2024年9月23日，法国国家气象研究中心
据研究人员介绍，藻类生占据了多种栖息地，包括冰雪环境，在那里它们可以开出红色的花朵。这些变化降低了雪的反照率，加速了雪的融化，并可能反作用于气候变化导致的积雪和冰川减少。量化这种反馈需要理解藻类繁盛随着气候变化的演变。然而，人们对红藻藻华的成因知之甚少。
该研究组开发了一种算法来分析来自欧洲阿尔卑斯山的5年卫星数据，并将藻华事件与类似颜色的撒哈拉沙漠沉积物分开。第二步，研究人员将藻华的发生与气象数据和降雪模拟相结合，以确定藻华的驱动因素。结果表明，藻类从地面向上迁移和开花需要液态水在整个雪柱中存在至少46天。有限的数据表明，适度的灰尘量提供了有利于开花的营养物质，大量的灰尘加速了融雪并将其持续时间缩短到开花所需的阈值以下。
在研究期间，藻华覆盖了海拔1800米以上地区的1.3%，将这些地区的融雪日期提前了4至21天。在气候变暖的情况下，最大积雪量将减少，而控制藻华发生的融雪持续时间对全球气温上升不太敏感。在这方面，藻华对融雪的影响要么保持稳定(RCP4.5)，要么降低(RCP8.5)。因此，阿尔卑斯山的藻华并不构成积极的气候反馈。
附：英文原文
Title: Snowmelt duration controls red algal blooms in the snow of the European Alps
Author: Roussel, Léon, Dumont, Marie, Gascoin, Simon, Monteiro, Diego, Bavay, Mathias, Nabat, Pierre, Ezzedine, Jade Abdellatif, Fructus, Mathieu, Lafaysse, Matthieu, Morin, Samuel, Maréchal, Eric
Issue&Volume: 2024-9-23
Abstract: Algae populate multiple habitats, including snow and ice, where they can form red blooms. These decrease snow albedo, accelerating snowmelt and potentially feeding back on snow and glacier decline caused by climate change. Quantifying this feedback requires the understanding of bloom evolution with climate change. Little, however, is known about the drivers of red snow blooms. Here, we develop an algorithm to analyze 5 y of satellite data from the European Alps and separate bloom occurrences from similarly colored Saharan dust depositions. In a second step, we combine the occurrences of blooms with meteorological data and snow simulations to identify the drivers of blooms. Results show that the upward migration of algae from the ground and blooming requires the presence of liquid water throughout the whole snow column for at least 46 d. Our limited data suggest that moderate dust amounts provide nutrients favorable to bloom, whereas large dust amounts hasten snowmelt and reduce its duration below the threshold required for blooming. Over the period studied, blooms cover 1.3% of the area above 1,800 m elevation, advancing the snow melt-out date by 4 to 21 d in these areas. Under warmer climates, maximum snow mass will decrease whereas snowmelt duration, that controls algal blooms’ occurrences, is less sensitive to global temperature increase. In this respect, the impact of bloom on snowmelt will either remain stable (RCP4.5) or decrease (RCP8.5). Algal blooms in the Alps therefore do not constitute a positive climate feedback.
DOI: 10.1073/pnas.2400362121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2400362121