Maloy Kumar Devnath Successfully Defends His Dissertation

The Antarctic region holds 90% of the Earth's freshwater. Antarctica's ice mass has been diminishing rapidly, with an estimated average loss of approximately ∼ 146 billion tons annually since 2002, according to the satellite measurements. The reduction in sea ice extent raises critical questions about its repercussions on ice sheet melting, as sea ice provides a protective barrier separating ice sheets from warm ocean currents and wave action. While Antarctic sea ice has been expanding until 2015, recent trends show a dramatic reversal with record low extents in February 2023. Understanding the relationship between sea ice changes and ice sheet melting is essential for deciphering the broader implications of global sea-level rise, a pressing concern for coastal communities, ecosystems, and policymakers. Furthermore, the nature of the sea ice retreat, especially after 2015, has not been well studied. This is important because anomalous events can retreat sea ice extent at a very high rate within a short period of time and can cause rapid losses by changing in the retreat onset timing, duration, and intensity. To address this, this research develops parameter free machine learning algorithms to detect anomalous melt events, variations in melt onset and duration, and to quantify the linkages or interactions between sea ice retreat and land ice or ice sheet melting. This thesis specifically aims to:

1. Design an effective parameter free machine learning algorithm to detect anomalous sea ice retreat events, which are characterized by negative changes.

2. Study the onset, duration, and intensity of the anomalous and steady state retreat events and how they evolve with time, affecting the sea ice area coverage(or loss in km2).

3. Quantify the linkages between sea ice retreat and ice sheet melting in regions experiencing anomalous melts.

By addressing these questions, this thesis contributes to a comprehensive understanding of the intricate interactions between sea ice retreat and ice sheet melting in the Antarctic region and their broader implications for global sea-level rise. Our study has found that anomalous retreat events, identified through the analysis of satellite images of sea ice extent, have prevailed since 2015 and have contributed significantly to total sea ice retreat. Furthermore, we have detected significant linkages between sea ice retreat and ice sheet melting.