Ocean Gyre Convergence Zone

Gyre Circulation

Gyre rotation Ω 0.25 rad/day

Ekman convergence k 0.50

Wind-driven windage α 3.0%

Debris count 1200

Live Readouts

Accumulation index

Mean radius

0 km

Simulated time elapsed

0 days

How it works

Subtropical wind systems (trade winds + westerlies) drive a rotating surface-current gyre. Because the Coriolis force deflects moving water, the net wind-driven (Ekman) transport is roughly 90° to the wind rather than along it — and around a closed gyre this transport converges toward the center from every direction, piling up water into a slight dome and pumping it slowly downward (Ekman pumping). Anything floating that can't sink with that downwelling gets left behind, concentrating near the center.

This simulator models the surface velocity field as a Rankine-like vortex plus a radial convergence term:

Tangential:  v_θ(r) = Ω·r            (r ≤ R_core)
             v_θ(r) = Ω·R_core²/r   (r > R_core)
Radial:      v_r(r) = −k·r·e^(−(r/L)²)   (inward, peaks near r ≈ L)
Wind drift:  v_wind = α·W  (constant "windage" push on exposed debris)
Total:       dx/dt = v_θ·θ̂ + v_r·r̂ + v_wind

Ω — Gyre rotation sets how fast the circulation spins (stronger wind stress curl → faster rotation).
k — Ekman convergence sets how strongly the radial inflow sweeps debris toward the center; k = 0 leaves debris orbiting on closed loops with no accumulation.
α — Windage is the fraction of wind speed directly imparted to debris riding above the water line — real drift-model studies use values of roughly 1–4% for low-profile plastic fragments, higher for objects that catch more wind.
Accumulation index is the share of particles inside the inner core radius — the model's stand-in for the real garbage patch's debris density, which is far lower than popular "trash island" imagery suggests: mostly diffuse fragments and microplastics, not a solid mat.

Real-world relevance: this convergence mechanism is why there are five major subtropical accumulation zones — most famously the Great Pacific Garbage Patch in the North Pacific Gyre — and why cleanup and monitoring efforts target the gyre centers rather than the open ocean at large.

Ocean surface Floating debris Core convergence zone

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