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Why two giant icebergs fertilize the ocean differently

A recently calved iceberg dumped meltwater and triggered a bloom, while a decades-grounded berg barely changed nearby waters.

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How are giant icebergs defined in this study?

They are icebergs exceeding 18 km in length.

When and from where did iceberg A-76 calve?

It calved from the western Ronne Ice Shelf on 13 May 2021.

Where did A-76A drift after calving?

Northward through the Weddell Sea into the Antarctic Circumpolar Current along iceberg alley.

How long had A-23A been grounded before it moved?

Its largest fragment grounded on the Weddell Sea continental shelf for more than 30 years.

How did mean shipboard chlorophyll compare around the two icebergs?

It was 8.5 times higher around A-76A (3.32 mg m−3) than around A-23A (0.39 mg m−3).

What peak in situ chlorophyll was measured at A-76A’s southern flank?

10.3 mg m−3.

How far from A-76A did satellite chlorophyll maxima extend?

Roughly 100 km from the iceberg.

What was the meteoric water fraction around A-76A versus typical pelagic background?

Fmet was 1.20–3.94% around A-76A, above the 1–2% Southern Ocean background.

Was Fmet enhanced around A-23A?

Generally no: 1.19–2.32%, within background levels.

How did surface nitrate compare around A-23A and A-76A?

Nitrate was much higher around A-23A (26.6 μM) than A-76A (1.3 μM).

Why might long grounding reduce A-23A’s fertilising power?

Decades of grounding and erosion may deplete surface sediments that supply micronutrients such as iron.