Observations of the Arctic reveal that the Arctic Ocean is covered by less ice each summer than the previous summer. If this warming trend continues, within 50 years the Arctic Ocean will be ice free during the summer months. This occurrence would in itself have little or no effect on global sea levels, since the melting of ice floating in water does not affect the water level. However, serious consequences to sea levels would eventually result, because __. Which of the following most logically completes the passage? ['in the spring, melting sea ice would cause more icebergs to be created and to drift south into shipping routes', 'significant changes in Arctic sea temperatures would be accompanied by changes in sea temperatures in more temperate parts of the world', 'such a warm Arctic Ocean would trigger the melting of massive landbased glaciers in the Arctic', 'large masses of floating sea ice would continue to form in the wintertime']