  We propose a new detection strategy for gravitational waves (GWs) below few
Hertz based on a correlated array of atom interferometers (AIs). Our proposal
allows to reduce the Newtonian Noise (NN) which limits all ground based GW
detectors below few Hertz, including previous atom interferometry-based
concepts. Using an array of long baseline AI gradiometers yields several
estimations of the NN, whose effect can thus be reduced via statistical
averaging. Considering the km baseline of current optical detectors, a NN
rejection of factor 2 could be achieved, and tested with existing AI array
geometries. Exploiting the correlation properties of the gravity acceleration
noise, we show that a 10-fold or more NN rejection is possible with a dedicated
configuration. Considering a conservative NN model and the current developments
in cold atom technology, we show that strain sensitivities below $1\times
10^{-19}/ \sqrt{\text{Hz}}$ in the $ 0.3-3 \ \text{Hz}$ frequency band can be
within reach, with a peak sensitivity of $3\times 10^{-23}/ \sqrt{\text{Hz}} $
at $2 \ \text{Hz}$. Our proposed configuration could extend the observation
window of current detectors by a decade and fill the gap between ground-based
and space-based instruments.
