A comparison of sea to air DMS flux measurements and the possible role of near- surface gradients

海洋和大气之间的气体交换速率对于全球地球化学循环以及预测和模拟未来气候变化极其重要，但目前仍难以准确量化。一些需要准确估计的重要问题包括海洋吸收人为二氧化碳的速度，以及量化其他重要气候活性气体的海洋来源，如科学家认为控制海洋上空云层形成的二甲基硫化物。我们计划测量水中二甲硫醚的浓度，以便我们能够利用这一数据，以及由我们的夏威夷大学项目合作伙伴开发的测量二甲硫醚海气通量的新技术，以便更好地了解控制大气和海洋之间气体转移的过程。我们认为，与风一样，波浪破碎产生的气泡数量将对空气-海洋气体交换产生重要影响。关于海水中二甲硫醚含量的大部分数据都是从船底泵入研究船的水中收集的。通常在5- 8米的深度。然而，为了计算从海洋转移到空气中的二甲基硫醚的数量，我们确实需要知道这种气体在海面上的浓度。每个人都认为从船体（即5- 8米）测量的浓度与在海面测量的浓度相同。然而，我们知道二甲硫醚是由水中的生物过程产生和消耗的，它会被阳光迅速破坏。因此，我们想检查二甲基硫醚在海面上的浓度与在船体深处的浓度之间是否存在差异。这将对计算海洋向大气供应的二甲基硫的实际数量产生重要影响。当我们想要比较DMS通量的直接估计值与间接估计值时，了解是否存在任何梯度也很重要，因为这将影响我们认为气泡在气-海气体转移中的重要性。我们计划在2007年夏天参加在北大西洋的一次研究航行，届时将有许多其他小组进行各种关键的测量和观察（测量海况、白浪和波浪破碎，并评估气泡和表面活性剂的作用）。

The rates at which gases exchange between the oceans and the atmosphere are extremely important to global biogeochemical cycles and to predicting and modelling future climate change, but quantifying them accurately currently remains elusive. Some important issues requiring accurate estimates include the rate at which anthropogenic carbon dioxide can be taken up by the oceans and quantifying the marine sources of other important climate active gases such as dimethyl sulphide that scientists believe control cloud formation over the oceans. We plan to measure concentrations of DMS in the water so that we can use this data, together with a new technique for measuring the air-sea flux of DMS to be made by our project partners from the University of Hawaii, in order to better understand the processes that control the transfer of gases between the atmosphere and the ocean. We think that as well as the wind, the amounts of bubbles made by breaking waves will have an important impact on air--sea gas exchange. Much of the data on the amount of DMS that is present in seawater is collected from water pumped into research ships from the bottom of the ship. This is usually at a depth of about 5-8m. However, in order to calculate the amount of DMS that is transferring from the sea to the air we really need to know the concentration of this gas at the sea surface. Everybody assumes that the concentrations measurements from the ship's hull (ie 5-8m) are the same as those made at the sea surface. However, we know that DMS is produced and consumed by biological processes in the water and that it is rapidly destroyed by sunlight. We therefore want to check whether there is a difference between dimethyl sulphide concentrations at the sea surface compared to the depths of ship hulls. This would be have important consequences for calcuating the actual amount of dimethyl sulphide that the ocean supplies to the atmosphere. It is also important to know if there are any gradients when we want to compare the direct estimates of the DMS flux with the indirect estimates as this would impact on how important we think the bubbles might be in air-sea gas transfer. We plan to participate in a research cruisein the North Atlantic Ocean in the suimmer of 2007 when there will be many other groups making a variety of key measurements and observations (measure seastate, whitecapping and wave breaking and evaluating the role of bubbles and surfactants air-sea gas exchange.