Guest essay by Rud Istvan
The abstract of a new Science paper by JPL’s Reager based on GRACE claims that AGW caused more landfall precipitation from 2002 to 2014, that ~3200 gigatons (cubic kilometers) was retained as groundwater, and that this slowed annual sea level rise by ~0.71mm/year. The paper is paywalled, but the phys.org report on it provides a key figure from Reager/JPL:
It is apparent from this JPL figure that the two basins with the most groundwater accumulation (dark blues) are the Amazon and the Congo. Unfortunately for JPL and for GRACE, those accumulations of ground water are physically impossible.
The Amazon basin drains to the sea via its river system, the largest in the world. Low elevations are covered by 5.5E+6km2 of relatively flat rainforest (blue on the following map) comprising [5.5/7.7] 71% of the entire basin. Manaus (red star) is 1500 km inland from the Atlantic, yet only 69 meters above sea level. The Amazon is navigable by ocean going cargo ships from the Atlantic all the way to Manaus. It will drain.
The Amazon has ITCZ determined wet/dry seasons. ‘Dry’ season June to October groundwater levels are about at local river levels. (Rainfall during the five-month Manaus ‘dry’ season (left image below) is ‘only’ about 80mm/month.) Most of the Amazon rainforest is at or just slightly above that ‘low’ river level. And it inundates during annual ‘wet’ seasons since already nearly saturated (right image). The rivers are slow moving, but wet season rainwater still drains to the sea by the next ‘dry’ season. There is no ability for the Amazon basin to retain extra ground water for years as JPL claims; it is already saturated.
The Congo River basin is the world’s second largest. The Congo has substantially more elevation change (scale in meters), so perhaps more potential ability to retain rainfall in unsaturated soils than the flat, saturated Amazon basin.
Central Africa has an ITCZ determined ‘wet’ season from October to March. Even at the beginning of the Congo wet season, almost half the basin soils are nearly or fully saturated. The rest of the basin saturates; then additional rainfall drains more rapidly to the sea than in the Amazon. Extra Congo basin water cannot be retained either, let alone accumulate hundreds of cubic kilometers over several years as JPL claims.
JPL scientists need remedial education in geography, geology, and hydrology before publishing such nonsense in Science. Ground truthing GRACE is not hard in this case based on their map. Another failure of climate science and peer review.
This quick post was easily excerpted from essay PseudoPrecision (concerning SLR) in my ebook Blowing Smoke.