Graduate Thesis Or Dissertation


Intertwined: Arctic Cyclones and Sea Ice in the Past, Present and Future Public Deposited
  • The Arctic climate system is changing rapidly. Models have estimated that by 2050 we will experience an ice-free Arctic during the summer. These large changes will have implications beyond the Arctic both through teleconnections affecting the weather in midlatitudes and through more human activities in the Arctic. One of the main components of the Arctic climate system are Arctic cyclones, which are responsible for momentum, heat, and energy transport from the tropics to the pole, and to a large part the everyday weather we experience. The passing cyclones can affect the sea ice cover in the Arctic by dynamic and thermodynamic influences but the strong sea ice decline in the Arctic can also affect the cyclones in the Arctic. This strong coupling between the sea ice and Arctic cyclones makes this an important topic in the warming climate. The aim of my dissertation research is to study how cyclones interact with the Arctic sea ice and upper ocean, and how these interactions are changing with lesser and thinner sea ice. First, the recent past (1979-2015) was studied by applying a cyclone tracking algorithm to three different reanalysis datasets (ERA-Interim, ERA5 and CFSR) and categorizing the detected cyclones based on different state variables (season, intensity, sea ice state) to provide an Arctic cyclone climatology with emphasis on cyclone-sea ice interactions. Accumulated Cyclone Energy (ACE) was used as one of the intensity metrics, along with cyclone central pressure, depth and DpDr. Our main findings included increased cyclone counts from the early 2000s onward in the cold season. The increase in the cyclone counts in the cold season was found to be related to decreased SIC in the cold and warm seasons. We also showed that there is a relationship between the cyclone intensity measured by ACE and the surface state. Less sea ice was shown to be related to higher cyclone intensities.Next, an ensemble of CMIP6 model output was utilized from 1985 - 2014 to determine how well the chosen models depict Arctic cyclones and their relationship with sea ice. A comprehensive climatology of Arctic cyclones and SIC was provided based on selected models from CMIP6 and the results were compared to ERA5 product. The models did closely match reanalysis data in declining sea ice during the warm season. However, we found that the models struggled to reproduce the strongly coupled relationship between the declining sea ice and Arctic cyclones. The models were not able to fully capture the local effects of SIC decline and its effects on the cyclogenesis, which led to an underestimation of Arctic cyclones in the CMIP6 models. The models also struggled with the intensity of the Arctic cyclones and the magnitude and sign of the difference compared to ERA5 product was affected by multiple different variables, such as the nominal resolution of themodels, their surface roughness and cyclogenesis location.Lastly, we focused on what the future of Arctic cyclones will look like by utilizing the SSP5- 8.5 Scenario MIP output for 2071-2100. We found that the models show no consistent increase in cyclone counts in the future, contradicting what one would expect based on previous research. We also found consistent increases in both seasons in cyclone intensities measured by ACE and central pressure. This highlights the importance of using the multiple different metrics to define the intensities of future Arctic cyclones. Using different types of intensity metrics can also give a more in depth understanding on the effects cyclones have on their environment, than any single metric alone.

Date Issued
  • 2022-05-27
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Last Modified
  • 2022-12-13
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