Reconstructing lake ice cover in subarctic lakes using a diatom- based inference model

A new quantitative diatom-based lake ice cover inference model was developed to reconstruct past ice cover histories and applied to four subarctic lakes. The used ice cover model is based on a calculated melting degree day value of +130 and a freezing degree day value of -30 for each lake. The reconstructed Holocene ice cover duration histories show similar trends to the independently reconstructed regional air temperature history. The ice cover duration was around 7days shorter than the average ice cover duration during the warmer early Holocene (approximately 10 to 6.5calibratedkyr B.P.) and around 3-5days longer during the cool Little Ice Age (approximately 500 to 100calibratedyr B.P.). Although the recent climate warming is represented by only 2-3 samples in the sediment series, these show a rising trend in the prolonged ice-free periods of up to 2days. Diatom-based ice cover inference models can provide a powerful tool to reconstruct past ice cover histories in remote and sensitive areas where no measured data are available. Key Points A quantitative diatom-based ice-cover model has been created Inferred past ice-cover trends are similar to the regional climate history Diatoms can provide a valuable tool to reconstruct past ice-cover regimes