Previous Seminars

High-resolution assessments at NERSC – overview and current developments in ReSIS

Speaker: 
Tobias Wolf (Climate Dynamics and Prediction)
Seminar Date: 
21. May 2019 - 11:15 - 11:45

In the first part of this presentation I will give an overview over the high-resolution studies and capabilities, the Climate Prediction and Dynamics Group has been working with so far. This part will highlight results from projects during the last years. Among these are the successful studies for the Bergen harbour authority, the TRAKT-2018 project and the study on the mitigation of domestic-wood-heating related pollution.

Is it really getting younger? Sea ice type and age in model simulations and satellite remote sensing products

Speaker: 
Polona Itkin (Sea Ice Modelling)
Seminar Date: 
16. April 2019 - 11:15 - 11:45

Sea ice type and age are one of the basic indicators of Arctic sea ice state. For a sea ice model to simulate sea ice type or age faithfully, both sea ice dynamics and thermodynamics need to be represented well. In contrast to sea ice thickness, ice age and type have been able to be retrieved from satellite observations relatively reliably for more than a decade. In this study we are using neXtSIM – ‘next generation sea ice model’ that uses Maxwell-elasto-brittle rheology to simulate sea ice motion and a thermodynamical model that accounts for healing of damaged ice through freezing.

The challenge of bounded, non-Gaussian, non-linear and multi-scale variables

Speaker: 
Craig Bishop
Affiliation: 
School of Earth Sciences and ARC Centre of Excellence for Climate Extremes University of Melbourne
Seminar Date: 
8. April 2019 - 11:00 - 12:00

Current state estimation or data assimilation techniques assume Gaussian uncertainties for both forecasts and observations. However, unbiased observations of bounded variables can be shown to have highly non-Gaussian uncertainties and observation error standard deviations that depend on the value of the unknown true state. In particular, the observation error variance of such observations must tend to zero as the unknown true state tends to zero.

Using climate reanalysis products to identify ecological memory patterns in drylands

Speaker: 
Erik Kusch
Seminar Date: 
29. March 2019 - 12:30 - 13:00

Repeated climate stress events may cause fundamental shifts in species compositions or ecosystem functioning. However, few studies document such shifts. One reason for higher stability of ecosystems than previously expected may be ecological stress memory of vegetation. The study of memory effects of large-scale vegetation may therefore aid in predictions of future changes in biome distributions and resilience assessments on ecosystem or even species level. Such information is invaluable for management oriented decision support systems.

Korea Satellite Remote Sensing of the Arctic

Speaker: 
Hyun-Cheol Kim
Affiliation: 
Korea Polar Research Institute (KOPRI)
Seminar Date: 
28. March 2019 - 15:00 - 15:30

Dr. Hyun-Cheol Kim is the director of Unit of Arctic Sea-Ice Prediction, Korea Polar Research Institute (KOPRI).
As a remote sensing scientist, he will give us a talk regarding the research activities of KOPRI.
After the seminar, NERSC and KOPRI will sign a MoU.

Sea Ice Parameter Retrieval with Physical Synergy of Active and Passive Satellite Data

Speaker: 
Dr. Shiming Xu
Affiliation: 
Department of Earth System Science, Tsinghua University, China
Seminar Date: 
27. March 2019 - 13:00 - 13:45

Sea ice is a key component in the global climate system. Satellite remote sensing is the major approach to the basin-scale observation of sea ice, informing the community of key findings including accelerated shrinkage and drastic thinning of the sea ice cover. As the major method for the estimation of sea ice thickness, satellite altimetry is hindered by the snow cover over the sea ice, which introduces large uncertainty to the sea ice thickness retrieval. Meanwhile, the snow over is a direct indicator of polar hydrological cycle, and a key modulating factor of air-ice-sea interaction.

Automated sea ice classification using Sentinel-1 imagery

Speaker: 
Jeong-Won Park (Ocean and Sea Ice Remote Sensing)
Seminar Date: 
26. March 2019 - 11:15 - 11:45

Sentinel-1A and 1B operate in Extra Wide swath dual-polarization mode over the Arctic Seas, and the two-satellite constellation provides the most frequent SAR observation of the Arctic sea ice ever. However, the use of Sentinel-1 for sea ice classification has not been popular because of relatively higher level of system noise and radiometric calibration issues. By taking advantage of my recent development on Sentinel-1 image noise correction, we suggest a fully automated SAR image-based sea ice classification scheme which can provide a potential near-real time service of sea ice charting.

Impact of sea ice sources on calibrating a wave-ice interaction model

Speaker: 
Sukun Cheng
Affiliation: 
NERSC
Seminar Date: 
22. March 2019 - 11:00 - 11:30

Because of the interaction between ocean wave and sea ice, reliable models for wave propagation in the ice-covered region is critical to sea ice morphology. We present calibration of a viscoelastic type wave-in-ice model with wave, wind, and ice data collected from the Beaufort and Chukchi seas in the autumn of 2015. The data were from multiple sources of in-situ and remote sensing measurements in the marginal ice zone during the ice advance season.

Using a regional ocean model to understand the structure and sampling variability of acoustic tomography arrivals in Fram Strait

Speaker: 
Florian Geyer (Polar Acoustics and Oceanography)
Seminar Date: 
5. March 2019 - 11:15 - 11:45

A regional ocean model for Fram Strait allows to understand the variability and structure of acoustic tomography arrivals. The eddy-permitting model (52 vertical layers and 4.5 km horizontal resolution) was evaluated using long-term moored hydrography data and time series of depth-range averaged temperature obtained from the inversion of acoustic tomography measurements. Geometric ray modelling on the ocean model fields reproduces the measured arrival structure of the acoustic tomography experiment.

Model Calibration Using Warping Metrics: With Application to Sea Ice Deformation in MPM-ice

Speaker: 
Christian Sampson
Affiliation: 
University of North Carolina in Chapel Hill
Seminar Date: 
25. February 2019 - 11:30 - 12:00

Sea Ice is a critical component of earth’s climate system and mediates a broad range of physical processes in the Arctic, such as ocean-atmosphere interaction. Increased warming in the Arctic has drastically changed sea ice dynamics in the region and the ice composition, thinner and more first year ice, and an increased marginal ice zone. Accurate representation of lead formation is now more important than ever for the calculation of important climatological variables, such as oceanic heat flux.