A 2000 year record of climate variations reconstructed from Haukadalsvatn, West Iceland

Geirsdóttir, Áslaug; Miller, Gifford H.; Thordarson, T.; Ólafsdóttir, Kristín

doi:10.1007/s10933-008-9253-z

Cited by 86 publications

(118 citation statements)

References 37 publications

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“…Detailed analyses of these periods at higher resolution, taking 0.25 or 0.5 cm subsamples, would help ascertain whether absolute temperatures during parts of the 18 th century were warmer or not than present. Palaeoclimate sequences have been produced from other lacustrine sites in NW Iceland, but all from lower altitudes (Doner, 2003;Caseldine et al, 2003;Geirsdóttir et al, 2009b). Axford et al (2009) produced temperature estimates from a chironomid sequence in NE Iceland through a comparison of the detrended correspondence analysis (DCA) scores with instrumental data, and then applied the relationships to the other fossil data.…”

Section: Discussionmentioning

confidence: 99%

“…They showed that the coolest conditions over the last 2000 years occurred in the 18 th and 19 th centuries, with a drop in average summer temperatures from the preceding millennium of 1-2°C, although the data resolution and dating controls did not allow further details to be defined. The study of Geirsdóttir et al (2009b) used proxies for productivity (biogenic silica -BSi and total organic carbon -TOC) and related them to spring temperature and cold/windy summers, respectively. Their reconstructions suggested significant cold periods from AD 1450 for ca.…”

Section: Discussionmentioning

confidence: 99%

“…Reconstruction of the last few centuries of climate in Iceland, often termed as the later part of the Little Ice Age (but see Ogilvie and Jónsson, 2001 for a critical review of the term and its Icelandic context), has relied largely on glacial histories (Stötter et al, 1999;Kirkbride and Dugmore, 2006;Geirsdóttir et al, 2009a), sea ice records interpreted from documentary sources (Ogilvie, 1984;Ogilvie, 2005), and palaeolimnological data (Axford et al, 2007(Axford et al, , 2009Geirsdóttir et al, 2009b). These records are however of variable temporal resolution and have tended to provide relatively poorly constrained proxy climate data.…”

Section: Introductionmentioning

confidence: 99%

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A chironomid-based reconstruction of summer temperatures in NW Iceland since AD 1650

et al. 2011

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Few studies currently exist that aim to validate a proxy chironomid-temperature reconstruction with instrumental temperature measurements. We used a reconstruction from a chironomid percentage abundance data set to produce quantitative summer temperature estimates since AD 1650 for NW Iceland through a transfer function approach, and validated the record against instrumental temperature measurements from Stykkishólmur in western Iceland. The core was dated through Pb-210, Cs-137 and tephra analyses (Hekla 1693) which produced a well-constrained dating model across the whole study period. Little catchment disturbance, as shown through geochemical (Itrax) and loss-on-ignition data, throughout the period further reinforce the premise that the chironomids were responding to temperature and not other catchment or within-lake variables. Particularly cold phases were identified between AD 1683-1710, AD 1765-1780 and AD 1890-1917, with relative drops in summer temperatures in the order of 1.5-2°C. The timing of these cold phases agree well with other evidence of cooler temperatures, notably increased extent of Little Ice Age (LIA) glaciers. Our evidence suggests that the magnitude of summer temperature cooling (1.5-2°C) was enough to force LIA Icelandic glaciers into their maximum Holocene extent, which is in accordance with previous modelling experiments for an Icelandic ice cap (Langjökull).

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A chironomid-based reconstruction of summer temperatures in NW Iceland since AD 1650

et al. 2011

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“…Our sites are mostly below 400 m (mean 218 m asl) and < 10 km from farms and thus could be expected to best reflect environmental changes as a result of human settlement and the introduction of domestic livestock. The data used in Geirsdóttir et al, (2009) and Geirsdóttir et al, (2013) comes from lakes with high altitude catchments. Hvítárvatn is a proglacial lake at 422 m asl and onethird of its watershed is part of Langjökull ice cap (Larsen et al, 2012).…”

Section: Land Surface Change Over 35kamentioning

confidence: 99%

“…In contrast a lake record contains a homogenised signal generated by changes across the altitudinal range of the catchment and across all its ecological and land management zones. The lake records considered by Geirsdóttir et al, (2009), for example, reflect an amalgamated record of a catchment where the largest area is above 500 m asl (Fig. 8C).…”

Section: Cross Scale Analysis Of Environmental Recordsmentioning

confidence: 99%

Late-Holocene land surface change in a coupled social–ecological system, southern Iceland: a cross-scale tephrochronology approach

Streeter

Dugmore

2014

Quaternary Science Reviews

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The chronological challenge of cross-scale analysis within coupled socioecological systems can be met with tephrochronology based on numerous well-dated tephra layers. We illustrate this with an enhanced chronology from Skaftártunga, south Iceland that is based on 200 stratigraphic profiles and 2635 individual tephra deposits from 23 different eruptions within the last 1140 years. We present new sediment-accumulation rate based dating of tephra layers from Grίmsvötn in AD 1432±5 and AD 1457±5. These and other tephras underpin an analysis of land surface stability across multiple scales. The aggregate regional sediment accumulation records suggest a relatively slow rate of land surface change which can be explained by climate and land use change over the period of human occupation of the island (after AD ~870), but the spatial patterning of change shows that it is more complex, with landscape scale hysteresis and path dependency making the relationship between climate and land surface instability contingent. An alternative steady state of much higher rates of sediment accumulation is seen in areas below 300 m asl after AD ~870 despite large variations in climate, with two phases of increased erosion, one related to vegetation change (AD 870-1206) and another related to climate (AD 1597(AD -1918. In areas above 300 m asl there is a short lived increase in erosion and related deposition after settlement (AD ~870-935) and then relatively little additional change to present. Spatial correlation between rates of sediment accumulation at different profiles decreases rapidly after AD ~935 from ~ 4 km to less than 250 m as the landscape becomes more heterogeneous. These new insights are only possible using high-resolution tephrochronology applied spatially across a landscape, an approach that can be applied to the large areas of the Earth's surface affected by the repeated fallout of cm-scale tephra layers.

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Radiocarbon age-offsets in an arctic lake reveal the long-term response of permafrost carbon to climate change

Gaglioti

Mann

Jones

et al. 2014

J. Geophys. Res. Biogeosci.

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Continued warming of the Arctic may cause permafrost to thaw and speed the decomposition of large stores of soil organic carbon (OC), thereby accentuating global warming. However, it is unclear if recent warming has raised the current rates of permafrost OC release to anomalous levels or to what extent soil carbon release is sensitive to climate forcing. Here we use a time series of radiocarbon age-offsets ( 14 C) between the bulk lake sediment and plant macrofossils deposited in an arctic lake as an archive for soil and permafrost OC release over the last 14,500 years. The lake traps and archives OC imported from the watershed and allows us to test whether prior warming events stimulated old carbon release and heightened age-offsets. Today, the age-offset (2 ka; thousand of calibrated years before A.D. 1950) and the depositional rate of ancient OC from the watershed into the lake are relatively low and similar to those during the Younger Dryas cold interval (occurring 12.9-11.7 ka). In contrast, age-offsets were higher (3.0-5.0 ka) when summer air temperatures were warmer than present during the Holocene Thermal Maximum (11.7-9.0 ka) and Bølling-Allerød periods (14.5-12.9 ka). During these warm times, permafrost thaw contributed to ancient OC depositional rates that were~10 times greater than today. Although permafrost OC was vulnerable to climate warming in the past, we suggest surface soil organic horizons and peat are presently limiting summer thaw and carbon release. As a result, the temperature threshold to trigger widespread permafrost OC release is higher than during previous warming events.

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A 2000 year record of climate variations reconstructed from Haukadalsvatn, West Iceland

Cited by 86 publications

References 37 publications

A chironomid-based reconstruction of summer temperatures in NW Iceland since AD 1650

A chironomid-based reconstruction of summer temperatures in NW Iceland since AD 1650

Late-Holocene land surface change in a coupled social–ecological system, southern Iceland: a cross-scale tephrochronology approach

Radiocarbon age-offsets in an arctic lake reveal the long-term response of permafrost carbon to climate change

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