| 英文摘要: | This grant supports an effort to assess and implement approaches to predict the timing of autumn freeze-up and spring-summer ice retreat in the Arctic coastal seas. The study is motivated by recognition that the Arctic Ocean is becoming more accessible for resource exploration, marine shipping, tourism and other activities, increasing the need for reliable seasonal predictions of ice conditions. The project will focus on regional scales addressing stakeholder needs. All Arctic coastal
seas and the channels of the Canadian Arctic Archipelago will be examined, but emphasis will be placed on the Chukchi and Beaufort Seas. This recognizes these regions as foci for resource exploration, where ships entering or exiting the Arctic Ocean via Bering Strait must pass, and as part of the seasonal bowhead whale migration route supporting subsistence hunting.
The core of the proposed approach is that the date of the spring/summer sea ice retreat to a given location (e.g., the continental shelf break) can be used to predict the date of the autumn advance back to that location (i.e. freeze-up), and hence the open water period. This reflects albedo feedback and ocean heat uptake processes that have always been part of the sea ice system. Briefly, earlier seasonal sea ice melt and retreat leads to earlier exposure of dark open water areas that readily absorb solar radiation, meaning more heat in the ocean mixed layer at summer's end, delaying autumn ice growth. This is manifested in observations that the upward trend in the open water period in the Chukchi Sea is driven more by later autumn return of ice than an earlier spring/summer retreat, and that there is a strong relationship between ice retreat and return in de-trended time series of the two variables.
Factors such as atmospheric variability and ocean heat transport are viewed as modulating expressions of albedo feedback and ocean heat uptake; such variables, along with seasonal climate forecasts, will be examined as additional predictors. It will be determined in which
sectors predictions are most and least skillful, the reasons for these differences, and whether
the changing sea ice regime (e.g., changing ice thickness) is changing predictability. In
addition, multiple processes, including winter atmospheric conditions, ocean heat transport, ice thickness and surface melt onset, will be examined as sources of predictability on the
date of retreat. The study will utilize satellite observations of sea ice extent and concentration, surface melt onset, ice motion, thickness and age, ocean heat flux measurements, and output
from the NCEP coupled Climate Forecast System, Version 2, along with fields of sea level pressure, temperature and other variables from two modern atmospheric reanalyses.
The Arctic Ocean, particularly the Chukchi and Beaufort seas, is of growing strategic importance
to our nation. The proposed
effort to provide skillful seasonal predictions of sea ice conditions at the regional scale
serves the goal of improving methods of connecting science with decision making through addressing diverse stakeholder needs, including marine
shipping agencies, extraction industries and subsistence hunting. Support is included for a graduate student and undergraduate students to help educate the next generation of scientists, and study results will be assimilated
into an Arctic climate course at the University of Colorado. |