Natural Radionuclides as Tracers of the Cycling and Fate of Particulate Organic Carbon on the Mackenzie Shelf: Participation in the Canadian Arctic Shelf Exchange Study(CASES)

天然放射性核素作为麦肯齐陆架颗粒有机碳循环和归宿的示踪剂：参与加拿大北极陆架交换研究（CASES）

• 批准号: 0136459
• 负责人: J Kirk Cochran
• 金额: $ 33.81万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-02-01 至 2006-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0136459&HistoricalAwards=false
• 关键词: Natural; Radionuclides; Tracers; Cycling; Fate

0136459CochranOf all the world oceans, the Arctic is unique in its persistent cover of sea ice, broad continental shelves that are loci for carbon cycling and strong annual variations in light intensity. Moreover the Arctic is perhaps the ocean most susceptible to showing the early effects of global warming. Although changes such as thinning ice cover may have natural causes, for example related to variations in the gradient of atmospheric pressure in the Arctic, they may also be related to changes in climate brought about by human activities. Climate warming may alter the cycling of carbon on arctic shelves through permanent reductions in ice cover and increases in riverine discharge. In turn these changes may lead to enhanced export of carbon to the slope and deep arctic basins.One of the most distinguishing features of the Arctic is its extensive shelf area, comprising about 30% of the basin area and receiving about 10% of the world river discharge. River discharge in the Arctic is dominated by the great Siberian rivers - the Yenisei, Lena and Ob. The Mackenzie River is fourth in importance after these, but is first in rank in terms of annual discharge of sediment. Moreover, it is the only North American analog of the large Siberian rivers, and in practical terms is the most readily studied.The potential importance of the river-dominated shelves to biogeochemical cycling in the Arctic has lead to an international effort --the Canadian Arctic Shelf Exchange Study (CASES)--organized by Canada to understand the consequences of sea- ice variability on the Mackenzie shelf. Based on prior involvement in Canadian-organized arctic programs in the Northeast and North Water Polynyas, the PI has been invited to participate in the CASES program. The research proposed here for the Mackenzie Shelf will build on the PI's prior efforts in the Arctic and elsewhere to use natural radionuclides as tracers for fluxes of particulate organic carbon and particles.CASES includes three month-long process cruises (in August 2002, 2003 and 2004) on the Mackenzie Shelf and a year-long period between the August 2003 and 2004 cruises during which the research icebreaker will over-winter. This research will be structured to take advantage of the possibility to sample the full annual cycle of productivity on the Mackenzie Shelf. Focus will be on the three distinct zones (an early season inner shelf pool of freshwater dubbed 'Lake Mackenzie' separated by an ice dam from a flaw-lead polynya and the arctic pack ice) that develop in the system, and employ natural radionuclides as tracers for the transport of particles and particulate organic carbon within and between the zones. We hypothesize that significant exchanges between the zones will occur in the spring through summer as the Mackenzie River freshet begins, the ice retreats offshore and productivity increases. We will test this hypothesis through the use of natural radionuclides to determine the presence of freshly input riverine sediments to the inner shelf, the rate of export of POC from the euphotic zone, and through mass balances, as indicators of the transport of particulate material through the zones. The radionuclides we will use include cosmogenic radionuclides (Be-7 and C-14) produced in the atmosphere from the interactions of cosmic rays with atmospheric gases, and radionuclides of the naturally occurring U-238 decay series (Th-234, Pb-210).

0136459COCHRANOF在整个世界海洋中，北极在其持续的海冰覆盖范围内是独一无二的，宽阔的大陆架子是碳循环的基因座，并且在光强度中的年度变化很强。而且，北极也许是最容易显示出全球变暖的早期影响的海洋。尽管诸如稀疏冰盖之类的变化可能具有自然原因，例如与北极大气压梯度的变化有关，它们也可能与人类活动带来的气候变化有关。气候变暖可能会通过永久减少冰盖和河流排放增加来改变北极货架上碳的循环。反过来，这些变化可能会导致碳和深北极盆地的出口增强。北极最显着的特征之一是其广阔的货架区域，约占盆地区域的30％，并获得了世界河流河流的约10％。北极的河流排放位于西伯利亚河流-Yenisei，Lena和OB。麦肯齐河（Mackenzie River）在这之后的重要性中排名第四，但在沉积物的年度排放量方面排名第一。此外，这是西伯利亚大河流中唯一的北美类似物，实际上是最容易研究的。在北极河流主导的货架对生物地球化学循环的潜在重要性，导致了国际努力 - 加拿大北极货架交换研究（案例） - 加拿大组织了加拿大的组织，以理解海上冰的影响。基于事先参与东北和北方水上的加拿大北极计划，PI已被邀请参加案件计划。在这里提出的麦肯齐架子的研究将基于PI在北极和其他地方的先前努力，将天然放射性核酸酯作为颗粒有机碳和颗粒的通量的示踪剂。Cases包括在Mackenzie Shelf和2003年8月在2003年之间进行的三个月过程（2002年8月，2003年和2004年8月，2002年和2004年）。这项研究将结构化，以利用麦肯齐架子上的全年生产率周期的可能性。重点将放在三个不同的区域（早期的季节内架子池的淡水池，称为“麦肯齐湖”，由冰坝与系统中形成的缺陷型Polynya和北极包装冰隔开，并在系统中发展起来，并使用天然放射性核素作为颗粒和颗粒有机碳内部和Zone之间的植物。我们假设，随着Mackenzie River Freshet的开始，冰层撤退和生产力提高，该区域之间的大量交流将在春季至夏季进行。我们将通过使用天然放射性核素来确定新鲜输入的河流沉积物到内架上的存在，POC从舒适区的出口速率以及通过质量平衡作为作为通过区域传输的指标，从而确定新鲜输入的河流沉积物的存在。我们将使用的放射性核素包括宇宙射线与大气气体与大气气体的相互作用以及自然存在的U-238衰减序列的放射性核素（TH-234，PB-210），在大气中产生的宇宙核核素（BE-7和C-14）。