Role of radiative forcing on the sea ice melt-growth cycle in a changing Arctic marine environment

由于全球变暖，北极海冰覆盖面积正在迅速减少，2012年9月再创新低。冰盖的减少正在对极地海洋环境产生明显的影响。然而，这种影响对未来气候变化、碳循环和生态系统的影响程度仍不确定。问题的根本在于地表辐射强迫如何影响海冰性质的变化，以及这些变化反过来又如何调节辐射强迫。这种相互作用构成了在北极运行的复杂气候反馈的基础。考虑到每年形成和融化的海冰面积的巨大（约1000万平方公里或大致相当于加拿大的面积），全面了解驱动这一循环的过程的重要性怎么强调都不为过。鉴于此，本研究的目标是研究1)辐射强迫与海冰表面融化演变之间的相互反馈；2)与多孔海冰结构和嵌入杂质的小尺度相互作用如何影响海冰内部的辐射传输；3)冰下辐射场和光学性质的变化对水柱加热和海冰融化速率的重要性。**这三个目标将有助于回答以下问题：海冰融化是如何在表面、内部和底部之间进行分配的，以及在上层海洋中保留了多少热量，这些热量会导致秋季冻结的延迟。我们预测未来气候的能力取决于对这些过程的了解。这些目标是相互关联的，但单独为硕士和博士研究提供合适和独特的项目。这项研究将提高我们对海冰过程和气候反馈的认识，培养北极环境研究的新学生，并最终通过改进气候预测使北方人受益，这将有助于社区和各级政府适应气候变化。******

The Arctic sea ice cover is in rapid decline due to global warming with yet another new record low reached in September 2012. The diminishing ice cover is having a discernible impact on the polar marine environment. However, the extent of this impact on future changes to climate, carbon cycling and ecosystems remains uncertain. At the root is how surface radiative forcing affects changes in sea ice properties, and how these changes in turn modulate the forcing. Such interactions form the base of complex climate feedbacks operating in the Arctic. Considering the vastness of the area of sea ice (~10 million km2 or roughly the size of Canada) that forms and then melts each year, the importance of a comprehensive understanding of the processes driving this cycle cannot be overstated.** Given this, the objectives to be addressed in the proposed research are to investigate 1) the reciprocal feedbacks between radiative forcing and the melt evolution of the sea ice surface, 2) how small-scale interactions with the porous sea ice structure and imbedded impurities affect radiative transfer within the sea ice interior, and 3) the importance of variable under-ice radiation fields and optical properties on water column heating and sea ice melt rates.** These three objectives will help answer questions about how sea ice melt is partitioned between surface, interior and bottom, and how much heat is retained in the upper ocean layers where it can cause a delay in the fall freeze-up. Our ability to predict future climate rests on understanding these processes. The objectives are interrelated, yet individually provide suitable and distinct projects for both MSc and PhD studies. This research will advance our knowledge of sea ice processes and climate feedbacks, train new students in Arctic environmental research and ultimately, benefit northerners by improving climate predictions that will help communities and various levels of government adapt to climate change.******