The role of snow in the thickening processes of lake ice at Lake Abashiri, Hokkaido, Japan

Abstract

To clarify the properties of lake ice at mid-latitudes subject to moderate air temperature, heavy snow and abundant solar radiation even in winter, we conducted field observations at Lake Abashiri in Japan for three winters and developed a one-dimensional (1-D) thermo-dynamical ice growth model. Using this model with meteorological data-sets, we examined the role of snow in the ice thickening process, as well as the Lake Abashiri ice phenology (including the interannual trend) for the past 55 years to compare with high latitude lakes. The ice was composed of two distinct layers: a snow ice (SI) layer and a congelation ice layer. The SI layer occupied a much greater fraction of total ice thickness than that at high latitude lakes. In-situ observations served to demonstrate the validity of the model. Freeze-up and break-up dates supplied by satellite imagery enabled further model validation prior to the availability of field data (2000/01–2015/16). Based on both observations and numerical experiments, it was found that one important role of snow is to moderate the variability of ice thickness caused by changes in meteorological conditions. Furthermore, ice thickness is more sensitive to snow depth than air temperature. When applied to an extended 55-year period (1961/62–2015/16) for which local meteorological observations are available, the mean dates of freeze-up and break-up, ice cover duration and ice thickness in February were estimated to be 12 December (no significant trend), 17 April (−1.7 d/decade), 127 d (−2.4 d/decade) and 43 cm (−1.4 cm/decade). For this long-term period, while snow still played an important role in ice growth, the surface air temperature warming trend was found to be a strong factor influencing ice growth, as reported for the high latitude lakes.

Keywords:

• lake
• ice thickness
• snow ice
• slush
• thermodynamic model
• freeze-up and break-up dates
• mid-latitudes

Acknowledgement

This study was carried out by the bilateral cooperative agreement between the Institute of Low Temperature Science (ILTS), Hokkaido University, and Abashiri City, and was financially supported partly by the Grant for Joint Research Program of ILTS. We sincerely thank Toshifumi Kawajiri of Nishi-Abashiri Fishermen’s Cooperative Association for his enormous support throughout the field observations, and the Fisheries Science Center of Abashiri City for their kind logistic support. We are very grateful to Takayuki Shiraiwa of ILTS for introducing us the field campaign at Lake Abashiri, Sumito Matoba of ILTS for kind arrangements regarding the measurement of δ¹⁸O and suggestions for our analysis and to Jun Nishioka of ILTS for financial support. We thank Eisho Kudo of the Okhotsk Ryu-hyo (drift ice) Museum for providing pictures. We also thank the Abashiri and Memanbetsu tourism associations for providing the records of ice thickness for ice fishing. We appreciate the help of Ryuta Kato and Jun-no Ishiyama of Hokkaido University with field observations. Comments from the anonymous reviewer were very helpful and to improve the manuscript.