Do ocean currents stick together? How ocean current coherence impact European climate

洋流会粘在一起吗？

• 批准号: 2890097
• 金额: --
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2890097
• 关键词: Do; ocean; currents; stick; together

The Atlantic meridional overturning circulation (AMOC) is a large-scale ocean circulation system comprised of currents that carry warm, shallow water northwards and return cold deep-water southwards. The AMOC is crucial in maintaining the relatively mild winter climate of Northwest Europe. A shutdown of the AMOC would strongly impact European temperature and precipitation variability.Meridional coherence is the idea that the AMOC functions as a coherent flow across the Atlantic basin (e.g. changes observed in the AMOC at one latitude will also be observed at other latitudes). It is generally accepted that the AMOC is meridionally coherent on long (decadal+) timescales [1]. On shorter timescales, it is not well understood where and how the meridional coherence breaks down, how the associated driving mechanisms change, or how these influence climate. The primary objective of this project is to use new techniques combining in situ and satellite data to investigate these questions. You will then use these observations to assess state-of-the-art climate model projections. This will lead to a better understanding of the influence of the AMOC on European climate.Methodology: RAPID is an international campaign that has been monitoring the AMOC since 2004 using a moored instruments array along a line at 26N. Techniques have been recently developed using satellite altimetry and gravimetry to estimate the AMOC strength at the RAPID line [2,3]. You will use the techniques developed at 26N to obtain direct estimates from satellite [2,3], providing a basis for extending the AMOC to the north and south of the RAPID line. This will enable you to reconstruct the first whole basin AMOC time series spanning 34S to 58N from satellite data alone. You will learn how to use both gridded and along-track sea level products. Gridded products (altimetry and gravimetry) will be used to provide a first estimate of a satellite-based AMOC across different latitudes. Higher resolution along-track satellite data (e.g. Jason, Sentinel-3A/B, Sentinel-6, CryoSat2) will be used to compare SSH data with RAPID moorings particularly near the coast (<50km), where the SSH signal is not very well resolved with gridded satellite products [2]. The approach will incorporate both standard altimetry products as well as higher resolution SAR altimetry and there is the potential in the latter part of the studentship for inclusion of data from the innovative SWOT mission. The incorporation of higher resolution along-track altimetry will provide significant improvements on existing methods to estimate AMOC strength, where coastal variability has been poorly resolved [2]. Other mooring arrays such as MOVE (16N), OSNAP (58N) and SAMBA (34S) will then be used to provide validation for the satellite-derived estimates of the AMOC. For latitudes in between the mooring arrays, density profiles from Argo floats (autonomous ocean profilers) will be used to fill data/knowledge gaps and provide further validation for the satellite derived AMOC estimates. You will use the resulting latitudinal estimates of the AMOC to investigate meridional coherence of the AMOC variability from annual to decadal time-scales. The overarching objective will be to assess the nature and evolution of the AMOC meridional coherence: where it holds, where it falls apart, its drivers and wider implications these results have for the North Atlantic climate system. Based on this new understanding, you will evaluate the ability of climate simulations (e.g. CMIP6) to adequately represent the observed AMOC characteristics and their connection to European climate.

大西洋纬向翻转环流是一个大规模的海洋环流系统，由将温暖的浅水向北输送并将寒冷的深水向南返回的洋流组成。AMOC对于保持西北欧相对温和的冬季气候至关重要。经向相干性是指AMOC作为一种相干流在大西洋盆地中发挥作用（例如，在某一纬度观测到的AMOC变化也将在其他纬度观测到）。人们普遍认为AMOC在长（十年+）时间尺度上是一致的[1]。在较短的时间尺度上，人们还不太清楚地了解，在哪里以及如何破坏的时空连贯性，相关的驱动机制如何变化，或者这些如何影响气候。该项目的主要目标是利用结合现场和卫星数据的新技术来调查这些问题。然后，您将使用这些观测结果来评估最先进的气候模型预测。这将导致更好地了解AMOC对欧洲气候的影响。方法：RAPID是一项国际运动，自2004年以来一直在监测AMOC使用系泊的仪器阵列沿着一条线在26 N。最近开发了利用卫星测高和重力测量来估计RAPID线上AMOC强度的技术[2，3]。您将使用在26 N开发的技术从卫星[2，3]获得直接估计，为将AMOC延伸到RAPID线的北部和南部提供基础。这将使您能够仅从卫星数据重建第一个横跨34 S到58 N的整个流域AMOC时间序列。您将学习如何使用网格和沿轨道海平面产品。将使用网格化产品（测高和重力测量）对不同纬度的星基AMOC进行初步估计。将使用更高分辨率的沿轨卫星数据（例如Jason、Sentinel-3A/B、Sentinel-6、CryoSat 2）将SSH数据与RAPID系泊进行比较，特别是在海岸附近（<50 km），在那里，SSH信号不能很好地用网格化卫星产品解析[2]。该方法将结合标准测高产品以及更高分辨率的合成孔径雷达测高，并有可能在后期的学生纳入数据从创新的SWOT使命。采用更高分辨率的沿航迹测高技术将大大改进现有的估算AMOC强度的方法，因为在这些方法中，海岸变率的分辨率很差[2]。其他系泊阵列，如MOVE（16 N）、OSNAP（58 N）和桑巴舞（34 S），将用于验证卫星得出的AMOC估计值。对于系泊阵列之间的纬度，Argo浮标（自主海洋剖面仪）的密度剖面图将用于填补数据/知识空白，并为卫星得出的AMOC估计值提供进一步验证。您将使用由此产生的AMOC纬度估计来研究从年度到十年时间尺度的AMOC变化的纬向一致性。总体目标将是评估AMOC区域一致性的性质和演变：它在哪里保持，它在哪里福尔斯分开，它的驱动因素以及这些结果对北大西洋气候系统的更广泛影响。基于这一新的认识，您将评估气候模拟（例如CMIP 6）充分代表观测到的AMOC特征及其与欧洲气候的联系的能力。