cc: jcole@geo.Arizona.EDU, sandy.tudhope@ed.ac.uk, k.briffa@uea.ac.uk, mhughes@ltrr.arizona.edu date: Fri, 11 May 2001 09:00:03 +0200 from: Keith Alverson subject: Re: comments? to: "Raymond S. Bradley" , Keith Alverson Dear All, Attached the word file that Ray sent you, this time without his electronic flu. Isabelle is the primary author but is out of town so I am dealing with it. This is for the PAGES contribution to the IGBP newsletter that will appear at the time of the congress in Amsterdam. If you are able to make some quick comments they would be greatly appreciated. Although the deadline is technically today, I can probably get away with early next week. Thanks for your help. Keith Ascii version: Recent Destruction and Alteration of Paleoarchives Isabelle Larocque and Keith Alverson PAGES International Project Office Warming has been measured over most parts of the globe during the late 20th century. But instrumental data provide only a limited perspective on this climate change. Because instrumental measurements cover mainly the period of industrialization, they offer little information with which to distinguish between natural and anthropogenic causes of the observed warming. Paleoarchives can provide such information by extending the climate reconstruction over decadal to millennial temporal scales. Furthermore, paleodata can be used to predict future ecosystem changes associated with climate change, based on ecosystem responses to climate changes in the past. Climatic variables such as temperature, salinity, pH, oxygen level, CO2 concentration, moisture balance and circulation strength can be quantitatively reconstructed using various biological indicators (pollen, chironomids, diatoms, cladocereans), isotopes, and other proxy measurements in lake and ocean sediments, corals, stalagmites, polar ice, tree rings, mountain glaciers and other paleoarchives. Although tapping the information contained in these paleoarchives has an enormous potential to contribute to our understanding of linkages between ecosystems and climate, recent anthropogenic factors are leading to the destruction of many of these unique sources of valuable information. A first example of destruction of paleoarchives is the ongoing widespread bleaching of corals. Measurements in corals have been used successfully to reconstruct sea surface temperature and salinity and even the surface circulation of the tropical oceans for the past several hundred years, and for isolated windows during the more distant past, often with a temporal resolution of only a few weeks (Gagan et al. 2000; Tudhope et al. 2001). Furthermore, corals have recorded past changes in the frequency and magnitude of El Nino events with direct consequences for predictability. Coral based reconstructions, for example, indicate a shift from primarily decadal ENSO variability in the 1800¹s to the interannual variability of the last century (Urban et al. 2000). Long coral based records also help to quantify the significance of the 1976 ENSO shift by providing a longer term record. Unfortunately, many corals have been destroyed in recent years. Warming of surface waters, often associated with El Nino events, has caused several types of coral to bleach in the Indian and Pacific Oceans (Strong 1998). Bleaching hurts coral reproduction in two ways: temperature damages reproductive organs producing fewer, less fit sperm and less eggs and, when a threshold temperature is crossed, the corals effectively starve themselves by ridding themselves of zooxhanthellae, the cells they rely on to supply their energy. Zooxhanthellae are photosynthetic and consume CO2 thereby making it easier for the corals to calcify. Expulsion of these cells is causing the white bleached color (Figures 1 and 2). Temperature is not the only factor causing the bleaching of corals, low salinity events from extreme episods of river runoff and diseases also contribute to the observed pattern of increased coral bleaching. While some studies show that corals can recover from bleaching, the repeated bleaching events forecast as a consequence of global warming would prevent maturation and recovering (Normile 2000). Death of corals being used to reconstruct paleoclimate is not a theoretical problem ­it is real. As one example, the Urvina Bay coral study site, the subject of published investigations, was wiped out by the 1982 El Nino and did not recover (T. Guilderson, personal communication). Scientists predict that as much as 30% of the reefs around the world will ecologically collapse within 10-20 years (Dawson et al. NOAA). The reefs at greatest risk are those in Southeast Asia, East Africa, and the Caribbean. An overview of areas susceptible to bleaching can be found on the internet at: psbsgil.nesdis.noaa.gov:8080/PSB/EPS/SST/clim&hot.html. Not only are coral archives under severe threat: alpine glaciers in both the tropics and temperate latitudes are melting. Ice cores from such glaciers have been used to reconstruct temperature, precipitation and atmospheric dust levels (Thompson 1998), and they provide information about climate dynamics, including changes in the strength of the Asian monsoon (Thompson et al. 2000) and ENSO frequency (Moore et al. in press). All mountain glaciers in tropical and temperate latitudes, with the exception of those in Scandinavia, are now rapidly retreating. As shown in figure 3, the volume of the summit glacier on Kilimanjaro (figure 4) has decreased by 81% between 1912 and 2000 (L. Thompson, personal communication). If this trend continues, there will soon be no paleoclimatic information stored in ice at high altitude, low-latitude sites. The only information will be what is left of the cores extracted last year by Lonnie Thompson and his group and stored in freezers at Ohio State University. Given the critical importance of the low latitude regions as drivers of climate on Earth, this loss will irreplaceably hobble our ability to use the past to predict the future. For an extensive overview of the status of glaciers around the world, see the world glacier monitoring service web site (http://www.geo.unizh.ch/wgms/). Other sources of paleodata have been significantly altered in recent decades and their integrity as archives is now threatened. The relationships between tree-ring properties and regional climate parameters for example, are widely used for reconstructing past climate. At high northern latitudes, tree-ring densities show a strong correlation with summer temperature. Transfer functions based estimates of temperature from tree rings in this region are accurate through the first part of the twentieth century. But during the second half of the twentieth century, tree width density was no longer linked to temperature (Briffa et al. 1998). Changes in the reaction of tree growth to temperature in subarctic Eurasia might be linked to an increase in winter precipitation that delays the period of growth (Vaganov 1999). Other possibilities include fertilization effects due to high atmospheric CO2 concentrations or nitrogen-bearing precipitation or the effects of acid rain or enhanced ultraviolet radiation (Briffa 1998). Irrespective of the exact cause, it is very possible that this recent significant perturbation in the ecology of high latitude tree growth is related to human activities. Similar changes have occurred in chironomid communities in the lakes of northern Sweden. Chironomid species assemblages recorded in lake sediments are used to make quantitative reconstruction of mean July air temperature. This method has been shown to reconstruct lake temperatures accurately during the last Quaternary period. However, in some lakes there is no modern analogue for the species assemblages in the most recent sediments (Figure 5, Bigler Submitted). The absence of correspondence in modern assemblages of this lake, compared to assemblages in a 100-lake training set in the area, indicates that factors such as fish introduction or acidification has modified the "natural" assemblages of this lake. For many paleoreconstructions, as in both the tree ring and chironomid examples above, quantification of past temperature changes is based on the concept of a transfer function. When human influences become so strong that the organisms used for such reconstruction are no longer reacting directly to climate but responding instead to other anthropogenic factors, these transfer functions cannot be applied. By changing biological assemblages or biological responses of organisms, anthropogenic factors can lead to potential misinterpretation of ecological responses to future climate change scenarios. A major obstacle standing in the way of producing reliable predictions of climate change and its ecological impacts is a lack of data on timescales longer than the short instrumental record. Recently initiated international global climate observation programs will need to be continuously operated for at least 50 years before they begin to provide information that is relevant to this problem. Natural archives of past climate variability can provide the same information now. Unfortunately, as we have argued above, some of the most valuable paleoclimate archives are being rapidly destroyed, largely due to human influences. We cannot afford such an irreversible loss. The IGBP-PAGES Past Global Changes program therefore calls for scientists and institutional partners to help establish immediately a coordinated international Global Paleoclimate Observing System (GPOS) to complement the recently established Global Climate Observing System (GCOS) that focus only on contemporary observations. There is no time to lose . Bigler, C., Larocque, I., Peglar, S., Birks, H.J.B., Hall, R.I. (Submitted). "Holocene environmental change: A quantitative multi-proxy study from a small lake in Abisko, Swedish Lapland." The Holocene. Briffa, K. R., F. H. Schweingruber, P. D. Jones, T. J. Osborn, S. G. Shiyatov and E. A. Vaganov (1998). "Reduced sensitivity of recent tree-growth to temperature at high northern latitudes." Nature 391: 678-682. Briffa, K. R., Schweingruber, F.H., Jones, P.D., Osborn, T.J., Harris, I.C., Shiyatov, S.G., Vaganov, E.A., Grudd, H. (1998). "Trees tell of past climates: but are they speaking less clearly today?" Phil. Trans. R. Soc. Lond. B 353: 65-73. Gagan, M. K., L. K. Ayliffe, J. W. Beck, J. E. Cole, E. R. M. Druffel, R. B. Dunbar and D. P. Schrag (2000). "New views of tropical paleoclimates from corals." Quaternary Science Reviews 19: 45-64. Moore, G. W. K., G. Holdsworth and K. Alverson (in press). "Extra-Tropical Response to ENSO 1736-1985 As Expressed In An Ice Core From The Saint Elias Mountain Range In Northwestern North America." Geophysical Research Letters. Normile, D. (2000). "Ninth International coral reef symposium: Reef migrations, bleaching effects stir the air in Bali." Science 290: 1282-1283. Thompson, L. G., Davies, M.E., Mosley-Thompson, E., Sowers, T.A., Henderson, K.A., Zagoronov, V.S., Lin, P.-N., Mikhalenko, V.N., Campen, R.K., Bolzan, J.F., Cole-Dai, J., Francou, B. (1998). "A 25,000-year tropical climate history from Bolivian ice cores." Science 282: 1858-1864. Thompson, L. G., T. Yao, E. Mosley-Thompson, M. E. Davis, K. A. Henderson and P.-N. Lin (2000). "A High-Resolution Millennial Record of the South Asian Monsoon from Himalayan Ice Cores." Science 289(5486): 1916-1919. Tudhope, A. W., C. P. Chilcott, M. T. McCulloch, E. R. Cook, J. Chappell, R. M. Ellam, D. W. Lea, J. M. Lough and G. B. Shimmield (2001). "Variability in the El Nino-Southern Oscillation Through a Glacial-Interglacial Cycle." Science 291(5508): 1511-1517. Urban, F. E., J. E. Cole and J. T. Overpeck (2000). "Influence of mean climate change on climate variability from a 155-year tropical Pacific coral record." Nature 407: 989-993. Vaganov, E. A., Highes, M.K., Kidyanov, A.V., Schweingruber, F.H., Silkin, P.P. (1999). "Influence of snowfall and meltiming on tree growth in subarctic Eurasia." Nature 400: 149-151. Figure Captions: Figure 1: Unbleached coral ­ take caption from slideset Figure 2: Bleached coral ­ take caption from slideset Figure 3: Total areal cover of the ice cap on Kilamanjaro from 1912 to present. Should the measured rate of retreat continue unchanged the ice cap will have vanished by around 2015. This figure is courtesy of Lonnie Thompson, unpublished data. Figure 4: Looking southeast over Kibo (5,895m) and Mawenzi (5,149m) Peaks of the Kilimanjaro massif. The Northern Icefield is the ice body in the foreground, draped over the crater rim, and the Western Breach is just to the right. When Hans Meyer first climbed Kibo in 1889 the crater rim was nearly encircled by ice, rendering entry to the crater difficult. Today only a small fraction of this ice remains (~15%); virtually all of the white area within the crater on this image is seasonal snowcover. Source: Douglas Hardy (http://www.geo.umass.edu/climate/tanzania/aerial.html) Photo credit: Capt. G. Mazula (fax +255-51-25551); date of photo unknown. Figure 5: Mean July temperature reconstructed using chironomids (Diptera: Chironomidae) in lake Vuoskkujavri, Northern Sweden. A decrease of 1.5 ƒC is observed through the last 10 000 years. The error bars represent the Root Mean Square Error of Prediction (RMSEP) of 1.96ƒC. The red dots indicate assemblages with no modern-analogues. The first two most recent samples have no modern analogues, assemblages might have been altered by fish introduction or acidification. -- Keith Alverson Executive Director PAGES International Project Office Bärenplatz 2, 3011 Bern Switzerland http://www.pages-igbp.org Tel: +41 31 312 31 33 Mobile: (+41) 079 641 9220 Fax: +41 31 312 31 68 > From: "Raymond S. Bradley" > Date: Thu, 10 May 2001 14:45:54 -0400 > To: Keith Alverson > Cc: jcole@geo.Arizona.EDU, sandy.tudhope@ed.ac.uk, k.briffa@uea.ac.uk, > mhughes@ltrr.arizona.edu > Subject: Re: comments? > > I suggest you get input from Julie Cole or Sandy Tudhope on the coral > business, (what about blowing up reefs?) and Keith Briffa or Malcolm Hughes > on the tree ring section. I'm not sure that it is quite as you state, but > better that they fix it. I'll cc this to all concerned for a hoefully) > quick response. > > Note I think it's cladocerans, and either speleothems or use stalactites > --these are most often sampled. > ray > > At 02:31 PM 05/09/2001 +0200, you wrote: >> Dear Ray and Tom, >> >> Attached is the draft PAGES contribution to the next IGBP newsletter which >> will highlight each of the core projects with a few pages. This issue will >> appear shortly before the Amsterdam congress and will be stuffed in the >> conference bags. Our submission is due Friday. If you have any comments they >> would be appreciated. >> >> Keith >> >> -- >> Keith Alverson >> Executive Director >> PAGES International Project Office >> Bärenplatz 2, 3011 Bern >> Switzerland >> http://www.pages-igbp.org >> Tel: +41 31 312 31 33 >> Mobile: (+41) 079 641 9220 >> Fax: +41 31 312 31 68 >> >> >> Attachment Converted: "C:\EUDORA\Attach\IGBPnews.doc" >> > > > Raymond S. Bradley > Professor and Head of Department > Department of Geosciences > University of Massachusetts > Amherst, MA 01003-5820 > Tel: 413-545-2120; Fax: 413-545-1200 > Climate System Research Center: 413-545-0659 > Climate System Research Center Web Site: > Paleoclimatology Book Web Site (1999): > http://www.geo.umass.edu/climate/paleo/html > Attachment Converted: "c:\eudora\attach\IGBPnews.doc"