The Arctic Ocean is turning blue. Abrupt Arctic warming and amplification is driving rapid sea ice decline and irreversible deglaciation of Greenland. The already emerging, substantial consequences for the planet and society are intensifying and yet, model-based projections lack validatory consensus. To date, we cannot anticipate how a blue Arctic responds to and will amplify an increasingly warmer future climate, nor how it will impact the wider planet and society. Climate projections are inconclusive as we critically lack key Arctic geological archives that preserve the answers. This “Arctic Challenge” of global significance can only be addressed by investigating processes, consequences, and impact of past “greenhouse” (warmer than present) states. The timeliness of i2B is tied into retrieval of revolutionary, new Arctic geological archives of past warmth and key breakthroughs in climate model performance that will be integrated in a concerted framework beyond state-of-the-art. i2B will deliver a ground-breaking, synergistic framework to answer the central question: “Why and what were the global ramifications of a “blue” (ice-free) Arctic during past warmer-than-present-climates?” This will be addressed through three connected, cross-disciplinary objectives integrating the expertise, knowledge, and skill-sets of three PIs and their different Arctic paleo-climate and modelling teams. i2B will quantify cryosphere (sea ice, land ice) change in a warmer world (O1) that will form the scientific basis for understanding the dynamics of Arctic cryosphere and ocean changes (O2), to enable quantitative assessment of the impact of Arctic change on ocean biosphere, climate extremes and society (O3) that will underpin future cryosphere-inclusive IPCC assessments. i2B will solve the “Arctic Challenge” with the synergistic multiplier of the 3 PIs` expert capabilities providing pioneering knowledge on how a blue Arctic impacts Earth’s climate during greenhouse climate states