Estimation of atmospheric nutrient inputs to the Atlantic Ocean from 50°N to 50°S based on large-scale field sampling: Fixed nitrogen and dry deposition of phosphorus
Estimation of atmospheric nutrient inputs to the Atlantic Ocean from 50°N to 50°S based on large-scale field sampling: Fixed nitrogen and dry deposition of phosphorus
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DOI：
10.1029/2009gb003634
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发表时间：
2010-07-16
影响因子：
5.2
通讯作者：
Ganzeveld, L.
中科院分区：
文献类型：
--
作者：
Baker, A. R.;Lesworth, T.;Ganzeveld, L.
据估计，由于过去 150 年人为排放量的增加，大气中进入海洋的氮输入量增加了三倍，预计至少在中短期内还会进一步增加。这些估计主要基于排放和大气传输模型，因为除了少数岛屿之外，有关偏远海洋大气氮浓度的观测数据非常少。在这里，我们使用在北纬 50 度至南 50 度之间横跨大西洋的 12 次长断面巡航中获得的雨水和气溶胶样本，作为对流域氮输入的气候学估计的基础。气候学适用于 2001-2005 年这 5 年，几乎所有的航行都发生在这期间，明确包括硝酸盐和铵的干湿沉积，以及对可溶性有机氮沉积的更不确定的估计。我们的结果表明，该地区的氮输入量约为 850-1420 Gmol (12-20 Tg) N yr(-1)，其中 78-85% 以湿沉降形式存在。北半球和湿润地区的输入量更大，并且湿润地区通过湿沉降输入的比例更大。我们对干输入估计的最大不确定性与沉积速度的变化有关，而我们对湿氮输入估计的最大不确定性是由于观测数据的数量有限且地理分布不均匀。我们还使用来自相同巡航的数据估计磷酸盐干沉积的下限类似于 0.19 Gmol P yr(-1)。我们将我们的结果与最近对大西洋氮和磷沉积的几个估计进行比较，并讨论了气候学中可能的不确定性来源，例如我们的采样引入的潜在季节性偏差。
Atmospheric nitrogen inputs to the ocean are estimated to have increased by up to a factor of three as a result of increased anthropogenic emissions over the last 150 years, with further increases expected in the short-to mid-term at least. Such estimates are largely based on emissions and atmospheric transport modeling, because, apart from a few island sites, there is very little observational data available for atmospheric nitrogen concentrations over the remote ocean. Here we use samples of rainwater and aerosol we obtained during 12 long-transect cruises across the Atlantic Ocean between 50 degrees N and 50 degrees S as the basis for a climatological estimate of nitrogen inputs to the basin. The climatology is for the 5 years 2001-2005, during which almost all of the cruises took place, and includes dry and wet deposition of nitrate and ammonium explicitly, together with a more uncertain estimate of soluble organic nitrogen deposition. Our results indicate that nitrogen inputs into the region were similar to 850-1420 Gmol (12-20 Tg) N yr(-1), with similar to 78-85% of this in the form of wet deposition. Inputs were greater in the Northern Hemisphere and in wet regions, and wet regions had a greater proportion of input via wet deposition. The largest uncertainty in our estimate of dry inputs is associated with variability in deposition velocities, while the largest uncertainty in our wet nitrogen input estimate is due to the limited amount and uneven geographic distribution of observational data. We also estimate a lower limit of dry deposition of phosphate to be similar to 0.19 Gmol P yr(-1), using data from the same cruises. We compare our results to several recent estimates of N and P deposition to the Atlantic and discuss the likely sources of uncertainty, such as the potential seasonal bias introduced by our sampling, on our climatology.