SOLAS 2018 - Poster
AGU 2016 - Oral Presentation Abstract
How do Greenhouse Gases Warm the Ocean? Investigation of the Response of the Ocean Thermal Skin Layer to Air-Sea Surface Heat Fluxes.
Abstract:
There is much evidence that the ocean is heating due to an increase in concentrations of greenhouse gases (GHG) in the atmosphere from human activities. GHGs absorbs infrared (IR) radiation and re-emits the radiation back to the oceans surface which is subsequently absorbed resulting in a rise in the ocean heat content. However, the incoming longwave radiation, LWin, is absorbed within the top micrometers of the oceans surface, where the thermal skin layer (TSL) exists and does not directly heat the upper few meters of the ocean. We are therefore motivated to investigate the physical mechanism between the absorption of IR radiation and its effect on heat transfer at the air-sea boundary. The hypothesis is that since heat lost through the air-sea interface is controlled by the TSL, which is directly influenced by the absorption and emission of IR radiation, the heat flow through the TSL adjusts to maintain the surface heat loss, and thus modulates the upper ocean heat content. This hypothesis is investigated through utilizing clouds to represent an increase in LWin and analyzing retrieved TSL vertical profiles from a shipboard IR spectrometer from two research cruises. The data is limited to night-time, no precipitation and low winds of < 2 m/s to remove effects of solar radiation, wind-driven shear and possibilities of TSL disruption. The results show independence between the turbulent fluxes and radiative fluxes which rules out the immediate release of heat from the absorption of the cloud infrared irradiance back into the atmosphere through processes such as evaporation. Instead, we observe the surplus energy, from absorbing increasing levels of LWin, adjusts the curvature of the TSL such that there is a lower gradient at the interface between the TSL and the mixed layer. The release of heat stored within the mixed layer is therefore hindered while the additional energy within the TSL is cycled back into the atmosphere. This results in heat beneath the TSL, which is a product of the absorption of solar radiation during the day, to be retained and cause an increase in upper ocean heat content.
Abstract:
There is much evidence that the ocean is heating due to an increase in concentrations of greenhouse gases (GHG) in the atmosphere from human activities. GHGs absorbs infrared (IR) radiation and re-emits the radiation back to the oceans surface which is subsequently absorbed resulting in a rise in the ocean heat content. However, the incoming longwave radiation, LWin, is absorbed within the top micrometers of the oceans surface, where the thermal skin layer (TSL) exists and does not directly heat the upper few meters of the ocean. We are therefore motivated to investigate the physical mechanism between the absorption of IR radiation and its effect on heat transfer at the air-sea boundary. The hypothesis is that since heat lost through the air-sea interface is controlled by the TSL, which is directly influenced by the absorption and emission of IR radiation, the heat flow through the TSL adjusts to maintain the surface heat loss, and thus modulates the upper ocean heat content. This hypothesis is investigated through utilizing clouds to represent an increase in LWin and analyzing retrieved TSL vertical profiles from a shipboard IR spectrometer from two research cruises. The data is limited to night-time, no precipitation and low winds of < 2 m/s to remove effects of solar radiation, wind-driven shear and possibilities of TSL disruption. The results show independence between the turbulent fluxes and radiative fluxes which rules out the immediate release of heat from the absorption of the cloud infrared irradiance back into the atmosphere through processes such as evaporation. Instead, we observe the surplus energy, from absorbing increasing levels of LWin, adjusts the curvature of the TSL such that there is a lower gradient at the interface between the TSL and the mixed layer. The release of heat stored within the mixed layer is therefore hindered while the additional energy within the TSL is cycled back into the atmosphere. This results in heat beneath the TSL, which is a product of the absorption of solar radiation during the day, to be retained and cause an increase in upper ocean heat content.
Ocean Sciences 2014 - Oral Presentation Abstract
RELATIONSHIP BETWEEN ATMOSPHERIC EMITTED INFRARED RADIATION AND THE GRADIENT OF THE THERMAL SKIN SST LAYER
Abstract:
Ocean heat content has recently been increasing and is likely due to increases in greenhouse gases which have raised the atmospheric emitted infrared (IR) radiation. However, this energy is absorbed in the thin electromagnetic skin layer on the aqueous side of the interface. This raises the conundrum of how is the ocean warmed by increasing incident IR radiation? The thermal skin layer (TSL) which exists over similar depths exhibits a strong temperature gradient to sustain the upward heat flux to the air-sea interface. Sensitivity of the TSL temperature gradient to incident IR could provide a mechanism for greenhouse gas heating of the ocean. Determination of TSL gradient utilizes vertical temperature profiles from shipboard-derived radiance spectra. Retrieval of these profiles requires the use of truncated singular value decomposition technique due to non-linearity and ill-conditioning of the inversion equation. Robustness of this technique is evaluated using synthetic datasets. Accurate estimates of the surface and sub-skin temperature of the first-guess profile are required to remove unphysical inversions in the retrieved profile. Changes in the retrieved TSL gradient with IR forcing are subsequently analyzed.
Abstract:
Ocean heat content has recently been increasing and is likely due to increases in greenhouse gases which have raised the atmospheric emitted infrared (IR) radiation. However, this energy is absorbed in the thin electromagnetic skin layer on the aqueous side of the interface. This raises the conundrum of how is the ocean warmed by increasing incident IR radiation? The thermal skin layer (TSL) which exists over similar depths exhibits a strong temperature gradient to sustain the upward heat flux to the air-sea interface. Sensitivity of the TSL temperature gradient to incident IR could provide a mechanism for greenhouse gas heating of the ocean. Determination of TSL gradient utilizes vertical temperature profiles from shipboard-derived radiance spectra. Retrieval of these profiles requires the use of truncated singular value decomposition technique due to non-linearity and ill-conditioning of the inversion equation. Robustness of this technique is evaluated using synthetic datasets. Accurate estimates of the surface and sub-skin temperature of the first-guess profile are required to remove unphysical inversions in the retrieved profile. Changes in the retrieved TSL gradient with IR forcing are subsequently analyzed.