Visible wavelength fluorescent dissolved organic matter (FDOM), usually defined as humic-like FDOM, plays important roles in marine carbon and iron cycles as biorefractory dissolved organic matter and organic ligands, respectively. The major fractions of FDOM in the open ocean have been considered to be of marine origin (autochthonous) according to linear relationships between FDOM and apparent oxygen utilization (AOU) in the mesopelagic (200–1000 m) and bathypelagic (>1000 m) layers. Recently, Yamashita et al. (2020) quantified allochthonous FDOM from the positive deviation of the general FDOM–AOU relationship in the bathypelagic layer and found that allochthonous FDOM derived from the Sea of Okhotsk was conservatively transported to the western North Pacific through the circulation of intermediate water, including North Pacific Intermediate Water (NPIW). However, the contribution of allochthonous FDOM from the Bering Sea, the other source region of NPIW, has not been evaluated. Here, we determined the distributions of allochthonous FDOM in the entire North Pacific, including the Sea of Okhotsk and the Bering Sea, and the spatial distribution of allochthonous FDOM in the density range of NPIW for the entire North Pacific. We found that the major source region of allochthonous FDOM in NPIW was the Sea of Okhotsk but not the Bering Sea, although the water mass contributing to the lower part of NPIW is known to be mainly derived from the Bering Sea. Such different contributions of allochthonous FDOM from the marginal seas are likely due to a lack of expansion of the dense shelf water, which forms at coastal polynya and interacts with shelf sediments with a strong tidal current, to the basin region of the Bering Sea. We also demonstrated that allochthonous FDOM derived from the shelf sediments of the Sea of Okhotsk was conservatively distributed to the wide area of the North Pacific through the circulation of intermediate water, particularly the upper part of NPIW. Furthermore, the negative deviations of the FDOM-AOU relationship in the bathypelagic layer were evident for other water masses, such as Antarctic Intermediate Water (AAIW), suggesting that FDOM can help determine the spatiotemporal distribution of NPIW and its mixing with other water masses, such as AAIW.

可见光波长的荧光溶解有机物（FDOM）通常被定义为腐殖质样的FDOM，在海洋碳和铁循环中分别作为难熔的溶解有机物和有机配体发挥重要作用。根据中度（200-1000 m）和深海（> 1000 m）层中FDOM与表观氧气利用率（AOU）之间的线性关系，公海中FDOM的主要部分被认为是海洋起源（自生的） 。最近，山下等人。（2020）从浮游上层的一般FDOM-AOU关系的正偏差中量化了异源FDOM，发现来自鄂霍次克海的异源FDOM通过中间水的循环被保守地运到了北太平洋西部，包括北太平洋中级水（NPIW）。但是，尚未评估来自NPIW另一个来源地区白令海的异源FDOM的贡献。在这里，我们确定了包括鄂霍次克海和白令海在内的整个北太平洋的异源FDOM的分布，以及整个北太平洋NPIW密度范围内的异源FDOM的空间分布。我们发现，NPIW中异源FDOM的主要来源地区是鄂霍次克海，但不是白令海，尽管众所周知，造成NPIW下部的水团主要来自白令海。来自边缘海的异源FDOM的这种不同贡献可能是由于缺乏密集的架子水，它形成于沿海的多年生植物，并以强烈的潮流与陆架沉积物相互作用，到达白令海盆地地区。我们还证明，通过中间水的循环，特别是NPIW的上部，从鄂霍次克海陆架沉积物衍生的异源FDOM保守地分布在北太平洋的广大地区。此外，对于其他水团，例如南极中间水（AAIW），在深浮层中FDOM-AOU关系的负偏差是明显的，这表明FDOM可以帮助确定NPIW的时空分布及其与其他水团的混合，例如AAIW。我们还证明，通过中间水的循环，特别是NPIW的上部，从鄂霍次克海陆架沉积物衍生的异源FDOM保守地分布在北太平洋的广大地区。此外，对于其他水团，例如南极中间水（AAIW），在深浮层中FDOM-AOU关系的负偏差是明显的，这表明FDOM可以帮助确定NPIW的时空分布及其与其他水团的混合，例如AAIW。我们还证明，通过中间水的循环，特别是NPIW的上部，从鄂霍次克海陆架沉积物衍生的异源FDOM保守地分布在北太平洋的广大地区。此外，对于其他水团，例如南极中间水（AAIW），在深浮层中FDOM-AOU关系的负偏差是明显的，这表明FDOM可以帮助确定NPIW的时空分布及其与其他水团的混合，例如AAIW。