The fate of lake ice in the North American Arctic

L C Brown,C R Duguay

doi:10.5194/tc-5-869-2011

Abstract

Abstract. Lakes comprise a large portion of the surface cover in northern North America, forming an important part of the cryosphere. The timing of lake ice phenological events (e.g. break-up/freeze-up) is a useful indicator of climate variability and change, which is of particular relevance in environmentally sensitive areas such as the North American Arctic. Further alterations to the present day ice regime could result in major ecosystem changes, such as species shifts and the disappearance of perennial ice cover. The Canadian Lake Ice Model (CLIMo) was used to simulate lake ice phenology across the North American Arctic from 1961–2100 using two climate scenarios produced by the Canadian Regional Climate Model (CRCM). Results from the 1961–1990 time period were validated using 15 locations across the Canadian Arctic, with both in situ ice cover observations from the Canadian Ice Database as well as additional ice cover simulations using nearby weather station data. Projected changes to the ice cover using the 30-year mean data between 1961–1990 and 2041–2070 suggest a shift in break-up and freeze-up dates for most areas ranging from 10–25 days earlier (break-up) and 0–15 days later (freeze-up). The resulting ice cover durations show mainly a 10–25 day reduction for the shallower lakes (3 and 10 m) and 10–30 day reduction for the deeper lakes (30 m). More extreme reductions of up to 60 days (excluding the loss of perennial ice cover) were shown in the coastal regions compared to the interior continental areas. The mean maximum ice thickness was shown to decrease by 10–60 cm with no snow cover and 5–50 cm with snow cover on the ice. Snow ice was also shown to increase through most of the study area with the exception of the Alaskan coastal areas.

Highlights

Lakes are a major feature across northern North America, forming an important part of the cryosphere, with their ice cover both playing a role in and responding to climate variability
Realistic representation of snow cover on a lake ice surface is important for accurate simulation of ice evolution (Brown and Duguay, 2011) because of snow’s important insulating role and contribution to snow ice growth
In order to represent the range of potential snow conditions on the lake ice surface, simulations are run with a “full snow cover” to represent 100 % of the snowfall accumulating on the ice, as well as a “no snow cover” simulation to represent the opposite conditions

Summary

Introduction

Lakes are a major feature across northern North America, forming an important part of the cryosphere, with their ice cover both playing a role in and responding to climate variability. Future changes in ice cover conditions due to changing climate conditions could impact the role of lakes on energy, water and biogeochemical processes in cold regions as well as socio-economic impacts in terms of transportation (ice roads) and recreation. Both long-term and short-term trends have been identified in ice phenology records and are typically associated with variations in air temperatures, while trends in ice thickness tend to be associated more with changes in snow cover (Brown and Duguay, 2010). Past changes to lake ice regimes have been inferred in the arctic using proxy methods such as diatoms (Smol, 1983, 1988; Douglas and Smol, 1999; Smol et al, 2005; Keatley et al, 2008) and sediment records (Tomkins et al, 2009)

Objectives

Results

Conclusion