Evolution of NAO and AMO strength and cyclicity derived from a 3-ka varve-thickness record from Iceland

2013 ◽  
Vol 69 ◽  
pp. 142-154 ◽  
Author(s):  
Kristín B. Ólafsdóttir ◽  
Áslaug Geirsdóttir ◽  
Gifford H. Miller ◽  
Darren J. Larsen
Keyword(s):  
Varve Thickness

scholarly journals Seasonal deposition processes and chronology of a varved Holocene lake sediment record from Chatyr Kol lake (Kyrgyz Republic)

Geochronology ◽  
2020 ◽  
Vol 2 (1) ◽  
pp. 133-154
Author(s):  
Julia Kalanke ◽  
Jens Mingram ◽  
Stefan Lauterbach ◽  
Ryskul Usubaliev ◽  
Rik Tjallingii ◽  
...  
Keyword(s):  
Kyrgyz Republic ◽  
Sediment Record ◽  
Spring Precipitation ◽  
Radiocarbon Dates ◽  
Thin Sections ◽  
Varve Thickness ◽  
210Pb And 137Cs ◽  
Plant Remains ◽  
Bulk Organic Matter ◽  
Deposition Processes

Abstract. Microfacies analysis of a sediment record from Chatyr Kol lake (Kyrgyz Republic) reveals the presence of seasonal laminae (varves) from the sediment base dated at 11 619±603 BP (years Before Present) up to ∼360±40 BP. The Chatvd19 floating varve chronology relies on replicate varve counts on overlapping petrographic thin sections with an uncertainty of ±5 %. The uppermost non-varved interval was chronologically constrained by 210Pb and 137Cs gamma spectrometry and interpolation based on varve thickness measurements of adjacent varved intervals with an assumed maximum uncertainty of 10 %. Six varve types were distinguished, are described in detail, and show a changing predominance of clastic-organic, clastic-calcitic or clastic-aragonitic, calcitic-clastic, organic-clastic, and clastic-diatom varves throughout the Holocene. Variations in varve thickness and the number and composition of seasonal sublayers are attributed to (1) changes in the amount of summer or winter/spring precipitation affecting local runoff and erosion and/or to (2) evaporative conditions during summer. Radiocarbon dating of bulk organic matter, daphnia remains, aquatic plant remains, and Ruppia maritima seeds reveals reservoir ages with a clear decreasing trend up core from ∼6150 years in the early Holocene, to ∼3000 years in the mid-Holocene, to ∼1000 years and less in the late Holocene and modern times. In contrast, two radiocarbon dates from terrestrial plant remains are in good agreement with the varve-based chronology.

Glacial Varve Thickness and 127 Years of Instrumental Climate Data: A Comparison

1997 ◽  
pp. 159-179
Author(s):  
Christian Ohlendorf ◽  
Frank Niessen ◽  
Helmut Weissert
Keyword(s):  
Climate Data ◽  
Varve Thickness

scholarly journals Solar activity expressed in a modern varve thickness sequence

2019 ◽  
Vol 56 (1) ◽  
pp. 32-46 ◽  
Author(s):  
Gary B. Hughes ◽  
Jordan Adams ◽  
Jaclyn M.H. Cockburn
Keyword(s):  
Solar Activity ◽  
Laminated Sediments ◽  
Varve Thickness ◽  
Ice Cap ◽  
Uv Emission ◽  
Depositional Settings ◽  
Climate Simulations ◽  
Direct Forcing ◽  
Climate Signals ◽  
Annually Laminated Sediments

Annually laminated sediments (varves) form in particular depositional settings, e.g., where seasonal climate produces fluctuations in runoff volume; variations in runoff affect the amount and type of sediment delivered to a catchment. Prior studies confirm that variations in selected varve traits correlate with inter-annual climate signals. In some locations, solar activity also appears to be expressed in varve characteristics, either through a direct effect or indirectly via influence of solar activity on climate. Evidence from proglacial Iceberg Lake, Alaska, indicates that solar activity may have directly contributed to varve deposition. A varve thickness sequence is compared to sunspot observations from 1610–1995 CE. Maunder and Dalton minima are clearly expressed in a varve power spectrogram; varve signal amplification beginning ca. 1950s CE coincides with increasing activity evident in a sunspot spectrogram, features that are only vaguely discernible in the raw time-series plots. Spectral relationships at sunspot periodicities are consistent with direct solar forcing of varve thickness, independent of any effect solar activity might otherwise have on climate. Simulations based on a meltwater model indicate that direct forcing could result from amplified ultraviolet (UV) emission during solar maxima, combined with lower UV albedo of glacial ice. The plausible forcing mechanism bolsters epistemology for concluding a cause–effect relationship: solar variability likely contributed directly to inter-decadal patterns in Iceberg Lake varve thicknesses. The putative effect could be enhanced at higher latitudes, where Earth’s atmosphere absorbs less of the UV energy emitted by the Sun; periods of lowered ozone concentration near the poles would exacerbate the natural abetting UV phenomena, potentially linking human activity to recent and accelerated polar ice cap melting.

Anomalous early 20th century sedimentation in proglacial Green Lake, British Columbia, Canada

2006 ◽  
Vol 43 (6) ◽  
pp. 671-678 ◽  
Author(s):  
Brian Menounos
Keyword(s):  
British Columbia ◽  
Air Temperature ◽  
Laminated Sediments ◽  
Annual Maximum ◽  
Coast Mountains ◽  
Varve Thickness ◽  
Green Lake ◽  
Daily Discharge ◽  
Temperature Records ◽  
Temperature Proxy

Annually laminated sediments were recovered from Green Lake, a proglacial lake in the southern Coast Mountains in British Columbia, to examine their potential as a temperature proxy. Varve thickness is moderately correlated with temperature anomalies (A.D. 1900–1994) and annual maximum mean daily discharge of Lillooet River (A.D. 1930–1999), but these relations are not stable through time. Following A.D. 1977, the relation between varve thickness and annual maximum mean daily discharge is stronger. Prior to A.D. 1977, varve thickness is correlated with March to October air temperature, which controls the intensity and duration of glacier runoff. Varve thickness is weakly correlated with reconstructed air temperature records for North America and the Northern Hemisphere for the period A.D. 1600–1976. Less extensive glacier cover may explain the lack of a clear temperature signal in the varved sediment record prior to A.D. 1600 and following A.D. 1977. The period of highest lake sedimentation, from A.D. 1920 to 1945, coincides with rapid retreat of glaciers in the watershed. The lack of a similar level of sedimentation in the varve chronology suggests that glacier recession during the period 1920–1945 was higher than at any time in the past 600 years.

A 1500-year record of temperature and glacial response inferred from varved Iceberg Lake, southcentral Alaska

2006 ◽  
Vol 66 (1) ◽  
pp. 12-24 ◽  
Author(s):  
Michael G. Loso ◽  
Robert S. Anderson ◽  
Suzanne P. Anderson ◽  
Paula J. Reimer
Keyword(s):  
Sediment Transport ◽  
20Th Century ◽  
Tree Ring ◽  
Ring Width ◽  
Warm Season ◽  
Tree Ring Width ◽  
Varve Thickness ◽  
Temperature Trends ◽  
Hemisphere Temperature ◽  
Southcentral Alaska

AbstractWe present a varve thickness chronology from glacier-dammed Iceberg Lake in the southern Alaska icefields. Radiogenic evidence confirms that laminations are annual and record continuous sediment deposition from A.D. 442 to A.D. 1998. Varve thickness is positively correlated with Northern Hemisphere temperature trends, and more strongly with a local, ∼600 yr long tree ring width chronology. Varve thickness increases in warm summers because of higher melt, runoff, and sediment transport (as expected), but also because shrinkage of the glacier dam allows shoreline regression that concentrates sediment in the smaller lake. Varve thickness provides a sensitive record of relative changes in warm season temperatures. Relative to the entire record, temperatures implied by this chronology were lowest around A.D. 600, warm between A.D. 1000 and A.D. 1300, cooler between A.D. 1500 and A.D. 1850, and have increased dramatically since then. Combined with stratigraphic evidence that contemporary jökulhlaups (which began in 1999) are unprecedented since at least A.D. 442, this record suggests that 20th century warming is more intense, and accompanied by more extensive glacier retreat, than the Medieval Warm Period or any other time in the last 1500 yr.

Long-term river discharge and multidecadal climate variability inferred from varved sediments, southwest Alaska

2011 ◽  
Vol 76 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Claire A. Kaufman ◽  
Scott F. Lamoureux ◽  
Darrell S. Kaufman
Keyword(s):  
Grain Size ◽  
Early 19Th Century ◽  
Varve Thickness ◽  
Hydroclimate Variability ◽  
Varved Sediment ◽  
Daily Discharge ◽  
Multidecadal Climate Variability ◽  
Instrumental Period ◽  
Annual Discharge

AbstractSedimentological analyses of 289 years (AD 1718–2006) of varved sediment from Shadow Bay, southwest Alaska, were used to investigate hydroclimate variability during and prior to the instrumental period. Varve thicknesses relate most strongly to total annual discharge (r2 = 0.75, n = 43, p < 0.0001). Maximum annual grain size depends most strongly on maximum spring daily discharge (r2 = 0.63, n = 43, p < 0.0001) and maximum annual daily discharge (r2 = 0.61, n = 43, p < 0.0001), while varve thickness is poorly correlated with maximum annual grain size (r2 = 0.004, n = 287, p = 0.33). Relations between varve thickness and annual climate variables (temperature, precipitation, North Pacific (NP) and Pacific Decadal Oscillation (PDO) indices) are insignificant. On multidecadal timescales, however, regime shifts in varve thickness and total annual discharge coincide with shifts in NP and PDO indices. Periods with increased varve thickness and total annual discharge were associated with warm PDO phases and a strengthened Aleutian Low. The varve-inferred record of PDO suggests that any periodicity in the PDO varied over time, and that the early 19th century marked a transition to a more frequent or detectable shifts.

Multiple hydroclimatic controls over recent sedimentation in proglacial Mirror Lake, southern Selwyn Mountains, Northwest Territories

2005 ◽  
Vol 42 (9) ◽  
pp. 1589-1599 ◽  
Author(s):  
Jessica D Tomkins ◽  
Scott F Lamoureux
Keyword(s):  
Northwest Territories ◽  
Summer Temperature ◽  
Sedimentary Record ◽  
Sediment Delivery ◽  
Late 20Th Century ◽  
Glacial Meltwater ◽  
Varve Thickness ◽  
Mirror Lake ◽  
Decadal Scale ◽  
The Impact

Varves from Mirror Lake, Northwest Territories (62°N, 128°W) reveal significant, but changing climatic influences on discharge and sedimentation on a decadal scale during the late 20th century. The complex hydroclimatic signal within the sediments indicates the difficulty in identifying a quantitative relationship between varve thickness and a single climatic variable. Regression of recent varve thickness with local meteorological data shows July temperature as the dominant control over sediment accumulation. In contrast, the dampening effects of increased snowfall on glacier ablation and resultant runoff reduce sediment delivery. Although the impact of snowfall does not appear to significantly weaken the relationship between summer temperature and varve formation, periods when multiple climatic factors control sediment delivery are characterized by distinctive varves containing two prominent silt units. Thus, the Mirror Lake hydrological system appears to shift between two general states. The first state involves a pronounced summer glacial meltwater phase due to dominant summer temperature influences on glacial melt, resulting in varves with one silt unit. This varve structure dominates the sedimentary record from A.D. 1670 to 1941, possibly reflecting a Little Ice Age influence in the study area. The second state operates in years when glacial meltwater discharge is delayed until August, due to increased snow cover, and the lake receives increased sediment-poor nival melt. These conditions lead to the formation of varves with two silt units corresponding to nival and glacial discharge phases and are common in the sedimentary record from A.D. 1390 to 1669 and A.D. 1942 to 1996.

Constructing paleoclimate networks from annually laminated lake sediments – the VARDA database

2020 ◽  
Author(s):  
Arne Ramisch ◽  
Alexander Brauser ◽  
Mario Dorn ◽  
Cecile Blanchet ◽  
Brian Brademann ◽  
...  
Keyword(s):  
Climate Change ◽  
Lake Sediments ◽  
Large Scale ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Volcanic Eruptions ◽  
Scale Model ◽  
Graph Database ◽  
Varve Thickness ◽  
Novel Approach

&lt;p&gt;Reconstructing global patterns of past climate change requires large-scale networks of paleoclimatic archives. Generating paleoclimatic networks relies on precise synchronization of individual records with robust age control. The detailed age constrains of continuous varved lake sediments and the good preservation of isochrones from supra-regional extreme events make these records ideal for constructing large scale continental paleoclimatic networks. Yet, a global synthesis of varved lake archives is missing.&lt;/p&gt;&lt;p&gt;Here we present the VARved sediments DAtabase 1.0 (VARDA 1.0), the first global data compilation for varve chronologies and associated palaeoclimatic proxy records. VARDA 1.0 uses a connected data model provided by a state-of-the-art graph database, enabling custom generations of synchronized paleoclimatic networks. We report on compilation strategies for the identification of varved lakes and assimilation of high-resolution chronologies. Existing chronologies have been re-assessed and harmonized using a novel approach that infers information on sedimentation rates enclosed in varve thickness records. This information provides detailed information on the priors required for Bayesian age-depth modelling and strongly improves these results. Additionally, a synthesis of tephra layers from volcanic eruptions provides supra-regional isochrones for synchronizing even distant varved lake records. The current version (VARDA 1.0) comprises 261 datasets from 95 varved lake archives, including chronological information from &lt;sup&gt;14&lt;/sup&gt;C dating and varve thickness measurements, but also palaeoclimatological proxy data. We further explore potential applications of such networks in paleoclimatic studies, such as identifying leads and lags of regional climate change, large-scale model-data comparisons or differentiated proxy responses between archives. The VARDA graph-database and user interface can be accessed online at https://varve.gfz-potsdam.de.&lt;/p&gt;

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