Wave Steepness and Rogue Waves in the Changing Climate in the North Atlantic

2015 ◽  
Author(s):  
Elzbieta M. Bitner-Gregersen ◽  
Alessandro Toffoli
Keyword(s):  
North Atlantic ◽  
Radiative Forcing ◽  
Rogue Waves ◽  
Wave Climate ◽  
Surface Elevation ◽  
Wave Steepness ◽  
Intergovernmental Panel ◽  
The North ◽  
The North Atlantic ◽  
Probability Description

Wave steepness is an important parameter not only for design and operations of marine structures but also for statistics of surface elevation as well as occurrence of rogue waves. The present study investigates potential changes of wave steepness in the future wave climate in the North Atlantic. The Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) uses four scenarios for future greenhouse gas concentrations in the atmosphere called Representative Concentration Pathways (RCP). Two of these scenarios with radiative forcing of 4.5 and 8.5 W/m2 by the end of the 21st century have been selected to project wave conditions in the North Atlantic. The analysis includes total sea, wind sea and swell. Changes of wave steepness for these wave systems are shown and compared with wave steepness derived from historical data. Long-term probability description of wave steepness variations is proposed. Consequences of changes in wave steepness for statistics of surface elevation and generation of rogue waves are demonstrated. Uncertainties associated with wave steepness projections are discussed.

Projected Changes in the Occurrence of Extreme and Rogue Waves in Future Climate in the North Atlantic

2017 ◽  
Author(s):  
Odin Gramstad ◽  
Elzbieta Bitner-Gregersen ◽  
Erik Vanem
Keyword(s):  
North Atlantic ◽  
Wave Spectrum ◽  
Wave Model ◽  
Rogue Waves ◽  
Wave Climate ◽  
Future Climate ◽  
The North ◽  
Wave Parameters ◽  
The Future ◽  
The North Atlantic

We investigate the future wave climate in the North Atlantic with respect to extreme events as well as on wave parameters that have previously not been considered in much details in the perspective of wave climate change, such as those associated with occurrence of rogue waves. A number of future wave projections is obtained by running the third generation wave model WAM with wind input derived from several global circulation models. In each case the wave model has been run for the 30-year historical period 1971–2000 and the future period 2071–2100 assuming the two different future climate scenarios RCP 4.5 and RCP 8.5. The wave model runs have been carried out by the Norwegian Meteorological Institute in Bergen, and the climate model result are taken from The Coupled Model Intercomparison Project phase 5 - CMIP5. In addition to the standard wave parameters such as significant wave height and peak period the wave model runs provided the full two-dimensional wave spectrum. This has enabled the study of a larger set of wave parameters. The focus of the present study is the projected future changes in occurrence of extreme sea states and extreme and rogue waves. The investigations are limited to parameters related to this in a few selected locations in the North Atlantic. Our results show that there are large uncertainties in many of the parameters considered in this study, and in many cases the different climate models and different model scenarios provide contradicting results with respect to the predicted change from past to future climate. There are, however, some situations for which a clearer tendency is observed.

Potential Changes of the North Atlantic Wind and Wave Climate and Occurrence of Rogue Waves

2016 ◽  
Author(s):  
Elzbieta M. Bitner-Gregersen
Keyword(s):  
Climate Change ◽  
21St Century ◽  
North Atlantic ◽  
Radiative Forcing ◽  
Climate Models ◽  
Rogue Waves ◽  
The Past ◽  
The North ◽  
The North Atlantic ◽  
Wave Conditions

The present study investigates potential changes of wind and wave conditions in one North Atlantic location in the 21st century. The Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) uses four scenarios for future greenhouse gas concentrations in the atmosphere called Representative Concentration Pathways (RCP). Two of these scenarios with radiative forcing of 4.5 and 8.5 W/m2 by the end of the 21st century have been selected to project wind and wave conditions in the North Atlantic. The third generation (3G) wave model WAM, forced by winds obtained from GFDL-CM3, EC-Earth, HADGEM2, IPS-CM5A-MR, MRI-GCGCM3 and MIROC5 climate models, has been used to project waves for these two scenarios for the historical period 1971–2000 and the future period 2071–2100. Long-term probabilistic description of wind and waves is provided and deviations between the past and future wind and wave conditions are demonstrated, given attention to the projections obtained by use of the GFDL-CM3 and EC-Earth climate models. Changes in extreme wind and waves are shown and uncertainties associated with climate change projections discussed. Occurrence of rogue-prone crossing sea states which may trigger generation of rogue waves in the past and future climate is also investigated.

Evolving Relative Importance of the Southern Ocean and North Atlantic in Anthropogenic Ocean Heat Uptake

2018 ◽  
Vol 31 (18) ◽  
pp. 7459-7479 ◽  
Author(s):  
Jia-Rui Shi ◽  
Shang-Ping Xie ◽  
Lynne D. Talley
Keyword(s):  
Southern Ocean ◽  
North Atlantic ◽  
Radiative Forcing ◽  
Meridional Overturning Circulation ◽  
Anthropogenic Heat ◽  
Anthropogenic Aerosols ◽  
Ocean Heat Uptake ◽  
The North ◽  
Heat Uptake ◽  
The North Atlantic

Ocean uptake of anthropogenic heat over the past 15 years has mostly occurred in the Southern Ocean, based on Argo float observations. This agrees with historical simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), where the Southern Ocean (south of 30°S) accounts for 72% ± 28% of global heat uptake, while the contribution from the North Atlantic north of 30°N is only 6%. Aerosols preferentially cool the Northern Hemisphere, and the effect on surface heat flux over the subpolar North Atlantic opposes the greenhouse gas (GHG) effect in nearly equal magnitude. This heat uptake compensation is associated with weakening (strengthening) of the Atlantic meridional overturning circulation (AMOC) in response to GHG (aerosol) radiative forcing. Aerosols are projected to decline in the near future, reinforcing the greenhouse effect on the North Atlantic heat uptake. As a result, the Southern Ocean, which will continue to take up anthropogenic heat largely through the mean upwelling of water from depth, will be joined by increased relative contribution from the North Atlantic because of substantial AMOC slowdown in the twenty-first century. In the RCP8.5 scenario, the percentage contribution to global uptake is projected to decrease to 48% ± 8% in the Southern Ocean and increase to 26% ± 6% in the northern North Atlantic. Despite the large uncertainty in the magnitude of projected aerosol forcing, our results suggest that anthropogenic aerosols, given their geographic distributions and temporal trajectories, strongly influence the high-latitude ocean heat uptake and interhemispheric asymmetry through AMOC change.

Why Is There an Early Spring Cooling Shift Downstream of the Tibetan Plateau?

2005 ◽  
Vol 18 (22) ◽  
pp. 4660-4668 ◽  
Author(s):  
Jian Li ◽  
Rucong Yu ◽  
Tianjun Zhou ◽  
Bin Wang
Keyword(s):  
Tibetan Plateau ◽  
North Africa ◽  
North Atlantic ◽  
Radiative Forcing ◽  
Temperature Shift ◽  
Early Spring ◽  
Climate Feedback ◽  
The Tibetan Plateau ◽  
The North ◽  
The North Atlantic

Abstract The temperature shift over the eastern flank of the Tibetan Plateau is examined using the last 50 yr of Chinese surface station observations. It was found that a strong cooling shift occurs in early spring (March and April) and late summer (July, August, and September) in contrast to the warming shift in other seasons. The cause of the March–April (MA) cooling is investigated in this study. The MA cooling shift on the lee side of the Tibetan Plateau is found to be not a local phenomenon, but rather it is associated with an eastward extension of a cooling signal originating from North Africa that is related to the North Atlantic Oscillation (NAO) in the previous winter. The midtropospheric westerlies over the North Atlantic and North Africa tend to intensify during positive NAO phases. The enhanced westerlies, after passing over the Tibetan Plateau, result in strengthened ascending motion against the lee side of the plateau, which favors the formation of midlevel stratiform clouds. The increased amount of stratus clouds induces a negative net cloud–radiative forcing, which thereby cools the surface air and triggers a positive cloud–temperature feedback. In this way, the cooling signal from the upstream could “jump” over the Tibetan Plateau and leave a footprint on its lee side. The continental stratiform cloud–climate feedback plays a significant role in the amplification of the cooling shift downstream of the Tibetan Plateau.

Infrared radiative forcing of a Saharan dust plume in the North Atlantic

1998 ◽  
Vol 29 ◽  
pp. S1301-S1302 ◽  
Author(s):  
P. Chazette ◽  
J. Pelon ◽  
I. Carrasco ◽  
V. Trouillet ◽  
F. Dulac
Keyword(s):  
North Atlantic ◽  
Radiative Forcing ◽  
Saharan Dust ◽  
The North ◽  
The North Atlantic

scholarly journals On the ability of statistical wind-wave models to capture the variability and long-term trends of the North Atlantic winter wave climate

2016 ◽  
Vol 103 ◽  
pp. 177-189 ◽  
Author(s):  
Adrián Martínez-Asensio ◽  
Marta Marcos ◽  
Michael N. Tsimplis ◽  
Gabriel Jordà ◽  
Xiangbo Feng ◽  
...  
Keyword(s):  
North Atlantic ◽  
Wind Wave ◽  
Wave Climate ◽  
The North ◽  
Long Term Trends ◽  
The North Atlantic ◽  
Wave Models

Atmospheric composition changes in CMIP6 experiments over the North Atlantic region

2020 ◽  
Author(s):  
Paul Griffiths ◽  
James Keeble ◽  
Fiona O'Connor ◽  
Alexander Archibald ◽  
John Pyle ◽  
...  
Keyword(s):  
North Atlantic ◽  
Radiative Forcing ◽  
Climate Model ◽  
Climate System ◽  
Atmospheric Composition ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
The North ◽  
North Atlantic Climate ◽  
The North Atlantic

<div> <div> <div> <p>A grand challenge in the field of chemistry-climate modelling is understanding the connection between anthropogenic emissions, atmospheric composition and the radiative forcing of trace gases and aerosols.</p> <p>The 6th phase of the Coupled Model Intercomparison Project (CMIP6) includes a number of climate model experiments that can be used for this purpose.  AerChemMIP [Collins et al.2017] focuses on calculating the radiative forcing of gases and aerosol particles over the period 1850 to 2100, and comprises several tiers of experiments designed to attribute the effect of changes in emissions. </p> <p>The UK Earth System Model, UKESM-1, is a novel climate model developed for CMIP6  [Sellar et al., 2019] and is a community research tool for studying past and future climate.  It includes a detailed treatment of tropospheric chemistry, interactive BVOC emissions and extensive stratospheric chemistry.</p> <p>The North Atlantic Climate System is an area of current interest [Robson et al., 2020] and is the focus of the UKRI 'ACSIS' project.  ACSIS brings together scientists from a range of different specialisms to understand complex changes in the North Atlantic climate system.    By understanding how these changes relate to external drivers of climate, such as human activity, or natural variability, ACSIS aims to improve our capability to detect, explain and predict changes in the North Atlantic climate system.</p> <p>We present an analysis of the evolution of atmospheric composition over the period 1950-2015. The work is based on a recent global multi-model evaluation of tropospheric ozone for CMIP6 [Griffiths et al., 2020] , but focuses on changes over the North Atlantic region in UKESM-1.  We draw on CMIP and AerChemMIP simulations to provide an initial survey of the response of this region to changing emissions , focusing on atmospheric composition and attempting attribution from a series of targeted experiments involving perturbed emissions .</p> </div> </div> </div>

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