  The Atlantic Meridional Overturning Circulation (MOC) is a crucial part of
the climate system because of its associated northward heat transport. The
present-day MOC is sensitive to freshwater anomalies and may collapse to a
state with a strongly reduced northward heat transport. A future collapse of
the Atlantic MOC has been identified as one of the most dangerous tipping
points in the climate system. It is therefore crucial to develop early warning
indicators for such a potential collapse based on relatively short time series.
So far, attempts to use indicators based on critical slowdown have been
marginally successful. Based on complex climate network reconstruction, we here
present a promising new indicator for the MOC collapse that efficiently
monitors spatial changes in deep ocean circulation. Through our analysis of the
performance of this indicator we formulate optimal locations of measurement of
the MOC to provide early warning signals of a collapse. Our results imply that
an increase in spatial resolution of the Atlantic MOC observations (i.e., at
more sections) can improve early detection, because the spatial coherence in
the deep ocean arising near the transition is better captured.
