Discuss how erosion of the Himalayan mountains influences the global carbon cycle. Distinguish between the roles of silicate and sulphide weathering.

The Himalaya, raised by the India–Eurasia plate collision, is the world's fastest-eroding orogen. Erosion continuously exposes fresh rock to air and water, making the range a major lever on the global carbon cycle — but recent isotopic evidence shows this lever works in both directions, not only as a carbon sink.

How erosion drives the carbon cycle

• Physical erosion (glacial plucking, landslides, river incision) supplies fresh mineral surfaces; chemical weathering rates therefore scale with erosion rate [1].
• Glacial retreat under a warming climate is enlarging this exposed surface area, raising the Himalaya's weathering throughput [2].
• Erosion also buries organic carbon in Indo-Gangetic and Bengal Fan sediments, an additional long-term sink.

Silicate weathering — the carbon sink

• Silicate minerals consume atmospheric CO₂, exporting it as bicarbonate to the oceans where it is locked into seafloor carbonates.
• This is the classic explanation for Cenozoic cooling over the last ~50 million years, tied to Himalayan uplift.
• In the upper Indus basin it draws down roughly 1.4 × 10⁵ mol CO₂/km²/year [2].

Sulphide weathering — the hidden carbon source

• Erosion exposes buried pyrite (FeS₂), which oxidises to sulphuric acid; this acid dissolves carbonate rock and releases CO₂ — the reverse of silicate weathering.
• A 2026 IISER Pune–Wadia Institute–IIT Roorkee study used δ³⁴S and δ¹⁸O isotopes of river sulphate to show this pathway releases about 4.4 × 10⁵ mol CO₂/km²/year, exceeding silicate drawdown [2].
• Hence the glaciated upper Indus basin is a net geological CO₂ source, while slower-eroding floodplains remain sinks [2]; similar sulphide-driven release is reported for the Tibetan Plateau [3].

Erosion thus makes mountains simultaneously a carbon sink and a carbon source, with the balance set by erosion rate and lithology. Strengthening Himalayan cryosphere and river-chemistry monitoring under the National Mission for Sustaining the Himalayan Ecosystem [4] would let India feed such regional fluxes into global carbon budgets — refining, rather than overturning, the uplift–cooling hypothesis.