Palaeoclimatological and palaeolimnological records from fossil midges and tree-rings: the role of the North Atlantic Oscillation in eastern Finland through the Medieval Climate Anomaly and Little Ice Age

Luoto, Tomi P.; Helama, Samuli

doi:10.1016/j.quascirev.2010.06.015

Cited by 52 publications

(63 citation statements)

References 48 publications

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“…Combined use of climate models and palaeoclimate data suggested that regional cooling could be expected over the study region approximately two decades after the solar irradiance decreases, this mechanism involving inertia in the oceanic response and shift towards the negative phase in the atmospheric oscillations pattern over the North Atlantic and European land areas (Shindell et al, 2001). Similar atmospheric patterns, possibly coupled with the solar irradiation variations, have generally been suggested forcing the cooler and wetter summer-time climates in the study region during the LIA (Helama et al, 2009c;Luoto and Helama, 2010). The suggested lag in climatic response (Shindell et al, 2001) would further validate our observation of the delayed regional cooling to the Maunder Minimum reduction of solar activity.…”

Section: Discussionsupporting

confidence: 59%

A palaeotemperature record for the Finnish Lakeland based on microdensitometric variations in tree rings

Helama¹,

Vartiainen²,

Holopainen

et al. 2014

Geochronometria

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X-ray based tree-ring data of maximum latewood densities (MXD) was combined for south-eastern Finland. This data originated from subfossil and modern pine (Pinus sylvestris L.) materials comprising a continuous dendroclimatic record over the past millennium. Calibrating and verifying the MXD chronologies against the instrumental temperature data showed a promising opportunity to reconstruct warm-season (May through September) temperature variability. A new palaeotemperature record correlated statistically significantly with the long instrumental temperature records in the region and adjacent areas since the 1740s. Comparisons with tree-ring based (MXD and tree-ring width) reconstructions from northern Fennoscandia and northern Finland exhibited consistent summer temperature variations through the Medieval Climate Anomaly, Little Ice Age, and the 20 th century warmth. A culmination of the LIA cooling during the early 18 th century appeared consistently with the Maunder Minimum, when the solar activity was drastically reduced. A number of coolest reconstructed events between AD 1407 and 1902 were coeval to years of crop failure and famine as documented in the agro-historical chronicles. Results indicate an encouraging possibility of warm-season temperature reconstructions using middle/south boreal tree-ring archives to detail and enhance the understanding of past interactions between humans, ecosystems and the earth.

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Section: Discussionsupporting

confidence: 59%

A palaeotemperature record for the Finnish Lakeland based on microdensitometric variations in tree rings

Helama¹,

Vartiainen²,

Holopainen

et al. 2014

Geochronometria

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“…NAO) is anticipated to result in contrasting trends in respective records, according to their target season sensitivity. These results are in line with a predominantly positive NAO phase during the MCA, associated with generally wet winters but dry summers (Trouet et al, 2009), while a negative NAO phase during the LIA has been linked with dry winters and wet summers (Luoto and Helama, 2010;Luoto et al, 2013;Luoto and Nevalainen, 2017). While the view of a prolonged positive phase during the 20 MCA has been challenged by recent proxy observations (Ortega et al, 2015), additional support of generally positive NAO phase overlapping the MCA have also been presented (Wassenburg et al, 2013;Baker et al, 2015).…”

Section: Fennoscandiasupporting

confidence: 60%

“…The strength of this peak is strongly related to snowmelt and, in fact, the 5 respective proxy data may be largely responding to antecedent snow conditions and thus winter precipitation. This has previously been described for eastern Finland, where a collection of proxy records reflecting either winter/spring or summer variability were found to exhibit contrasting hydroclimatic trends in respective variables through the MCA and LIA (Luoto and Helama, 2010). Therefore, the observed division of proxy records according to their indications of climate becoming either wetter or drier through the MCA-LIA transition, may reflect, at least partly, their response to precipitation in either 10 winter/spring or summer.…”

Section: Fennoscandiasupporting

confidence: 54%

“…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.…”

Section: Fennoscandiamentioning

confidence: 99%

“…However, it is also possible that part of these deviations arise from varying sensitivity of the proxies to different seasons. While most of the studied proxy records likely represent hydroclimatic variations during summer, at least four of the records indicating relatively drier LIA (Luoto and Helama, 2010;Berntsson et al, 2015;Saarni et al, 2016) may actually reflect climatic and environmental factors attributable to boreal winter/spring phenomena, such as flooding, erosion, stream flow. In boreal settings, an outstanding peak in runoff is generally attained during the spring season.…”

Section: Fennoscandiamentioning

confidence: 99%

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

Nevalainen

Luoto

2011

Ecohydrology

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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.

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Palaeoclimatological and palaeolimnological records from fossil midges and tree-rings: the role of the North Atlantic Oscillation in eastern Finland through the Medieval Climate Anomaly and Little Ice Age

Cited by 52 publications

References 48 publications

A palaeotemperature record for the Finnish Lakeland based on microdensitometric variations in tree rings

A palaeotemperature record for the Finnish Lakeland based on microdensitometric variations in tree rings

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

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

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