"The surface energy budget of the model during the melting periods showed that the net downwelling short-wave surface flux [the net solar energy at the surface] was the largest contributor to the melting energy, indicating that the cloud clearing effect of föhn events is likely to be the most important factor for increased melting relative to non-föhn days."Thus, glacier melt on the Antarctic Peninsula, one of many so-called 'canaries in the coal mine' for CAGW, is not primarily dependent upon alarmist claims of radiative forcing from man-made CO2, but rather natural variations in cloud cover and solar energy received at the surface.
The paper comes on the heels of another paper published a few days ago finding Arctic sea ice extent linked to absorption of sunlight by clouds, a similar mechanism governing net shortwave solar energy received by the surface.
Thus, given these two new papers, solar energy modulated by cloud cover may be the dominant factor controlling ice extent/mass in both the Arctic and Antarctic, not radiative forcing from man-made CO2.
1University of Manchester, Centre for Atmospheric Science, SEAES, Manchester, UK
2British Antarctic Survey, Cambridge, UK
*now at: School of Earth and Environment, University of Leeds, Leeds, UK
Abstract. Mesoscale model simulations are presented of a westerly föhn event over the Antarctic Peninsula mountain ridge and onto the Larsen C ice shelf, just south of the recently collapsed Larsen B ice shelf. Aircraft observations showed the presence of föhn jets descending near the ice shelf surface with maximum wind speeds at 250–350 m in height. Surface flux measurements suggested that melting was occurring. Simulated profiles of wind speed, temperature and wind direction were very similar to the observations. However, the good match only occurred at a model time corresponding to ~9 h before the aircraft observations were made since the model föhn jets died down after this. This was despite the fact that the model was nudged towards analysis for heights greater than ~1.15 km above the surface.
Timing issues aside, the otherwise good comparison between the model and observations gave confidence that the model flow structure was similar to that in reality. Details of the model jet structure are explored and discussed and are found to have ramifications for the placement of automatic weather station (AWS) stations on the ice shelf in order to detect föhn flow. Cross sections of the flow are also examined and were found to compare well to the aircraft measurements. Gravity wave breaking above the mountain crest likely created a~situation similar to hydraulic flow and allowed föhn flow and ice shelf surface warming to occur despite strong upwind blocking, which in previous studies of this region has generally not been considered. Our results therefore suggest that reduced upwind blocking, due to wind speed increases or stability decreases, might not result in an increased likelihood of föhn events over the Antarctic Peninsula, as previously suggested.
The surface energy budget of the model during the melting periods showed that the net downwelling short-wave surface flux [the net solar energy at the surface] was the largest contributor to the melting energy, indicating that the cloud clearing effect of föhn events is likely to be the most important factor for increased melting relative to non-föhn days. The results also indicate that the warmth of the föhn jets through sensible heat flux ("SH") may not be critical in causing melting beyond boundary layer stabilisation effects (which may help to prevent cloud cover and suppress loss of heat by convection) and are actually cancelled by latent heat flux ("LH") effects (snow ablation). It was found that ground heat flux ("GRD") was likely to be an important factor when considering the changing surface energy budget for the southern regions of the ice shelf as the climate warms.
Atmos. Chem. Phys., 14, 9481-9509, 2014
www.atmos-chem-phys.net/14/9481/2014/ doi:10.5194/acp-14-9481-2014 |
1University of Manchester, Centre for Atmospheric Science, SEAES, Manchester, UK
2British Antarctic Survey, Cambridge, UK
*now at: School of Earth and Environment, University of Leeds, Leeds, UK
Abstract. Mesoscale model simulations are presented of a westerly föhn event over the Antarctic Peninsula mountain ridge and onto the Larsen C ice shelf, just south of the recently collapsed Larsen B ice shelf. Aircraft observations showed the presence of föhn jets descending near the ice shelf surface with maximum wind speeds at 250–350 m in height. Surface flux measurements suggested that melting was occurring. Simulated profiles of wind speed, temperature and wind direction were very similar to the observations. However, the good match only occurred at a model time corresponding to ~9 h before the aircraft observations were made since the model föhn jets died down after this. This was despite the fact that the model was nudged towards analysis for heights greater than ~1.15 km above the surface.
Timing issues aside, the otherwise good comparison between the model and observations gave confidence that the model flow structure was similar to that in reality. Details of the model jet structure are explored and discussed and are found to have ramifications for the placement of automatic weather station (AWS) stations on the ice shelf in order to detect föhn flow. Cross sections of the flow are also examined and were found to compare well to the aircraft measurements. Gravity wave breaking above the mountain crest likely created a~situation similar to hydraulic flow and allowed föhn flow and ice shelf surface warming to occur despite strong upwind blocking, which in previous studies of this region has generally not been considered. Our results therefore suggest that reduced upwind blocking, due to wind speed increases or stability decreases, might not result in an increased likelihood of föhn events over the Antarctic Peninsula, as previously suggested.
The surface energy budget of the model during the melting periods showed that the net downwelling short-wave surface flux [the net solar energy at the surface] was the largest contributor to the melting energy, indicating that the cloud clearing effect of föhn events is likely to be the most important factor for increased melting relative to non-föhn days. The results also indicate that the warmth of the föhn jets through sensible heat flux ("SH") may not be critical in causing melting beyond boundary layer stabilisation effects (which may help to prevent cloud cover and suppress loss of heat by convection) and are actually cancelled by latent heat flux ("LH") effects (snow ablation). It was found that ground heat flux ("GRD") was likely to be an important factor when considering the changing surface energy budget for the southern regions of the ice shelf as the climate warms.
Commenting as anonymous because I don't want to set up another account.
ReplyDeleteYou do realize that this is a study done by models. The anti-AGW mantra is that models don't work.
Live by the sword, die by the sword...
Of course I realize it is a modeled study and comment on the serious flawed assumptions in the models regarding SST forcing
DeleteThe point is even with the overheated, falsified radiative forcing assumptions of the models, greenhouse forcing is still not the "largest contributor" to melting energy.
Commenting anonymously so I don't have to set up another account.
ReplyDeleteSo you then claim that the study you cite is worthless. Which makes your claim worthless.
"The article (or at least the abstract) admits that their model isn't accurate.
"However, the good match only occurred at a model time corresponding to ~9 h before the aircraft observations were made since the model föhn jets died down after this. This was despite the fact that the model was nudged towards analysis for heights greater than ~1.15 km above the surface."
It also admits that they "nudged" their model.
You can't have it both ways. This model study admits to its own flaws, you accept its results and disproving the effects of CO2, while you simultaneously discredit the models that support the effects of CO2.
Either way, you end up with nothing, since you cannot accept the findings of this (self-admitted) imperfect model that you propound as disproving the affects of CO2 unless you accept the (self-admitted) imperfect IPCC model that you propound as ineffective at proving the effects of CO2.
If this is a model (it is) and it admits to being imperfect (it does), and you criticize IPCC models for being imperfect models (and you do), then your reliance on this model (which both you and the modelers admit is inaccurate) to disprove the effects of CO2 is not only unjustified, but patently hypocritical.
Sorry but that's total bull
DeleteI don't by any means "accept its results" and I absolutely do in thousands of posts explain why all the models, including this one, are overheated with CO2 radiative forcing.
What you just don't seem to understand is that, despite the models [including this one] being overheated with CO2 radiative forcing, the authors STILL find that CO2 radiative forcing is NOT the dominant contributor to melt energy, and instead net solar shortwave is the dominant forcing.
Based upon hundreds of other papers reviewed on this site, net solar shortwave is the dominant forcing not only for the Antarctic Peninsula, but the entire globe as well. Therefore, this paper is useful in the sense of confirming the neglected solar forcing of climate, which still exceeds the exaggerated radiative forcing assumptions of this model and others.