Thomas A. Cahill

1. Aerosols and Climate, Past and Present Results from the UC Davis Physics Department NSF/NOAA Greenland site Thomas A. Cahill Professor Emeritus of Physics and Atmospheric Sciences, and Head, UC Davis DELTA Group

2. Origins of the Program: In 2003, NSF decided to upgrade the Summit site to year round operation. Based on our work in ACE-Asia, NSF asked me to design, implement, and operate a year round aerosol program • This has been from the beginning a cooperative effort – • Prof. Roger Bales, U. California, Merced, • Prof. Joe McConnell, Desert Research Inst, U Nevada, Reno, and • Prof. Thomas A. Cahill, Physics Dept./DELTA Group, U Calif, Davis • co – Principal Investigators • At U. California, Davis, Dept. of Physics/ *DELTA Group, • Dr. David Barnes, DRUM instrumentation, beta mass • Prof. Kevin Perry, now U. Utah, S-XRF analysis at ALS Berkeley, • Dr. Jason Snyder, data reduction and archiving • Dr. Nick Spada, S-XRF at Stanford SSRL, optical data • And at Summit – • Prof. John Burkhart, now U. Oslo, who set up the original site • Those wonderful techs who keep things working in brutal conditions Collection and Analysis of Greenland GEOSummit Aerosols, NSF Arctic Observational Network (AON) Program Award #: 1638402, 7/1/2016 – 6/30/2021

3. Goals: Task #1: To establish the transfer function from aerosols to the snow surface to dust in ice cores, (with Prof. Joe McConnell, Desert Research Institute) Task #2: To provide current aerosol data in the Arctic for climate analyses Constraints: There was very little mass to measure, requiring extreme sensitivity, and we had to operate in a shipping container under the 2 m of snow (until 2007) Our response: Particle collection by size and time using a DRUM sampler, 8 stage (10 to 0.09 µm diameter), continuous, 12 to 48 weeks Particle analysis 12 hr time resolution, , 32 elements, UC Davis S-XRF analysis at Berkeley and Stanford SSRL , detection limits to 0.02 ng/m3, and optical absorption, 8 wavelengths, 350 to 750 nm

4. The DELTA Group slotted 8 DRUM Impactor, our key aerosol instrument in the mammoth ACE-Asia study, 2001 • 8 size ranges: • Inlet ( ~ 10) to 5.0 μm • 5.0 to 2.5 μm • 2.5 to 1.15 μm • 1.15 to 0.75 μm • 0.75 to 0.56 μm • 0.56 to 0.34 μm • 0.34 to 0.26 μm • 0.26 to 0.09 μm • 10.4 l/min, critical orifice control, ¼ hp pump • 8 - 6.5 x 168 mm Mylar strips • For a 168 day run, 1 mm/day, time resolution = 12 hr. • Field portable • 10 kg, 43 × 22× 13 cm To pump Dominates deposition Optically efficient aerosols Deep lung capture 43 cm

5. Synchrotron-X-Ray Fluorescence (S-XRF) in 0.5 mm steps, gives 12 hr time resolution, while in 30 sec duration it gives about 32 elements with 100 x sensitivity of standard XRF. 10,000 cts/channel Background without use of the plane polarized x-rays Co57 standard for dead time At Greenland, MDLs down to 0.02 ng/m3 1 ct/channel

6. Background to Task #1: Aerosols and Ice Cores CO2 today Antarctic cores Greenland cores Ice Age Ice Age Ice Age Ice Age Taupo Toba Dust concentration in ice cores

7. Greenland Ice Cores - the mysterious Younger Dryas - rapidly into, and out of, ice age temperatures Dryas: ± 10 C in~150 years (1,2) Younger Dryas ± 9 C in ~ 22 years (5,7) Paris Accords: +1.5 C (2 C?) in 85 years

8. Task #1: How does the dust in the cores compare to the dust aerosols above the cores? At Summit, most aerosol dust is in particles < 5 µm

9. Since we know the size and composition, we can calculate which aerosols deposit onto the snow and into ice cores. They are almost all larger then 5 µm diameter. .

10. So what have we learned? • Ice cores (crustal particles) • The deposition of soils into the Greenland ice cores represents only the small very coarse fraction of the aerosols above the ice sheet • The aerosols that do not deposit are the ones that are most optically active • These aerosols represent a significant increase in the Earth albedo and thus represent a cooling influence • Thus there was much more cooling by dust during the Younger Dryas than previously thought.

11. Background to Task #2: Current aerosols: The maximum dust mode is usually somewhere in the size range from 5.0 to 0.75 µm diameter, and occurs in Spring Data gap Data gap Missing samples Typically industrial aerosols from US and Europe

12. This is also the period of maximum Chinese dust storms. Dust Storm over Gobi Desert April, 2001 Beijing

13. We were measuring dust in Beijing and Japan as part of ACE-Asia, using the same instrumentation we are using at Greenland 35 Dust storm (from Gobi) Calcium aerosols Beijing April 10, 2001 10 to 5 12,463 ng/m3 5 to 2.5 9,402ng/m3 2.5 to 1.15 5,127 ng/m3 1.15 to 0.75 1,218 ng/m3 Assume the same aerosol decrease in 2,000 km steps 185 Japan 2000 km, ACE Asia Tango forested rural site Japan 2,000 km April 12,2001 Calcium aerosols 10 to 5 1,046 ( 8%) 5 to 2.5 1,371 (15%) 2.5 to 1.15 976 (19%) 1.15 to 0.75 247 (20%)

14. Back trajectories from Greenland pick up the areas impacted by the Chinese aerosols. 35 We had no capability at Greenland in 2001, but we can compare to 2005 but with increased uncertainties 6.7 1.3 Maximum dust event Calcium aerosols ng/m3 Greenland April 10, 2005 measure 10 to 5 0.5 5 to 2.5 2.0 2.5 to 1.15 0.9 1.15 to 0.75 1.0 0.8

15. Maximum dust event Calcium aerosols ng/m3 Greenland April 10, 2005 2005 2001 measure model 10 to 5 0.5 0.025 ± 0.025 5 to 2.5 2.0 0.4 ± 0.4 2.5 to 1.15 0.9 0.8 ± 0.8 1.15 to 0.75 1.0 0.25 ± 0.25 measure to model 10 to 5 x 20 5 to 2.5 x 5 2.5 to 1.15 x 1.1 (3 ± 2) 1.15 to 0.75 x 4 35 6.7 Modeled 0.8 Measured 0.9 1.3 The iron/calcium ratio at Greenland is about the same as Gobi desert dust storms.

16. Robert Hoeller Paved road

17. The maximum dust storm in Spring, 2005 China

18. Higher time resolution (6 hr) data began in 2009. Start of Spring aerosol transport window, with dust showing the fine particle “tail” of long distance transport

19. The soil is closely accompanied by high sulfur levels characteristic of China, but the sulfur is in finer modes and not coated onto the particles

20. Industrial zinc, as shown by a) particle sizes finer than soil, and b) a crustal Enrichment Factor EF x 15

21. March 1, 2013 –Sulfur and zinc but no soil – North America

22. Soil levels peak in Spring, have the elemental ratios of Gobi desert soils, and show a fine particle “tail” showing long distance transport China North America

23. Termination of the dust transport window Local?

24. Association of dust and sulfates, an association from trajectories, not coatings.

25. So what have we learned? • Greenland aerosols (crustal particles)– • There really isn’t a lot of dust • Most of the annual dust seen at Summit occurs in the months from March until June • The Sahara is occasionally seen (VanCuren et al 2012) • When dust sources can be identified, they most often lead to northern China, • Elemental ratios match the Gobi (not Taklimakan) • Timing roughly matches Chinese dust storms (ideal would be simultaneous sampling in China and Greenland) • Semi-quantitative model of transport works

26. These results also solve a long standing question – where does the extra sulfur come from in the ice cores? China

27. Volcanic aerosols at Greenland Summit?Eyjafyallajokull, April 17, 2010

28. Composite map of the volcanic ash cloud spanning 14–25 April 2010 Summit

29. Grimsvötn May 24, 2011

30. No impact was seen in any crustal material at Greenland, as the 500 m trajectory went NW Grimsvötn

31. The 500 m AGL trajectories were well away from Iceland during and after the Grimsvötn eruption, but the 1,000 m AGL trajectory north of Iceland could have been influenced after May 24.

32. This is supported by the highest sulfur reading seen at Greenland, 2003 - 2014

33. So what have we learned? • Greenland aerosols (volcanic)– • On one occasion, a volcanic eruption in Kamchatka, Russia, was seen (VanCuren et al 2011) • Crustal materials from the eruptions of Eyjafjallajokull and Grimsvötn did not seriously impact the Summit site • Unfavorable meteorology for transport in Spring, • Downslope winds from Summit at night • 3,400 m elevation versus height of Icelandic plumes • But sulfur was seen after Grimsvötn.

34. So what have we learned? (other aerosols)While coarse potassium is from soil, fine and very fine potassium are robust tracers of wood smoke

35. Sea salt incursions are common in winter

36. Periodic short lived plumes of very fine industrial aerosols are occasionally observed Spring Asian sulfur enhancement

37. High time resolution industrial metals. Note the 12 hr shift – copper and zinc versus nickel, arsenic and bromine

38. HYSPLIT isentropic backward trajectory for May 15, 2004 at Summit Recall: site of Gobi desert dust in Spring Norilsk Sudbury

39. Changes in the program 2016 - 2021 • Return to longer runs, • Gains sensitivity for trace elements • Time resolution regained via 250 µm S-XRF • Better time registration using Summit diesel exhaust • New Analytical options • Proton induced X-ray Emission (PIXE) for better light elements – sodium through chlorine * • Proton Elastic Scattering Analysis (PESA) for hydrogen as an organic surrogate – allows mass closure • Optical backscattering to get the single scattering albedo • The UC Davis DELTA Group is now solely responsible for data access (ACADIS and http://delta.ucdavis.edu) • *PIXE is the method we used to confirm the validity of the “Vinland Map” which supports the Icelandic Norse sagas

40. Thank you for the invitation. • We have all this data (2.5 million values plus uncertainties) and we hope you will have fun using it • We expect to post the 2015 – 2017 data next October • I will post this talk at http://delta.ucdavis.edu • Personally, I have always wanted to visit Iceland, since • Iceland was key to my validating the “Vinland Map” • I wrote it into my Science Fiction novels

41. VanCuren, Richard, Thomas Cahill, John Burkhart, David Barnes, Yongjing Zhao, Kevin Perry, Steven Cliff, and Joe McConnell, Aerosols and their sources at Summit Greenland – First results of continuous size- and time-resolved sampling. Atmospheric Environment, 52:82-97 (2012) doi:10.1016/j.atmosenv.2011.10.047 • The current data are available: https://arcticdata.io/catalog/#view/urn:uuid:e9136a64-661f-470d-9b3a-72f31d54d066 , Roger Bales et al, open 11 files, Aerosol Chemistry 2003 - 2013 (20 Mb) • The new data (2014 – 2021) will be available in Excel spread sheets from http://delta.ucdavis.edu and ACADIS • Publications on our technology and full quality assurance documentation are included at the same web site in DRUM Quality Assurance Protocols ver 1/2017 (DQAP ver 1/2017) • Instructions on typical uses of the data are being developed • Nick Spada and I will be happy to help you use these data for your own ends, with only an acknowledgement to NSF for support for this work - tacahill@ucdavis.edu

42. Technology slides (4)

43. UC Davis DRUM sampler in tunnel under circa 6 feet of snow

44. Greenland DRUM strips against white backgroundDate scale is approximate; fine soot from Summit diesels will set final dates 10 to 5.0 5.0 to 2.5 2.5 to1.15 1.15 to 0.75 0.75 to 0.56 0.56 to 0.34 0.34 to 0.26 0.26 to 0.09 July 16 2015 8/1 9/1 10/1 11/1 12/1 1/1 2/1 3/1 4/1 5/1 June 1

45. The UC Davis/Lawrence Berkeley NL Advanced Light Source aerosol S-XRF microprobe –450,000 analyses, mostly for climate studies, continuous DRUM 8 size modes, each with 32 elements, to pg/m3, 1999 – 2017 DRUM strip X-ray beam

46. Synchrotron-X-Ray Fluorescence (S-XRF) spectrum, 30 sec, and AXIL analysis of a remote area aerosol sample. The polarized S-XRF beam suppresses the background by a factor of about 100 versus standard XRF. 10,000 cts/channel Background without use of the plane polarized x-rays Co57 standard for dead time At Greenland, MDLs down to 0.02 ng/m3 1 ct/channel

47. Historical slide (1)

48. The Vinland Map – circa 1453- contrast and color enhanced. Note the many square patches over worm holes