the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 18 Feb 2025
The Complex Teleconnections and Feedback Mechanisms between Mainland Indochina's Southwest Monsoon and Arctic Ocean Climate Variability
Abstract. In recent decades, the Arctic climate has changed significantly, especially with a rapid decrease in Arctic Sea ice (ASI) extent in September. This study explores how natural climate variations, specifically linked to the Mainland Indochina Southwest Monsoon (MSWM), affect ASI in September using 40 years of data (1981–2020). The study found that strong MSWM years are associated with less ASI drifting to the Atlantic basin during September, leading to increased sea ice particularly in the Beaufort Sea area. Conversely, weak MSWM years tend to correspond with decreased ASI in certain locations. The MSWM influences the North Atlantic Oscillation (NAO) and North Pacific Oscillation (NPO), altering their typical patterns during strong and weak MSWM years due to interactions between monsoonal heating and the atmosphere-ocean system. During strong MSWM years, a positive NAO and negative NPO weaken the Beaufort Sea High Pressure (BSHP), whereas, during weak MSWM years, the reverse occurs, strengthening the BSHP. And the intensity of the BSHP influences Arctic air-sea interaction, influencing the movement of cold airmass and the track of the transpolar drift stream. This leads to increased sea ice formation during strong MSWM years and decreased formation during weak MSWM years in the Beaufort-Chukchi Sea region.
- Preprint
(3297 KB) - Metadata XML
-
Supplement
(1105 KB) - BibTeX
- EndNote
Status: final response (author comments only)
-
RC1: 'Comment on egusphere-2025-521', Anonymous Referee #1, 08 Mar 2025
The review of “The Complex Teleconnections and Feedback Mechanisms between Mainland Indochina's Southwest Monsoon and Arctic Ocean Climate Variability” manuscript by Kyaw Than Oo and colleagues.
The reviewed manuscript deals with the interesting teleconections between Mainland Indochina Southwest Monsoon and Arctic extratropical climate variability of the Northern Hemisphere (actually not only Arctic as the title claims because NAO is definitely not an Arctic index). Despite the subject being interesting, I recommend rejecting the manuscript basing on it having (1) not enough novelty and (2) not being convincing on the causality and even its direction.
That said, the manuscript is generally well written. The methodology used is correct, the language and general layout of the text are very good. So why do I propose to reject it?
(1) Practically everything the manuscript does is showing correlation between the monsoon in the studied area and some phenomena in the Arctic and generally extratropical Northern Hemisphere. The correlations are well known which the (generally) correct literature review shows, especially the teleconnections with Arctic Ocean sea ice variability, NAO, high pressure system over Siberia etc. They have been shown in multiple papers. I agree that the difference in using a slightly different study area and a new monsoon index could be a reason for a new paper (a weak reason because the paper would still repeat the findings of many previous ones) but there is an even greater problem.
(2) The manuscripts tries to state that it is the Mainland Indochina Southwest Monsoon which influences Arctic sea ice, NAO and surface air pressure over Siberia (rather than the other way) without any evidence for that except for rather vague statements about Rossby waves. The problem is that the literature generally agrees on the inverse direction of causality so what the authors do here is an extraordinary claim which should require extraordinary evidence and no such evidence is provided. For example the cited Chatterjee et al. (2021) states that the mechanism of this teleconnection is "propagation of Rossby wave trains from northwest Europe towards East Asia", while Krishnamurti et al., (2015), which the authors wrongly classify as agreeing with their direction of causality, claims that "The warm phase of [Atlantic Multidecadal Oscillation] may influence the monsoon through the summer North Atlantic Oscillation (SNAO)". As for the Arctic sea ice, Guo et al, (2014), also cited, show how "spring Arctic sea ice impacts the East Asian summer monsoon" (the very title of the paper). The temporal difference strongly implies the direction of influence and I find it a fault of the manuscript that it did not try looking at correlations with time lags, the simplest way to establish what is influenced by what. There is only one paper agreeing with the direction the authors try to push, Grunseich & Wang, (2016). Even as I disagree with it, I have to admit it makes a better case than the reviewed manuscript.
The direction of the influence NAO -> temperature of Siberia and hence also the local high pressure system is pretty obvious because NAO is the index of zonal circulation of the Atlantic sector and Siberia is downwind of this very circulation. The Arctic sea ice <-> NAO relation is more interesting with NAO causing the ice movement variability the manuscript attributes to the monsoon, while the extent of summer sea ice influencing the wintertime NAO through Siberian snow amount, then Siberian high pressure system, then Rossby waves to and from the stratosphere (there is a lot of literature on this, some it that cited in the manuscript). The same zonal circulation makes the strength of the monsoon dependable on both the temperature of the North Atlantic (AMO) and the mid-latitude western circulation (NAO) because both influence the temperature of inner Eurasia. The reason for a possible inverse influence is not so obvious and considering the statistically significant correlation of NAO and Arctic Circulation (AO), the index of mid-latitude Northern Hemisphere zonal circulation, this would also require an explanation of how the monsoon on south-eastern Asia is able to influence the circulation of almost the whole Northern Hemisphere. The problem I see here is that one could take any parameter anywhere which correlates with NAO or AO and make a similar paper claiming that the parameter somehow controls the zonal circulation of the Northern Hemisphere. If proven (for example thanks to its predictive nature), such relationship would be a discovery but without such evidence, it would be very dubious. We know of such influences which do exist, especially for wintertime NAO (not the season studied in the paper) but so far not for other seasons.
I concentrated my critique on the NAO and Arctic sea ice teleconnection as those topics are closest to me, but the same is probably true about the Pacific indexes the manuscript writes about.
I also have some minor comments, mostly of language nature.
- In lines 152-152 the authors say they “conducted substantial examination tests to check the dependability structures”. This requires improving.
- The sentence in lines 341-342 has no verb and is generally impossible to understand: “Homogeneous sea level pressure (SLP) anomalies, there are significant positive and negative correlations between rainfall over specific regions.”.
Citation: https://doi.org/10.5194/egusphere-2025-521-RC1 -
RC2: 'Comment on egusphere-2025-521', Anonymous Referee #2, 03 Sep 2025
Comments:
This study found that interannual variation of Mainland Indochina Southwest Monsoon (MSWM) intensity has a close relation with the Arctic sea ice (ASI) extent in September. The authors argued that MSWM impacts ASI in September via modulating the NPO and NAO, as well as the Beaufort Sea high Pressure. Results obtained in this study are interesting and enhance our understanding of the mechanism behind recent ASI loss. This manuscript can be accepted after the following revision.
In the introduction, I suggest the authors briefly the notable impacts of Arctic sea ice loss on global climate. In particular, recent studies have shown that Arctic sea ice loss could exert notable impacts on tropical climate, including the ENSO, tropical cyclone activity and the Indian Ocean dipole.
Influence of winter Arctic sea ice anomalies on the following autumn Indian Ocean Dipole development. Journal of Climate, 38(13), 3109-3129 (2025).
Interdecadal Variation in the Impact of Arctic Sea Ice on the El Niño-Southern Oscillation: The Role of Atmospheric Mean Flow. Journal of Climate, 37(21), 5483-5506 (2024)
Impact of the winter Arctic sea ice anomaly on the following summer tropical cyclone genesis frequency over the western North Pacific. Climate Dynamics, 61, 3971-3988 (2023).
Lines 182-183: sea level pressure (SLP)->SLP
There are many indices that can be used to describe MSWM intensity. Therefore, the authors should examine whether the results obtained in this study are sensitive to the selection of the index.
Line 191: sea-level pressure (SLP)->SLP
Fig. 7d shows that the correlations between SMII and ASI are weak and insignificant over the Beaufort Sea. Therefore, the results obtained in this study are questionable.
To confirm that interannual variation of MSWM indeed has a close relationship with the NPO and NAO, the authors need to calculate the correlation coefficients between the NPO/NAO indices and SMII. Following studies provide the definitions of the NPO and NAO.
Impacts of winter NPO on subsequent winter ENSO: sensitivity to the definition of NPO index. Climate Dynamics, 50, 375–389 (2018).
The changing relationship between interannual variations of the North Atlantic Oscillation and northern tropical Atlantic SST. Journal of Climate, 28, 485–504 (2015).
Lines 318-320: This description is incorrect. The strength of the Aleutian Low is not related to the NPO. This is because the first EOF mode of SLP anomalies over the North Pacific is the interannual variation of AL intensity, while the second EOF mode is the NPO. Meridional shift of the AL has a close relationship with the NPO.
Enhanced impact of the Aleutian Low on increasing the Central Pacific ENSO in recent decades. Npj Climate and Atmospheric Science, 6, 29 (2023).
The impact of MSWM on NPO and NAO should be confirmed by performing numerical experiments, such as LBM experiments forced by monsoon heating.
It should be noted that there is a close relationship between ENSO and the MSWM and ASI. Therefore, the ENSO signal must be removed from the MSWM intensity index and other variables, in order to ensure that any connection established between the ASI and MSWM is not the result of ENSO's common impact.
Citation: https://doi.org/10.5194/egusphere-2025-521-RC2
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 435 | 78 | 16 | 529 | 20 | 10 | 22 |
- HTML: 435
- PDF: 78
- XML: 16
- Total: 529
- Supplement: 20
- BibTeX: 10
- EndNote: 22
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1