tumblr api 401错误

I've got some code that is supposed to post some data to a authenticated user's blog:

var url = "http://api.tumblr.com/v2/blog/"+_ctx.blog.name+".tumblr.com/post",
    data = {
        type: 'text',
        title: _S.shareTitle,
        body: _S.shareDesc,
        api_key: 'CONSUMER_API_KEY'
    };

$.ajax({
    type: "POST",
    url: url,
    dataType: 'json',
    data: data,
    success: function(response){
        console.log(response);
    },
    error: function(jqxhr, status, error){
        console.log(status+' - '+error);
    }
});

But I'm getting a 401 Not Authorized error every time. I looked over the API documentation and see that the blog/BLOGNAME/post endpoint requires OAuth tokens to be set, but what is the parameter name for the access token? Can anyone help?