Arctic Sea Ice : Forum

Cryosphere => Arctic background => Topic started by: ArcticMelt on February 16, 2017, 12:39:02 PM

Title: Current temperature in Greenland at a maximum of 140 thousand years?
Post by: ArcticMelt on February 16, 2017, 12:39:02 PM
On 1 July 1993, after five years of drilling, the Greenland Ice Sheet Project Two (GISP2,) penetrated through the ice sheet and 1.55 meters into bedrock recovering an ice core 3053.44 meters in depth, the deepest ice core recovered in the world at the time.

http://www.gisp2.sr.unh.edu/ (http://www.gisp2.sr.unh.edu/)

An analysis of the ice core got  temperature reconstruction was in past.
Title: Re: Current temperature in Greenland at a maximum of 140 thousand years?
Post by: ArcticMelt on February 16, 2017, 12:54:41 PM
This reconstruction ends with 1905 and represents the average values at intervals of 10-25 years.

ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/isotopes/gisp2_temp_accum_alley2000.txt

But what is the average annual temperature at the top of Greenland now?

ftp://ftp.ncdc.noaa.gov/pub/data/gsod/
There is a temperature measuring stations GISP2 (1989-1997) and SUMMIT (1998-2017). Files with the code 049999-00003 and 044160-99999. In total there are 8329 values of the average daily temperature for the period 1989-2017 years. As a result, it is more than 23 years of observations, which is comparable with the intervals in the ice core.

The average annual temperature in these modern measurement data is equal to - 28.3 degrees Celsius. It is half a degree Celsius higher than any temperatures in the ice core.

Title: Re: Current temperature in Greenland at a maximum of 140 thousand years?
Post by: Neven on February 16, 2017, 01:09:52 PM
Nice graph, ArcticMelt. Maybe you could send it to Don Easterbrook. ;-)

But is it an apples to apples comparison. In other words, what are the difficulties when splicing current temps to that graph?
Title: Re: Current temperature in Greenland at a maximum of 140 thousand years?
Post by: ArcticMelt on February 16, 2017, 01:24:40 PM
Thanks for the suggestion. )

But is it an apples to apples comparison. In other words, what are the difficulties when splicing current temps to that graph?

I think in addition be interested this work.

http://onlinelibrary.wiley.com/doi/10.1002/grl.50456/pdf (http://onlinelibrary.wiley.com/doi/10.1002/grl.50456/pdf)

Recent warming at Summit, Greenland: Global context and implications.
Title: Re: Current temperature in Greenland at a maximum of 140 thousand years?
Post by: DrTskoul on February 16, 2017, 01:41:59 PM
Great data!!!
Title: Re: Current temperature in Greenland at a maximum of 140 thousand years?
Post by: ArcticMelt on February 16, 2017, 01:48:22 PM
In addition, probably modern temperature is slightly higher than on my chart as the current station (Summit) is a little colder drilling locations (GISP2).

The distance between them is less than a kilometer.

http://berkeleyearth.lbl.gov/stations/155346 (http://berkeleyearth.lbl.gov/stations/155346)
SUMMIT
Latitude:   72.5830 ± 0.0005 N
Longitude:   38.4500 ± 0.0005 W
Elevation:   3,207.00 ± 0.05 m

http://berkeleyearth.lbl.gov/stations/14820 (http://berkeleyearth.lbl.gov/stations/14820)
GISP2
Latitude:   72.5800 ± 0.0050 N
Longitude:   38.4600 ± 0.0050 W
Elevation:   3,205.00 ± 0.05 m

Summit on 2 meters above and to the north GISP2. The difference in temperature measurement can be 0.4 degrees Celsius.

http://journals.ametsoc.org/doi/pdf/10.1175/1520-0450(2001)040%3C0741%3AADYOTO%3E2.0.CO%3B2 (http://journals.ametsoc.org/doi/pdf/10.1175/1520-0450(2001)040%3C0741%3AADYOTO%3E2.0.CO%3B2)
Title: Re: Current temperature in Greenland at a maximum of 140 thousand years?
Post by: ArcticMelt on February 16, 2017, 02:15:41 PM
Also some statistics. The warmest years at the top of Greenland were 2010 and 2016. Then was -25,6 и -26,2 С.
Title: Re: Current temperature in Greenland at a maximum of 140 thousand years?
Post by: ArcticMelt on February 16, 2017, 02:32:26 PM
But is it an apples to apples comparison. In other words, what are the difficulties when splicing current temps to that graph?

Another important indicator is the number of years with the melting on the Summit.

http://onlinelibrary.wiley.com/doi/10.1002/grl.50456/pdf (http://onlinelibrary.wiley.com/doi/10.1002/grl.50456/pdf)

Quote
The brief record surface melt in July 2012, which extended over the traditional dry snow facies, including Summit, was unprecedented during the satellite era [Nghiem et al., 2012]. Prior to this event, the most recent melt event at Summit occurred in 1889, which was one of only eight such events to have occurred in the past ~1500 years [Clausenet al., 1988; Meese et al., 1994]. Summit melt frequency has varied throughout the Holocene, ranging from once per ~82 years from 5500 to 8500 BP, to once per ~250 years from 1000 to 4000 BP [Alley and Anandakrishnan, 1995].

http://blog.hotwhopper.com/2016/01/greenland-really-has-been-melting-can.html (http://blog.hotwhopper.com/2016/01/greenland-really-has-been-melting-can.html)

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F3.bp.blogspot.com%2F-kTHBdHbaT_Y%2FVovpdjZp9LI%2FAAAAAAAALi0%2FUQ8TVbSgMY4%2Fs640%2FGISP2%252Bmelts.gif&hash=aec412be654cc500e88ce6d05b949e4c)

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F1.bp.blogspot.com%2F-2aAm9AR-CnE%2FVovra4MJ4MI%2FAAAAAAAALjE%2Fbb_rfIV1nwY%2Fs1600%2FGreenland%252Bmelt%252Bevents.png&hash=1ae5e84ddc11ed0fbf330e48f6475f8b)
Title: Re: Current temperature in Greenland at a maximum of 140 thousand years?
Post by: ArcticMelt on February 16, 2017, 03:04:23 PM
Some difference between the two indicators (the temperature reconstruction of the core and summit melt frequency) may be due to the fact that summer in the Northern Hemisphere is now warming slower than average annual temperatures. Past warming were caused by astronomical factors (Milankovitch cycles).
https://en.wikipedia.org/wiki/Milankovitch_cycles (https://en.wikipedia.org/wiki/Milankovitch_cycles)

Summit melt frequency in West Antarctica is reversed.
http://www.whoi.edu/cms/files/DasAlley2008_31763.pdf (http://www.whoi.edu/cms/files/DasAlley2008_31763.pdf)
Rise in frequency of surface melting at Siple Dome through the Holocene: Evidence for increasing marine influence on the climate of West Antarctica.
Title: Re: Current temperature in Greenland at a maximum of 140 thousand years?
Post by: ArcticMelt on February 17, 2017, 07:41:41 AM
Today I found another paper on the topic of temperature reconstructions from GISP2.

http://onlinelibrary.wiley.com/doi/10.1029/2011GL049444/full (http://onlinelibrary.wiley.com/doi/10.1029/2011GL049444/full)
High variability of Greenland surface temperature over the past 4000 years estimated from trapped air in an ice core
Quote
The current decadal average surface temperature (2001–2010) at the GISP2 site is −29.9°C.

It is unclear why they have different values of current temperature?

Title: Re: Current temperature in Greenland at a maximum of 140 thousand years?
Post by: ArcticMelt on February 17, 2017, 07:55:55 AM
Strangely, they think GIPS2 contrary colder current station.

Quote
[11] To place the Greenland temperature proxy reconstruction into a historical context, we incorporate two additional Summit temperature records. One record is obtained from a compilation of Summit Automatic Weather Station ∼2 m surface air temperature (SAT) observations (hereafter AWS or in-situ record) that spans 23 years (1987–2010). The AWS were situated within 20 km of the GISP 2 coring site and within 25 m elevation of the ice sheet topographical summit (Figure 1, top, red line). The series begins in May 1987 with Automatic Weather Station data after Stearns and Weidner [1991]. Shuman et al. [2001] merge this record with data from the Greenland Climate Network (GC-Net) AWS data [Steffen and Box, 2001] to produce the first 12 years of this compilation. Gaps before June 1996 are in-filled using daily passive microwave emission brightness temperatures. GC-Net data then comprise the period spanning June 1996 to December 2003 with gaps in-filled by Danish Meteorological Institute (DMI) Summit AWS data [Vaarby-Laursen, 2010]. The DMI data exclusively form this data series from January 2004 through December 2010.