous aerosol simulations focus on the Antarctic, Greenland, and the Himalayas. Measurements from locations in the Antarctic show clean conditions with no detectable trend over the past 150 years. Historical atmospheric deposition of BC and sulfur in Greenland shows strong trends and is primarily influenced by emissions from early twentieth century agricultural and domestic practices. Models fail to reproduce observations of a sharp eightfold BC increase in Greenland at the beginning of the twentieth century that could be due to the only threefold increase in the North American emission inventory. BC deposition in Greenland is about 10 times greater than in Antarctica and 10 times less than in Tibet. The Himalayas show the most complicated transport patterns, due to the complex terrain and dynamical regimes of this region. Projections of future climate based on the four CMIP5 Representative Concentration Pathways indicate further dramatic advances of pollution to the Tibetan Plateau along with decreasing BC deposition fluxes in Greenland and the Antarctic."
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Re: Antarctic Weather and Meteorology
« Reply #31 on: August 09, 2013, 10:41:14 PM »
According to the linked reference, changes in Southern Hemisphere, SH, cloud cover associated with the ozone hole over Antarctica (and the associated southward drift of the circumpolar winds) has contributed to a significant increase in radiative forcing in the SH.  As the increasing in GHG over Antarctica should have much the same effect on winds and clouds; it is reasonable to expect that this increase in SH radiative heating will continue into the future:

Grise, K. M., L. M. Polvani, G. Tselioudis, Y. Wu, and M. D. Zelinka (2013), The ozone hole indirect effect: Cloud-radiative anomalies accompanying the poleward shift of the eddy-driven jet in the Southern Hemisphere, Geophys. Res. Lett., 40, doi:10.1002/grl.50675.
http://onlinelibrary.wiley.com/doi/10.1002/grl.50675/abstract

"Abstract
This study quantifies the response of the clouds and the radiative budget of the Southern Hemisphere (SH) to the poleward shift in the tropospheric circulation induced by the development of the Antarctic ozone hole. Single forcing climate model integrations, in which only stratospheric ozone depletion is specified, indicate that (1) high-level and midlevel clouds closely follow the poleward shift in the SH midlatitude jet and that (2) low-level clouds decrease across most of the Southern Ocean. Similar cloud anomalies are found in satellite observations during periods when the jet is anomalously poleward. The hemispheric annual mean radiation response to the cloud anomalies is calculated to be approximately +0.25 W m−2, arising largely from the reduction of the total cloud fraction at SH midlatitudes during austral summer. While these dynamically induced cloud and radiation anomalies are considerable and are supported by observational evidence, quantitative uncertainties remain from model biases in mean-state cloud-radiative processes."
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Re: Antarctic Weather and Meteorology
« Reply #32 on: August 19, 2013, 11:48:51 PM »
The article at the following weblink indicates that during the 2013 season the Antarctic has experienced record breaking swings in its meteorological conditions possibly portending future instabilities for Antarctica:

http://antarcticsun.usap.gov/science/contenthandler.cfm?id=2860
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Re: Antarctic Weather and Meteorology
« Reply #33 on: August 22, 2013, 01:45:06 AM »
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Re: Antarctic Weather and Meteorology
« Reply #34 on: August 27, 2013, 05:11:35 PM »
The two attached images related to the Antarctic ozone hole come from the linked web article; and the first attached image gives an idea of the size of the Antarctic ozone hole; while the second attached image shows where the ozone layer exists in a typical atmosphere.  The occurrence of the hole has greatly accelerated Antarctic ice mass loss beyond anything observed in the paleo-record, thus significantly increasing the risk of abrupt SLR this century:

http://www.mnn.com/green-tech/research-innovations/blogs/joe-farman-ozone-hole-discoverer-dies-at-82#
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Re: Antarctic Weather and Meteorology
« Reply #35 on: August 27, 2013, 05:29:11 PM »
The following linked article provides further elaboration (see my reply #31 in this thread) about how the Antarctic ozone hole and increasing GHG can move cloud cover over the Southern Ocean southward thus increasing the local radiative forcing:



http://www.huffingtonpost.com/2013/08/09/antarctic-ozone-hole_n_3731877.html

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Re: Antarctic Weather and Meteorology
« Reply #36 on: August 27, 2013, 06:12:49 PM »
The accompanying 2011 image (from the following link) indicates that "normally" more evaporation comes from the Southern Ocean during the austral winter than during the austral summer.  If cloud cover continues to move southward, this pattern may change:


http://www.iac.ethz.ch/groups/wernli/research/water_transport

Editiorial Note: See also the possible increase in radiative forcing over the Southern Ocean discussed in reply #65 of the "Forcing" thread; which would also affect the future evaporation patterns from the Southern Ocean; which could accelerate future regional warming as water vapor is a GHG.
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Re: Antarctic Weather and Meteorology
« Reply #37 on: September 04, 2013, 04:31:43 AM »
According to the following link at wunderground, August 2013 was the warmest August on record for the South Pole:

http://www.wunderground.com/blog/weatherhistorian/show.html
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Re: Antarctic Weather and Meteorology
« Reply #38 on: September 05, 2013, 05:41:37 AM »

The following website provides an hourly weather forecast for the Ferrigno Glacier; which could help identify weather an increase/change in coastal wind may serve to drive more warm CDW towards the Ferrigno Ice Tongue and grounding line:


http://www.yr.no/place/Antarctica/Other/Ferrigno_Glacier/hour_by_hour.html
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Re: Antarctic Weather and Meteorology
« Reply #39 on: September 05, 2013, 05:38:55 PM »
The information at the following link indicates that data released by the World Meteorological Organisation shows that the ozone layer over Antarctica would recover between the years 2050 and 2100.  On this matter I have the following comments:
(a) When the ozone hole is healed the surface temperatures for Antarctica should increase more rapidly.
(b) It is possible that ocean-ice interaction on the Thwaites Glacier, TG, might push ice mass loss from TG beyond the tipping point, before the ozone hole is healed.
(c) The linked article does not address the likelihood that increasing GHG (particularly methane over Antarctica) will keep the circumpolar wind speeds high (and shifted Southward) even after the ozone hole is healed (assuming that the World Metorological Organisation's projections are correct about the timing of the Antarctic ozone hole healing itself):



http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=11120187
« Last Edit: September 18, 2013, 02:17:10 AM by AbruptSLR »
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Re: Antarctic Weather and Meteorology
« Reply #40 on: September 07, 2013, 04:29:23 PM »
The following link indicates that not only was August the warmest August on record (see also reply #37 in this thread), but that the austral winter of 2013 was the warmest austral winter since record taking began at the South Pole in 1957.  Furthermore, the article indicates that the austral winter of 2013 was also the windier austral winters on record, which not only can drive warm ocean water towards ice sheets, but which can also scour snow off of Antarctica and into the ocean:

http://scienceblog.com/66290/south-pole-experiences-more-record-heat-in-august-to-end-warmest-winter-ever/#FHHuEdKAxduc27A2.99
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Re: Antarctic Weather and Meteorology
« Reply #41 on: September 07, 2013, 10:47:45 PM »
The following two abstracts are taken from the proceedings of the following IGSOC sponsored symposia, and they are relevant to the task of baselineing meteorological and climate trends for Antarctica:


International Symposium on Changes in Glaciers and Ice Sheets: observations, modelling and environmental interactions; 28 July–2 August; Beijing, China; Contact: Secretary General, International Glaciological Society


http://www.igsoc.org/symposia/2013/beijing/proceedings/procsfiles/procabstracts_62.htm


Multiple climate shifts in the Southern Hemisphere over the past three centuries based on glaciological and geochemical investigations in central Antarctic snow pits and ice cores
Alexey EKAYKIN, Anna KOZACHEK
Corresponding author: Alexey Ekaykin
Corresponding author e-mail: ekaykin@aari.ru
"Based on data from geochemical and glaciological investigations in snow pits and on shallow cores, regional stack series of the air temperature and the snow accumulation rate in central Antarctica (Vostok station area) have been obtained for the last 350 years. It has been shown that these parameters varied quasi-periodically with the wavelength of 30–60 years superimposed on the slight positive trend. The correlation of the newly obtained records with the circulation indices of the Southern Hemisphere (SH) shows that the central Antarctic climate is mainly governed by the type of the circulation in the SH: under conditions of zonal circulation the negative anomalies of temperature and precipitation rate are observed, whereas the sign of the anomalies is opposite during the meridional circulation. It has been found that in the 1970s the sign of the relationship between many climatic parameters has changed, which is likely related to the rearrangement of the climatic system of the SH. The data suggest that during the past 350 years such events have happened at least five times. We have also analyzed the recent warming observed in the region of Vostok station in the 2010s. The data on the snow isotope content from the snow pits indeed confirm that this period was warmer than average, although the temperature increase in the decade 2000–2010 was not the highest in the whole 350 year record. Finally, our data suggest that the isotope content of the central Antarctic snow is governed by the summer temperature rather than by mean annual temperature, which is interpreted as the influence of the ‘post-depositional’ effects."

Variation characteristics of nitrate in the superficial snow on the transit from Zhongshan base to Dome Argus, East Antarctica
Guitao SHI
Corresponding author: Guitao Shi
Corresponding author e-mail: shiguitao@pric.gov.cn
"In the Antarctic inlands, the main sources of nitrate in the snow are still controversial, and the nitrate air-to-snow transfer mechanism remains under discussion, although there is a large amount of data from surface snow and ice core sampled over Antarctica. Therefore, characterizing the spatial variation of nitrate in the superficial snow remains significant for further understanding of the sources and post-depositional processes of nitrate in the Antarctic inlands. In this study, 120 superficial snow samples were collected during the 2011/12 Antarctic summer season and the variation characteristics of nitrate in the surface snow in the profile of Zhongshan base to Dome Argus were investigated. The results showed that nitrate concentrations varied from 38.47 μg L–1 to 316.17 μg L–1, with an average of 146.6 μg L–1. Nitrate in the superficial snow along the transit showed a moderate-intensity variation, with a variation coefficient of 0.478, indicating the different main sources or post-depositional processes in varied geographical zones along the transit. The results of the correlation analysis indicated that altitude, distance to coastline, accumulation rate and coexistence impurities as well as the isotopic compositions of water were important factors controlling nitrate concentrations in the superficial snow. Nitrate concentrations increased with an increase in altitude by and large, with a level constant with the altitude below 2000 m. Nitrate levels rose with increasing distance to the coastline and decreased with the reduction in accumulation rate. In the superficial snow samples, nitrate correlated well with calcium and sulfate, with the confidence level >99.9%, probably indicating their common sources. The good correlation between nitrate concentrations and δ18O suggested that temperature was also an important factor influencing nitrate levels, the lower temperature probably relating to the higher nitrate concentrations in the Antarctic inland superficial snow."
« Last Edit: September 07, 2013, 10:57:55 PM by AbruptSLR »
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Re: Antarctic Weather and Meteorology
« Reply #42 on: September 18, 2013, 02:18:08 AM »
The linked article below discusses the findings of results indicating the importance of the influence of the Antarctic ozone hole, not only on the Southern Ocean and the AIS, but also on areas as far away as the Amazon Rain Forest:

http://green.blogs.nytimes.com/2013/02/01/from-ozone-depletion-enduring-effects/?_r=0

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Re: Antarctic Weather and Meteorology
« Reply #43 on: September 18, 2013, 04:42:24 PM »
The following linked reference indicates both how important the Amundsen- Bellingshausen Seas Low (ABSL) is to influencing the climate of West Antarctica, and how poorly the current CMIP5 models represent this critical behavior.

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00813.1


Hosking, J. Scott, Andrew Orr, Gareth J. Marshall, John Turner, Tony Phillips, 2013: The Influence of the Amundsen–Bellingshausen Seas Low on the Climate of West Antarctica and Its Representation in Coupled Climate Model Simulations. J. Climate, 26, 6633–6648. doi: http://dx.doi.org/10.1175/JCLI-D-12-00813.1

Abstract:
"In contrast to earlier studies, the authors describe the climatological deep low pressure system that exists over the South Pacific sector of the Southern Ocean, referred to as the Amundsen–Bellingshausen Seas low (ABSL), in terms of its relative (rather than actual) central pressure by removing the background area-averaged mean sea level pressure (MSLP). Doing so removes much of the influence of large-scale variability across the ABSL sector region (e.g., due to the southern annular mode), allowing a clearer understanding of ABSL variability and its effect on the regional climate of West Antarctica. Using ECMWF Interim Re-Analysis (ERA-Interim) fields, the annual cycle of the relative central pressure of the ABSL for the period from 1979 to 2011 shows a minimum (maximum) during winter (summer), differing considerably from the earlier studies based on actual central pressure, which suggests a semiannual oscillation. The annual cycle of the longitudinal position of the ABSL is insensitive to the background pressure, and shows it shifting westward from  250° to  220°E between summer and winter, in agreement with earlier studies. The authors demonstrate that ABSL variability, and in particular its longitudinal position, play an important role in controlling the surface climate of West Antarctica and the surrounding ocean by quantifying its influence on key meteorological parameters. Examination of the ABSL annual cycle in 17 CMIP5 climate models run with historical forcing shows that the majority of them have definite biases, especially in terms of longitudinal position, and a correspondingly poor representation of West Antarctic climate."

The detailed back-up for this paper can be found at:

http://www.antarctica.ac.uk/data/absl/

The attached image from this website of the ABSL Relative Central Pressure Anomaly indicates that since about 2007 the anomaly has trended towards the positive side (which is not good for WAIS stability).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #44 on: September 18, 2013, 06:45:42 PM »
The linked reference about the SH stationary wave's response to the ozone hole and GHG, could portend increased blocking pattern in the SH; which could create more extreme weather and increase risk of abrupt ice mass loss:

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00160.1?af=R

Southern hemisphere stationary wave response to changes of ozone and greenhouse gases
Lei Wang; Paul J. Kushner; and Darryn W. Waugh; Journal of Climate 2013; doi: http://dx.doi.org/10.1175/JCLI-D-13-00160.1

Abstract:
"The southern hemisphere (SH) stratospheric stationary wave amplitude increased significantly in late spring and early summer during the last two decades of the 20th century. To explore the underlying cause and the separate effects of anthropogenic forcing from ozone depleting substances (ODSs) and greenhouse gases (GHGs) in the past and projected SH stationary wave evolution, we examine a suite of chemistry climate model simulations. The model simulations produce trends in the wave amplitude similar to observed, although somewhat weaker. In simulations with changing ODSs, this increase in amplitude is reproduced during the ozone depletion period, and is reversed during the ozone recovery period. This response is related to changes in the strength and timing of the breakdown of the SH polar vortex associated with ozone depletion and recovery. GHG increases have little impact on the simulated stratospheric stationary wave amplitude, but are projected to induce an eastward phase shift of the waves. This phase shift is linked to the strengthening of the subtropical jets driven by GHG forcing via sea surface warming."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #45 on: December 12, 2013, 07:31:16 PM »
The quote from the following link indicates that the Antarctic ozone hole may be healed by 2070, but by that time it is likely that increases GHGs will keep the circumpolar westerly winds at high velocities (thus continuing to promote the upwelling of warm CDW):

http://www.bbc.co.uk/news/science-environment-25344563

Dr Strahan said: “We can project how quickly we think chlorine will decline in the coming decades and use this, as well as our knowledge of temperatures in Antarctica, to predict that the ozone hole will probably go away in 2070, give or take 10 years.”
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #46 on: January 19, 2014, 08:13:08 PM »
I provide the following link for those who would like to periodically monitor the status of the Antarctic ozone hole:

http://ozonewatch.gsfc.nasa.gov/monthly/SH.html

Furthermore, I would like to state the obvious by noting that the Antarctic ozone hole was not present in any of the paleo-climates that current GCMs are calibrated to, and the formation of the Antarctic ozone hole has significantly increased the probability of ASLR contribution from the WAIS this century (as compared to past interglacial periods).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #47 on: February 01, 2014, 12:40:28 AM »
The attached image from NOAA indicates that over the past 180-day the surface temperature anomaly in the Amundsen Sea (see arrow) was about 2 to 4 degrees C above normal:
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #48 on: February 04, 2014, 06:38:32 PM »
CryoSat has observed patterns (see attached png) in the Antarctic snow pack/ice surface associated with the strong katabatic winds.  While the data discussed in the following extract and linked website do not extend to the coasts, these katabatic wind can/do cause scour of snow into the ocean which contributes to SLR:

Extract: "Antarctica has some of the strongest and most persistent winds on Earth, which leave permanent erosional and depositional features on the surface and in the snow pack. The scientists found that that these wind-driven features modify CryoSat’s radar measurements in such a way as to produce the pattern that has been detected. "

http://www.esa.int/Our_Activities/Observing_the_Earth/CryoSat/CryoSat_detects_hidden_Antarctic_pattern
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AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #49 on: February 18, 2014, 10:49:49 AM »
The attached image of Antarctic atmospheric pressure patterns (from the linked source) shows how far west (close to the Ross Sea) the ABSL currently is.  When and El Nino event occurs (possibly in the 2014-2015 austral summer), one can expect the ABSL to migrate towards the east, thus directing more warm-CDW into the ASE:

http://www.weather-forecast.com/maps/Antarctica

For those who are interested in the ABSL, I recommend scanning through this entire thread.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson