Ginny Selz, PhD
Senior Program Director, Repair
July 7, 2026
The frozen Arctic has long served as a stabilizing feature in Earth’s climate system, linked to predictable weather patterns and ocean circulation across the globe. As the region warms, its stabilizing influence is eroding with risks of becoming a driver of global disruption.
Rising greenhouse gas concentrations are driving higher ocean and atmospheric temperatures, contributing to a loss of almost 50 percent of summer sea ice extent over the last 40 years. Recent winters have also had back-to-back years of record-low ice extent in 2025 and 2026. Growing evidence warns that continued sea ice loss is contributing to tipping points that, if crossed, would drive irreversible ecosystem changes and potentially trigger climate feedback loops with severe impacts.
Frozen land and ocean surfaces in the Arctic and elsewhere underpin Earth’s climate system because of their ability to reflect heat energy away from the planet. As sea ice declines, darker ocean water absorbs more heat, which contributes to regional warming that is nearly four times faster than the global average.
Loss of sea ice is already having profound impacts on Arctic ecosystems, communities, the ocean, and the global climate system. Even under best-case emission scenarios where society reduces and removes greenhouse gas pollution, the Arctic will still become largely ice-free within decades, an area-based threshold that is defined by scientists and represents about an 85 percent decrease from the estimated pre-industrial summer sea ice extent.
Given these risks, Ocean Visions is supporting targeted research efforts to explore whether new approaches could help slow the loss of sea ice alongside broader efforts in reducing greenhouse gas emissions and removing legacy carbon to gradually slow, stabilize, and ultimately reverse the planet’s warming.
One emerging area of research is investigating whether and how clouds in the Arctic could play a role in slowing the loss of sea ice. This area of research is part of a broader set of strategies outlined in Ocean Visions’ Arctic Sea Ice Road Maps and is currently being advanced in parallel with the potential for marine cloud brightening in the Arctic, and potential for reducing ice export.
This is the first of a three-part series explaining these approaches.
What is Mixed-Phase Cloud Thinning?
Mixed-phase clouds are clouds that contain both supercooled water droplets and ice crystals. These clouds occur globally, and at high latitudes where they play an important role in regulating Earth’s climate.
In the Arctic winter, when there is little or no sunlight, mixed-phase clouds can have a net warming effect by trapping heat near Earth’s surface, contributing to warmer temperatures that can accelerate sea ice loss.
Researchers are studying whether it may be possible to reduce some of that warming effect through a proposed approach called mixed-phase cloud thinning, and if any resulting cooling could impact sea ice.
The idea is based on a naturally occurring process where tiny particles called ice-nucleating particles can cause supercooled liquid droplets inside clouds to freeze into ice crystals. Those ice crystals then fall out of the cloud more quickly, sometimes as precipitation, which then ‘thins’ the cloud (making it less dense) and changes both its reflective and insulative properties. Some countries, including the US, already introduce ice-nucleating particles to clouds to increase precipitation through a method commonly known as cloud seeding.
By analyzing models and historical observations, Ocean Visions-funded scientists are investigating whether introducing ice-nucleating particles into Arctic mixed-phase clouds during low- to no-sunlight periods could enhance this process of cloud thinning enough to cool the surface below and potentially help preserve sea ice. However, during sunlit periods, these same clouds can have a cooling effect because they reflect incoming solar radiation. Therefore, this approach targets low- to no-light conditions.
While early modeling studies suggest mixed-phase cloud thinning could potentially cool parts of the Arctic and increase sea ice extent under some scenarios, research is at an early stage. Many questions remain unanswered about feasibility, effectiveness, risks, and governance.
What Ocean Visions is Doing
Ocean Visions launched the Arctic Sea Ice Restoration Research Fund to help advance responsible research into approaches that may help slow the loss of Arctic sea ice.
The Fund builds on Ocean Visions’ Arctic sea ice road maps, which evaluate 21 potential approaches to slowing Arctic sea ice loss. The road maps identify major knowledge gaps and the most important next steps to better understand each approach. An expert workshop identified mixed-phase cloud thinning as a first research priority from the list of approaches to pursue.
Based on this, Ocean Visions held an international competition, solicited proposals, and selected four mixed-phase cloud thinning projects after a rigorous scientific peer review. These projects join a small collection of research supported by other organizations, demonstrating that studies into this approach are under-resourced but growing.
Ocean Visions doesn’t advocate for deployment of any potential climate intervention at this time. Instead, the focus is on supporting responsible, transparent research so that any future decision making is informed by evidence—including governance, ethical, and societal dimensions of the work.
Mixed-phase cloud thinning applied as an Arctic climate intervention is still highly uncertain. But given the pace of Arctic change and the growing risks associated with continued sea ice loss, Ocean Visions believes it is urgent to responsibly investigate all possible approaches to forestall further loss.
Mixed-Phased Cloud Thinning Research Through the Ocean Visions Arctic Sea Ice Restoration Research Fund
Through our Arctic Sea Ice Restoration Research Fund, Ocean Visions is supporting two projects focused on mixed-phase cloud thinning and two projects focused on combined approaches of mixed-phase cloud thinning and marine cloud brightening.
- Bounding the Potential of Mixed-Phase Cloud Thinning to Slow Arctic Sea Ice Loss: Combines satellite observations with climate model simulations to estimate how much cooling mixed-phase cloud thinning could realistically achieve and whether that cooling could meaningfully preserve Arctic sea ice.
- Observation-Based Assessment of Mixed-Phase Cloud Thinning for Reducing Sea Ice Loss in Northern Alaska Communities: Uses observations and modeling to study how often the relevant cloud conditions occur, whether cloud changes could increase sea ice, and how Indigenous Peoples and Arctic communities view research into this approach.
- Leveraging Next-Generation Satellite and Suborbital Observations to Guide Mixed-Phase Cloud Thinning for Arctic Sea-Ice Preservation: Develops new Arctic cloud observation tools using recently launched satellites and aircraft observations to better understand where and when the cloud conditions needed for mixed-phase cloud thinning may exist.
- Susceptibility of Arctic Sea Ice Energy Budget to Variations in Supercooled Clouds: Uses observations and an advanced regional model to determine when, where, and to what extent these clouds influence sea ice to identify the conditions where this approach may or may not be effective.
Together, these projects will help build the targeted scientific understanding needed to evaluate mixed-phase cloud thinning rigorously and responsibly. Through continued investments in research, collaboration, and public dialogue, we can help build the knowledge base needed for discussions that consider the opportunities, risks, and tradeoffs associated with these proposed interventions, informing decisions about their potential role, if any, in responding to climate change and limiting its impacts.