The article examines the response of the stratosphere-to-troposphere transport of ozone to a high-emissions climate change scenario (RCP8.5) using a set of time-slice simulations with WACCM. The focus is over North America and the spring transition of the Pacific jet following previous works, and the response to GHG and SST are separated. The results show increased ozone transport into the troposphere in that region peaking in late winter. The paper is well written and results are clearly presented and adequately discussed. However, there are some important issues that need to be discussed before the paper can be published, which I listed below as major comments.

Major comments:

- Figure 2 shows that the increase in ozone transport into the troposphere is dominated by GHG. This is in contrast with the results in the rest of the paper, which demonstrate a fundamental role of the SST for O3S in the lower stratosphere and upper troposphere (UTLS). How should we interpret this difference? Does it imply that changes in the lower stratospheric reservoir do not translate into tropospheric ozone, contrary to what is typically considered? Or does it reflect a disconnection between UTLS and the deep intrusions reaching the middle-lower troposphere? Or something else? This should be discussed in the manuscript.

- Figure 5 suggests that GHG enhance substantially the ozone concentrations in the extratropical lower stratosphere reservoir, but then in Figures 6 and 7 the GHG have no effect. Does this mean that the ozone local production (rather than the transport by the BDC) is enhanced with GHG increase? If so, it seems quite an important point to make, given that the ozone enhancement is larger than that due to SST.

- The lower stratospheric ozone reservoir changes show a pattern that resemble the stationary wave response to a positive ENSO phase SST anomaly. As stated in the paper, other models could produce different SST patterns leading to different stationary waves and thus ozone changes. Nevertheless, the increase in ozone STT is consistent across models. What does this mean for the role of the ozone wave-like anomalies on the zonal mean trends? The answer could go in the direction of the response to zonal mean SST dominating over the response to SST zonal anomalies, as found in Chrysanthou et al. (2020). A discussion on this point would improve the paper.

- In lines 105-107 the ODS are said to increase from the pre-industrial to the RCP8.5 end-of-century simulations (note that it would be convenient to state here by how much they do increase in order to quantify their effect). However, in Line 437 it is stated “with additional effects from reduced ODS”. I suspect this confusion is due to the different simulations considered in Dietmuller et al. (2021) versus this manuscript. Please, clarify what is the role of ODS if any in your analysis. Also, even though the role of ODS is not explicitly examined in this work given the comparison to pre-industrial conditions, previous studies have shown that ODS decline is the dominant forcing of global ozone STT increase over the century (Banerjee et al. 2016, Meul et al. 2018, Abalos et al. 2020). This is an important point that should be clearly stated in the paper in order to avoid confusion.

Minor comments:

- L88: Please specify how stratospheric ozone loss is treated in the troposphere. There are different ways in which this has been made and it is beneficial to explicitly include this information.

- L92-93: “to remove interannual variability driven by the ocean (e.g. variability due to ENSO)” It is true that there is no variability in your experiments. However, a clear ENSO signal shows up in the climatology of the SST change, presumably due to more frequent/intense events. So you are not really removing this effect (and indeed you refer to it later on). So I suggest rephrasing this.

- L121-124 seem in contradiction with L117-120. Please clarify what you mean.

- L241: Is this robust also across climate models?

- L253: Is the amplified surface warming related to changes in sea ice? I assume sea ice is also imposed as a boundary condition?

- Fig. 4: Top row: are there negative values in low latitudes or is it an effect of the colorbar? What are the units of O3S? Caption: “stationary wave (contou*r*s, long-term zonal...) ”. Stationary waves are not a physical magnitude, change to something like “Stationary waves visualized by geopotential height deviation from the long-term mean zonal mean (contours, in meters)”

- L312: Why is the modified flow implied by the wave phase tilt?

Technical:

- L167: “distribution of median dates” : remove “median”

- Fig. 2 caption: What does the box show?

- L122: “still coincide with roughly 10-35%” → “still imply roughly a 10-35%”

- L259: “purely chemical changes in the atmosphere” Strictly, this applies to all climate change impacts, do you mean chemical changes in the *stratosphere*? - L316: Fig. 4k → Fig. 4g

- L334: 235ºE-260ºE: does this correspond to the box in Fig. 2? If so, please add it.

- L389: “=” should be “)”

The paper by Elsbury et al. deals with the response of ozone STT and North Pacific jet to RCP8.5 forcing over the western North America region which is a well-known hot spot of ozone STT. This is a very interesting paper on the main mechanisms of future ozone STT over western North America. It is well written and structured, and the results are nicely presented. My only concern is the terminology of the experiments and the associated discussion which I find misleading. I would be happy to suggest publication of the manuscript in ACP once my comments below are addressed:

Comments:

1. The future SSTs mainly result from the future GHGs. What the authors present is a decomposition of the overall GHGs effect in that of SSTs and the residual of GHGs (including also the ODSs) which to my understanding is mainly the chemical effect. The EXP2 described with term RCP8.5 is the one that represents the whole GHGs effect. Therefore, using the terms “RCP8.5 SSTs” and “RCP8.5 GHGs” is somehow misleading as both constitute the overall GHGs effect (term “RCP8.5”). The same applies to the corresponding discussion.  

2. I find the term “RCP8.5 GHGs” misleading, as this also includes the ODSs impact on future ozone STT. Although, the authors nicely discuss the limitations of their approach in the conclusions, I feel that the term “RCP8.5 GHGs” gives the impression that ODSs are not included, and someone must specifically find that information (that are included) in the text.

3. Moreover, I am a bit puzzled with how ODSs are treated in the simulations. The authors state (P4, L105-107) “There are also increased concentrations of ozone-depleting substances (ODS; e.g., chlorofluorocarbons) relative to the preindustrial experiment, due to the long lifetimes of these substances, which were emitted prior to the Montreal Protocol.”, but in the Conclusions they attribute higher ozone concentrations also “…from reduced ODSs” (P19, L437). Is the latter statement referring to a comparison with respect to the present period? If yes, the comparison presented is relative to the preindustrial period. Please clarify this. 

Minor Comments:

L32-L33:  Recently Zanis et al. (2022) studied the climate change penalty and benefit on ozone air-quality using simulations from CMIP6 ESMs. I believe this reference can be included here.

L82: What is the resolution of WACCM model near the tropopause?

L88: How is tropopause defined in WACCM?

L218: Please include degree symbols (and where else applicable).

L271: Maybe “The 200 hPa O3S”.

References

Zanis, P., D. Akritidis, S. Turnock, V. Naik, S. Szopa, A.K. Georgoulias, S.E. Bauer, M. Deushi, L.W Horowitz, J. Keeble, P. Le Sager, F.M. O'Connor, N. Oshima, K. Tsigaridis, and T. van Noije, 2022: Climate change penalty and benefit on surface ozone: A global perspective based on CMIP6 earth system models. Environ. Res. Lett., 17, no. 2, 024014, doi:10.1088/1748-9326/ac4a34.