PaleoBloom

Studying the geological history of Earth’s glacial biosphere — and what it means for today

PaleoBloom is a Leverhulme Fellowship awarded to Chris Williamson exploring how and where ice-adapted life has thrived and/or survived through deep time, and how this knowledge can help us protect today’s cryo-biodiversity as the planet rapidly warms. We focus on the microbial “glacial-biosphere,” especially glacier algae — ice-dwelling microalgae that form summer blooms, drive local food webs, recycle carbon, and darken ice surfaces, thereby enhancing melt. By reconstructing when and where these communities could thrive and persist through past glacial/interglacial periods, we aim to map where we are most at risk of losing ancient, ecologically important lineages in the coming decades.

Why this matters

Frozen landscapes were extensive throughout much of Earth’s history, whereas today’s glaciers and ice sheets are their last remnants, and they are shrinking fast. The work of MicroLab and others has shown that today’s glaciers host distinct, productive microbial communities dominated by glacier algae — organisms that both sustain life on the ice and feedback on climate by reducing ice albedo. In our recent iDAPT project, we showed how glacier algae originated in the Ordovician, ~520–455 million years ago, and have persisted through major glacial–interglacial cycles, underscoring their resilience. Yet we know nothing about the distribution, magnitude or importance of this glacial biosphere throughout deep time. During mass glaciations, glacier algae and ice-adapted life may have been a major component of the world’s biosphere, cycling carbon and nutrients, driving food webs and interacting with ice albedo and melt like they do today. During interglacials, restricted populations may have survived in icy refugia, seeding the cryosphere during subsequent glaciations. These populations could be important reserves of glacial biodiversity. By recreating the most recent geological history of glacier algal communities, PaleoBloom hopes to identify where these more ancient populations are located and risk assess the chance of their loss as climate change proceeds.

Big questions

  1. How widespread and important was Earth’s glacial-biosphere through-out mass glaciations?
  2. Where did ice-dependent communities survive during warm intervals?
  3. Which contemporary communities are most at risk, and which regions may hold genetically rich source populations?

Our approach

PaleoBloom repurposes GA_BLOOM, a process-based model of glacier-algal bloom dynamics driven by key physical forcings (sunlight, temperature, snowpack height), to simulate algal biomass on ice at daily resolution. GA_BLOOM was developed by MicroLab@Bristol and has been used to simulate and study glacier algal blooms across the contemporary Greenland Ice Sheet (e.g. Williamson et al. 2020). For PaleoBloom, instead of modern reanalysis, we will drive GA_BLOOM with HadCM3 paleoclimate simulations spanning the Phanerozoic, plus high-resolution temporal slices every ~4,000 years for the last 3.6 million years provided by the BRIDGE research group, also based in the School of Geographcial Sciences at the University of Bristol. This “offline” setup allows us to test persistence and bloom potential across radically different climates and configurations of continents and mountains. We will also run sensitivity analyses using alternative paleogeographies (Scotese and Getech reconstructions) and orbital settings to bracket uncertainty.

Focus periods

  1. Late Ordovician (~444 Ma, Hirnantian Glaciation): When glacier algae first evolved, we test their potential distribution and Earth-system role during an icehouse world.
  2. Paleocene–Eocene Thermal Maximum (~55 Ma): A hyperthermal interval with little to no continental ice—an extreme bottleneck for ice-dependent life and a deep-time analogue for rapid warming today.
  3. Last 127,000 years (Eemian → LGM → present): Reconstructing the recent history of glacier-algal blooms to identify likely icy refugia and highlight present-day hotspots where losing ice would erase ancient, potentially genetically rich populations

What PaleoBloom will deliver

First global reconstructions of the potential extent and intensity of glacier-algal blooms across key intervals in Earth history.

Refugia maps indicating where ice-adapted communities likely survived warm periods—actionable intelligence for prioritising conservation of cryo-biodiversity under accelerated melt.

High-impact publications on (i) the significance and resilience of the glacial-biosphere through major glaciations and interglacials; (ii) the recent geological history of the glacial-biosphere and its current vulnerability.

Foundations for future work on how ice-adapted life influences biogeochemical cycles and climate feedbacks across geological time.

Team and collaborators

PaleoBloom is an independent Leverhulme Fellowship awarded to Chris Williamson, head of MicroLab@Bristol. He will work closely with colleagues in the BRIDGE research group who will provide vital HadCM3 outputs and guidance on paleoclimate modelling.

Contact

If you’re interested in PaleoBloom or other MicroLab@Bristol projects please drop Chris an email at: c.williamson@bristol.ac.uk