Ole Rieke: Observed interannual variability of modified Circumpolar Deep Water in the Denman region, East Antarctica controlled by zonal wind
The Denman region is one of a few key regions in East Antarctica that shows high ice shelf melt rates and warm modified Circumpolar Deep Water (mCDW) on the continental shelf, but very little is known about the variability of this warm water and its drivers.
In this study we analyse all available hydrographic observations from the Denman region continental shelf since 2004.
We find that mCDW has been consistently present on the continental shelf since at least 2004 as a relatively thin layer (<200m), focused on the continental shelf break, the eastern part of the shelf and the deep Denman trough near the Denman ice shelf front. The mCDW layer exhibits strong interannual variability in its maximum temperature and thickness. Maximum mCDW temperature varies between -1.3°C in 2025 and 0°C in 2023. This variability coincides with changes in zonal winds over the shelf break and the Antarctic Slope Current. Weaker coastal easterlies are associated with a weaker Antarctic Slope Current and warmer mCDW intrusions onto the continental shelf. A strong trend in zonal winds towards weaker easterlies over the last 20 years favours warm mCDW intrusions onto the shelf, consistent with three of the warmest mCDW on record since 2021. Future projections suggest this trend may continue, potentially leading to warming and thickening of the mCDW layer on the continental shelf.
This has potential implications for ice shelf melt rates and is therefore of interest to ocean and cryosphere communities.