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This dataset contains subfossil chironomid (Diptera: Chironomidae) species counts and the corresponding chironomid-inferred summer temperatures from a sediment core recovered from Lake N14 in southern Greenland. The record covers the period from approximately 13,800 to 9,900 years ago (cal BP). These data were generated for the study named below, which should be consulted for details and cited when using these data. Medeiros, A.S., Chipman, M., Francis, D.R., Hamerlik, L., Langdon, P., Puleo, P.J.K., Schellinger, G., Steigleder, R., Walker, I.R., Woodroffe, S., and Axford, Y. 2022. A continent-scale chironomid training set for reconstructing arctic temperatures. Quaternary Science Reviews 294, 107728. DOI 10.1016/j.quascirev.2022.107728. 

This dataset includes chironomid species assemblage data and air temperature estimates from 400+ lakes across northern North America, Greenland, Iceland, and Svalbard to inform interpretations of Holocene subfossil chironomid assemblages used in paleolimnological reconstruction. This calibration-set was developed by re-identifying and taxonomically harmonizing chironomids in previously described surface sediment samples, with identifications made at finer taxonomic resolution than in original publications (which are cited in the publication describing this dataset, Medeiros et al. 2022 Quaternary Science Reviews, and should be cited by dataset users). Site summer air temperatures are newly estimated with a consistent method using the WorldClim 2.1 gridded bioclimatic dataset. The large geographic coverage of this dataset is intended to provide climatic analogs for a wide range of Holocene climates in the northwest North Atlantic region and North American Arctic, including Greenland. For many of these regions, modern calibration data for paleoclimate proxies are sparse despite keen interest in paleoclimate reconstructions from high latitudes. Dataset users should consult and cite the following source publication: Medeiros, A.S., Chipman, M., Francis, D.R., Hamerlik, L., Langdon, P., Puleo, P.J.K., Schellinger, G., Steigleder, R., Walker, I.R., Woodroffe, S., and Axford, Y. 2022. A continent-scale chironomid training set for reconstructing arctic temperatures. Quaternary Science Reviews 294, 107728. DOI 10.1016/j.quascirev.2022.107728. 

Abstract In the southern Great Lakes Region, North America, between 19,000 and 8,000 years ago, temperatures rose by 2.5–6.5°C and sprucePiceaforests/woodlands were replaced by mixed‐deciduous or pinePinusforests. The demise ofPiceaforests/woodlands during the last deglaciation offers a model system for studying how changing climate and disturbance regimes interact to trigger declines of dominant species and vegetation‐type conversions.The role of rising temperatures in driving the regional demise ofPiceaforests/woodlands is widely accepted, but the role of fire is poorly understood. We studied the effect of changing fire activity onPiceadeclines and rates of vegetation composition change using fossil pollen and macroscopic charcoal from five high‐resolution lake sediment records.The decline ofPiceaforests/woodlands followed two distinct patterns. At two sites (Stotzel‐Leis and Silver Lake), fire activity reached maximum levels during the declines and both charcoal accumulation rates and fire frequency were significantly and positively associated with vegetation composition change rates. At these sites,Piceadeclined to low levels by 14 kyr BP and was largely replaced by deciduous hardwood taxa like ashFraxinus, hop‐hornbeam/hornbeamOstrya/Carpinusand elmUlmus. However, this ecosystem transition was reversible, asPiceare‐established at lower abundances during the Younger Dryas.At the other three sites, there was no statistical relationship between charcoal accumulation and vegetation composition change rates, though fire frequency was a significant predictor of rates of vegetation change at Appleman Lake and Triangle Lake Bog. At these sites,Piceadeclined gradually over several thousand years, was replaced by deciduous hardwoods and high levels ofPinusand did not re‐establish during the Younger Dryas.Synthesis. Fire does not appear to have been necessary for the climate‐driven loss ofPiceawoodlands during the last deglaciation, but increased fire frequency accelerated the decline ofPiceain some areas by clearing the way for thermophilous deciduous hardwood taxa. Hence, warming and intensified fire regimes likely interacted in the past to cause abrupt losses of coniferous forests and could again in the coming decades.