Seasonal formation of clastic-biogenic varves: the potential for palaeoenvironmental interpretations

Ojala, Antti E. K.; Kosonen, Emilia; Weckström, Jan; Korkonen, Sanna; Korhola, Atte

doi:10.1080/11035897.2013.801925

Cited by 37 publications

(65 citation statements)

References 34 publications

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“…Itkonen and Salonen (1994) showed that total varve thickness of three Finnish lakes were corrrelated with both temperature and precipitation, correlation being weaker for precipitation. Nevetheless, sediment trap studies clearly but 30 qualitatively showed the sensitivity of such systems to varying hydroclimate conditions (Ojala et al 2013;Rydberg and Martinez-Cortizas 2014).…”

Section: Mixed (Clastic-biogenic) Varvesmentioning

confidence: 99%

Arctic hydroclimate variability during the last 2000 years – current understanding and research challenges

Linderholm¹,

Nicolle²,

Francus³

et al. 2017

Preprint

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Abstract. Along with Arctic amplification, changes in Arctic hydroclimate have become increasingly apparent. Reanalysis data show increasing trends in Arctic temperature and precipitation over the 20 th century, but changes are not homogenous 30 across seasons or space. The observed hydroclimate changes are expected to continue, and possibly accelerate, in the coming century, not only affecting pan-Arctic natural ecosystems and human activities, but also lower latitudes through changes in atmospheric and oceanic circulation. However, a lack of spatiotemporal observational data makes reliable quantification of Arctic hydroclimate change difficult, especially in a long-term context. To understand hydroclimate variability and the mechanisms driving observed changes, beyond the instrumental record, climate proxies are needed. Here we bring together 35 the current understanding of Arctic hydroclimate during the past 2000 years, as inferred from natural archives and proxies and palaeoclimate model simulations. Inadequate proxy data coverage is apparent, with distinct data gaps in most of Eurasia and parts of North America, which makes robust assessments for the whole Arctic currently impossible. Hydroclimate proxies and climate models indicate that the Medieval Climate Anomaly (MCA) was anomalously wet, while conditions Clim. Past Discuss., doi:10.5194/cp-2017Discuss., doi:10.5194/cp- -34, 2017 Manuscript under review for journal Clim. Past Discussion started: 17 March 2017 c Author(s) 2017. CC-BY 3.0 License. 2 were in general drier during the Little Ice Age (LIA), relative to the last 2000 years. However, it is clear that there are large regional differences, which are especially evident during the LIA. Due to the spatiotemporal differences in Arctic hydroclimate, we recommend detailed regional studies, e.g. including field reconstructions, to disentangle spatial patterns and potential forcing factors. At present, it is only possible to carry out regional syntheses for a few areas of the Arctic, e.g. Fennoscandia, Greenland and western North America. To fully assess pan-Arctic hydroclimate variability for the last two 5 millennia additional proxy records are required.

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Section: Mixed (Clastic-biogenic) Varvesmentioning

confidence: 99%

Arctic hydroclimate variability during the last 2000 years – current understanding and research challenges

Linderholm¹,

Nicolle²,

Francus³

et al. 2017

Preprint

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“…However, as the seasonal periods for the sediment traps were not identical during the two years, some overlap between the seasons might have taken place. For a more detailed description of the sediment traps and their set-up see Ojala et al (2013). The single deposition basin is proved to effectively trap most of the sedimented allochthonous and autochthonous matter (Ojala and Alenius, 2005).…”

Section: Sediment Trapsmentioning

confidence: 99%

“…The bedrock consists of deeply eroded coarse-grained granites partly overlain by till or a mixture of till and silt (Kujansuu et al, 1981). The sediment in the deepest part of Lake Nautajärvi contains clastic-biogenic type varves (Ojala, 2001;Ojala et al, 2013). Climate around the area is continental, July usually being the warmest month (mean temperature 15 to 18°C) and January or February the coldest (-5 to -12°C) (Finnish Meteorological Institute, 2012).…”

Section: Study Sitementioning

confidence: 99%

“…1) correspond well with the major seasonal changes in the lake. Weather during years 2009 and 2010, when the sediment traps were in operation, differed considerably; winter of 2009 was relatively mild while 2010 was a year of strong seasonal contrast with a harsh winter and heavy snowfall followed by a hot and dry summer (Finnish Meteorological Institute, 2012;Ojala et al, 2013).…”

Section: Study Sitementioning

confidence: 99%

“…1) were used in the study by Ojala et al (2013) in order to assess their impact on annually laminated varve formation in Lake Nautajärvi. The same variables were expected to have a strong impact on species composition determined for the trapping periods of the two consecutive years.…”

Section: Environmental Variablesmentioning

confidence: 99%

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Seasonality of chrysophyte cyst and diatom assemblages in varved Lake Nautajärvi – implications for palaeolimnological studies

et al. 2017

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Phytoplankton species composition is strongly affected by seasons, which should be taken into account in palaeolimnological studies. Although chrysophyte cysts and diatoms are widely used as palaeobioindicators in palaeolimnological studies, only recently have attempts been made to use their modern deposition from sediment trap data to provide more detailed, seasonal-based environmental reconstructions. In this study sediment traps were used to record seasonality of chrysophyte cysts and diatoms during two climatically different years 2009 and 2010 in an annually laminated Lake Nautajärvi, Finland, and this seasonal data was then compared with the fossil record derived from the surface sediment of the lake. The overall changes in cyst and diatom assemblages between years and seasons are subtle. For both groups, no clear connection to any particular season could be detected in the sediment surface. Despite the climatological differences between the study years, the inter-annual accumulation rates of both algal groups were surprisingly similar, whereas the intra-annual accumulation rates differed substantially. This and the high amount of taxa occurring during all seasons in the trap samples implies that primary producers are more dependent on prevailing seasonal limnological conditions than on rapid, shortly lived episodes. Redundancy analysis (RDA) revealed that chrysophyte cyst assemblages from the spring sediment trap are mainly controlled by the spring discharge intensity, a surrogate variable of spring weather conditions, whereas precipitation and air temperature have the strongest impact on the summer assemblages. However, only discharge explains statistically significantly the variance in the cyst data. Precipitation and air temperature have the strongest impact on the diatom summer samples, whereas the spring sediment trap sample of the snowy and harsh winter of 2010 was strongly correlated with the spring discharge. However, none of the measured environmental variables explains the variance in the diatom data statistically significantly. The similarity between the algae found in the sediment traps and surface sediment sample suggests that within small and shallow lakes without any extreme environmental settings the surface sediment sample represents well the lake's overall algal composition and can thus be used in palaeolimnological studies.

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Reconstructing lake bottom water temperatures and their seasonal variability in the Dead Sea Basin during MIS5e

Brall

Gardien

Ariztegui

et al. 2022

The Depositional Record

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Interglacial periods are characterised by thick accumulations of halite units in the Dead Sea Basin. During these intervals, small water droplets (fluid inclusions, FIs) were entrapped in the halite crystals which serve as windows to estimate the chemistry and physical properties of the primary lake water conditions. Brillouin spectroscopy is used here to reconstruct annual resolution temperatures from a halite core section in the Dead Sea Basin during the onset of Marine Isotope Stage 5e (ca 130 ka) of the Last Interglacial. Lake bottom temperatures can be inferred based on the occurrence of coarse/fine halite facies, as observed today with the formation of equivalent halite facies during winter/summer seasons in the Dead Sea. A recurring increase in lake bottom temperatures is found along the direction of coarse halite layers in three successive years. Moreover, low FI entrapment temperatures were detected in layers of fine (cumulate) halite facies. These results imply a twofold stronger seasonality in the Dead Sea Basin compared to today, with colder winters at the onset of Marine Isotope Stage 5e. The results therefore highlight the potential of using cyclic salt deposits to reconstruct seasonal temperature variability for numerous evaporitic environments in the geological record.

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Seasonal formation of clastic-biogenic varves: the potential for palaeoenvironmental interpretations

Cited by 37 publications

References 34 publications

Arctic hydroclimate variability during the last 2000 years – current understanding and research challenges

Arctic hydroclimate variability during the last 2000 years – current understanding and research challenges

Seasonality of chrysophyte cyst and diatom assemblages in varved Lake Nautajärvi – implications for palaeolimnological studies

Reconstructing lake bottom water temperatures and their seasonal variability in the Dead Sea Basin during MIS5e

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