Dear all,
We are pleased to invite you to the next WISE Webinar on the topic of Waves in the high latitudes on 21/11/2024 at 09:00 am -10:00 am Paris time (4:00 pm - 5:00 pm Beijing time, 7:00 pm - 8:00 pm Melbourne time).
Join us via https://tudelft.zoom.us/my/wisezoominars on 21st November at 9:00 -10.00AM Paris time!
First speaker: Joey Voermans, University of Melbourne
Title: Wave attenuation from ICESat-2 observations
Abstract:
Advances in our modelling capacity of wave-ice interactions are hindered by the limited availability of wave observations in sea ice and, particularly, under a broad range of wave and sea ice conditions. Satellite remote sensing provides opportunities to vastly expand the observational dataset of waves in sea ice and the study of wave-ice interactions. Brouwer et al. (2022) demonstrated a clear reduction of observed wave energy into the Antarctic Marginal Ice Zone (MIZ) as derived from ICESat-2 observations. Here, we build upon the work of Brouwer et al. (2022) to estimate the wave attenuation rate in the Antarctic MIZ under a wide variety of sea ice conditions. Overall statistics of the observations reveal a linear increase in the wave attenuation rate with relative distance into the MIZ. Attenuation rates are well-sorted with wave frequency, where highest attenuation rates are observed for the shortest waves. We find that both the magnitude and frequency dependence of the ICESat-2 estimated wave attenuation rates are consistent with in situ observations. We further highlight that the misalignment between the incident wave direction and the measurement transect, and the inhomogeneity of the ice pack may lead to significant local fluctuations and negative values in the estimated wave attenuation rate when evaluating individual transects. The strong dependence of the overall statistics of the wave attenuation rate on the wave frequency and the relative distance into the MIZ may provide alternative routes in parameterizing wave-ice interactions in the Antarctic environment at global and climate scales.
Second speaker: Alberto Meucii, CSIRO + University of Melbourne
Title: Evaluation and Calibration of Global Spectral Wave Models for ETC-Generated Wind Wave Conditions Supporting Extreme Sea Level Modelling for the Australian Climate Service
Abstract:
Global spectral wave models play a critical role in the modelling and assessment of Extreme Sea Levels along coastlines worldwide. In certain regions, wave setup can be a crucial factor for the safety of coastal communities, particularly along Southern Hemisphere coastlines exposed to the highly energetic sea states of the Southern Ocean. Extreme wind wave events are common in these areas due to frequent Extra-Tropical Cyclones (ETCs) throughout the year. However, spectral wave models face challenges in accurately representing ETC-generated wind wave extremes. To evaluate the performance of our global spectral wave models, we conducted an assessment using wave model simulations to represent the 1-in-100-year sea state generated by a Southern Ocean ETC in April 2021. We collected in situ and remote sensing observations, tracking the storm from its generation through to its decay phase and impact on the southeast Australian coastline. We compared these observations with data from reanalysis and hindcast global wave models. While model accuracy was high for wind speeds up to 20 m/s, discrepancies arose in simulating the air-sea momentum exchange at wind speeds between 20 and 35 m/s, a hallmark of ETCs. These discrepancies likely stem from underestimations of extreme wind speeds in ERA5 used as wind forcing. In response, we developed calibration adjustments for our global spectral wave models to account for extreme wind speeds and implemented these calibration tests in the 40-year Australian Climate Service (ACS) Wave Hindcast. The wind speed calibration performs similarly across both Irregular-Regular-Irregular (IRI) grid schemes and SMC grid approaches, though some discrepancies remain in the highest wind wave extremes in the storm regions, likely due to the propagation scheme used. In this talk, we will start by discussing the findings from the April 2021 ETC case study and how these have guided a broader calibration approach for the SMC grid ACS wave hindcast. Ultimately, we will showcase the varied wind wave climate conditions approaching the boundaries of a national-scale coupled wave-hydrodynamic model for coastal hazards and discuss the potential impacts of ETC-generated wind wave conditions on regional high-resolution studies.
Please note that WISE Webinars including the Q&A will be recorded and posted on the WISE YouTube Channel afterwards (https://www.youtube.com/@wisezoominars). By participating, you consent to any information you share to be included in the recording and shared.
Best wishes,
Tripp, Alvise, Morteza, Ton, Qingxiang and Bernard.
(The WISE Webinar organizing committee)