SGER: Direct Cross-Slope Ventilation of the ACC at the Western Scotia Ridge

摘要项目负责人：Laurence padman提案号：0830398标题：SGER：西斯科舍脊ACC的直接跨坡通风知识价值：南极海洋与大气科学计划资助了这项名为“南极斜坡溪流十字路口”（ACROSS）的探索性研究项目。这项研究将是美国对国际极地年（IPY）天气性南极陆架斜坡相互作用（SASSI）主题的更大背景的贡献。SASSI是一个组织结构，旨在整合南极大陆周围与陆架斜坡相互作用有关的研究，包括与南极底水形成有关的研究。南极底水驱动全球经向海洋环流的下肢，有助于调节全球气候。南极大陆架上的相互作用形成了稠密的海水，以各种方式使深海下沉或通风。现有资料表明，威德尔海地区贡献了大约50%的南极底水。ACROSS将特别探索南极环极流（ACC）深处南斯科舍脊附近直接通风的重要性，相对于通过向上混合底部被困的密集威德尔海深水流出物的间接通风。（本区域其他国家的补充努力将提供将深层ACC与AABW形成联系起来的信息。）到目前为止，人们一直认为通风的间接机制成立，但以前的区域研究（例如国际DOVETAIL， 1997-2000年和英国ALBATROSS， 1999年）的水文证据表明可能存在直接过程。此外，声学和水文测量的反演模型和估计表明，该地区的河床混合率非常高（约2-3个数量级）。升高的混合可能是由风应力或深海洋流与地形或潮汐与地形的相互作用驱动的。确定哪种通风机制占主导地位对于理解全球气候变化非常重要，因为假设的直接通风机制应该对变化的冰架条件做出相当迅速的反应，例如2002年一个月内3200平方公里的拉森B冰架部分的惊人损失。该项目将需要直接进行小规模的湍流测量，从而可以确定湍动混合，并可以在2009年初阿根廷RV Puerto Deseado的30天巡航中评估驱动混合的因素。该地区建立的潮汐模型将有助于指导采样，从而有助于解决模型之间震级不一致的原因。由西班牙资助的用于量化南极坡流对直接通风贡献的水文测量和低声多普勒电流测量以及系泊设施的增强，在一个单独的补充项目（Alejandro Orsi NSF-0818061）中进行。更广泛的影响：这个SGER项目将利用一个非凡的现场机会，利用国际极地年期间开展的广泛的国际大陆架斜坡海洋环流研究。阿根廷（ACROSS）、西班牙（E-SASSI）和巴西（SOS）的合作努力集中在本研究的特定区域。该合作提供了更广泛的区域覆盖，并包括一个示踪计划，该计划将有助于量化AABW的净通气量以及生物学研究。美国国际极地年在更广泛地区的几项投资进一步补充了ACROSS，包括与英国联合的美国极地等环流混合实验（DIMES），德雷克海峡南极环极流动力学和运输的深入研究以及南极半岛西部帕尔默长期生态系统研究（LTER）站点的SASSI研究。作为SASSI的一部分，还有许多其他的国际努力正在进行中。这些努力正在由国际南极区（iAnZone）小组进行协调，该小组是SCOR/SCAR（海洋研究科学委员会/南极研究科学委员会）的附属项目。该提案将支持一名女性技术人员在海上运行剖面仪并处理数据。ACROSS的微观结构数据将经过处理，并通过国际SASSI和WOCE南大洋地图集网站提供给国内和国际合作者。

AbstractPI: Laurence PadmanProposal Number: 0830398Title: SGER: Direct Cross-Slope Ventilation of the ACC at the Western Scotia RidgeIntellectual merit: The Antarctic Ocean & Atmospheric Sciences Program funded this Small Grant for Exploratory Research project entitled Antarctic CRossroads Of Slope Streams (ACROSS). This study will be a US contribution to the larger context of the International Polar Year (IPY) Synoptic Antarctic Shelf Slope Interactions (SASSI) theme. SASSI is an organizational structure to integrate studies around the Antarctic continent that pertain to the shelf slope interactions including those that pertain to formation of Antarctic Bottom Water. Antarctic Bottom Water drives the lower limb of global meridional ocean circulation that helps to regulate global climate. Interactions on Antarctic shelves form dense water which sinks or ventilates the deep ocean in a variety of ways. Available information suggests that the Weddell Sea region contributes about 50% of Antarctic Bottom Water. ACROSS will specifically explore the importance of direct ventilation in the vicinity of the South Scotia Ridge of the deep Antarctic Circumpolar Current (ACC) relative to indirect ventilation through upward mixing of bottom-trapped outflows of dense Weddell Sea Deep Water. (Complementary efforts by others in the region will provide information linking the deep ACC to AABW formation.) Until now, it has been presumed that the indirect mechanism of ventilation holds but hydrographic evidence from previous regional studies (e.g. international DOVETAIL, 1997-2000 and UK ALBATROSS, 1999) suggests the possibility of the direct processes. Furthermore, inverse modeling and estimates from acoustic and hydrographic measurements implicate extraordinarily high (by 2-3 orders of magnitude) diapycnal mixing rates in this region. Elevated mixing may be driven by wind stress or the interactions of abyssal currents with topography or tides with topography. Determining which ventilation mechanisms prevail is important for understanding global climate change since the hypothesized direct ventilation mechanism should respond quite rapidly to changing shelf conditions such as the spectacular loss of a 3200 km2 section of the Larsen B Ice Shelf over one month in 2002. This project will entail direct small scale turbulence measurements from which diapycnal mixing can be determined and factors driving that mixing can be evaluated on a 30 day cruise of the Argentine RV Puerto Deseado in early 2009. Established tidal models for the region will help guide sampling, which in turn should help to resolve the reasons for inconsistent magnitudes between the models. Hydrographic and lowered acoustic Doppler current measurements as well as augmentation of moorings funded by the Spanish to achieve quantification of the Antarctic Slope Current contribution to direct ventilation are covered in a separate complementary project (Alejandro Orsi NSF-0818061). Broader impacts: This SGER project will take advantage of an extraordinary field opportunity that leverages a broad array of international shelf-slope ocean circulation studies being carried out during the IPY. Cooperative Argentine (ACROSS), Spanish (E-SASSI) and Brazilian (SOS) efforts are focused in the specific region of this study. The cooperation affords broader regional coverage and includes a tracer program that will help to quantify the net ventilation rates of AABW as well as biological studies. ACROSS is further complemented by several US IPY investments in broader region including the US Diapycnal Isopycnal Mixing Experiments (DIMES) that is joint with the UK, an intensive study of the dynamics and transport of the Antarctic Circumpolar Current in the Drake Passage and a SASSI study in the Palmer Long Term Ecosystem Research (LTER) site on the western dies of the Antarctic Peninsula. There are numerous other international efforts that are underway as part of the SASSI umbrella. Such efforts are being coordinated the international Antarctic Zone (iAnZone) group, which is a SCOR/SCAR (Scientific Committee for Ocean Research/Scientific Committee for Antarctic Research) affiliated program. A female technician will be supported by this proposal to run the profiler at sea and to process the data. The ACROSS microstructure data will be processed and made available to national and international collaborators via the international SASSI and WOCE Southern Ocean Atlas web sites.