The 1783–1784 CE Laki eruption in Iceland was one of the largest, in terms of the mass of SO2emitted, high‐latitude eruptions in the last millennium, but the seasonal and regional climate response was heterogeneous in space and time. Although the eruption did not begin until early June, tree‐ring maximum latewood density (MXD) reconstructions from Alaska suggest that the entire 1783 summer was extraordinarily cold. We use high‐resolution quantitative wood anatomy, climate model simulations, and proxy systems modeling to resolve the intra‐annual climate effects of the Laki eruption on temperatures over northwestern North America. We measured wood anatomical characteristics of white spruce (
- Award ID(s):
- 1743738
- NSF-PAR ID:
- 10176364
- Date Published:
- Journal Name:
- The Holocene
- Volume:
- 29
- Issue:
- 11
- ISSN:
- 0959-6836
- Page Range / eLocation ID:
- 1817 to 1830
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Picea glauca ) trees from two northern Alaska sites. Earlywood cell characteristics of the 1783 ring are normal, while latewood cell wall thickness is significantly and anomalously reduced compared to non‐eruption years. Combined with complementary evidence from climate model experiments and proxy systems modeling, these features indicate an abrupt and premature cessation of cell wall thickening due to a rapid temperature decrease toward the end of the growing season. Reconstructions using conventional annual resolution MXD likely over‐estimate total growing season cooling in this year, while ring width fails to capture this abrupt late‐summer volcanic signal. Our study has implications not only for the interpretation of the climatic impacts of the Laki eruption in North America, but more broadly demonstrates the importance of timing and internal variability when comparing proxy temperature reconstructions and climate model simulations. It further demonstrates the value of developing cellular‐scale tree‐ring proxy measurements for paleoclimatology. -
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Proxy evidence is necessary to place current temperature and hydroclimatic changes in a long‐term context and to assess the full range of natural and anthropogenic climate forcings. Here, we present the first millennium‐length reconstruction of late summer (August–September) temperature variability for the Mediterranean region. We compiled 132 maximum latewood density (MXD) tree‐ring series of living and relict
Pinus heldreichii trees from a network of four high‐elevation sites in the Pindus Mountains of Greece. Forty series reach back into the first millennium and the oldest sample dates to 575 CE. At annual to decadal scales, the record correlates significantly with August–September temperatures over the Balkan Peninsula and northeastern Mediterranean (r 1950–2014= 0.71,p < 0.001). We produce two reconstructions emphasizing interannual and decadal scale variance over the past millennium. Analysis of temperature extremes reveals the coldest summers occurred in 1035, 1117, 1217, 1884 and 1959 and the coldest decades were 1061–1070 and 1811–1820. The warmest summers occurred in 1240 and 1474, and the warmest decades were 1141–1150 and 1481–1490. Comparison of this new reconstruction with MXD‐based summer temperature reconstructions across Europe reveals synchronized occurrences of extreme cool summers in the northeastern Mediterranean, and an antiphase‐relationship with warm summer temperatures over the British Isles and Scandinavia. This temperature dipole is related to anomalies in the latitudinal position of the North Atlantic Jet. Despite the representation of common atmospheric forcing patterns, the occurrence of warm extremes is limited to few events, suggesting potential weaknesses of MXD to record warm temperature anomalies. In addition, we acknowledge problems in the observational data to capture local temperature variability due to small scale topographic differences in this high‐elevation landscape. At a broader geographical scale, the occurrence of common cold summer extremes is restricted to years with volcanically induced changes in radiative forcing. -
Abstract. We evaluate a range of blue intensity (BI) tree-ringparameters in eight conifer species (12 sites) from Tasmania and New Zealandfor their dendroclimatic potential, and as surrogate wood anatomicalproxies. Using a dataset of ca. 10–15 trees per site, we measured earlywoodmaximum blue intensity (EWB), latewood minimum blue intensity (LWB), and theassociated delta blue intensity (DB) parameter for dendrochronologicalanalysis. No resin extraction was performed, impacting low-frequency trends.Therefore, we focused only on the high-frequency signal by detrending alltree-ring and climate data using a 20-year cubic smoothing spline. All BIparameters express low relative variance and weak signal strength comparedto ring width. Correlation analysis and principal component regressionexperiments identified a weak and variable climate response for mostring-width chronologies. However, for most sites, the EWB data, despite weaksignal strength, expressed strong coherence with summer temperatures.Significant correlations for LWB were also noted, but the sign of therelationship for most species is opposite to that reported for all coniferspecies in the Northern Hemisphere. DB results were mixed but performedbetter for the Tasmanian sites when combined through principal componentregression methods than for New Zealand. Using the fullmulti-species/parameter network, excellent summer temperature calibrationwas identified for both Tasmania and New Zealand ranging from 52 % to78 % explained variance for split periods (1901–1950/1951–1995), withequally robust independent validation (coefficient of efficiency = 0.41 to0.77). Comparison of the Tasmanian BI reconstruction with a quantitativewood anatomical (QWA) reconstruction shows that these parameters recordessentially the same strong high-frequency summer temperature signal.Despite these excellent results, a substantial challenge exists with thecapture of potential secular-scale climate trends. Although DB, band-pass,and other signal processing methods may help with this issue, substantiallymore experimentation is needed in conjunction with comparative analysis withring density and QWA measurements.more » « less
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Abstract Summer temperatures across eastern North America (hereafter East) will soon reach a level consistently above any observation experienced during the instrumental period. Increasing temperatures will have negative impacts on natural (e.g., water, plant and animal communities) and human (e.g., health, infrastructure, economies) systems upon which the large and growing centres of human population across the region depend. Within the network of Northern Hemisphere tree‐ring temperature proxy records, one of the most obvious geographic holes is the East, where few temperature‐sensitive proxies exist. Here we present the first steps towards building a network of temperature‐sensitive proxy records across the East using blue light intensity (BI) methods applied to the tree rings of multiple temperature sensitive tree species situated from North Carolina to Maine, USA. Our overall objective is to report on the most viable species for BI analysis across different regions of the East (e.g., Southeast US, Midwest US, Northeast US/Canadian Maritimes) by exploring temporal (e.g., since ca. 1900) and spatial relationships between instrumental temperatures and BI metrics. We found BI to be a strong predictor of March–October mean air temperature (
R 2= 0.61) across the Northeast US/eastern Canada, and Sep‐Oct maximum air temperature (R 2= 0.42) across the Southeast US. Of all species tested,Tsuga canadensis andPicea rubens contained the strongest BI temperature signal. Adding more BI sites from these and potentially other species, as well as inclusion of other temperature proxies (e.g., ring widths) will allow for the development of a skilful broad‐scale and long‐term temperature field reconstruction across the East. -
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Abstract Two large volcanic eruptions contributed to extreme cold temperatures during the early 1800s, one of the coldest phases of the Little Ice Age. While impacts from the massive 1815 Tambora eruption in Indonesia are relatively well‐documented, much less is known regarding an unidentified volcanic event around 1809. Here, we describe the spatial extent, duration, and magnitude of cold conditions following this eruption in northwestern North America using a high‐resolution network of tree‐ring records that capture past warm‐season temperature variability. Extreme and persistent cold temperatures were centered around the Gulf of Alaska, the adjacent Wrangell‐St Elias Mountains, and the southern Yukon, while cold anomalies diminished with distance from this core region. This distinct spatial pattern of temperature anomalies suggests that a weak Aleutian Low and conditions similar to a negative phase of the Pacific Decadal Oscillation could have contributed to regional cold extremes after the 1809 eruption.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1177/0959683619862037
