scholarly journals Impact of Cyclonic Ocean Eddies on Upper Ocean Thermodynamic Response to Typhoon Soudelor

2019 ◽  
Vol 11 (8) ◽  
pp. 938 ◽  
Author(s):  
Jue Ning ◽  
Qing Xu ◽  
Han Zhang ◽  
Tao Wang ◽  
Kaiguo Fan
Keyword(s):  
Vertical Mixing ◽  
Heat Content ◽  
Mesoscale Eddies ◽  
Upper Ocean ◽  
Surface Cooling ◽  
Ocean Eddies ◽  
Horizontal Advection ◽  
Content Change ◽  
Order Of Magnitude ◽  
The Impact

By using multiplatform satellite datasets, Argo observations and numerical model data, the upper ocean thermodynamic responses to Super Typhoon Soudelor are investigated with a focus on the impact of an ocean cyclonic eddy (CE). In addition to the significant surface cooling inside the CE region, an abnormally large rising in subsurface temperature is observed. The maximum warming and heat content change (HCC) reach up to 4.37 °C and 1.73 GJ/m2, respectively. Moreover, the HCC is an order of magnitude larger than that calculated from statistical analysis of Argo profile data in the previous study which only considered the effects caused by typhoons. Meanwhile, the subsurface warming outside the CE is merely 1.74 °C with HCC of 0.39 GJ/m2. Previous studies suggested that typhoon-induced vertical mixing is the primary factor causing subsurface warming but these studies ignored an important mechanism related to the horizontal advection caused by the rotation and movement of mesoscale eddies. This study documents that the eddy-induced horizontal advection has a great impact on the upper ocean responses to typhoons. Therefore, the influence of eddies should be considered when studying the responses of upper ocean to typhoons with pre-existing mesoscale eddies.

Numerical Investigation of the Upper Ocean Response to the Typhoon Winnie (1997) Using an Air-Sea Coupled Model

2013 ◽  
Vol 726-731 ◽  
pp. 3443-3446
Author(s):  
Li Wen Huang ◽  
Yi Jun Ge
Keyword(s):  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Vertical Mixing ◽  
Coupled Model ◽  
Upper Ocean ◽  
Surface Mixed Layer ◽  
Large Area ◽  
Surface Cooling ◽  
Sea Temperature ◽  
The Impact

In order to investigate the impact of air-sea interaction on the ocean surface mixed layer, Typhoon Winnie (1997) was numerical simulated with a two-way air-sea coupled model MCM (Mesoscale Coupled Model). It shows that the Sea Surface Temperature (SST) decreases over a large area with a magnitude up to 4°C. The sea temperature at 30-50 m depth increases about 1°C corresponding to the surface cooling. Moreover, the oceanic mixed layer depth deepens by 20-30 m. It can be included that these variations in the upper ocean are mainly due to vertical mixing induced by the wind stress of the typhoon.

scholarly journals A Limited Effect of Sub-Tropical Typhoons on Phytoplankton Dynamics

2020 ◽  
Author(s):  
Fei Chai ◽  
Yuntao Wang ◽  
Xiaogang Xing ◽  
Yunwei Yan ◽  
Huijie Xue ◽  
...  
Keyword(s):  
Primary Production ◽  
Vertical Mixing ◽  
Remote Sensing Data ◽  
Upper Ocean ◽  
Northwest Pacific ◽  
Limited Effect ◽  
Significant Drop ◽  
Northwest Pacific Ocean ◽  
Temporal Sampling ◽  
The Impact

Abstract. Typhoons are assumed to stimulate ocean primary production through the upward mixing of nutrients into the surface ocean, based largely on observations of increased surface chlorophyll concentrations following the passage of typhoons. This surface chlorophyll enhancement, seen on occasion by satellites, more often is undetected due to intense cloud coverage. Daily data from a BGC-Argo profiling float revealed the upper-ocean response to Typhoon Trami in the Northwest Pacific Ocean. Temperature and chlorophyll changed rapidly, with a significant drop in sea surface temperature and surge in surface chlorophyll associated with strong vertical mixing, which was only partially captured by satellite observations. However, no net increase in vertically integrated chlorophyll was observed during Typhoon Trami or in its wake. Contrary to the prevailing dogma, the results show that typhoons likely have limited effect on net ocean primary production. Observed surface chlorophyll enhancements during and immediately following typhoons in tropical and subtropical waters are more likely associated with surface entrainment of deep chlorophyll maxima. Moreover, the findings demonstrate that remote sensing data alone can overestimate the impact of storms on primary production in all oceans. Full understanding of the impact of storms on upper ocean productivity can only be achieved with ocean observing robots dedicated to high-resolution temporal sampling in the path of storms.

scholarly journals Southern Ocean heat storage, reemergence, and winter sea ice decline induced by summertime winds

2020 ◽  
pp. 1-47
Author(s):  
Edward W. Doddridge ◽  
John Marshall ◽  
Hajoon Song ◽  
Jean-Michel Campin ◽  
Maxwell Kelley
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Mixed Layer ◽  
Vertical Mixing ◽  
Heat Content ◽  
Ice Cover ◽  
Sea Surface ◽  
Surface Mixed Layer ◽  
Surface Cooling ◽  
Westerly Winds

AbstractThe observational record shows a substantial 40-year upward trend in summertime westerly winds over the Southern Ocean, as characterised by the Southern Annular Mode (SAM) index. Enhanced summertime westerly winds have been linked to cold summertime sea surface temperature (SST) anomalies. Previous studies have suggested that Ekman transport or upwelling is responsible for this seasonal cooling. Here, another process is presented in which enhanced vertical mixing, driven by summertime wind anomalies, moves heat downwards, cooling the sea surface and simultaneously warming the subsurface waters. The anomalously cold SSTs draw heat from the atmosphere into the ocean, leading to increased depth-integrated ocean heat content. The subsurface heat is returned to the surface mixed layer during the autumn and winter as the mixed layer deepens, leading to anomalously warm SSTs and potentially reducing sea ice cover. Observational analyses and numerical experiments support our proposed mechanism, showing that enhanced vertical mixing produces subsurface warming and cools the surface mixed layer. Nevertheless, the dominant driver of surface cooling remains uncertain; the relative importance of advective and mixing contributions to the surface cooling is model dependent. Modeling results suggest that sea ice volume is more sensitive to summertime winds than sea ice extent, implying that enhanced summertime westerly winds may lead to thinner sea ice in the following winter, if not lesser ice extent. Thus, strong summertime winds could precondition the sea ice cover for a rapid retreat in the following melt season.

scholarly journals Observation-Based Estimates of Surface Cooling Inhibition by Heavy Rainfall under Tropical Cyclones

2013 ◽  
Vol 43 (1) ◽  
pp. 205-221 ◽  
Author(s):  
Nicolas C. Jourdain ◽  
Matthieu Lengaigne ◽  
Jérome Vialard ◽  
Gurvan Madec ◽  
Christophe E. Menkes ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Bay Of Bengal ◽  
Cold Water ◽  
Mixed Layer Depth ◽  
Vertical Mixing ◽  
Dilution Effect ◽  
Global Scale ◽  
Surface Cooling ◽  
Ocean Reanalysis ◽  
The Impact

Abstract Tropical cyclones drive intense ocean vertical mixing that explains most of the surface cooling observed in their wake (the “cold wake”). In this paper, the authors investigate the influence of cyclonic rainfall on the cold wake at a global scale over the 2002–09 period. For each cyclone, the cold wake intensity and accumulated rainfall are obtained from satellite data and precyclone oceanic stratification from the Global Eddy-Permitting Ocean Reanalysis (GLORYS2). The impact of precipitation on the cold wake is estimated by assuming that cooling is entirely due to vertical mixing and that an extra amount of energy (corresponding to the energy used to mix the rain layer into the ocean) would be available for mixing the ocean column in the hypothetical case with no rain. The positive buoyancy flux of rainfall reduces the mixed layer depth after the cyclone passage, hence reducing cold water entrainment. The resulting reduction in cold wake amplitude is generally small (median of 0.07 K for a median 1 K cold wake) but not negligible (>19% for 10% of the cases). Despite similar cyclonic rainfall, the effect of rain on the cold wake is strongest in the Arabian Sea and weak in the Bay of Bengal. An analytical approach with a linearly stratified ocean allows attributing this difference to the presence of barrier layers in the Bay of Bengal. The authors also show that the cold wake is generally a “salty wake” because entrainment of subsurface saltier water overwhelms the dilution effect of rainfall. Finally, rainfall temperature has a negligible influence on the cold wake.

The impact of mesoscale eddies on plankton dynamics in the upper ocean

1996 ◽  
Vol 43 (11-12) ◽  
pp. 1807-1832 ◽  
Author(s):  
C.L. Smith ◽  
K.J. Richards ◽  
M.J.R. Fasham
Keyword(s):  
Mesoscale Eddies ◽  
Upper Ocean ◽  
Plankton Dynamics ◽  
The Impact

Uncertainty in modeled upper ocean heat content change

2013 ◽  
Vol 42 (3-4) ◽  
pp. 823-842 ◽  
Author(s):  
Robin Tokmakian ◽  
Peter Challenor
Keyword(s):  
Heat Content ◽  
Ocean Heat Content ◽  
Upper Ocean ◽  
Upper Ocean Heat Content ◽  
Content Change

scholarly journals Horizontal ice flow impacts the firn structure of Greenland's percolation zone

2020 ◽  
Vol 14 (5) ◽  
pp. 1703-1712 ◽  
Author(s):  
Rosemary Leone ◽  
Joel Harper ◽  
Toby Meierbachtol ◽  
Neil Humphrey
Keyword(s):  
Pore Space ◽  
Ice Core ◽  
Heat Content ◽  
Greenland Ice Sheet ◽  
Ice Flow ◽  
One Dimensional ◽  
Climate Gradients ◽  
Horizontal Advection ◽  
The Impact ◽  
Percolation Zone

Abstract. One-dimensional simulations of firn evolution neglect horizontal advection from ice flow, which transports the firn column across climate gradients as it is buried by accumulation. Using a suite of model runs, we demonstrate the impacts of horizontal advection on the development of firn density, temperature, and the stratigraphy of melt features through the Greenland ice sheet percolation zone. The simulations isolate processes in synthetic runs and investigate four specific transects and an ice core site. Relative to one-dimensional simulations, the horizontal advection process tends to increase the pore close-off depth, reduce the heat content, and decrease the frequency of melt features with depth by emplacing firn sourced from higher locations under increasingly warm and melt-affected surface conditions. Preservation of the advected pore space and cold content is strongly dependent upon the depth of meltwater infiltration. Horizontal ice flow interacts with topography, climate gradients, and meltwater infiltration to influence the evolution of the firn column structure; the interaction between these variables modulates the impact of horizontal advection on firn at locations around Greenland. Pore close-off and firn temperature are mainly impacted in the lowermost 20–30 km of the percolation zone, which may be relevant to migration of the lower percolation zone. Relatively high in the percolation zone, however, the stratigraphy of melt features can have an advection-derived component that should not be conflated with changing climate.

scholarly journals The Impact of the Amazon–Orinoco River Plume on Enthalpy Flux and Air–Sea Interaction within Caribbean Sea Tropical Cyclones

2019 ◽  
Vol 147 (3) ◽  
pp. 931-950 ◽  
Author(s):  
Johna E. Rudzin ◽  
Lynn K. Shay ◽  
Benjamin Jaimes de la Cruz
Keyword(s):  
Heat Flux ◽  
Heat Budget ◽  
Potential Temperature ◽  
Caribbean Sea ◽  
River Plume ◽  
Sea Surface ◽  
Upper Ocean ◽  
Surface Cooling ◽  
Orinoco River ◽  
The Impact

Abstract The influence of the Amazon–Orinoco River plume in the Caribbean Sea on latent and sensible heat flux (enthalpy flux) and tropical cyclone (TC) intensity is investigated for Hurricanes Ivan (2004), Emily (2005), Dean (2007), and Felix (2007) using dropwindsonde data, satellite sea surface temperature (SST), and the SMARTS climatology. Relationships among enthalpy fluxes, ocean heat content relative to the 26°C isotherm depth (OHC), and SST during storm passage are diagnosed. Results indicate that sea surface cooling in the river plume, a low-OHC region, is comparable to that in the warm eddy region, which has high OHC. An isothermal layer heat budget shows that upper-ocean cooling in the river plume can be explained predominantly by sea-to-air heat flux, rather than by entrainment flux from the thermocline. The latter two findings suggest that relatively large upper-ocean stratification in the plume regime limited entrainment cooling, sustaining SST and enthalpy flux. Inspection of atmospheric variables indicates that deep moderate wind shear is prevalent, and equivalent potential temperature is enhanced over the river plume region for most of these storms. Thus, sustained surface fluxes in this region may have provided warm, moist boundary layer conditions, which may have helped these storms to rapidly intensify even over relatively low-OHC waters and moderate shear. These findings are important because several Caribbean Sea TCs, including these cases, have been underforecast with respect to intensity and/or rapid intensifications, yet minimal upper-ocean observations exist to understand air–sea interaction during TCs in the salinity-stratified Amazon–Orinoco plume regime.

scholarly journals Metrics of hurricane-ocean interaction: vertically-integrated or vertically-averaged ocean temperature?

2009 ◽  
Vol 6 (2) ◽  
pp. 909-951 ◽  
Author(s):  
J. F. Price
Keyword(s):  
Thermal Field ◽  
Vertical Mixing ◽  
Heat Content ◽  
Ocean Temperature ◽  
Surface Cooling ◽  
Continental Shelves ◽  
Hurricane Intensification ◽  
Sea Surface Cooling ◽  
Integrated Or ◽  
High Range

Abstract. The ocean thermal field is often represented in hurricane-ocean interaction by a metric termed the upper Ocean Heat Content (OHC), the vertical integral of ocean temperature in excess of 26°C. High values of OHC have proven useful for identifying ocean regions that are especially favorable for hurricane intensification. Nevertheless, it is argued here that a more direct and robust metric of the ocean thermal field may be afforded by a vertical average of temperature, in one version from the surface to 100 m, a typical depth of vertical mixing by a mature hurricane. OHC and the depth-averaged temperature, dubbed T100, are well correlated over the deep open ocean in the high range of OHC, OHC≥75 kJ cm−2. They are poorly correlated in the low range of OHC, ≤50 kJ cm−2, in part because OHC is degenerate when evaluated on cool ocean temperatures ≤26°C. OHC and T100 can be qualitatively different also over shallow continental shelves: OHC will generally indicate comparatively low values regardless of the ocean temperature, while T100 will take on high values over a shelf that is warm and upwelling neutral or negative, since there will be little cool water that could be mixed into the surface layer. Some limited evidence is that continental shelves may be regions of comparatively small sea surface cooling during a hurricane passage, but more research is clearly required on this important issue.

Multidecadal changes in ENSO properties in the recharge oscillator conceptual model

2020 ◽  
Author(s):  
Lander R. Crespo ◽  
Belen Rodriguez-Fonseca ◽  
Irene Polo ◽  
Noel Keenlyside ◽  
Dietmar Dommenget
Keyword(s):  
Lead Time ◽  
Southern Oscillation ◽  
Heat Content ◽  
Ocean Heat Content ◽  
Water Volume ◽  
Upper Ocean ◽  
Upper Ocean Heat Content ◽  
Discharge Mechanism ◽  
The Impact ◽  
Observational Record

<p><span>We use a simple conceptual recharge oscillator model for the tropical Pacific to identify multidecadal changes in El Niño-Southern Oscillation (ENSO) statistics and dynamics during the observational record. The model, defined by only two variables, sea surface temperature (SST) and warm water volume (WWV), is fitted to the observations for the period 1901-2010. The variability of ENSO has increased during the 20<sup>th</sup> century. The model simulates similar changes in variance of SST and WWV. The cross-correlation between SST and WWV also shows significant changes during the observational record. From the 1970s onwards, both observations and model output show that the SST drives WWV anomalies with a lead-time of 10 months and the WWV feedbacks onto the SST with a lead-time of about 8 months. The latter is reminiscent of a recharge-discharge mechanism of the upper ocean heat content. Before the 1970s only the impact of SST on WWV, through implied wind changes, is observed and is reproduced by the model. The periodicity of ENSO has also changed; ENSO has become more frequent changing from a 7-yr periodicity in the beginning of 20<sup>th</sup> century to a 5-yr periodicity in the recent decades. We find that the full recharge-discharge mechanism of the equatorial upper ocean heat content that characterizes the dynamics of the ReOsc model is only observed from the 1970s onwards and is likely to be a consequence of a stronger observed coupling between WWV and SST and of the leading role of the thermocline feedback. The</span><span> degrading quality in the observations for earlier periods can also partly explain the decadal changes in the ENSO interactions. We find that the Atlantic Multidecadal Variability and global warming can partly explain the observed and simulated multidecadal changes in ENSO properties.</span></p>

Sign in / Sign up

Export Citation Format

Share Document