The influence of the climate change on krill based Southern Ocean ecosystem is studied intensively last decade. To study the possible connections between Antarctic Peninsula regional climate warming and ecosystem changes the data of Antarctic krill density (KRILLBASE data) and of surface air temperature (READER data) were used. Decadal variability of winter temperature on the regional scale was analyzed. We apply Fourier and wavelet analysis to the averaged temperature anomaly time series and note the oscillations with 3-8 year periods and a decadal oscillation with a period of about 16 years. Preliminary analysis of Antarctic krill density variations shows about 8-year variability as well. Correlation coefficient between krill density data and temperature anomalies is small (less 0.2) however is increased significantly to 0.4 when applying 1-year data shift (krill density after anomalies occurrence). The 3-8 year periods possibly related to the ENSO variations and connected to sea ice change.