Bromine explosions and corresponding ozone depletion events are common in the Arctic spring. The snowpack on sea ice and sea salt aerosols (SSA) are both thought to release bromine, but the relative contribution of each source is not yet known. Furthermore, the role of atmospheric conditions is not fully understood. Long‐term measurements of bromine monoxide (BrO) provide useful insight into the underlying processes of bromine activation. Here we present a 4‐year data set (2016–2019) of springtime BrO partial columns retrieved from Multi‐AXis Differential Optical Absorption Spectroscopy (MAX‐DOAS) measurements in Eureka, Canada (80.1°N, 86.4°W, 610 m asl). Due to the elevation of the measurement site, the instrument often measures BrO in the free troposphere, except during strong wind episodes and storms that generate a deep boundary layer. Enhanced vertical mixing due to strong winds leads to increasing BrO values and reduced ozone depletion. We find that BrO enhancements show two modes differentiated by local wind direction and air mass history. Longer time spent by the airmass in first‐year sea ice areas corresponds to increased BrO for one of these modes only. Furthermore, we argue that snow on multiyear ice might also contribute to bromine release. High aerosol optical depth is required to maintain lofted BrO, and we show that the presence of coarse‐mode aerosols (>0.5 μm, likely SSA) is a necessary and sufficient condition for observing BrO at our elevated measurement site in Eureka. This work highlights the importance of considering variable local conditions when characterizing bromine activation.

中文翻译：

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加拿大高北极地区四个卤素激活季节对流层一氧化溴的测量

北极春天常发生溴爆炸和相应的臭氧消耗事件。海冰和海盐气溶胶（SSA）上的积雪都被认为会释放出溴，但是每种来源的相对贡献尚不清楚。此外，还没有完全了解大气条件的作用。一氧化溴（BrO）的长期测量为深入了解溴的活化过程提供了有用的见识。这里我们展示了从加拿大尤里卡（80.1°N，86.4°W，610 m asl的Multi-AXis差分光学吸收光谱法（MAX-DOAS）测量中检索到的春季BrO偏色谱柱的4年数据集（2016-2019）。 ）。由于测量地点的高度，该仪器通常在自由对流层中测量BrO，除非在强风发作和产生深边界层的暴风雨期间。由于强风而导致的垂直混合增强，导致BrO值增加，并且臭氧消耗减少。我们发现BrO增强显示出两种模式，这两种模式根据本地风向和空气质量历史而有所不同。在第一年海冰区气团花费的时间更长，仅对应于其中一种模式的BrO升高。此外，我们认为多年制冰上的积雪也可能导致溴释放。需要高的气溶胶光学深度来维持放高的BrO，我们证明存在粗模式的气溶胶（在第一年海冰区气团花费的时间更长，仅对应于其中一种模式的BrO升高。此外，我们认为多年制冰上的积雪也可能导致溴释放。需要高的气溶胶光学深度来维持放高的BrO，我们证明存在粗模式的气溶胶（在第一年海冰区气团花费的时间更长，仅对应于其中一种模式的BrO升高。此外，我们认为多年制冰上的积雪也可能导致溴释放。需要高的气溶胶光学深度来维持放高的BrO，我们证明存在粗模式的气溶胶（> 0.5  μ米，可能SSA）是用于我们在尤里卡升高的测定部位观察的BrO的充分必要条件。这项工作强调了表征溴活化时考虑可变的局部条件的重要性。