Thesis Defense - Master of Science Anna Poltronieri

Master of Science Anna Poltronieri will Friday June 20th, 2025, at 10:00 hold her Thesis Defense for the PhD degree in Science. The title of the thesis is:

« On the Future of Arctic Sea Ice - Projections, Dynamics, and Human Impacts »

Abstract:

Arctic sea ice (ASI) is a critical component of the Earth’s climate system, serving as both a regulator of energy exchange and a sensitive indicator of climate change. Over recent decades, ASI has experienced a dramatic decline in both extent and thickness, driven by rising global temperatures and amplified by Arctic feedback mechanisms. This decline is a key driver of Arctic amplification, a phenomenon where the Arctic region warms nearly four times faster than the global average. The consequences of this rapid warming extend beyond the Arctic, affecting local ecosystems, global climate systems, and human activities. Despite significant advances in observational tools and climate modeling, projecting the future of ASI remains challenging due to the complex interplay of feedback mechanisms and increasing variability in the ice cover. Even the most advanced models in the latest phase of the Coupled Model Intercomparison Project (CMIP6) show significant discrepancies in predicting the timing and temperature threshold of complete ASI loss, highlighting the challenges of accurately representing ASI dynamics.

The scope of this thesis is to investigate the future of ASI through three interconnected studies. The first study develops an observation-based projection of the September ASI area — the time of year when ASI extent reaches its annual minimum — revealing an accelerated decline in response to rising global mean temperatures. Our results narrow the spread found in CMIP6 model predictions, placing the complete loss of September ASI cover (area below 1 million km2) between 1.5°C and 2.2°C above pre-industrial levels. The second study investigates the variability in year-to-year fluctuations of the September ASI area across models participating in CMIP6, under varying levels of greenhouse gas emissions. It identifies a consistent pattern of increasing variability as ASI nears complete loss, with the most pronounced effects observed in the Central Arctic. These findings suggest a loss of stability in this historically stable region as ASI decline progresses, highlighting a shift in Arctic dynamics. Lastly, the third study explores the effects of black carbon emissions from Arctic shipping, an activity that is growing rapidly in response to the decline in ASI cover. It compares the impacts of two major maritime routes — the Northern Sea Route and the Transpolar Sea Route — on ASI, revealing regionally distinct changes in ASI reflectivity between the two pathways and underscoring the importance of careful planning for anthropogenic activities in the region.

Supervisory Committee:

  • Professor Martin Rypdal, IMS, UiT (Main Supervisor)

  • Professor Peter Ditlevsen, University of Copenhagen (UCPH)

  • Professor Niklas Boers, Freie Universität Berlin / Potsdam Institute for Climate Impact Research

  • Professor Per Jakobsen, IMS, UiT

  • Professor Rune Graversen, IFT, UiT

Evaluation Committee:

  • 1st Opponent: Professor Igor Polyakov, Department of Atmospheric Sciences, University of Alaska

  • 2nd Opponent: Professor Peter Ashwin, Department of Mathematics and Statistics, University of Exeter, UK

  • Internal member and leader of the committee: Associate Professor Marta Panizzut, IMS UiT

Streaming:

The defence and trial lecture will be streamed from these following links at Panopto:

Defence (10:00 - 14:00)
Trial Lecture (08:00 - 09:00)

Thesis:

The thesis is available at Munin Here.

When: 20.06.25 kl 10.00–14.00
Where: Auditorium B302, Realfagbygget
Location / Campus: Digitalt, Tromsø
Target group: Employees, Students, Guests, Invited, Enhet
E-mail: daniels.sliks@uit.no
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