scholarly journals Reduction in meridional heat export contributes to recent Indian Ocean warming

2021 ◽  
Author(s):  
Josh K. Willis
Keyword(s):  
Indian Ocean ◽  
Heat Transport ◽  
Heat Budget ◽  
Ocean Warming ◽  
Western Boundary ◽  
Southern Boundary ◽  
Agulhas Current ◽  
Indian Ocean Warming ◽  
The Indian Ocean ◽  
Warming Rate

Abstract Since 2000, the Indian Ocean has warmed more rapidly than the Atlantic or Pacific. Air-sea fluxes alone cannot explain the rapid Indian Ocean warming, which has so far been linked to an increase in temperature transport into the basin through the Indonesian Throughflow (ITF). Here, we investigate the role that the heat transport out of the basin at 36°S plays in the warming. Adding the heat transport out of the basin to the ITF temperature transport into the basin, we calculate the decadal mean Indian Ocean heat budget over the 2010s. We find that heat convergence increased within the Indian Ocean over 2000-2019. The heat convergence over the 2010s is the same order as the warming rate, and thus the net air-sea fluxes are near zero. This is a significant change from previous analyses using trans-basin hydrographic sections from 1987, 2002, and 2009, which all found divergences of heat. A two year time series shows that seasonal aliasing is not responsible for the decadal change. The anomalous ocean heat convergence over the 2010s compared to previous estimates is due to changes in ocean currents at both the southern boundary (33%) and the ITF (67%). We hypothesize that the changes at the southern boundary are linked to an observed broadening of the Agulhas Current, implying that temperature and velocity data at the western boundary are crucial to constrain heat budget changes.

Projected future changes of meridional heat transport and heat balance of the Indian Ocean

2020 ◽  
Author(s):  
Jie Ma ◽  
Ming Feng ◽  
Jian Lan ◽  
Dunxin Hu
Keyword(s):  
Indian Ocean ◽  
Heat Transport ◽  
Ocean Circulation ◽  
Heat Balance ◽  
Future Climate Change ◽  
Change Scenario ◽  
Western Boundary ◽  
Additional Contribution ◽  
Agulhas Current ◽  
The Indian Ocean

<p>An ocean downscaling model product, forced under the RCP8.5 future climate change scenario, has been used to understand the ocean heat balance of the Indian Ocean in a warming climate. Towards the end of the 21th century, the model simulates a significant reduction of Indonesian Throughflow (ITF) transport, which reduces the Pacific to Indian Ocean heat transport by 0.20 PW; whereas across S in the southern Indian Ocean (SIO), the southward heat transport is reduced by 0.28 PW, mainly contributed from the weakening western boundary current, the Agulhas Current (0.21 PW). The projected weakening of the Agulhas Current is to compensate for the reduction of the ITF transport, with additional contribution from the spin-down of the SIO subtropical gyre. Thus, being amplified by the ocean circulation changes in the SIO, the projected Indian Ocean warming trend is much faster than the direct air-sea heat flux input.</p>

Warming of the Indian Ocean weakens the Atlantic Niño - El Niño Southern Oscillation connection 

2021 ◽  
Author(s):  
Shreya Dhame ◽  
Andréa Taschetto ◽  
Agus Santoso ◽  
Giovanni Liguori ◽  
Katrin Meissner
Keyword(s):  
Indian Ocean ◽  
Atlantic Ocean ◽  
Southern Oscillation ◽  
Warming Trend ◽  
Equatorial Pacific ◽  
Ocean Warming ◽  
The West ◽  
Indian Ocean Warming ◽  
The Indian Ocean ◽  
Mean State

<p>The tropical Indian Ocean has warmed by 1 degree Celsius since the mid-twentieth century. This warming is likely to continue as the atmospheric carbon dioxide levels keep rising. Here, we discuss how the warming trend could influence the El Niño Southern Oscillation (ENSO) via interaction with the Pacific and the Atlantic Ocean mean state and variability. The warming trend leads to the strengthening of easterlies in the western equatorial Pacific, subsequent downwelling and increase of the mixed later depth in the west, and an increase in the subsurface temperature gradient across the equatorial Pacific. In the eastern equatorial Pacific, the response of upwelling ocean currents to surface wind stress decreases, resulting in a weakening of ENSO amplitude. The Indian Ocean warming influences ENSO via the Atlantic Ocean as well. There, it is associated with the strengthening of equatorial easterly winds, and anomalous warming in the west and upwelling induced cooling in the east, especially in austral winter, during the peak of the Atlantic Niño. Consequently, this results in a decrease of the amplitude of Atlantic Niño events and weakening of the Atlantic Niño-ENSO teleconnection, thereby hindering the transition of El Niño events to La Niña events. Thus, the Indian Ocean warming trend is found to modulate tropical Pacific and Atlantic mean state and variability, with implications for ENSO predictability under a warming climate.</p>

scholarly journals A New Type of the Indian Ocean Dipole since the Mid-1970s

2013 ◽  
Vol 26 (3) ◽  
pp. 959-972 ◽  
Author(s):  
Yan Du ◽  
Wenju Cai ◽  
Yanling Wu
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Climate Models ◽  
Tropical Indian Ocean ◽  
Ocean Warming ◽  
Peak Time ◽  
Austral Winter ◽  
Indian Ocean Warming ◽  
New Type ◽  
The Indian Ocean

Abstract The tropical Indian Ocean dipole/zonal mode (IOD) is phase locked with the austral winter and spring seasons. This study describes three types of the IOD in terms of their peak time and duration. In particular, the authors focus on a new type that develops in May–June and matures in July–August, which is distinctively different from the canonical IOD, which may develop later and peak in September–November or persist from June to November. Such “unseasonable” IOD events are only observed since the mid-1970s, a period after which the tropical Indian Ocean has a closer relationship with the Pacific Ocean. The unseasonable IOD is an intrinsic mode of the Indian Ocean and occurs without an ensuing El Niño. A change in winds along the equator is identified as a major forcing. The wind change is in turn related to a weakening Walker circulation in the Indian Ocean sector in austral winter, which is in part forced by the rapid Indian Ocean warming. Thus, although the occurrence of the unseasonable IOD may be partially influenced by oceanic variability, the authors’ results suggest an influence from the Indian Ocean warming. This suggestion, however, awaits further investigation using fully coupled climate models.

scholarly journals Opposite Annular Responses of the Northern and Southern Hemispheres to Indian Ocean Warming

2010 ◽  
Vol 23 (13) ◽  
pp. 3720-3738 ◽  
Author(s):  
Shuanglin Li ◽  
Judith Perlwitz ◽  
Martin P. Hoerling ◽  
Xiaoting Chen
Keyword(s):  
Indian Ocean ◽  
General Circulation ◽  
Stratospheric Ozone ◽  
Tropical Indian Ocean ◽  
General Circulation Models ◽  
Ocean Warming ◽  
Boreal Winter ◽  
Annular Mode ◽  
Indian Ocean Warming ◽  
The Indian Ocean

Abstract Atmospheric circulation changes during boreal winter of the second half of the twentieth century exhibit a trend toward the positive polarity of both the Northern Hemisphere annular mode (NAM) and the Southern Hemisphere annular mode (SAM). This has occurred in concert with other trends in the climate system, most notably a warming of the Indian Ocean. This study explores whether the tropical Indian Ocean warming played a role in forcing these annular trends. Five different atmospheric general circulation models (AGCMs) are forced with an idealized, transient warming of Indian Ocean sea surface temperature anomalies (SSTA); the results of this indicate that the warming contributed to the annular trend in the NH but offset the annular trend in SH. The latter result implies that the Indian Ocean warming may have partly cancelled the influence of the stratospheric ozone depletion over the southern polar area, which itself forced a trend toward the positive phase of the SAM. Diagnosis of the physical mechanisms for the annular responses indicates that the direct impact of the diabatic heating induced by the Indian Ocean warming does not account for the annular response in the extratropics. Instead, interactions between the forced stationary wave anomalies and transient eddies is key for the formation of annular structures.

scholarly journals Historic Yangtze flooding of 2020 tied to extreme Indian Ocean conditions

2021 ◽  
Vol 118 (12) ◽  
pp. e2022255118
Author(s):  
Zhen-Qiang Zhou ◽  
Shang-Ping Xie ◽  
Renhe Zhang
Keyword(s):  
Indian Ocean ◽  
East Asia ◽  
El Niño ◽  
El Nino ◽  
Summer Rainfall ◽  
Ocean Warming ◽  
Northwest Pacific ◽  
Indian Ocean Warming ◽  
Yangtze Basin ◽  
The Indian Ocean

Heavy monsoon rainfall ravaged a large swath of East Asia in summer 2020. Severe flooding of the Yangtze River displaced millions of residents in the midst of a historic public health crisis. This extreme rainy season was not anticipated from El Niño conditions. Using observations and model experiments, we show that the record strong Indian Ocean Dipole event in 2019 is an important contributor to the extreme Yangtze flooding of 2020. This Indian Ocean mode and a weak El Niño in the Pacific excite downwelling oceanic Rossby waves that propagate slowly westward south of the equator. At a mooring in the Southwest Indian Ocean, the thermocline deepens by a record 70 m in late 2019. The deepened thermocline helps sustain the Indian Ocean warming through the 2020 summer. The Indian Ocean warming forces an anomalous anticyclone in the lower troposphere over the Indo-Northwest Pacific region and intensifies the upper-level westerly jet over East Asia, leading to heavy summer rainfall in the Yangtze Basin. These coupled ocean-atmosphere processes beyond the equatorial Pacific provide predictability. Indeed, dynamic models initialized with observed ocean state predicted the heavy summer rainfall in the Yangtze Basin as early as April 2020.

scholarly journals Step Increase in Eastern U.S. Precipitation Linked to Indian Ocean Warming

2020 ◽  
Vol 47 (17) ◽  
Author(s):  
Courtenay Strong ◽  
Gregory J. McCabe ◽  
Alexander Weech
Keyword(s):  
Indian Ocean ◽  
Ocean Warming ◽  
Indian Ocean Warming

Why is Indian Ocean warming consistently?

2011 ◽  
Vol 110 (3-4) ◽  
pp. 709-719 ◽  
Author(s):  
Suryachandra A. Rao ◽  
Ashish R. Dhakate ◽  
Subodh K. Saha ◽  
Somnath Mahapatra ◽  
Hemantkumar S. Chaudhari ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Ocean Warming ◽  
Indian Ocean Warming
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