Mixed layer heat budget in the Mozambique channel: Interannual variability and influence of Rossby waves

IF 2.3 3区 地球科学 Q2 OCEANOGRAPHY
D. Mawren , J. Hermes , C.J.C. Reason
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引用次数: 0

Abstract

The evolution of the mixed layer temperature anomalies in the Mozambique Channel is analysed using a mixed layer heat budget covering sub-seasonal to interannual time scales. Sub-seasonal variations in mixed layer temperature are largely dominated by surface heat fluxes, except along the southern coast of Mozambique and Madagascar, where both the advection and the residual terms become significant. The northern Channel is dominated by the mean flow while the southern Channel is modulated by both the mean and eddy terms. Minimum heat gain through advection is observed in the channel during January–February when the Northeast Madagascar current opposes the northwesterly monsoonal winds. During the 1997/98 El Niño/positive Indian Ocean dipole, extreme warming and coral bleaching events were noted in the northern Channel. Such warming was linked with the relaxation of local winds, positive heat gain from the atmosphere and the shedding of large anticyclonic eddies northwest of Madagascar, associated with the arrival of downwelling Rossby waves. By contrast, upwelling Rossby waves and large cyclonic eddies in the Channel occurred during the 1998–2001 protracted La Niña, but only the northern part of the Channel experienced significant negative anomalies in mixed layer temperature. While no coral bleaching hotspots were noted in the northern Channel in summer 1999/2000 due to negative anomalies in advection, marine heatwaves occurred in the southern Channel during that summer. Finally, the protracted 1998–2001 La Niña was the last time that substantial upwelling Rossby wave activity occurred in the tropical South Indian Ocean; recent La Niña events showed muted or weak upwelling Rossby wave activity, including the recent 2020–2022 protracted event. Post-2001 also occurs at the same time as a stronger warming trend in the southwest Indian Ocean region.

莫桑比克海峡混合层热量预算:年际变化和罗斯比波的影响
利用混合层热量预算分析了莫桑比克海峡混合层温度异常的演变,涵盖了从亚季节到年际的时间尺度。混合层温度的季以下变化主要由地表热通量主导,但莫桑比克和马达加斯加南部沿海除外,在那里平流和残余项都很重要。北部海峡主要受平均流的影响,而南部海峡则受平均和涡旋项的影响。在 1 月至 2 月期间,当马达加斯加东北洋流与西北季风对峙时,海峡中通过平流获得的热量最少。在 1997/98 年厄尔尼诺/正印度洋偶极期间,海峡北部出现了极端变暖和珊瑚白化现象。这种变暖与当地风力减弱、大气热量增加和马达加斯加西北部大型反气旋涡旋的消失有关,与下沉罗斯比波的到来有关。相比之下,1998-2001 年长期拉尼娜现象期间,英吉利海峡出现了上涌的罗斯比波和大型气旋漩涡,但只有英吉利海峡北部的混合层温度出现了明显的负异常。1999/2000 年夏季,由于负对流异常,英吉利海峡北部没有出现珊瑚漂白热点,但该年夏季英吉利海峡南部出现了海洋热浪。最后,1998-2001 年旷日持久的拉尼娜现象是热带南印度洋最后一次出现大量上涌罗斯比波活动;最近的拉尼娜现象显示出上涌罗斯比波活动不明显或微弱,包括最近 2020-2022 年旷日持久的拉尼娜现象。2001 年后,西南印度洋地区也同时出现了较强的变暖趋势。
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来源期刊
CiteScore
4.60
自引率
4.20%
发文量
144
审稿时长
18.3 weeks
期刊介绍: Deep-Sea Research Part I: Oceanographic Research Papers is devoted to the publication of the results of original scientific research, including theoretical work of evident oceanographic applicability; and the solution of instrumental or methodological problems with evidence of successful use. The journal is distinguished by its interdisciplinary nature and its breadth, covering the geological, physical, chemical and biological aspects of the ocean and its boundaries with the sea floor and the atmosphere. In addition to regular "Research Papers" and "Instruments and Methods" papers, briefer communications may be published as "Notes". Supplemental matter, such as extensive data tables or graphs and multimedia content, may be published as electronic appendices.
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