historical sunspot data dating back to , strong relationship between ) in the varve record of Santa Barbara basin, California. Santa Barbara Basin varve record of to AD. sediment radioisotope dates serve as valuable racy of 14C dates in sediments from the South-. A varve is an annual layer of sediment or sedimentary rock. The word 'varve' derives from the A well-known marine example of varve sediments are those found in the Santa Barbara basin, off California. Wohlfarth, B. (), The chronology of the Last Termination: A review of radiocarbon-dated, high- resolution.
Paleoclimatic evidence for widespread anomalies and events is collected in Tables through for the six time slices for which SBB flood deposits are documented during the past two millennia. Perturbations in global atmospheric circulation can manifest themselves by floods in one region and by drought in another.
To a lesser extent the same consideration is valid for temperature anomalies. We caution that 84 temporal correlation does not necessarily imply common causation, and that the dating accuracy of paleoclimatic evidence degrades with increasing age.
Nevertheless, the large matrices of evidence permit the formulation of reasonable hypotheses for several flood events. Not all listed evidence necessarily correlates with SBB flood deposits, and some SBB floods may represent merely local weather extremes. Our discussion starts with the ca.
Schimmelmann and others assembled much regional and global evidence for rapid, intense cooling aroundwith an equatorward shift of prevailing wind patterns and associated storm tracks. Atmospheric cooling in the wake of the eruption of the Peruvian volcano Huaynaputina in is a likely cause references in Schimmelmann and others ; Zielinskialthough another, unidentified volcanic eruption at about the same time may have been decisive for the magnitude of paleoclimatic anomalies in the Northern Hemisphere Gervais and MacDonald Table 1- 1 lists 29 additional corroborating multidisciplinary lines of evidence for the global disturbance of atmospheric circulation in the first decade of the 17th century.
All ages are in calendar years AD. The numerous data sources listed earlier by Schimmelmann and others for the ca. Coldest summer of the last millennium on the Northern Hemisphere; Jones and others Coldest year in Ostfriesland, Germany, within time period ; Gla- ser Cold summer shown in many European tree-ring data; Briffa and others Kola peninsula, Russia, year tree-ring record shows very cold summer temperature; Gervais and MacDonald The driest 7-year episode in years, recorded in northeastern Virginia tree rings; Stahle and others The period to had the second highest drought frequency of the past years in the Sierra Nevada Hughes and Brown This SBB flood event correlates with Southern and Central California regional records of increased contemporaneous wetness, and also with reports of climatic change at about the same time elsewhere Table Ice cores from both hemispheres indicate an abrupt global reorganization of atmospheric circulation around Kreutz and othersat a time widely considered to mark the beginning of the Little Ice Age glaciation had started earlier in some regions surrounding the North Atlantic; Grove A large increase in flood magnitude is reported for the upper Mississippi at the transition to the Little Ice Age Knox The various global paleoclimatic temperature and precipitation responses feature distinct regional differences, but most temperature records suggest cooling in the early 15th century.
One factor for this predominant cooling may have been decreasing solar irradiance Beer and othersyet oceanographic mechanisms for triggering the LIA have been proposed for example, Broecker The majority of evidence in Table is consistent with an SBB flood occurring during the late s to early s. Notes as in Table No low-growth years in Sierra Nevada sequoia tree-ring record, Cali- fornia, suggesting absence of drought; Hughes and Brown Predominantly cold summer temperatures in the Northern Hemi- sphere Jones and othersbut Sierra Nevada tree-ring records show regionally mild temperatures Scuderi,; Graumlich, s Adverse tree growth conditions, eastern Norway, based on tree-rings; Kalela-Brundin Volcanic event recorded in Dye 3 ice core, Greenland; Fisher and oth- ers Time period yr AD Descriptions of paleoclimatic evidence; source of data Drought in Mali, Africa, causing the abandonment of Timbuktu in by the Mali empire to the Tuareg nomads.
The evidence for this regional drought is strong, but trees in the environments studied by Stine may not have recorded brief wet spells within an overall dry period.
Varve - Wikipedia
Drought would have reduced vegetation cover and thus prepared the soil in the Santa Barbara region for erosion, enabling intermittent severe storms to produce a mid-size SBB flood deposit. The Sierra Nevada tree-ring record might not reflect mid-winter and late-winter storms.A 1500-year Record of Temperature and Glacial Response from Varved Iceberg Lake
The period was the second warmest century of the millennium in the Northern Hemisphere, surpassed only by the last century Jones and others Sierra Nevada tree-ring records show predominantly mild temperatures for the growing season during the first half of the 11th century Scuderi; Graumlich A cold spell around the s is recorded in Sierra Nevada tree rings Graumlich An intermittent cold spell may have interrupted a relatively warm climate regime.
This may have triggered the SBB flood event, by shifting mid-latitude storm tracks equatorward, either via expansion of the circumpolar vortex, or via persistent ridges of high pressure. The preponderance of the evidence in Table points towards the late s or early s as a likely age for this SBB flood deposit. Third coldest summer of the last millennium on the Northern Hemi- sphere; Jones and others Tree-ring evidence for volcanic-induced frost in California and Nevada; LaMarche and Hirschboeck Transition from year warm period to year cold interval in Sierra Nevada; s predominantly cold; Graumlich Time period yr AD Descriptions of paleoclimatic evidence; source of data Winter temperature below average in western central Europe; Pfister and others Fourth coldest decade of summer temperatures of the last millennium on the Southern Hemisphere; Jones and others Sedimentary evidence for severe drought on Yucatan peninsula that cen- tered on and lasted until Hodell and others Other evi- dence for aridity on Yucatan peninsula and in central Mexico listed by Metcalfe and others Yucatan drought 14C-dated to and by Curtis and others Onset of markedly drier conditions on the Bolivian-Peruvian altiplano causing the demise and eventual collapse of the Tiwanaku culture sur- rounding Lake Titicaca.
The Quelccaya records D and E are anchored securely by the A. Record G is based on counting of annual growth bands in a stalagmite without specified precision. The period had the highest drought frequency of the past years in the Sierra Nevada Hughes and Brown Limited regional evidence from Mono Lake and the Sierra Nevada suggests wet conditions, or at least absence of drought Table1- 4.
Cultural changes were observed in South America that were presumably linked to climatic changes Thompson and others This very thick SBB flood layer is varve-count-dated to a time-period when the Sierra Nevada was free of severe drought and the Pacific Ocean off Santa Barbara was entering the most unstable marine climatic interval of the Holocene Table Tree-ring evidence for a cold spell around in the Sierra Nevada Scuderi is not supported by a record from Colorado where no frost damage to tree-growth occurs from until Brunstein Ample archeological and paleobotanical 14C-dated evidence points towards dramatic climatic changes in South America and the Caribbean at around 14C-dated.
The actual age of the SBB flood layer may be ca. The period was one of the three periods with the highest drought frequency of the past years in the Sierra Nevada Hughes and Brown No low-growth years in Sierra Nevada sequoia tree-ring record, California, suggesting absence of drought; Hughes and Brown Strong Sierra Nevada tree-ring evidence for frost, presumably due to volca- nic eruptions; Scuderi Notable frost-rings in Bristlecone Pines at Almagre Mountain, Colorado, likely due to volcanic eruption; Brunstein Dry fog in Europe and Middle East, due to very large volcanic eruption; Stothers and Rampino, ; Stothers End of drought on Yucatan; Hodell and others ; Curtis and others Time period yr AD Descriptions of paleoclimatic evidence; source of data No low-growth years in Sierra Nevada sequoia tree-ring record, California, suggesting absence of drought; Hughes and Brown Sierra Nevada tree-ring evidence for frost damage, presumably due to volca- nic eruption of Mt.
Etna Scuderi No tree-ring evidence for frost damage at Almagre Mountain, Colorado; Brunstein Etna eruption; Stothers and Rampino Climatic Implications for Transitions of Ancient Civilizations. Consequently, coastal Peruvian cultures rise and fall in antiphase with highland altiplano cultures. The sketch of South American cultural successions Figure 2F; adapted from Thompson indeed suggests a correlation between climatic and societal changes. These cultural responses to climate change, as well as corroborating evidence from other cultures, were reviewed by deMenocal Sierra Nevada tree-ring evidence for very cold late-season temperature; second coldest year mean; Scuderi Sierra Nevada tree-ring evidence for frost Scuderi,probably due to large volcanic eruption of Mt.
Vesuvius Stothers and Rampino Several trees show frost-rings at Almagre Mountain, Colorado; Brunstein Etna; Stothers and Rampino The Sun as a Forcing Factor. A recent study by Hodell and others provides the strongest evidence yet for causal linkages between solar activity, large-scale changes in atmospheric circulation as expressed by the occurrence of droughts on the Yucatan peninsula, and societal changes in Maya cultures. Most SBB flood deposits seem to have occurred at times shortly following major droughts on the Yucatan peninsula.
Yucatan droughts were reported to express a prominent ca. Although we do not subscribe to the view that SBB flood deposits are triggered via a fast- forcing mechanism in the wake of solar changes van Geel and others ; with reply by Schimmelmann and othersit now seems possible that fluctuations of solar activity at least prepare the stage for potential large-scale Southern California flooding every ca.
In the past two millennia this SBB flood scenario skipped a beat only three times, and never skipped twice Figure 3. If the past years of flood record have any forecasting value, our generation may have an opportunity to witness historically unprecedented flooding of Southern California.
Both records exhibit strong ca. Santa Barbara Basin flood deposits horizontal lines occur in close proximity to peaks of d18O, which coincide with drought conditions on Yucatan, and in most cases also with decreased D14C associated with an increase in solar output note the D14C scales are inverted.
Conclusions The six major flood deposits in the Santa Barbara Basin within the past two millennia are dated by varve-counting, characterized by their microscopic composition, and are interpreted via comparison with multidisciplinary paleoclimatic evidence: We thank Brian Constantino for assistance with X-radiography, Colin Harvey for training in grain size analysis, and Maria Mastalerz for microscopic interpretation of plant debris.
Gregg Garfin provided insight about the interpretation of tree-ring evidence. Secular climatic oscillations as indicated by catastrophic floods in the Spanish Mediterranean coastal area 14th—19th centuries. The role of the sun in climate forcing. Quat Sci Rev July temperature during the second millennium recon- structed from Idaho tree rings.
There was a problem providing the content you requested
Geophys Res Lett Climate paradigms for the last millennium. Past Global Changes 8 March: De Geer and his co-workers and students made trips to other countries and continents to investigate varved sediments.
Ernst Antevs studied sites from Long IslandU. By this stage, other geologists were investigating varve sequences, including Matti Sauramo who constructed a varve chronology of the last deglaciation in Finland. Since then, there have been revisions as new sites are discovered, and old ones reassessed. At present, the Swedish varve chronology is based on thousands of sites, and covers 13, varve years. Inalthough varves were considered likely to give similar information to dendrochronologythey were considered "too uncertain" for use on a long-term timescale.
The light layer usually comprises a coarser laminaset, a group of conformable laminae, consisting of silt and fine sand deposited under higher energy conditions when meltwater introduces sediment load into the lake water. During winter months, when meltwater and associated suspended sediment input is reduced, and often when the lake surface freezes, fine clay -size sediment is deposited forming a dark coloured laminaset.
In addition to seasonal variation of sedimentary processes and deposition, varve formation requires the absence of bioturbation.
Consequently, varves commonly form under anoxic conditions.