Interplay between seasonal arctic sea-ice processes and halocline stability - towards understanding arctic gas and matter fluxes

由于全球气候变化，北极的海冰覆盖面积发生了巨大变化。在目前的状态下，北极冰盖发挥着重要作用，因为它保护了地表水，即所谓的北极盐跃层（盐度分层），使其免受夏季阳光的加热。此外，盐跃层是由盐形成和稳定的，盐在海水冻结过程中被排除在晶体结构之外。与此同时，盐跃层在冰盖和下面温暖的大西洋沃茨之间提供了一道屏障，有助于保护北极海冰。这种平衡现在被北极冰盖的整体变薄和夏季范围的减少所扰乱。此外，海水中还含有气体和重要的地球化学痕量物质，这些物质在不同的海冰过程中被捕获、影响和排斥。因此，北极海冰影响大气、冰和上层水柱之间的气体和物质通量。随着冰的移动，也有一种运输，例如，在所谓的跨极地漂移从西伯利亚大陆架地区，在北极，向南进入北欧海。根据“新北极”，它被认为是北极已经转移到一个不同的操作模式。然而，人们在很大程度上不知道这个新系统是如何工作的，演变以及它将如何影响海冰形成过程和盐跃层稳定性，从而影响气体和物质通量。为了进行这种调查，我们需要北极中部一年中的上层水柱和海冰覆盖的样本，科学倡议MOSAiC提供了这样一个机会。从冰和上层水柱中提取的水的稳定同位素（δ 18 O和δ 18 D）包含关于源沃茨和冻结过程的信息，这些结果将与天然气和地球化学调查（来自伙伴项目）直接相关。重要的可能是例如风暴、融化过程、积雪、池塘形成和海冰老化。这些对海冰核心和北极中部上层水柱内季节性海冰过程进行的面向过程的研究将为了解北冰洋盐跃层稳定性以及气体和物质通量作出重要贡献。气体和物质的非保守行为相对于同位素的保守行为之间的差异提供了获得进一步重要信息的机会，例如关于再冻结过程的信息。

As a result of global climate change the sea-ice cover in the Arctic has changed dramatically. In its present state, the Arctic ice cover plays an important role, as it shields the surface water, the so-called Arctic halocline (salinity stratification), from heating in the summer sunlight. In addition, the halocline is formed and stabilized by the salt, which is excluded from the crystal structure during the freezing process of seawater. At the same time, the halocline provides a barrier between the ice cover and the underlying warm Atlantic waters and contributes in return to the preservation of the Arctic sea-ice cover. This balance is now disturbed by an overall much thinner Arctic ice cover and its reduced summer extent. In addition seawater contains gases and important biogeochemical trace substances that are trapped, influenced and rejected by different sea-ice process. Thereby arctic sea ice influences the gas and matter fluxes between atmosphere, ice and upper water column. With the ice movement there is also a transport, e.g. in the so-called Transpolar Drift from the Siberian shelf areas, over the North Pole, southwards into the Nordic seas.In the light of the "new Arctic" it is assumed that the Arctic has already shifted to a different mode of operation. However, it is largely unknown how this new system works, evolves and how it will affect sea-ice formation processes and halocline stability and thus gas and matter fluxes. For such investigations we need samples of the upper water column and the sea-ice cover from the central Arctic over the course of the year, and the scientific initiative MOSAiC provides such an opportunity. Stable isotopes of the water (18O and D) taken from ice and upper water column contain information on the source waters and the freezing processes and these results will be directly linked to gas and biogeochemical investigations (from partner projects). Important might be e.g. storms, melting processes, snow cover, pond formation and aging of sea-ice. These process-oriented studies of seasonal sea-ice processes within sea-ice cores and the upper water column of the central Arctic will provide an important contribution to the understanding of the Arctic Ocean halocline stability as well as gas and matter fluxes. The discrepancy between non-conservative behavior of gases and substances relative to the conservative behavior of the isotopes offers the chance to derive further important information, e.g. on refreezing processes.