RAPID: Wintertime Hydrography of the Chukchi Sea

来自太平洋的水通过美国和俄罗斯之间的白令海峡进入北极地区，随后向北流过宽阔而浅的楚科奇海。在冬季的几个月里，水接近冰点，含有高浓度的营养物质。随着春天太阳的回归，这些营养物质刺激了大量的浮游植物，反过来又支持了大部分的海洋生物。最近有人假设，除了通过白令海峡的远程来源外，营养物质还可以从楚科奇大陆架的沉积物中混入当地的水中。这种情况发生在冬季冰层上有小开口，很快就会重新冻结。这个过程使表层水密度增加，然后下沉到底部，搅动营养物质。从2020年12月到2021年2月，美国海岸警卫队切割机极地星星将在楚科奇海执行使命，这为在一年中的这个关键时刻收集水的测量值提供了难得的机会。我们建议为该船配备一个易于使用的便携式系统，每天发射两次一次性探头，以获取温度和盐含量的分布。这项研究将揭示冷水是如何以及在哪里被转化的。 通过将这些冬季数据与其他海洋考察队在前一个秋季和次年春季收集的测量数据进行比较，我们可以更好地了解北极生态系统中接近冰点的冬季水的作用。“极地星星号”巡航的结果将被纳入现有的社区外展计划，让当地社区参与进来。太平洋冬季水通过白令海峡向北流动，是营养物质的主要来源，每年春天楚科奇海大陆架都会产生大量的生产力。在一年中寒冷的几个月里，冬季的海水在穿越大陆架的过程中，受到沿海冰穴的影响，会发生变化。最近有人认为，这种水团的转变也发生在整个楚科奇大陆架的小铅。如果这是真的，这将对区域生态系统产生重大影响，因为对流翻转很容易到达底部，将沉积物中的硝酸盐混合到水柱中。USCG Polar星星最近决定于2020年12月至2021年2月在楚科奇海进行使命，这为在水体转变发生的非常时期收集剖面提供了一个非凡的机会。该提案寻求资金，为极地星星配备两个易于使用的便携式系统，每天发射两次温度/盐度探测器。这将为冬季水的形成和转化提供一个罕见的视角，包括它发生的程度，大气强迫以及新通风水的路径。将冬季数据与前一个秋季和随后的春季/夏季收集的测量数据进行比较，将使我们能够确定寒冷，高营养水的演变和命运，并更好地了解其在区域生态系统中的作用。调查人员将担任其中一次夏季巡航的首席科学家-这是2021年8月在楚科奇海进行的NSF资助的实地项目，需要对大陆架进行大规模的水文调查。作为这一努力的一部分，将开展一项外联方案，包括一名PolartREC教师和对当地社区的访问。极地星星冬季巡航的结果将被纳入这个推广计划，为夏季测量提供更广泛的背景。这个奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

Water from the Pacific Ocean enters the Arctic domain through the Bering Strait, between the US and Russia, and subsequently flows northward across the wide and shallow Chukchi Sea. During the winter months, the water is near the freezing point and contains high concentrations of nutrients. As the sun returns in the spring, these nutrients spur large phytoplankton blooms that in turn support much of the marine life. It has recently been hypothesized that, in addition to the remote source via the Bering Strait, nutrients can be mixed into the water locally from the sediments of the Chukchi shelf. This happens when there are small openings in the ice during winter that quickly re-freeze. This process makes the surface water denser, which then sinks to the bottom and stirs up the nutrients. From December 2020 to February 2021, the US Coast Guard Cutter Polar Star will be conducting a mission in the Chukchi Sea, which offers a rare opportunity to collect measurements of the water during this critical time of the year. We propose to outfit the ship with an easy-to-use portable system whereby expendable probes are launched twice daily to obtain profiles of temperature and salt content. This study will reveal how and where the cold water is being transformed. By comparing these winter data with measurements collected the previous fall and following spring by other oceanographic expeditions, we can better understand the role of the near-freezing winter water in the Arctic ecosystem. The results from the Polar Star cruise will be incorporated into an existing community outreach program that engages local communities. Pacific-origin winter water that flows northward through the Bering Strait is the predominant source of nutrients that spur the large productivity occurring each spring on the Chukchi Sea shelf. During its transit across the shelf during the cold months of the year, the winter water can undergo modification when subject to coastal polynyas. Recently it has been argued that this water mass transformation also takes place in small leads throughout the entire Chukchi shelf. If true, this has significant consequences for the regional ecosystem, since the convective overturning can readily reach the bottom and mix nitrate from the sediments into the water column. The recent decision for the USCG Polar Star to conduct a mission in the Chukchi Sea from December 2020 to February 2021 offers an extraordinary opportunity to collect profiles during the very time that the water mass transformation takes place. This proposal seeks funds to outfit the Polar Star with two easy-to-use portable systems for launching temperature/salinity probes twice daily. This will provide a rare view of winter water formation and transformation, including the degree to which it occurs, the atmospheric forcing, and the pathways of the newly ventilated water. Comparing the winter data to measurements collected in the previous fall and following spring/summer will enable us to determine the evolution and fate of the cold, high-nutrient water and better understand its role in the regional ecosystem. The investigator will be chief scientist on one of the summer cruises – an NSF funded field program in the Chukchi Sea in August 2021 that entails a broadscale hydrographic survey of the shelf. As part of that effort, an outreach program will be carried out including a PolarTREC teacher and visits to local communities. The results from the Polar Star winter cruise will be incorporated into this outreach program to provide a broader context for the summertime measurements.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.