Generation of the ocean's permanent pycnocline in the ice-covered Southern Ocean

永久性密度跃层（PP）是海洋的主要组织特征--一种升高的分层界面，将与大气交换热量和碳的近地表沃茨与储存这些示踪剂长达数千年的深层沃茨分开。然而，尽管海洋在气候中的作用有着基本的基础，并且经过几十年的研究，但控制PP形成的过程仍然未知。PycnoGen将通过为PP的建立生成第一个基于观察的机械范式来解决这一关键的知识差距。为了实现这一目标，该项目将致力于四个目标：（O 1）开发一套先进的、长续航力的自主机器人系统和分布式传感器网络技术，以测量极地冰下海洋;（O2）以产生同类第一，通过O 1中的创新技术实现的过程目标观测-在季节性冰的代表性区域中PP的形成-（O3）根据O2的观测结果，确定控制PP形成和流动的过程;和（O 4）评估PP从其形成区投射到全球海洋的机制，PP对海洋通风和翻转的大尺度影响，以及该系统对关键气候强迫的敏感性。PycnoGen将通过以下方式在海洋学和气候科学方面留下有影响力和持久的遗产：（i）通过O 1的技术突破，使国际极地海洋观测能力发生重大变化;（ii）制作PP形成（O2）的基准观测数据集，准备作为从根本上推进气候尺度海洋模型的发射台;以及（iii）改变我们对海洋气候系统（O3-O 4）最重要组成部分之一的机械理解，对许多高级别的全球气候变化问题产生深远影响。

The permanent pycnocline (PP) is the ocean's main organising feature - an interface of elevated stratification that sets apart near-surface waters exchanging heat and carbon with the atmosphere from deeper waters storing those tracers for as long as millennia. Yet despite its basic underpinning of the ocean's role in climate, and decades of investigation, the processes governing the PP's formation remain unknown. PycnoGen will tackle this critical knowledge gap by generating the first observationally-grounded mechanistic paradigm for the establishment of the PP. To accomplish this, the project will address four objectives: (O1) to develop a suite of cutting-edge, long-endurance autonomous robotic system and distributed sensor network technologies to measure the polar oceans under ice; (O2) to generate first-of-a-kind, process-targeted observations - enabled by the innovative technologies in O1 - of the PP's formation in a representative region of the seasonally ice-covered Southern Ocean, where the PP originates; (O3) to determine the processes controlling the formation of, and flow across, the PP from the observations in O2; and (O4) to assess the mechanisms by which the PP is projected from its formation region into the global ocean, the PP's large-scale impacts on oceanic ventilation and overturning, and the system's sensitivities to key climate forcings. PycnoGen will leave an influential and long-lasting legacy in oceanography and climate science by: (i) generating a step change in international capability for polar ocean observation, through the technological breakthroughs in O1; (ii) producing a benchmark observational data set of the PP's formation (in O2), poised to serve as a launchpad to fundamentally advance climate-scale ocean models; and (iii) transforming our mechanistic understanding of one of the foremost components of the ocean-climate system (in O3-O4), with profound ramifications for many high-ranking global climate change problems.