Marika Holland

About Marika's Work

Marika Holland is a climate scientist investigating how polar sea ice is affected by and in turn impacts global climate dynamics. Holland primarily uses climate models that simulate Earth’s past and future climate system to unravel the physical processes underlying sea ice response to warming conditions. She then integrates her findings into climate models, thereby improving the models’ ability to predict changes in ice cover, global climate, and associated coastal and maritime ecosystems.

Sea ice has a high surface albedo: it reflects most solar radiation back into space. Because of this reflectivity, it acts as a barrier between the ocean and the atmosphere, and its presence or absence dramatically changes how these Earth systems interact in polar regions. In early work, Holland analyzed polar warming across an ensemble of different climate model projections and determined that the magnitude of polar warming is tied to the initial sea ice conditions, particularly ice thickness. The thinner the ice at the start of the projection period, the greater the degree and spread of polar warming across future years. Holland characterized an ice-albedo feedback loop that accelerates ice loss: as ice melts, the dark ocean is exposed and the ice surface is covered with melt ponds that absorb more sunlight than the highly reflective ice, which in turn increases the ice melt rate. Holland posited that as ice thins past a critical threshold, this feedback loop could cause abrupt and rapid loss of sea ice. Indeed, the Arctic experienced record-setting summer ice loss soon after the study’s publication. Holland has incorporated these and other physical processes and feedbacks (such as black carbon cycling) into the Community Earth System Model, a state-of-the-art climate model used by researchers worldwide. She has also designed climate model ensembles to disentangle the relative impact of natural climate variability (from fluctuations such as El Niño) versus human-caused (anthropogenic) forces (such as greenhouse gas emissions) in sea ice dynamics. She identified anthropogenic aerosols—which can reflect or absorb solar radiation, depending on particle size and composition—as a major source of uncertainty in polar climate simulations, catalyzing a new area of research.

In another line of work, Holland explores the downstream effects of polar climate change on marine ecosystems. Working in collaboration with biologists, her projections of sea ice loss informed the decision to add Emperor penguins to the endangered species list. How Earth’s polar regions evolve has profound implications for sea level rise, coastal planning policy, and maritime safety. With deep understanding of numerical models and the physical processes at work in polar climates, Holland is advancing our ability to predict polar climate change under historically unprecedented conditions.