Regional Solar Radiation Management Using Autonomously Assembled Space-Based Sunshade Arrays: A Conceptual Study for Ocean Heat Regulation

The global ocean is the largest reservoir of excess heat in the Earth system. Against a backdrop of a persistent, and recently accelerating, Earth Energy Imbalance (EEI) — observed to have reached roughly 1.8 W/m^2 in 2023, more than double its early-2000s level (Mauritsen et al., 2025, AGU Advances) — the ocean, and in particular the Pacific, which accounts for nearly half of global ocean area, is absorbing and storing additional solar energy at a substantial and measurable rate. A body of prior work has explored space-based solar radiation management (SSRM), most maturely in the form of large sunshade or occulting-disk structures near the Sun-Earth L1 Lagrange point (Early, 1989; Angel, 2006; Sanchez & McInnes, 2015; Fuglesang & Miciano, 2021). Building on this literature, this paper poses and performs a first-order evaluation of a different question: rather than pursuing globally uniform cooling, can a large number of modular, AI-robot-assembled and -maintained reflective/shading units deliver controllable, reversible, regional reductions in solar input to a specific ocean basin (the Pacific, as a case study), targeting ocean heat uptake directly as the physical quantity of interest? We first build a first-principles (Fermi) order-of-magnitude model: using the Pacific's area (~1.6525x10^8 km^2), a representative absorbed-shortwave flux at the ocean surface (~185 W/m^2), and recent observed EEI data, we estimate that a persistent, near-fully-reflective reduction of roughly 0.6-1.2% of the solar energy reaching the Pacific would, in principle, be sufficient to offset the area-weighted share of the currently observed excess heat uptake attributed to that basin. This is the paper's central quantitative result. It is roughly one-third to one-half smaller than the ~1.7-1.8% global radiation reduction target used in prior work aimed at offsetting a CO2-doubling-equivalent warming (Sanchez & McInnes, 2015), suggesting that a region-focused, ocean-heat-budget-targeted intervention may be worth investigating on physical grounds. We then construct three engineering-scale scenarios (Models A/B/C, corresponding to 1%, 5%, and 10% equivalent shaded area of the Pacific), estimating total shading-unit mass and the corresponding order of magnitude in heavy-launch missions (10^10-10^12 kg; 10^5-10^7 launches at current heavy-lift payload scales), cross-checked against literature-derived mass estimates for global L1 sunshade proposals (order 10^10-10^11 kg), which fall in the same order of magnitude. We further argue that a geometric constraint largely overlooked in casual discussion of this idea makes a single, fixed structure at either geostationary orbit (GEO) or L1 poorly suited to persistent, basin-exclusive shading: GEO structures cannot maintain a fixed Sun-shade-target alignment as the solar declination varies seasonally, while an L1 structure's umbra spreads into a penumbra whose width grows with distance, making it difficult to confine a meaningful shading effect to one ocean basin without affecting neighbouring ones. We therefore propose that a more realistic engineering path is not a single giant structure but a reconfigurable swarm in low-Earth or highly elliptical orbit, providing intermittent, adjustable partial shading during local daylight hours over the target basin, coupled to an AI-driven ocean-observation feedback loop. Every major claim in this paper is tagged with an evidence grade (A: observational evidence; B: established mathematical/physical models; C: demonstrated engineering technology; D: this paper's own derivation; E: untested hypothesis), to keep existing scientific consensus clearly separated from this paper's original proposals, and we catalogue a set of unresolved climatic side effects (regional precipitation, monsoon and ENSO response, marine ecology) and governance questions. This paper is positioned as an exploratory, order-of-magnitude (Fermi) analysis, intended to provide a falsifiable starting point for subsequent coupled climate-model simulation and engineering feasibility work, not as an implementation plan.