Estimates of basal melt from Greenland: a driver for sea level changes

格陵兰岛基底融化的估计：海平面变化的驱动因素

• 批准号: 313848278
• 负责人: Dr. Oliver Huhn
• 金额: --
• 依托单位: Abteilung Ozeanographie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/313848278?language=en
• 关键词: Estimates; basal; melt; Greenland; driver

Mass loss from the Greenland Ice Sheet (GrIS) increased significantly over the past two decades. Besides the growing influence on sea level rise, the pathways and the amount of GrIS melt water imported into the interior of the ocean could have crucial consequences for the ventilation and formation of deep water and hence the strength of the climate-relevant Atlantic meridional overturning circulation (AMOC). In most climate and coupled ocean-sea ice models weak convection leads to a weaker AMOC and a regionally changing sea level. It is thought that the arrival of additional melt water in the deep-water formation region could strengthen the density stratification and thus weaken or even suppress deep convection. Some publications concluded that the GrIS melt has already slowed down the AMOC in the twentieth century, while others found that the additional freshwater from GrIS has not exerted any influence on deep water formation yet. The main result of the first phase is, that for the first time, submarine melt water (SMW) from GrIS was unambiguously identified outside of fjords. SMW fractions are highest in the upper 200 – 300m below the mixed layer and mostly confined at the Greenland and Canadian slope and shelf. The strong dilution of SMW in the upper ocean and the relatively small SMW percentages compared to the abundance of fresh Polar Water indicate that SMW is not a main player for LSW formation yet. The mechanism leading to the episodic occurrence of He excess anomalies in the deep water masses is uncertain. Based on the salinity – SMW relation, it could herald episodic East Greenland Current spill jets events that contains SMW bearing water with densities larger than 27.5. However, these results are based on a small noble gas data set.The objectives for the continuation phase are: (1) Quantify SMW fractions from GrIS in the Greenland boundary current, the Labrador and the Irminger Sea using much more detailed data sets (He, Ne, CFCs, SF6) than was available until now and by applying the noble gas excess method and an OMP (2) Assess the SMW signature in the area of origin of the EGC spill jet, evaluate which density classes are affected and whether more events with SMW in spill jets are found in 2018 and 2019 compared to 1994 and 2015(3) Calculate SMW fluxes using velocity measurements and the ventilation time inferred from transient tracers as CFCs and SF6(4) Assess how much the formation of LSW and the ventilation of other relevant water masses in the Labrador and Irminger Sea changed. Analyze the processes responsible and estimate how much SMW needs to be present on which key locations to significantly influence formation and ventilation of the relevant water masses. With this information estimate the time period until the SMW signal is sufficiently strong to fulfil this criterion.

在过去的二十年中，格陵兰冰盖（GRIS）的质量损失显着增加。除了对海平面上升的影响不断增长之外，进口到海底的谷物融化水融化了水可能对深水的通风和形成以及气候与气候相关的大西洋子午线倾倒循环（AMOC）的强度产生至关重要的后果。在大多数气候和耦合的海洋冰模型中，弱转化率较弱会导致AMOC较弱和区域变化的海平面。人们认为，额外的熔体水在深水形成区域中的到来可以增强密度分层，从而弱甚至抑制深层连接。一些出版物得出的结论是，Gris融化已经在20世纪放慢了AMOC，而其他人发现，Gris的额外淡水尚未到期对深水形成的影响。第一阶段的主要结果是，从峡湾之外，明确鉴定出了Gris的海底熔体水（SMW）。在混合层以下200 - 300m的上部，SMW的分数最高，大部分位于格陵兰和加拿大斜坡和架子上。与新鲜极地水的抽象相比，上海中SMW的强稀释度和相对小的SMW百分比表明SMW并不是LSW组的主要参与者。导致HE的发作发生的机制超过了深水质量的异常。根据盐度 - SMW关系，它可能会预示着East Greenland当前的溢出喷气机事件，其中包含SMW轴承水，其密度大于27.5。但是，这些结果基于一个小的贵重气数据集。延续阶段的目标是：（1）使用更详细的数据集（HE，NE，CFC，SF6，sfc，sf6）来量化GRIS中的SMW分数，Labrador和Irminger Sea，与直到现在的no no no no no no no no no no no no no no smp smp smp a smp（2）相比，smc smp（2）与1994年和2015年（3）相比，JET，评估哪些密度类别受到影响，以及是否在2018年和2019年发现了更多的SMW溢出喷气机，使用速度测量值计算SMW通量，以及从临时示踪剂（CFCS和SF6）（SF6和SF6（4）评估LSSW和其他相关水量的数量的通风时间）。分析负责的过程，并估计需要在哪些关键位置存在多少SMW，以显着影响相关水质量的形成和通风。通过此信息，估计了SMW信号足以满足此标准的时间段。