Simulations and Projections of Winter Sea Ice in the Barents Sea by CMIP6 Climate Models

Abstract

Dramatic changes in the sea ice characteristics in the Barents Sea have potential consequences for the weather and climate systems of mid-latitude continents, Arctic ecosystems, and fisheries, as well as Arctic maritime navigation. Simulations and projections of winter sea ice in the Barents Sea based on the latest 41 climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) are investigated in this study. Results show that most CMIP6 models overestimate winter sea ice in the Barents Sea and underestimate its decreasing trend. The discrepancy is mainly attributed to the simulation bias towards an overly weak ocean heat transport through the Barents Sea Opening and the underestimation of its increasing trend. The methods of observation-based model selection and emergent constraint were used to project future winter sea ice changes in the Barents Sea. Projections indicate that sea ice in the Barents Sea will continue to decline in a warming climate and that a winter ice-free Barents Sea will occur for the first time during 2042–2089 under the Shared Socioeconomic Pathway 585 (SSP5-8.5). Even in the observation-based selected models, the sensitivity of winter sea ice in the Barents Sea to global warming is weaker than observed, indicating that a winter ice-free Barents Sea might occur earlier than projected by the CMIP6 simulations.

摘要

巴伦支海海冰的变化对中纬度大陆的天气和气候系统、北极生态系统、渔业以及北极航运等都具有潜在的影响。本文基于第六次国际耦合模式比较计划(CMIP6)的41个气候模式对巴伦支海冬季海冰的模拟和预估进行了研究。研究结果显示,大多数CMIP6气候模式存在高估巴伦支海冬季海冰覆盖范围和低估海冰覆盖范围下降趋势的共性偏差。这种共性偏差主要与CMIP6气候模式对经过巴伦支海的海洋极向热输送模拟偏弱及低估海洋极向热输送的增加趋势有关。为了减少CMIP6气候模式对巴伦支海海冰预估的不确定性,本文采用模式优选与涌现约束的方法对巴伦支海未来冬季海冰进行了预估。预估的结果表明,气候变暖背景下,巴伦支海冬季海冰将持续减少,在SSP5-8.5排放情景下,巴伦支海将在2042–2089年间首次出现冬季无冰现象。但是,即使根据观测海冰覆盖范围优选的CMIP6气候模式仍低估了巴伦支海冬季海冰对全球变暖的敏感性,这也表明巴伦支海未来首次出现冬季无冰的时间可能比CMIP6气候模式预估的更早。