1. Collaborative Research: Arctic Surface Air Temperatures (SAT): Analysis and Reconstruction of Integrated Data Sets for Arctic System Science PIs: Ignatius G. Rigor, Axel Schweiger, & Harry Stern Polar Science Center, APL/UW Collaborators: Jeff Key, NOAA/NESDIS Joey Comiso, NASA/GSFC Study of Arctic System Science (SASS) Investigator Meeting, March 26-27, 2006

2. Outline:  Introduction Motivation, Problems The Plan  Some Science Questions  Data Products Collaborative Research: Arctic Surface Air Temperatures (SAT): Analysis and Reconstruction of Integrated Data Sets for Arctic System Science Study of Arctic System Science (SASS) Investigator Meeting, March 26-27, 2006

3. Motivation: Trends in Arctic Sea Ice Extent (Stroeve et al. 2005, from http://nsidc.org)  Greatest decreases occurred north of Alaska. 2002

4. Alaska +2°C warmer Greenland Siberia +2°C warmer –1°C colder Arctic Climate Impacts Assessment (ACIA) Report 2004 Surface Temperature Trends 1954 – 2003 (Chapman and Walsh 1999; updated) Arctic Sea Ice Extent 1900 – 2003 Arctic Temperature 1900 – 2003 (Jones et al. 1999; updated) Motivation: Decreases in sea ice are usually attributed to increases in temperature ? We plan to fill this “VOID”!

5. Plan: Fill “VOID” using observations, satellite and reanalysis data. (From http://IABP.apl.washington.edu)  Begin in 1893 with the drift of the Fram.  Observations increase in 1979 with IABP.  Satellite estimates also begin in ~1979. Alaska Greenland Siberia

6. Observations from the International Arctic Buoy Programme

7. Surface Air Temperature (SAT) Climatology from IABP/POLES SAT analysis 12-hourly fields have been analyzed from 1979 to present. The IABP/POLES SAT fields show that coldest region in the Arctic is over Siberia during winter. Over the Arctic Ocean, the coldest area is north of the Canadian Archipelago, and during summer the air temperature is close to the freezing point of sea ice.AsiaArcticOcean NorthAmerica Europe PACPACIIFFIICCPACPACIIFFIICCIFIC ATLANTIC

8. Surface Air Temperature (SAT) Trends from IABP/POLES SAT analysis Temperatures have warmed during all seasons, especially during winter and spring Some cooling is noted during winter and fall in the Canadian Arctic. (IABP SAT data from 1979 – 1998. Adapted from Rigor et al. 2000) Winter (DJF)Spring (MAM)Summer (JJA)Fall (SON)AsiaArcticOcean NorthAmerica Europe PACPACIIFFIICCPACPACIIFFIICCIFIC ATLANTIC

9. Some Hurdles: Discrepancies between Winter (DJF) Trends 1982-1999 ERA-40 NCEP APP-X (AVHRR) Comiso AVHRR IABP/POLES TOVS

10. NCEP ERA-40 Despite the good spatial/temporal correlation shown in trend figures, there are biases that need to be resolved! Some Hurdles: Seasonal Mean NCEP & ERA-40 SAT 1960 1970 1980 1990 2000 Summer (JJA), T NP = -1.1°C 3 2 1 Winter (DJF), T NP = -32°C -17 -19 -25 -7 -11 -15 256 -9 -13 -17 Fall (SON), T NP = -18°C Spring (MAM), T NP = -22°C

11. Comparison of daily averaged Surface Air Temperatures (SAT) from ERA-40 and North Pole (NP) Drifting Stations at corresponding gridpoints in ERA-40. Note that ERA-40 SATs are considerably warmer than NP observations across the temperature range. Differences are greatest for low (winter) temperatures. Blue line shows regression fit, green corresponds to 0 bias/gain=1. Some Hurdles: NP-Stations vs. ERA-40

12. Comparison between the SAT observations from buoy 1301, which drifted between Ellesmere Island and Greenland, and the SAT estimates from ERA-40 at the coinciding locations. The SAT observations from the buoy appear to be consistently warm-biased indicating a possible calibration issue for this particular buoy, or ERA-40 may not be able to resolve subgrid-scale variations in SAT in the Canadian Archipelago. Some Hurdles: Buoy Obs. Vs. ERA-40

13. Comparison with of buoy 1101 with ERA-40. The near constant offset between the ERA-40 and the Buoy observation may point to a sensor calibration issue for this particular buoy? Some Hurdles: Buoy Obs. Vs. ERA-40

14. SAT Reconstuction: Arctic SAT Observations 1893 - 2003  Map of in situ Arctic SAT observations. The dots over land show the locations of meteorological land stations. The colors indicate stations established prior to 1950 (blue), and “super stations” established by 1901 (red).  Over the Arctic Ocean the dots show the daily locations of IABP buoys (grey), Russian DARMS buoys (green), AIDJEX (magenta), the manned drifting stations (blue), and Nansen’s ship Fram (red). Alaska Greenland Russia

15. EOF Reconstruction of January 1990 SAT Field (We will actually use a fancier method called Reduced Space Optimal Interpolation.)

16. Why didn’t warmer temperatures during the 1930’s decrease sea ice? Has the correlation between the AO and Arctic climate broken? Arctic Temperature 1900 – 2003 Arctic Sea Ice Extent 1900 – 2000 AO INDEX 1900 – 2000 Some Science Questions: How does Arctic SAT vary on multi-decadal time scales? Are variations related to large-scale modes, e.g. AO?

17. Arctic Surface Air Temperatures for the Past 100 Years Analysis and Reconstruction of an Integrated Data Set Data Products ARCSS-SAT: A SAT data set that provides the “best” estimates of SAT from 1979–present. These data will be analyzed on a 100-km resolution Equal Area Scalable Earth (EASE) grid from 50°N–90°N. ARCSS-SAT-REC: A reconstructed SAT data set (monthly and higher temporal resolution if supported by the error analysis) that provide estimates of SAT from 1901–present, at 100-km resolution from 50°N–90°N. ARCSS-SAT-REC-GLOBAL: The monthly data set will be blended with the monthly global SAT data set of Jones et al. 1999.

18. Arctic Surface Air Temperatures for the Past 100 Years Analysis and Reconstruction of an Integrated Data Set What have we done so far… Reconciling differences between SAT data. Participated in International Workshop on Advances in the Use of Historical marine Climate Data (MARCDAT-II), primarily to learn more about data reconstruction. Presentations & Outreach –MARCDAT-II –Marine Sciences of Alaska Symposium –Alaska Fisheries Science Center Seminar –Polar Weekend at Pacific Science Center –Press interviews with NY Times, etc.

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20. Spare Slides

21. Arctic Surface Air Temperatures for the Past 100 Years Analysis and Reconstruction of an Integrated Data Set Summary & Hurdles Accurate fields of Arctic surface air temperature (SAT) are needed for climate studies, but a robust gridded data set of SAT of sufficient length is not available over the entire Arctic. The ACIA (2004) report exhibits a “data void” over the Arctic Ocean. Over the Arctic Ocean, the SAT data sets with wide spatial coverage begin in 1979 with buoy observations and satellite-derived surface temperatures. We plan to produce authoritative SAT data sets covering the Arctic Ocean from 1901 to present, which will be used to better understand Arctic climate change. However, there are discrepancies between the in situ, satellite-derived, and reanalysis data, e.g. the satellite estimates of trends show cooling over the Arctic during winter where the in situ estimates show warming.

22. Arctic Surface Air Temperatures for the Past 100 Years Analysis and Reconstruction of an Integrated Data Set Plan Reconcile the differences between the various SAT data sets obtained from in situ observations, reanalysis, and satellites. These data will be filtered and bias-adjusted as appropriate. Produce an objectively analyzed, gridded field of SAT observations with error variances established through careful cross-validation, resulting in a “best estimate” field of SAT that minimizes the errors and biases in the original input data sets. Produce a reconstructed gridded field of SAT from 1901 to present, using long-term records from “super-stations” and EOF reconstruction techniques. We will conduct a careful error analysis on the reconstructed fields to provide error bars that vary in time and space to guide future climate analysis on this data set.

23. Arctic Surface Air Temperatures for the Past 100 Years Analysis and Reconstruction of an Integrated Data Set Some Sciences Questions we hope to answer… Are the increases in Arctic SAT the primary driver of decreases in SIE? If so, then why isn’t there a comparable decrease in SIE during the 1930’s? How does Arctic SAT vary on multi-decadal time scales? Are changes in Arctic SAT related to large-scale modes of variability (e.g. Arctic Oscillation) over the longer record? Do Global Climate Models correctly represent SAT variability over the Arctic Ocean?

24. Arctic Surface Air Temperatures for the Past 100 Years Analysis and Reconstruction of an Integrated Data Set SASS Projects that need good SAT Arctic Temperatures  Carbon (?) Greening of the Arctic Heat Budget Humans and Hydrology Melt water and Ice Discharge Modes of Covariability  Social-Ecological (?) Sunlight

25. Discrepancies between Spring (MAM) Trends 1982-1999 ERA-40 NCEP APP-X (AVHRR) Comiso AVHRR IABP/POLES TOVS

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