PP31B-1484
Fluctuations in Tree Ring Cellulose d18O during the Little Ice Age Correlate with Solar Activity
The Maunder Minimum (AD1645-1715), when sunspots became exceedingly rare, is known to coincide with the coldest period during the Little Ice Age. This is a useful period to investigate possible linkage between solar activity and climate because variation in solar activity was different from that of today. The solar cycle length was longer (14 and 28 years) than that of today (11 and 22 years) hence any climate archives that have similar periodic changes could be separated from other internal climate forcing. We have reported that Greenland temperature variations coincided with decadal-scale variability in solar activity during the Maunder Minimum (Miyahara et al. 2008). Here we report interannual and intra-annual relative humidity (RH) variations in central Japan during that period, using tree ring cellulose d18O in a 382-year-old Japanese cedar tree (Cryptomeria japonica). The isotopic composition of tree rings can be a powerful tool to study the relationship between solar activity and climate, because we can directly compare solar activity (D14C) and climate (d18O) with little dating error. The climate proxy obtained using tree ring cellulose d18O is correlated both negatively and positively with RH and d18O in precipitation, respectively. Since d18O in precipitation is negatively correlated with the amount of precipitation in the monsoon area, tree ring cellulose d18O can be a reliable proxy for past RH and/or amount of precipitation in the area of the interest. Tree ring cellulose d18O of the cedar tree during AD1938-1998 in fact correlates significantly with the mean RH in June in central Japan. Tree ring d18O inferred RH variability during the Maunder Minimum shows distinct high RH spikes with an approximate 14-year quasiperiodicity. All nine solar minima during AD1640-1756 deduced from tree ring D14C coincided with high RH spikes, and seven of which coincided within 1-year. Interannual RH variations also coincided with Greenland temperature during this period. These results suggest that weakening of solar activity at solar minima caused distinct hemispheric scale climate change during the Maunder Minimum. We discuss the mechanism in which the solar activity variation caused the climate change, based on intra-annual RH variability and further data analysis of interannual RH variability. H. Miyahara et al., Earth Planet. Sci. Lett. 272, 1-2, 290-295 (2008).
PP31B-1485
Pliocene Arctic forests: climate reconstructions from a 3 million year old site on Bylot Island derived from stable isotope values of fossil wood.
Studies of Pliocene climate have in recent years begun to gain more prominence in scientific circles. This is because the Pliocene represents the last period when global temperatures were as warm as projections of future climate. One of the most intriguing facets of the Pliocene, are the vast numbers of forest sites that have been discovered well north of the modern boreal tree-line. These forest sites contain numerous fossils of flora and fauna with remarkable preservation, affording the opportunity to reconstruct climate and palaeoecology during this time. This study presents palaeotemperature reconstructions using tree-rings and isotopes of fossil wood from five specimens. Bylot Island, located just north of Baffin Island in the Canadian Arctic is home to a 3 million year old fossil forest site. δ18O values and tree-ring widths of fossil wood were used to reconstruct annual climate variability. Palaeoclimatic modeling of tree isotope values implies growing season temperatures of 8-13°C (warm month mean), and estimated isotope values of precipitation of 18.3 per mil (δ18O). Both palaeotemperature estimates and source water calculations are comparable to those found in a modern Boreal Forest near tree-line. Preliminary investigations of similar aged sites from the Yukon also indicate similar isotopic values suggesting that climate throughout the Arctic region was on the order of 3°C warmer than present at this time.
PP31B-1486
Spatial and temporal variations in oxygen isotopic ratios of tree-ring cellulose in Japan during last three centuries
We present here the first result of a network on yearly resolutions of tree-ring cellulose δ18O measurements in Japan, containing 7 sites from sub-boreal (Hokkaido) to sub-tropical (Kagoshima) regions, 4 of which extend over 250 years. Because the tree-ring δ18O directly reflects δ18O of precipitation (water vapor) and local relative humidity without any large biological effects, it is one of the most promising proxies in the tree ring for reconstruction of past water cycles. Although it is necessary to clarify spatial pattern of tree-ring δ18O variations for reconstruction of past water cycles, it has never been tried outside of Europe or North America. Japanese islands are located between Eurasian continents and Pacific Ocean and partly influenced by East Asian Summer Monsoon, in which δ18O of precipitation shows minimum in summer, opposite to high latitudes such as Europe. There are some common characteristics in short and long-term variability of the tree-ring δ18O in Japan. Short-term variations in tree-ring δ18O are well correlated with those of local summer relative humidity near the sample sites, among which southwestern and northeastern Japan can be categorized into different groups according to their inter-annual variability. There is a long-term decreasing trend of the tree-ring δ18O from the 18th century, possibly reflecting the gradual enhancement of East Asian Summer Monsoon after Little Ice Age, but it increased again after late 19th or early 20th centuries at most sites due to regional decreases in relative humidity with global warming. In the 18th century, abrupt decadal-scale drops in the tree-ring δ18O were often observed at some sites only in southwestern Japan, possibly showing short-term enhancements of Asian Summer Monsoon during Little Ice Age.
PP31B-1487
Understanding oxygen isotope environmental signals in tree ring sequences from New York State
The development of proxy climate records and analyses that allow for investigation and comparison of widespread regions will enhance the global understanding of past climate change through better correlations of significant events among different locations. Trees with a global distribution ranging from the tropics to the subarctic are an ideal medium from which to develop high-resolution isotopic records equivalent to those from varved lake sequences. However, in order to interpret the isotope record in the tree rings, proper calibration sites must be selected and studied. Here we present the results of a constructed calibration data set of oxygen isotopes in tree rings (1942 to 2003 A.D.) from four different locations, ranging from western, south central, central and southeastern New York State. Species studied for this project include eastern hemlock, eastern white pine, white spruce and tuliptree. The data set indicates that there is a clear regional signal in the oxygen isotope data, which indicates different precipitation sources areas for the four sites; these data have a total range of 25‰ to 33‰ V-SMOW. It is anticipated that this calibration data set will be used to calibrate older time-series spanning the Holocene from NE USA.
PP31B-1488
Oxygen Isotopes in Tree Rings: A 345 Year Record of Precipitation in Amazonia
The Amazon basin is one of the world's key centers of atmospheric convection and acts as an engine for global hydrologic circulation. Despite its importance, a paucity of high resolution climate data exists for this region, in large part due to a poor instrumental record. The oxygen isotopic measurement of meteoric water has been used extensively to reconstruct past temperatures derived from ice cores, corals, and tree rings but is only recently recognized as a precipitation proxy in the tropics. Here we present a continuous, highly resolved (intra-annual), 345 year oxygen isotopic record from the Madre de Dios department in Southeastern Peru. Using tropical hardwood species Dipteryx micrantha, we present oxygen (and carbon) isotopic data from digested tree ring cellulose. We also present some of the first intra-annual (early wood versus late wood) isotopic data on this old growth tropical species. We demonstrate the utility of Amazon tropical tree rings to accurately record rainfall. We also identify that this meteoric water was delivered to the region via the South American Low-level Jet (SALLJ), which develops over the Atlantic and is the major water source during the South American Summer Monsoon.
PP31B-1489
1,000 Years of Climatic Variability in the Upper Colorado River Basin, USA
The Upper Colorado River Basin (UCRB) is an essential water resource region in the United States. Seven western U.S. states, including water-hungry California, depend on water originating in the UCRB to support rising populations, agriculture, and infrastructure. Predictions that drought and depletion of water resources will intensify in the next several decades due to human-induced climate warming makes it essential that the natural patterns and causes of drought in the UCRB are understood. In particular, droughts that occurred during the Medieval Period (~ A.D. 900-1200) are of interest because temperatures are known to have been elevated during this time. We present a new 1,000-year tree-ring reconstruction for part of the UCRB using Pinus edulis (two-needle Pinyon) samples from northeastern Utah. We evaluate variability in the summer (JJA) and annual Palmer Drought Severity Index (PDSI) for the Uinta Mountains region, and use wavelet and other analyses to determine the importance of the El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) in determining the timing and duration of droughts in the region. We conclude that while intense droughts did occur during the Medieval Period and throughout the record, water shortages may not be spatially and temporally uniform throughout the UCRB and the western U.S.
PP31B-1490
A Multi-Tree Perspective of Oxygen Isotope Variability in Longleaf Pine (Pinus palustris Mill.) Trees From Big Thicket National Preserve, Texas
When trees utilize water from the upper portion of the soil column instead of deeper groundwater sources, a portion of the cellulose δ18O reflects the δ18O of soil water, which in turn is related to precipitation. Tropical cyclones can produce precipitation depleted in 18O by as much as 10--20‰ relative to normal precipitation. Therefore, oxygen isotope ratios of tree-ring cellulose can record information about past climate variability. However, factors such as soil moisture heterogeneity, canopy position, location within the stand or exposure may result in inconsistencies in the cellulose δ18O of individual trees in the same stand. These complexities may lead to difficulty utilizing single-tree oxygen isotope chronologies to characterize tropical cyclone events or regional climate variability. This study examined the seasonal (earlywood and latewood) δ18O of four individual trees growing in the same stand from 1982--2006 to determine the degree to which individual trees correlate to one another. Each tree was growing in the upper canopy, was similar in age, and occupied a location within the stand. Between-tree latewood δ18O correlations ranged between 0.41 and 0.58. All but one latewood series exhibited an overall negative trend over the 25-year period. Initial earlywood δ18O ratios display a similar negative trend. Time series correlations between individual latewood δ18O chronologies and monthly precipitation totals revealed no significant relationships of this data to fall precipitation. When the four latewood δ18O chronologies were averaged together, a significant seasonal (July--October) correlation was found (r= --0.55, p< 0.01). An autoregressive model (AR-1) was applied to each individual latewood isotope series to pinpoint years where cellulose δ18O indicated a depletion event. The resulting models were compared with local precipitation records to determine their accuracy in recording rains from tropical cyclone events. Although individual trees did record depletions associated with tropical cyclones, they did not necessarily record synchronous events. When the model was applied to the average isotope chronology, it accurately detected 40% of the known storms in the instrumental record. Although the isotope model detected a low percentage of known tropical cyclone events, the combined δ18O chronology exhibited a statistically significant relationship with fall precipitation not present in the ring-width chronologies at this site.
PP31B-1491
Seasonal, Inter-annual and Long Term Trends in the Element Composition of Tropical Tree Rings
The inorganic composition of Rhizophora mucronata wood was studied on 11 stem discs collected from two mangrove forests in Kenya. The aim of this preliminary study was to assess if elements could be used as proxies of environmental and/or anthropogenic change. Earlywood and late wood were separated and analyzed on ICP-MS and ICP-OES. A remarkable synchronicity was found between ring width and Mg/Ca and Mn/Ca ratios, both of which have been used as soil pH proxies. However, there was also a negative correlation between Ca and ring width, indicating a dilution effect at higher growth rates. The essential elements P and K were significantly higher in fast growing plantation trees, suggesting that these elements might be useful as nutrient proxies in mangrove wood. A high correlation was found between Ca and Sr in the wood, indicating that probably no differentiation is made by the tree during incorporation of these elements in the wood. Since Sr/Ca of seawater is related to salinity, we suggest that the Sr/Ca in the wood could be used as a salinity proxy for tree species growing in brackish waters. Finally, a high-resolution study was also conducted using LA-ICP-MS, which revealed a high spatial variability within one ring. This high variability was the result of different concentrations in each wood cell type analyzed. The heavy metals (Cu, Zn, Pb and Cr), as well as Ba, had highest concentrations in the fibers and lowest in the vessels. On the other hand, B, Mn, Ca, P, and Sr were highest in the rays and vessels and lowest in the fibers, while Mg was the highest in the rays, but lowest in the vessels. The implications of these results for the use of trace elements to delimit chemical ring boundaries in tropical trees will be discussed.
PP31B-1492
Can tree ring chemistry indicate soil salt concentrations?
Soil salt concentrations are a major ecological concern, especially in coastal zones and colder climates where road salt is heavily applied. To test if trees could be an archive of soil salinity, we collected sediment and tree stem disks along a transect from a salt-marsh inland. The two species of tree studied were Pinus taeda (Loblolly Pine) and Juniperus virginiana (Eastern Red Cedar). Soil and individual tree rings were analyzed by ICP-OES to determine elemental concentrations. We hypothesized that Sr/Ca ratios in the wood would provide an excellent proxy of soil salinity. Strontium mimics calcium biologically, so Sr/Ca ratios are often taken up in the same ratio as is found in the environment, and at salinities less than 5, Sr/Ca ratios in water typically show a strong positive correlation with salinity. We found that every element studied (Mg, Mn, K, Sr, Ca, Ba, and S) reacted very similarly in the pines. For soil sodium levels less than 60 μg/g, all element concentrations increased sharply, but at 60 μg/g and higher, the element concentrations decreased gradually. In the cedars, a linear correlation was established with each of the elements versus sodium in the soil with R2 values ranging from 0.01 (sulfur) to 0.50 (magnesium). The relationships are not robust, but there is some promise that this tool may eventually be developed.
PP31B-1493
Using Forest Fertilization Trials For Quantifying Element Mobility Across Tree Rings In European Beech
Dendrochemistry might offer very promising potential to study the long-term changes in soil fertility, providing that the wood chemical content does reflect the soil chemical composition and stays, at least partially, unchanged after wood formation. Numerous forest fertilization trials were set up in the early 90's in France to evaluate our ability to correct soil cations deficiency following acidification. Today, they constitute useful experimental designs for understanding how soil fertility changes impact the wood chemical content and for quantifying element mobility across rings. Here, we present results from dendrochemical analyses conducted in European beech (Fagus sylvatica) fertilization experiments to evaluate the ability of wood nutrient content to provide biomarkers for temporal and spatial monitoring of soil conditions. Wood micro-elemental analysis was first performed using synchrotron X-ray fluorescence. Furthermore, we also conducted one of the first attempts to use SEM-EDS (Scanning Electron Microscopy – Energy Dispersive Spectrometer) for measuring tree-ring elemental composition. Our results confirmed the potential of the wood composition to record spatial changes of soil chemical content, as induced by fertilization. Interestingly, the fertilization not only modified the wood content of the major elements (i.e. Ca, K, Mn) but also led to important changes in the bio- availability of some poorly-studied trace elements that were detected in the wood (e.g. Hg), thus leading to promising research perspectives. On the other hand, most elements showed important post-growth mobility that precludes their easy use for temporal monitoring in beech. Finally, we showed that the fast and non- destructive SEM-EDS method could be favourably applied to the dendrochemical analysis of many elements.
PP31B-1494
Laser ablation ICP-MS measurements of trace metals in Douglas-fir: a preliminary analysis with submonthly temporal resolution
Tree-ring cores were collected from a long-lived Douglas-fir (Pseudotsuga menziesii) at Double Springs Pass in the Lost River Range of central Idaho. The tree-rings were dated to 16XX - a minimum age as the pith was not reached during coring because of internal decay. Three sections of the core - with date ranges of 1642-67, 1823-61, and 1971-2005 - were removed for laser ablation ICP-MS analysis. Samples were analyzed by using an Element2 high resolution ICP-MS operating with mass resolution (m/ Δm) of 400, and a New Wave Nd-YAG 213 nm laser system, with a spot size of 40 μm, a repetition rate of 20 Hz, and a fluence of 9-10 J/cm2. Intensities of Ca, Fe, Co, Ni, Cu, Zn, As, Sr, and Ba were collected in continuous traverses with a scan speed of 20 μm/sec, providing an effective spatial resolution of ~40 μm (~2s/analysis), or roughly a 1 to 2 week temporal resolution. Late wood ablated significantly better than early wood, leading to a clear annual signal in background-corrected intensities. Strong correlations occur among Ca-Sr±Ba, which generally exhibit low-amplitude variations, and among Ni-Cu- Zn, which generally exhibit high-amplitude variations. For some annual cycles, all data vary sympathetically, but in others the maxima in Ni-Cu-Zn vs. Ca-Sr are offset by several months. Most importantly, some elements, especially Co and As, exhibit long-term, possibly decadal variations, that may relate to climate factors such as the Pacific Decadal Oscillation. These data hold promise both for chemo-dendrochronology in wood that lacks obvious tree rings, and for characterizing climate variability in the late Holocene.