Intralake training set of fossil Cladocera for paleohydrological inferences: evidence for multicentennial drought during the Medieval Climate Anomaly

Abstract

We investigated an intralake surface sediment data set for fossil Cladocera from Lake Pieni‐Kauro, eastern Finland, with an objective to develop a paleohydrological inference model for lake level reconstructions. The Cladocera assemblages showed high heterogeneity among the sampling sites according to the water depth gradient, thus enabling the construction of a quantitative inference model for water level reconstructions. The strongest model was developed using weighted averaging with classical deshrinking regression. This model had a jackknifed coefficient of determination of 0.79 and a root mean squared error of prediction of 0.79 m. We tested the performance of the model on previously available Cladocera stratigraphy and Cladocera‐based and chironomid‐based lake level reconstructions from Lake Iso Lehmälampi, southern Finland. The lake level reconstructions, based on different proxies and independent inference models, showed high levels of similarity, indicating a period of lower water table during the Medieval Climate Anomaly around 1000 ad. The results suggest that the applicability of intralake paleohydrological models may not be regionally restricted when applied to similar lake types and, therefore, provide an alternative perspective on paleolimnological training set design and paleoclimatological inferences. Copyright © 2011 John Wiley & Sons, Ltd.

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

“…Again, this phase overlapped with a phase of strongly declining accumulation of peatland pine trees. These results were supported by taphonomical interpretation (Gastaldo, 1988) of the depositional histories, especially their dissimilarities, and by comparisons with palaeolimnological reconstructions of water level fluctuations during the MCA and LIA (Luoto, 2009;Nevalainen et al, 2011;Nevalainen and Luoto, 2012). Similar to 15 the study conducted in west-central Sweden (Gunnarson, 2008), the depositional histories in southeastern Finland were found to reflect past hydroclimatic variations.…”

“…The highest correlation between any pair of sites of 0.83 is obtained between the two cladorecan-based lake water depth reconstructions from southern Finland (FIN08 and FIN14; Nevalainen et al, 2011;. The highest inter-proxy correlation, on the other hand, of 0.72 was found between the cladoceran-based 20 lake water depth reconstruction (FIN07; Nevalainen and Luoto, 2012) and FIN12, where both multi-proxy records represent southern Finland recently described by Helama et al (2017a). Among the Swedish data, the highest correlation of 0.42 was obtained between the peat humification index (SWE03; Gunnarson et al, 2003) and a chironomid-based record of catchment erosion (SWE05; Berntsson et al, 2015).…”

“…In addition to outlining the hydroclimatic evolution during the past 2 ka, these data are expected to reflect the varying conditions through the MCA (here, 1000-1200 CE) and LIA (here, 1550-1750 CE). The records are derived from depositional histories of subfossil trees (Gunnarson et al, 2003;Gunnarson, 2008;Helama et al, 2017a), estimates of peat humification (Gunnarson et al, 2003;Andersson and Schoning, 2010), sediment grain-size (Si/Ti; Berntsson et al, 2015), varve thickness (Saarni et al, 2015), varve minerogenic lamina ('light sum' sensu Saarni et al, 5 2016), plant macrofossils (Väliranta et al, 2007), as well as chironomids and cladoceran assemblages (Luoto, 2009;Luoto and Helama, 2010;Nevalainen et al, 2011Nevalainen et al, , 2013Nevalainen and Luoto, 2012;Luoto and Nevalainen, 2015;Berntsson et al, 2015). These records originate from Sweden and Finland and represent inland areas east of the Scandinavian Mountains.…”

Rereading a tree-ring database to illustrate depositional histories of subfossil trees

“…Abbreviations: LA, Latitude; LO, longitude; NR, the number of rings, NS, the number of tree-ring series; NT, the number of trees; LS, the mean length of the series in years; FY and LA, the first (FY) and last (LY) calendar year (A.D.) of the site chronology; and LC, the total length of the chronology in years. (Luoto, 2009;Nevalainen et al, 2011;Nevalainen and Luoto, 2012). Lit-1 and Lit-2 are tree-ring sites studied by Pukienė (1997) and Edvardsson et al (2016), respectively.…”

“…Several palaeolimnological studies have recently concentrated on Lake Iso Lehmälampi (Luoto, 2009;Nevalainen et al, 2011;Nevalainen and Luoto, 2012) situated in southern Finland (60.33° N; 24.60° E). This site may represent an ideal comparison with tree-ring chronologies for several reasons.…”