Abstract Submissions

[willaguiar]

Hello everyone, Im submitting an abstract on our results for the School and Workshop on Polar Climates: Theoretical, Observational and Modelling Advances. Please let me know your thoughts on it. Deadline for submission is April 1st. Download abstract here

[adele-morrison]

Suggested revised abstract:

Ocean surface vertical resolution controls Dense Shelf Water formation around Antarctica

The formation of deep and bottom waters in polar regions is a major control on oceanic carbon and heat uptake and is the main process that ventilates the deep and abyssal ocean. Nevertheless, ocean models often fail to accurately represent the formation of the two main dense waters that fill the deep and abyssal oceans, Antarctic Bottom Water and North Atlantic Deep Water (NADW). This study probes a model that has a good representation of dense water formation over the Antarctic continental shelf to investigate how sensitive the dense water formation is to the model configuration. In particular, we test how the thickness of the ocean top vertical layer alters the production of NADW and Antarctic Dense Shelf Water (DSW), a precursor of Antarctic Bottom Water. Several sensitivity studies are run with the ACCESS-OM2-01 and the MOM6 Pan-Antarctic ocean-sea ice models, with varying top cell thickness. We find that increasing the thickness of the top vertical layer decreases the rate of DSW production over the Antarctic continental shelf in both ACCESS-OM2 and MOM6, with a 60% decrease when the upper layer is increased from 1m to 5m thick. This result is insensitive to the choice of boundary layer mixing scheme, and occurs with both the K-profile parameterisation (KPP) and energetics based planetary boundary layer (ePBL) parameterisations. Ocean only, single column experiments show that the decrease in dense water formation is caused by a more buoyant surface layer in simulations with thicker surface cells. In contrast, the production of the densest NADW waters in the Labrador Sea increases as the top ocean cell thickens. We hypothesise that the differing responses between the Antarctic and North Atlantic dense water formation to vertical resolution is due to convection in the North Atlantic being driven primarily by heat fluxes, while convection at the Antarctic margins is primarily salt-driven.

[AndyHoggANU]

I found the last few sentences confusing. Can I suggest:

Ocean only, single column experiments show that the decrease in dense water formation is caused by a less dense surface layer in simulations with thicker surface cells.

In contrast to the Antarctic region, in the North Atlantic Ocean the production of the densest NADW waters in the Labrador Sea increases as the top ocean cell thickens.

[willaguiar]

Hi!

I will use our recent results to submit an abstract for AMOS session number 8.2 on High-resolution modeling. Here is the abstract below... let me know of any suggestions you have! Word limit: 250, currently 247

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Title: Dense Shelf Water sensitivity to ocean surface cell thickness in the Antarctic Shelf

Dense Shelf Water (DSW) formation in the Antarctic continental shelf alters the atmospheric carbon uptake, being the main process by which Antarctic Bottom Waters form. Despite its importance, most ocean models cannot simulate DSW formation and flow through the continental slope (i.e., overflow) due to the fine resolution required by these processes. In models using z* as a coordinate, the surface vertical resolution can alter processes relevant to the DSW formation, such as the surface Ekman transport and the parameterized vertical salt transport in the surface boundary layer. Nevertheless, no assessments exist on the DSW formation sensitivity to the surface vertical resolution. In this work, we varied the surface ocean cell of two DSW-forming models from 1m to 5m thick as a simple resolution sensitivity test for the DSW formation. We used the ACCESS-OM2 and the Pan-Antarctic ocean and sea ice models, each employing a different boundary layer parameterization. Thickening the surface cell to 5m in ACCESS-OM2 decreased the DSW formation by 45% (1.5 Sv) and ceased the DSW overflow after 10 years of simulation. In the Pan-Antarctic, thickening the surface cell reduced the DSW formation by 34% (1.5 Sv) and the DSW overflow by 67% (2.5 Sv) after 10 simulation years. DSW formation reduction in 5m experiments is explained by a southward shift in the surface Ekman transports, bringing light offshore waters to the Antarctic coast and making the continental shelf DSW-resistant. This response is independent of the boundary layer scheme employed.

[adele-morrison]

Good idea to submit this for AMOS! Some thoughts:

Suggest avoiding "Dense Shelf Water" jargon in the title for people that don't know what this is. Alternate title suggestion: Sensitivity of Antarctic dense water formation to surface vertical resolution Possibly could even try to avoid the DSW acronym throughout the whole abstract?

I think there's evidence for carbon impact on glacial timescales, but probably less evidence for carbon impact relevant on global warming timescales. Maybe easier just to use the overturning motivation? e.g.

Dense Shelf Water (DSW) formation on the Antarctic continental shelf drives the abyssal overturning circulation, being the main process by which Antarctic Bottom Waters form. Despite its importance, most ocean models cannot simulate DSW formation and flow down the continental slope (i.e., overflows) due to the fine resolution required by these processes. In models using z* vertical coordinates, the surface vertical resolution can alter processes relevant to the DSW formation, such as the surface Ekman transport and the parameterized vertical salt transport in the surface boundary layer. Nevertheless, no assessments exist on the DSW formation sensitivity to the surface vertical resolution.

An optional alternative to these last 2 sentences if we don't want to give away the results and make it sound a bit more novel/unexpected: "While many studies have looked at the impact of horizontal resolution and vertical resolution in the deep ocean on the overflows, no studies have investigated whether surface vertical resolution impacts dense water formation."

In this work, we varied the surface ocean cell of two DSW-forming models from 1m to 5m thickness as a simple vertical resolution sensitivity test for the DSW formation. We used the ACCESS-OM2 and the Pan-Antarctic ocean and sea ice models, each employing a different boundary layer parameterization. Thickening the surface cell to 5m in ACCESS-OM2 decreased the DSW formation by 45% (1.5 Sv) and ceased the DSW overflow after 10 years of simulation. In the Pan-Antarctic, thickening the surface cell reduced the DSW formation by 34% (1.5 Sv) and the DSW overflow by 67% (2.5 Sv) after 10 simulation years. DSW formation reduction in 5m experiments is explained by a southward shift in the surface Ekman transports, bringing light offshore waters to the Antarctic coast and making the continental shelf DSW-resistant. This response is independent of the boundary layer scheme employed.

I'm not sure about the term "DSW-resistant". Maybe "prohibiting DSW formation" ?

[willaguiar]

Thanks Adele.

Here is an update text, in which I removed the DSW term.

Sensitivity of Antarctic dense water formation to surface vertical resolution

Dense water formation on the Antarctic continental shelf drives the abyssal overturning circulation, being the main process by which Antarctic Bottom Waters form. Despite its importance, most ocean models cannot simulate dense water formation at the Antarctic coast and flow down the continental slope (i.e., overflow) due to the fine resolution required by these processes. While many studies have looked at the impact of horizontal and vertical resolution in the deep ocean on the overflows, no studies have investigated whether surface vertical resolution impacts dense water formation. In this work, we varied the surface ocean cell of two dense water-forming models from 1m to 5m thickness as a simple vertical resolution sensitivity test. We used the ACCESS-OM2 and the Pan-Antarctic ocean and sea ice models, each employing a different boundary layer parameterization. Thickening the surface cell to 5m in ACCESS-OM2 decreased the dense water formation at the Antarctic continental shelf by 45% (1.5 Sv) and ceased its overflow through the continental slope after 10 years of simulation. In the Pan-Antarctic, thickening the surface cell reduced the Antarctic dense water formation by 34% (1.5 Sv) and its overflow by 67% (2.5 Sv) after 10 simulation years. The dense water formation reduction in 5m experiments is explained by a southward shift in the surface Ekman transports, bringing light offshore waters to the coast and prohibiting its formation at the Antarctic continental shelf. This response is independent of the boundary layer scheme employed.