Jussi Grießinger

New perspective on spring vegetation phenology and global climate change based on Tibetan Plateau tree-ring data

Significance Inconsistent results regarding the rate of change in spring phenology and its relation to climatic drivers on the Tibetan Plateau have been obtained in the past. We introduce and describe here an innovative approach based on tree-ring data, which converts daily weather data into indices of the start (and end) of the growing season. This method provides a unique long-term record of vegetation phenological variability over the period 1960–2014. This approach could further be extended to other forested regions of the world. Scaling up the analysis would provide additional information on phenological responses of terrestrial ecosystems to the ongoing climate change across the Northern Hemisphere. Phenological responses of vegetation to climate, in particular to the ongoing warming trend, have received much attention. However, divergent results from the analyses of remote sensing data have been obtained for the Tibetan Plateau (TP), the world’s largest high-elevation region. This study provides a perspective on vegetation phenology shifts during 1960–2014, gained using an innovative approach based on a well-validated, process-based, tree-ring growth model that is independent of temporal changes in technical properties and image quality of remote sensing products. Twenty composite site chronologies were analyzed, comprising about 3,000 trees from forested areas across the TP. We found that the start of the growing season (SOS) has advanced, on average, by 0.28 d/y over the period 1960–2014. The end of the growing season (EOS) has been delayed, by an estimated 0.33 d/y during 1982–2014. No significant changes in SOS or EOS were observed during 1960–1981. April–June and August–September minimum temperatures are the main climatic drivers for SOS and EOS, respectively. An increase of 1 °C in April–June minimum temperature shifted the dates of xylem phenology by 6 to 7 d, lengthening the period of tree-ring formation. This study extends the chronology of TP phenology farther back in time and reconciles the disparate views on SOS derived from remote sensing data. Scaling up this analysis may improve understanding of climate change effects and related phenological and plant productivity on a global scale.

Influence of the Indian Ocean Dipole on tree-ring δ18O of monsoonal Southeast Tibet

We present a newly developed, annually resolved tree-ring cellulose δ18O chronology for the southeastern Tibetan Plateau (TP) from Sikkim larch (Larix griffithii), spanning between 1684 and 2012. Comparisons with local and regional climate data reveal strong positive correlations with monthly sunshine hours, temperature and daily temperature amplitude as well as strong negative correlations with relative humidity, vapor pressure, rain days per month and cloud cover of August. Relationships with local and regional tree-ring δ18O chronologies are stable and highly significant. Over the 20th century, we find no long-term climatic trends. This is consistent with other tree-ring δ18O chronologies of other tree species south of the Himalayas, but contrasts with results from isotope studies north of the Himalayas. This suggests stable macroclimatic flow patterns throughout the last centuries for the southern tree stands. In terms of large-scale climate dynamics, we find evidence of a significant 30-year wave influencing our tree-ring oxygen chronology, most probably induced by the Indian Ocean Dipole and influencing tree-ring oxygen isotope chronologies along the southeastern Himalaya and the southeastern rim of the TP. This pattern is spatially and temporarily consistent among the chronologies and has apparently strengthened during the last century. During periods of strong positive dipole mode activity, the dipole mode index shows positive correlations with the δ18O of tree-rings on the southeastern TP.

Air mass origin signals in δ (18)O of tree-ring cellulose revealed by back-trajectory modeling at the monsoonal Tibetan plateau.

A profound consideration of stable oxygen isotope source water origins is a precondition for an unambiguous palaeoenvironmental interpretation of terrestrial δ18O archives. To stress the influence of air mass origins on widely used δ18O tree-ring chronologies, we conducted correlation analyses between six annually resolved δ18O tree-ring cellulose (δ18OTC

Earlywood and Latewood Stable Carbon and Oxygen Isotope Variations in Two Pine Species in Southwestern China during the Recent Decades

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An updated multi-temporal glacier inventory for the Patagonian Andes with changes between the Little Ice Age and 2016

) chronologies and mean annual air package origins obtained from backward trajectory modeling. This novel approach has been tested for a transect at the southeastern Tibetan plateau (TP), where air masses with different isotopic composition overlap. Detailed examinations of daily precipitation amounts and monthly precipitation δ18O values (δ18OP

Dendroecological Perspectives on Climate Change on the Southern Tibetan Plateau

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Imprints of Climate Signals in a 204 Year δ18O Tree-Ring Record of Nothofagus pumilio From Perito Moreno Glacier, Southern Patagonia (50°S)

) were conducted with the ERA Interim and Laboratoire de Météorologie Dynamique General Circulation Model (LMDZiso) data, respectively. Particularly the southernmost study sites are influenced by a distinct amount effect. Here, air package origin δ18OTC

Late Holocene Asian summer monsoon variability reflected by δ18O in tree‐rings from Tibetan junipers

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Reconstructing glacier retreat since the Little Ice Age in SE Tibet by glacier mapping and equilibrium line altitude calculation

relations are generally weaker in contrast to our northern located study sites. We found that tree-ring isotope signatures at dry sites with less rain days per year tend to be influenced stronger by air mass origin than tree-ring isotope values at semi-humid sites. That implies that the local hydroclimate history inferred from δ18OTC

A shift in cloud cover over the southeastern Tibetan Plateau since 1600: evidence from regional tree-ring δ18O and its linkages to tropical oceans

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